Thomas Guerrero - Academia.edu (original) (raw)
Papers by Thomas Guerrero
Medical dosimetry : official journal of the American Association of Medical Dosimetrists, 2004
Treatment planning of thoracic patients having upper lobe lesions and a pacemaker presents quite ... more Treatment planning of thoracic patients having upper lobe lesions and a pacemaker presents quite a challenge. It is necessary to avoid the pacemaker as well as other critical structures in order to deliver the prescribed dose for local control. This case demonstrates the utilization of noncoplanar beams and asymmetric fields to limit the radiation dose to the pacemaker. The dose to the pacemaker was quantified by the information represented in the dose-volume histogram (DVH) of the computerized tomography (CT)-based treatment plan. The delivered dose was verified utilizing thermoluminescent dosimeters (TLDs) placed on the patient. Measurements of the daily dose from all of the treatment fields to include the open jaws during portal imaging were taken to sum the total possible dose the pacemaker may receive. The allowable dose to the pacemaker is dependent upon individual manufacturers. It was found that with proper treatment planning and appropriate precautions, a patient is able to...
Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology, Jan 5, 2018
There are two significant challenges when implementing functional-guided radiotherapy using 4DCT-... more There are two significant challenges when implementing functional-guided radiotherapy using 4DCT-ventilation imaging: (1) lack of knowledge of realistic patient specific dosimetric goals for functional lung and (2) ensuring consistent plan quality across multiple planners. Knowledge-based planning (KBP) is positioned to address both concerns. A KBP model was created from 30 previously planned functional-guided lung patients. Standard organs at risk (OAR) in lung radiotherapy and a ventilation contour delineating areas of high ventilation were included. Model validation compared dose-metrics to standard OARs and functional dose-metrics from 20 independent cases that were planned with and without KBP. A significant improvement was observed for KBP optimized plans in V20Gy and mean dose to functional lung (p = 0.005 and 0.001, respectively), V20Gy and mean dose to total lung minus GTV (p = 0.002 and 0.01, respectively), and mean doses to esophagus (p = 0.005). The current work develope...
International Journal of Computer Assisted Radiology and Surgery, 2017
Purpose Four-dimensional computed tomography (4DCT) images are often marred by artifacts that sub... more Purpose Four-dimensional computed tomography (4DCT) images are often marred by artifacts that substantially degrade image quality and confound image interpretation. Human observation remains the standard method of 4DCT artifact evaluation, which is time-consuming and subjective. We develop a method to automatically identify and reduce artifacts in cine 4DCT images. Methods We proposed an algorithm that consisted of two main stages: deformable image registration and respiratory motion simulation. Specifically, each 4DCT phase image was registered to the breath-holding CT image using the blockmatching method, with erroneous spatial matches removed by the least median of squares filter and the full displacement vector field generated by the moving least squares interpolation. The lung's respiratory motion trajectory was then recovered from the displacement vector field using the parameterized polynomial function, with fitting parameters estimated by combinatorial optimization. In this way, arti
International Journal of Radiation Oncology*Biology*Physics, 2016
Purpose-4DCT-ventilation is an exciting imaging modality that uses 4DCT data to calculate lung fu... more Purpose-4DCT-ventilation is an exciting imaging modality that uses 4DCT data to calculate lung function maps. The development of clinical trials is underway to use 4DCT-ventilation imaging to preferentially spare functional lung in patients undergoing radiotherapy. The purpose of this work was to generate data to aide with clinical trial design by retrospectively characterizing dosimetric and functional profiles for patients with different stages of lung cancer disease Methods and Materials-A total of 118 lung cancer patients (36% stage I and 64% stage III) from 2 institutions were used for the study. A 4DCT-ventilation map was calculated using the patient's 4DCT imaging, deformable image registration, and a density-change based algorithm. In order to assess each patient's spatial ventilation profile both quantitative and qualitative metrics were developed including an observer-based defect observation and metrics based on the ventilation in each lung third. For each patient we used the clinical doses to calculate weighted mean lung doses (fMLD) and metrics that assessed the interplay between the spatial location of the dose and high-functioning lung. Results-Both qualitative and quantitative metrics revealed a significant difference in functional profiles between the 2 stage groups (p<0.01). We determined that 65% of stage III and 28% of stage I patients had ventilation defects. Average fMLD was 19.6 Gy and 5.4 Gy for stage III and I patients respectively with both groups containing patients with large spatial overlap between dose and high-function regions.
International journal of radiation oncology, biology, physics, Jan 25, 2015
A new form of functional imaging has been proposed in the form of 4-dimensional computed tomograp... more A new form of functional imaging has been proposed in the form of 4-dimensional computed tomography (4DCT) ventilation. Because 4DCTs are acquired as part of routine care for lung cancer patients, calculating ventilation maps from 4DCTs provides spatial lung function information without added dosimetric or monetary cost to the patient. Before 4DCT-ventilation is implemented it needs to be clinically validated. Pulmonary function tests (PFTs) provide a clinically established way of evaluating lung function. The purpose of our work was to perform a clinical validation by comparing 4DCT-ventilation metrics with PFT data. Ninety-eight lung cancer patients with pretreatment 4DCT and PFT data were included in the study. Pulmonary function test metrics used to diagnose obstructive lung disease were recorded: forced expiratory volume in 1 second (FEV1) and FEV1/forced vital capacity. Four-dimensional CT data sets and spatial registration were used to compute 4DCT-ventilation images using a ...
Journal of Applied Clinical Medical Physics, 2008
A three-dimensional (3D) optical flow program that includes a multi-resolution feature has been d... more A three-dimensional (3D) optical flow program that includes a multi-resolution feature has been developed and applied to 3D anatomic structure and gross tumor volume (GTV) contour mapping for four-dimensional computed tomography (4D CT) data. The present study includes contour mapping for actual CT data sets from 3 patients and also for a thoracic phantom in which the displacement for each voxel was known. Of the CT data sets for the actual patients, one set was used to map lung and GTV contours over all respiration phases, and the other two were studied using only the end inspiration and end expiration phases, in which the displacements between phases were the largest. Including the residual motion in the 4D CT data and motion from table shaking, the optical flow calculation agrees with the known displacement to within 1 mm. Excluding errors not introduced by the optical flow algorithm, agreement for a displacement magnitude of 24 mm can be within 0.1 mm. The mapped contours in 4D CT images of lungs, liver, esophagus, GTV, and other structures for actual patients were acceptable to clinicians. The 3D optical flow program is a good tool for contour mapping of anatomic structure and tumor volume across 4D CT scans.
Physics in Medicine and Biology, 2012
To determine the spatial overlap agreement between four-dimensional computed tomography (4D CT) v... more To determine the spatial overlap agreement between four-dimensional computed tomography (4D CT) ventilation and single photon emission computed tomography (SPECT) perfusion hypo-functioning pulmonary defect regions in a patient population with malignant airway stenosis. Treatment planning 4D CT images were obtained retrospectively for ten lung cancer patients with radiographically demonstrated airway obstruction due to gross tumor volume. Each patient also received a SPECT perfusion study within one week of the planning 4D CT, and prior to the initiation of treatment. Deformable image registration was used to map corresponding lung tissue elements between the extreme component phase images, from which quantitative three-dimensional (3D) images representing the local pulmonary specific ventilation were constructed. Semi-automated segmentation of the percentile perfusion distribution was performed to identify regional defects distal to the known obstructing lesion. Semi-automated segmentation was similarly performed by multiple observers to delineate corresponding defect regions depicted on 4D CT ventilation. Normalized Dice similarity coefficient (NDSC) indices were determined for each observer between SPECT perfusion and 4D CT ventilation defect regions to assess spatial overlap agreement. Tidal volumes determined from 4D CT ventilation were evaluated versus measurements obtained from lung parenchyma segmentation. Linear regression resulted in a linear fit with slope = 1.01 (R² = 0.99). Respective values for the average DSC, NDSC(1 mm) and NDSC(2 mm) for all cases and multiple observers were 0.78, 0.88 and 0.99, indicating that, on average, spatial overlap agreement between ventilation and perfusion defect regions was comparable to the threshold for agreement within 1-2 mm uncertainty. Corresponding coefficients of variation for all metrics were similarly in the range: 0.10%-19%. This study is the first to quantitatively assess 3D spatial overlap agreement between clinically acquired SPECT perfusion and specific ventilation from 4D CT. Results suggest high correlation between methods within the sub-population of lung cancer patients with malignant airway stenosis.
Radiotherapy and Oncology, 2013
This study quantifies pulmonary radiation toxicity in patients who received proton therapy for es... more This study quantifies pulmonary radiation toxicity in patients who received proton therapy for esophagus cancer. Materials/methods: We retrospectively studied 100 esophagus cancer patients treated with proton therapy. The linearity of the enhanced FDG uptake vs. proton dose was evaluated using the Akaike Information Criterion (AIC). Pneumonitis symptoms (RP) were assessed using the Common Toxicity Criteria for Adverse Events version 4.0 (CTCAEv4). The interaction of the imaging response with dosimetric parameters and symptoms was evaluated. Results: The RP scores were: 0 grade 4/5, 7 grade 3, 20 grade 2, 37 grade 1, and 36 grade 0. Each dosimetric parameter was significantly higher for the symptomatic group. The AIC winning models were 30 linear, 52 linear quadratic, and 18 linear logarithmic. There was no significant difference in the linear coefficient between models. The slope of the FDG vs. proton dose response was 0.022 for the symptomatic and 0.012 for the asymptomatic (p = 0.014). Combining dosimetric parameters with the slope did not improve the sensitivity or accuracy in identifying symptomatic cases. Conclusions: The proton radiation dose response on FDG PET/CT imaging exhibited a predominantly linear dose response on modeling. Symptomatic patients had a higher dose response slope.
Radiation Oncology, 2014
Background: A retrospective analysis is performed to determine if pre-treatment [ 18 F]-2-fluoro-... more Background: A retrospective analysis is performed to determine if pre-treatment [ 18 F]-2-fluoro-2-deoxyglucose positron emission tomography/computed tomography (FDG PET/CT) image derived parameters can predict radiation pneumonitis (RP) clinical symptoms in lung cancer patients. Methods and Materials: We retrospectively studied 100 non-small cell lung cancer (NSCLC) patients who underwent FDG PET/CT imaging before initiation of radiotherapy (RT). Pneumonitis symptoms were evaluated using the Common Terminology Criteria for Adverse Events version 4.0 (CTCAEv4) from the consensus of 5 clinicians. Using the cumulative distribution of pre-treatment standard uptake values (SUV) within the lungs, the 80th to 95th percentile SUV values (SUV 80 to SUV 95) were determined. The effect of pre-RT FDG uptake, dose, patient and treatment characteristics on pulmonary toxicity was studied using multiple logistic regression. Results: The study subjects were treated with 3D conformal RT (n = 23), intensity modulated RT (n = 64), and proton therapy (n = 13). Multiple logistic regression analysis demonstrated that elevated pre-RT lung FDG uptake on staging FDG PET was related to development of RP symptoms after RT. A patient of average age and V 30 with SUV 95 = 1.5 was an estimated 6.9 times more likely to develop grade ≥ 2 radiation pneumonitis when compared to a patient with SUV 95 = 0.5 of the same age and identical V 30. Receiver operating characteristic curve analysis showed the area under the curve was 0.78 (95% CI = 0.69-0.87). The CT imaging and dosimetry parameters were found to be poor predictors of RP symptoms. Conclusions: The pretreatment pulmonary FDG uptake, as quantified by the SUV 95 , predicted symptoms of RP in this study. Elevation in this pre-treatment biomarker identifies a patient group at high risk for post-treatment symptomatic RP.
Physics in Medicine and Biology, 2013
Rationale and Objectives-Landmark point-pairs provide a strategy to assess deformable image regis... more Rationale and Objectives-Landmark point-pairs provide a strategy to assess deformable image registration (DIR) accuracy in terms of the spatial registration of the underlying anatomy depicted in medical images. In this study, we propose to augment a publicly available database (www.dir-lab.com) of medical images with large sets of manually identified anatomic feature pairs between breath-hold computed tomography (BH-CT) images for DIR spatial accuracy evaluation. Materials and Methods-10 BH-CT image pairs were randomly selected from the COPDgene study cases. Each patient had received CT imaging of the entire thorax in the supine position at 1/4 th dose normal expiration and maximum effort full dose inspiration. Using dedicated in-house software, an imaging expert manually identified large sets of anatomic feature pairs between images. Estimates of inter-and intra-observer spatial variation in feature localization were determined by repeat measurements of multiple observers over subsets of randomly selected features. Results-7298 anatomic landmark features were manually paired between the 10 sets of images. Quantity of feature pairs per case ranged from 447 to 1172. Average 3D Euclidean landmark displacements varied substantially among cases, ranging from 12.29 (SD: 6.39) to 30.90 (SD: 14.05) mm. Repeat registration of uniformly sampled subsets of 150 landmarks for each case yielded estimates of observer localization error, which ranged in average from 0.58 (SD: 0.87) to 1.06 (SD: 2.38) mm for each case. Conclusions-The additions to the online web database (www.dir-lab.com) described in this work will broaden the applicability of the reference data, providing a freely available common dataset for targeted critical evaluation of DIR spatial accuracy performance in multiple clinical settings. Estimates of observer variance in feature localization suggest consistent spatial accuracy for all observers across both 4D CT and COPDgene patient cohorts.
Physics in Medicine and Biology, 2004
The purpose of this work was to develop and validate an automated method for intrathoracic tumour... more The purpose of this work was to develop and validate an automated method for intrathoracic tumour motion estimation from breath-hold computed tomography (BH CT) imaging using the three-dimensional optical flow method (3D OFM). A modified 3D OFM algorithm provided 3D displacement vectors for each voxel which were used to map tumour voxels on expiration BH CT onto inspiration BH CT images. A thoracic phantom and simulated expiration/inspiration BH CT pairs were used for validation. The 3D OFM was applied to the measured inspiration and expiration BH CT images from one lung cancer and one oesophageal cancer patient. The resulting displacements were plotted in histogram format and analysed to provide insight regarding the tumour motion. The phantom tumour displacement was measured as 1.20 and 2.40 cm with full-width at tenth maximum (FWTM) for the distribution of displacement estimates of 0.008 and 0.006 cm, respectively. The maximum error of any single voxel&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s motion estimate was 1.1 mm along the z-dimension or approximately one-third of the z-dimension voxel size. The simulated BH CT pairs revealed an rms error of less than 0.25 mm. The displacement of the oesophageal tumours was nonuniform and up to 1.4 cm, this was a new finding. A lung tumour maximum displacement of 2.4 cm was found in the case evaluated. In conclusion, 3D OFM provided an accurate estimation of intrathoracic tumour motion, with estimated errors less than the voxel dimension in a simulated motion phantom study. Surprisingly, oesophageal tumour motion was large and nonuniform, with greatest motion occurring at the gastro-oesophageal junction.
Medical Physics, 2014
Block matching is a well-known strategy for estimating corresponding voxel locations between a pa... more Block matching is a well-known strategy for estimating corresponding voxel locations between a pair of images according to an image similarity metric. Though robust to issues such as image noise and large magnitude voxel displacements, the estimated point matches are not guaranteed to be spatially accurate. However, the underlying optimization problem solved by the block matching procedure is similar in structure to the class of optimization problem associated with B-spline based registration methods. By exploiting this relationship, the authors derive a numerical method for computing a global minimizer to a constrained B-spline registration problem that incorporates the robustness of block matching with the global smoothness properties inherent to B-spline parameterization. Methods: The method reformulates the traditional B-spline registration problem as a basis pursuit problem describing the minimal l 1-perturbation to block match pairs required to produce a B-spline fitting error within a given tolerance. The sparsity pattern of the optimal perturbation then defines a voxel point cloud subset on which the B-spline fit is a global minimizer to a constrained variant of the B-spline registration problem. As opposed to traditional B-spline algorithms, the optimization step involving the actual image data is addressed by block matching. Results: The performance of the method is measured in terms of spatial accuracy using ten inhale/exhale thoracic CT image pairs (available for download at www.dir-lab.com) obtained from the COPDgene dataset and corresponding sets of expert-determined landmark point pairs. The results of the validation procedure demonstrate that the method can achieve a high spatial accuracy on a significantly complex image set. Conclusions: The proposed methodology is demonstrated to achieve a high spatial accuracy and is generalizable in that in can employ any displacement field parameterization described as a least squares fit to block match generated estimates. Thus, the framework allows for a wide range of image similarity block match metric and physical modeling combinations.
Medical Physics, 2012
ABSTRACT Purpose: An exciting form of ventilation imaging is being developed based on 4-dimension... more ABSTRACT Purpose: An exciting form of ventilation imaging is being developed based on 4-dimensional computed tomography (4DCT) data. Because 4DCTs are routine for thoracic radiation therapy, calculating ventilation maps from 4DCT data does not add extra dosimetric or monetary cost. Studies have discussed designing treatment plans to avoid highly-ventilated areas of the lung. However, the hypothesis that using ventilation in treatment planning can reduce thoracic toxicity remains to be tested. The purpose of our work was to determine whether incorporating ventilation-based functional information could improve prediction for clinical thoracic toxicity. Methods: The study used 96 lung cancer patients, 17 of whom developed radiation pneumonitis (CTCAE 3.0 Grade>=3). Pre-treatment 4DCT data, spatial registration, and a density-change based model were used to compute pre-treatment ventilation maps for each patient. Using dose and ventilation, we calculated dose-volume and dose-function histograms, mean lung doses (MLD), and ventilation-weighted MLD (fMLD). The ventilation-weighted dosimetric values were compared between the pneumonitis group and the non-pneumonitis group using a two-sample t-test. The ventilation-based functional data were incorporated into a predictive dose-response model and maximum likelihood was used to determine whether incorporating functional data could significantly improve the model fit to clinical toxicity data. Results: Specific patient examples illustrate that using functional dose metrics can lead to better estimates of toxicity. The fMLD was higher for patients that developed pneumonitis (20.8 Gy) than for those that did not (18.9 Gy), however, the results were not significant (p=0.251). Although fMLD improved model fit over using MLD, the difference in fits was not found to be significant (p=0.312). Conclusions: This is the first study that has attempted to link irradiating ventilated portions of the lung to clinical outcomes. Although promising data were presented, the results were not statistically significant. Future work will include more patients and further functional information with perfusion imaging.
International Journal of Radiation Oncology*Biology*Physics, 2013
Purpose-Four-dimensional computed tomography (4DCT)-based ventilation is an emerging imaging moda... more Purpose-Four-dimensional computed tomography (4DCT)-based ventilation is an emerging imaging modality that can be used in the thoracic treatment planning process. The clinical benefit of using ventilation images in radiation treatment plans remains to be tested. The purpose of the current work was to test the potential benefit of using ventilation in treatment planning by evaluating whether dose to highly ventilated regions of the lung resulted in increased incidence of clinical toxicity. Methods and Materials-Pretreatment 4DCT data were used to compute pretreatment ventilation images for 96 lung cancer patients. Ventilation images were calculated using 4DCT data, deformable image registration, and a density-change based algorithm. Dose-volume and ventilation-based dose function metrics were computed for each patient. The ability of the dosevolume and ventilation-based dose-function metrics to predict for severe (grade 3+) radiation pneumonitis was assessed using logistic regression analysis, area under the curve (AUC) metrics, and bootstrap methods. Results-A specific patient example is presented that demonstrates how incorporating ventilation-based functional information can help separate patients with and without toxicity. The logistic regression significance values were all lower for the dose-function metrics (range P=. 093-.250) than for their dose-volume equivalents (range, P=.331-.580). The AUC values were all greater for the dose-function metrics (range, 0.569-0.620) than for their dose-volume equivalents (range, 0.500-0.544). Bootstrap results revealed an improvement in model fit using
International Journal of Radiation Oncology*Biology*Physics, 2007
Purpose: To investigate the ability of four-dimensional computed tomography (4D CT)-derived venti... more Purpose: To investigate the ability of four-dimensional computed tomography (4D CT)-derived ventilation images to identify regions of highly functional lung for avoidance in intensitymodulated radiotherapy (IMRT) planning in locally advanced non-small cell lung cancer (NSCLC). Methods and Materials: The treatment planning records from 21 patients with stage III NSCLC were selected. Ventilation images were generated from the 4D CT sets, and each was imported into the treatment-planning system. Ninety percentile functional volumes (PFV90), constituting the 10% of the lung volume where the highest ventilation occurs, were generated. Baseline IMRT plans were generated using the lung volume constraint on V20 (<35%), and two additional plans were generated using constraints on the PFV90 without a volume constraint. Dose-volume (DVH) and dose-function (DFH) histograms were generated and used to evaluate the PTV coverage, lung volume, and functional parameters for comparison of the plans. Results: The mean dose to the PFV90 was reduced by 2.9 Gy, and the DFH at 5 Gy (F5) was reduced by 9.6% (SE=2.03%). The F5, F10, V5, and V10 were all significantly reduced from the baseline values. We identified a favorable subset of patients for whom there was a further significant improvement in the mean lung dose. Conclusions: 4D CT-derived ventilation regions were successfully utilized as avoidance structures to reduce the DVH and DFH at 5 Gy in all the cases. In a subset, there was also a
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](International Journal of Radiation Oncology*Biology*Physics, 2007
Purpose: To quantify the relationship between the local radiation dose received and the posttreat... more Purpose: To quantify the relationship between the local radiation dose received and the posttreatment positron emission tomography/computed tomography (PET/CT) [ 18 F]2-fluoro-2-deoxyglucose (FDG) uptake in the lung. Methods and Materials: The data from 36 patients treated for esophageal cancer with thoracic radiotherapy who underwent restaging PET/CT imaging between 4 and 12 weeks after radiotherapy completion were evaluated. Their treatment planning CT was registered with the restaging PET/CT. Using histogram analysis, the voxel average FDG-PET uptake vs. radiation dose was obtained for each case. Hierarchical linear regression models for each patient were applied to study the variation in the linear trends between cases. Deviation of the dose-response curve from a linear model was tested. Results: The median time between radiotherapy completion and FDG-PET imaging was 40 days (range, 26-70 days). The median of the mean standard uptake value in the lung that received 0-5 Gy was 0.63 (range, 0.36-1.27), 5-10 Gy was 0.77 (range, 0.40-1.35), 10-20 Gy was 0.80 (range, 0.40-1.72), and >20 Gy was 1.08 (range, 0.44-2.63). A hierarchical linear regression model of the radiation dose and normalized FDG uptake per case found an adequate fit with the linear model, and the addition of quadratic and logarithmic functions did not improve the fit. The 36 cases had a posterior mean of slopes range of 0.0048-0.069. Conclusion: The regional dose vs. radiation pneumonitis response was evaluated with FDG-PET/CT imaging. Statistical modeling found a linear relationship. The slope of this relationship varied over an order of magnitude, reflecting the range of the underlying biological response to radiation among the study population.
International Journal of Radiation Oncology*Biology*Physics, 2007
Purpose: To assess quantitatively the impact of incorporating functional lung imaging into intens... more Purpose: To assess quantitatively the impact of incorporating functional lung imaging into intensity-modulated radiation therapy planning for locally advanced non-small cell lung cancer (NSCLC). Methods and Materials: Sixteen patients with advanced-stage NSCLC who underwent radiotherapy were included in this study. Before radiotherapy, each patient underwent lung perfusion imaging with single-photonemission computed tomography and X-ray computed tomography (SPECT-CT). The SPECT-CT was registered with simulation CT and was used to segment the 50-and 90-percentile hyperperfusion lung (F50 lung and F90 lung). Two IMRT plans were designed and compared in each patient: an anatomic plan using simulation CT alone and a functional plan using SPECT-CT in addition to the simulation CT. Dosimetric parameters of the two types of plans were compared in terms of tumor coverage and avoidance of normal tissues. Results: In incorporating perfusion information in IMRT planning, the median reductions in the mean doses to the F50 and F90 lung in the functional plan were 2.2 and 4.2 Gy, respectively, compared with those in the anatomic plans. The median reductions in the percentage of volume irradiated with >5 Gy, >10 Gy, and >20 Gy in the functional plans were 7.1%, 6.0%, and 5.1%, respectively, for F50 lung, and 11.7%, 12.0%, and 6.8%, respectively, for F90 lung. A greater degree of sparing of the functional lung was achieved for patients with large perfusion defects compared with those with relatively uniform perfusion distribution. Conclusion: Function-guided IMRT planning appears to be effective in preserving functional lung in locally advanced-stage NSCLC patients.
International Journal of Radiation Oncology*Biology*Physics, 2008
Purpose-To compare three-dimensional (3D) and 4D computed tomography (CT)-based treatment plans f... more Purpose-To compare three-dimensional (3D) and 4D computed tomography (CT)-based treatment plans for proton therapy or intensity-modulated radiation therapy (IMRT) for esophageal cancer in terms of doses to the lung, heart, and spinal cord and variations in target coverage and normal tissue sparing. Materials and Methods-IMRT and proton plans for 15 patients with distal esophageal cancer were designed from the 3D average CT scans and then recalculated on 10 4D CT data sets. Dosimetric data were compared for tumor coverage and normal tissue sparing. Results-Compared with IMRT, median lung volumes exposed to 5,10, and 20 Gy and mean lung dose were reduced by 35.6%, 20.5%,5.8%, and 5.1 Gy for a two-beam proton plan and by 17.4%, 8.4%,5%, and 2.9 Gy for a three-beam proton plan. The greater lung sparing in the two-beam proton plan was achieved at the expense of less conformity to the target (conformity index CI=1.99) and greater irradiation of the heart (heart-V40=41.8%) compared with the IMRT plan(CI=1.55, heart-V40=35.7%) or the three-beam proton plan (CI=1.46, heart-V40=27.7%). Target coverage differed by more than 2% between the 3D and 4D plans for patients with substantial diaphragm motion in the three-beam proton and IMRT plans. The difference in spinal cord maximum dose between 3D and 4D plans could exceed 5 Gy for the proton plans partly owing to variations in stomach gas-filling. Conclusions-Proton therapy provided significantly better sparing of lung than did IMRT. Diaphragm motion and stomach gas-filling must be considered in evaluating target coverage and cord doses.
International Journal of Radiation Oncology*Biology*Physics, 2007
Purpose: To demonstrate that high-resolution computed tomography (CT) can be used to quantify los... more Purpose: To demonstrate that high-resolution computed tomography (CT) can be used to quantify loss of pulmonary compliance in irradiated mice. Methods and Materials: Computed tomography images of three nonirradiated (controls) and three irradiated mice were obtained 200 days after a single dose of 16-Gy Co (60) thoracic irradiation. While intubated, each animal was imaged at static breath-hold pressures of 2, 10, and 18 cm H 2 O. A deformable image registration algorithm was used to calculate changes in air volume between adjacent-pressure CT image pairs (e.g., 2 and 10 cm H 2 O), and functional images of pulmonary compliance were generated. The mass-specific compliance was calculated as the change in volume divided by the pressure difference between the 2 image sets and the mass of lung tissue. Results: For the irradiated mice, the lung parenchyma mean CT values ranged from ؊314 (؎ 11) Hounsfield units (HU) to ؊378 (؎ 11) HU. For the control mice, the mean CT values ranged from ؊549 (؎ 11) HU to ؊633 (؎ 11) HU. Irradiated mice had a 60% (45, 74%; 95% confidence interval) lower mass-specific compliance than did the controls (0.039 [؎ 0.0038] vs. 0.106 [؎ 0.0038] mL air per cm H 2 O per g lung) from the 2-cm to 10-cm H 2 O CT image pair. The difference in compliance between groups was less pronounced at the higher distending pressures. Conclusion: High-resolution CT was used to quantify a reduction in mass-specific compliance following whole lung irradiation in mice. This small animal radiation injury model and assay may be useful in the study of lung injury.
International Journal of Radiation Oncology*Biology*Physics, 2003
respiratory motion, was determined such that the dose reduction in the CTV due to respiratory mot... more respiratory motion, was determined such that the dose reduction in the CTV due to respiratory motion was Յ 0.1% of the prescription dose. The influence of the planning dose distribution on the target margin was examined, and incorporated in the margin minimization. To achieve mean target position during the pre-planning imaging, the active breathing control (ABC) device is currently used during the CT scanning. However, CT images acquired using respiratory gating or respiratory correlated CT imaging, which have been developed for radiotherapy, can also be applied to extrapolate the treatment target at the mean position. S234
Medical dosimetry : official journal of the American Association of Medical Dosimetrists, 2004
Treatment planning of thoracic patients having upper lobe lesions and a pacemaker presents quite ... more Treatment planning of thoracic patients having upper lobe lesions and a pacemaker presents quite a challenge. It is necessary to avoid the pacemaker as well as other critical structures in order to deliver the prescribed dose for local control. This case demonstrates the utilization of noncoplanar beams and asymmetric fields to limit the radiation dose to the pacemaker. The dose to the pacemaker was quantified by the information represented in the dose-volume histogram (DVH) of the computerized tomography (CT)-based treatment plan. The delivered dose was verified utilizing thermoluminescent dosimeters (TLDs) placed on the patient. Measurements of the daily dose from all of the treatment fields to include the open jaws during portal imaging were taken to sum the total possible dose the pacemaker may receive. The allowable dose to the pacemaker is dependent upon individual manufacturers. It was found that with proper treatment planning and appropriate precautions, a patient is able to...
Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology, Jan 5, 2018
There are two significant challenges when implementing functional-guided radiotherapy using 4DCT-... more There are two significant challenges when implementing functional-guided radiotherapy using 4DCT-ventilation imaging: (1) lack of knowledge of realistic patient specific dosimetric goals for functional lung and (2) ensuring consistent plan quality across multiple planners. Knowledge-based planning (KBP) is positioned to address both concerns. A KBP model was created from 30 previously planned functional-guided lung patients. Standard organs at risk (OAR) in lung radiotherapy and a ventilation contour delineating areas of high ventilation were included. Model validation compared dose-metrics to standard OARs and functional dose-metrics from 20 independent cases that were planned with and without KBP. A significant improvement was observed for KBP optimized plans in V20Gy and mean dose to functional lung (p = 0.005 and 0.001, respectively), V20Gy and mean dose to total lung minus GTV (p = 0.002 and 0.01, respectively), and mean doses to esophagus (p = 0.005). The current work develope...
International Journal of Computer Assisted Radiology and Surgery, 2017
Purpose Four-dimensional computed tomography (4DCT) images are often marred by artifacts that sub... more Purpose Four-dimensional computed tomography (4DCT) images are often marred by artifacts that substantially degrade image quality and confound image interpretation. Human observation remains the standard method of 4DCT artifact evaluation, which is time-consuming and subjective. We develop a method to automatically identify and reduce artifacts in cine 4DCT images. Methods We proposed an algorithm that consisted of two main stages: deformable image registration and respiratory motion simulation. Specifically, each 4DCT phase image was registered to the breath-holding CT image using the blockmatching method, with erroneous spatial matches removed by the least median of squares filter and the full displacement vector field generated by the moving least squares interpolation. The lung's respiratory motion trajectory was then recovered from the displacement vector field using the parameterized polynomial function, with fitting parameters estimated by combinatorial optimization. In this way, arti
International Journal of Radiation Oncology*Biology*Physics, 2016
Purpose-4DCT-ventilation is an exciting imaging modality that uses 4DCT data to calculate lung fu... more Purpose-4DCT-ventilation is an exciting imaging modality that uses 4DCT data to calculate lung function maps. The development of clinical trials is underway to use 4DCT-ventilation imaging to preferentially spare functional lung in patients undergoing radiotherapy. The purpose of this work was to generate data to aide with clinical trial design by retrospectively characterizing dosimetric and functional profiles for patients with different stages of lung cancer disease Methods and Materials-A total of 118 lung cancer patients (36% stage I and 64% stage III) from 2 institutions were used for the study. A 4DCT-ventilation map was calculated using the patient's 4DCT imaging, deformable image registration, and a density-change based algorithm. In order to assess each patient's spatial ventilation profile both quantitative and qualitative metrics were developed including an observer-based defect observation and metrics based on the ventilation in each lung third. For each patient we used the clinical doses to calculate weighted mean lung doses (fMLD) and metrics that assessed the interplay between the spatial location of the dose and high-functioning lung. Results-Both qualitative and quantitative metrics revealed a significant difference in functional profiles between the 2 stage groups (p<0.01). We determined that 65% of stage III and 28% of stage I patients had ventilation defects. Average fMLD was 19.6 Gy and 5.4 Gy for stage III and I patients respectively with both groups containing patients with large spatial overlap between dose and high-function regions.
International journal of radiation oncology, biology, physics, Jan 25, 2015
A new form of functional imaging has been proposed in the form of 4-dimensional computed tomograp... more A new form of functional imaging has been proposed in the form of 4-dimensional computed tomography (4DCT) ventilation. Because 4DCTs are acquired as part of routine care for lung cancer patients, calculating ventilation maps from 4DCTs provides spatial lung function information without added dosimetric or monetary cost to the patient. Before 4DCT-ventilation is implemented it needs to be clinically validated. Pulmonary function tests (PFTs) provide a clinically established way of evaluating lung function. The purpose of our work was to perform a clinical validation by comparing 4DCT-ventilation metrics with PFT data. Ninety-eight lung cancer patients with pretreatment 4DCT and PFT data were included in the study. Pulmonary function test metrics used to diagnose obstructive lung disease were recorded: forced expiratory volume in 1 second (FEV1) and FEV1/forced vital capacity. Four-dimensional CT data sets and spatial registration were used to compute 4DCT-ventilation images using a ...
Journal of Applied Clinical Medical Physics, 2008
A three-dimensional (3D) optical flow program that includes a multi-resolution feature has been d... more A three-dimensional (3D) optical flow program that includes a multi-resolution feature has been developed and applied to 3D anatomic structure and gross tumor volume (GTV) contour mapping for four-dimensional computed tomography (4D CT) data. The present study includes contour mapping for actual CT data sets from 3 patients and also for a thoracic phantom in which the displacement for each voxel was known. Of the CT data sets for the actual patients, one set was used to map lung and GTV contours over all respiration phases, and the other two were studied using only the end inspiration and end expiration phases, in which the displacements between phases were the largest. Including the residual motion in the 4D CT data and motion from table shaking, the optical flow calculation agrees with the known displacement to within 1 mm. Excluding errors not introduced by the optical flow algorithm, agreement for a displacement magnitude of 24 mm can be within 0.1 mm. The mapped contours in 4D CT images of lungs, liver, esophagus, GTV, and other structures for actual patients were acceptable to clinicians. The 3D optical flow program is a good tool for contour mapping of anatomic structure and tumor volume across 4D CT scans.
Physics in Medicine and Biology, 2012
To determine the spatial overlap agreement between four-dimensional computed tomography (4D CT) v... more To determine the spatial overlap agreement between four-dimensional computed tomography (4D CT) ventilation and single photon emission computed tomography (SPECT) perfusion hypo-functioning pulmonary defect regions in a patient population with malignant airway stenosis. Treatment planning 4D CT images were obtained retrospectively for ten lung cancer patients with radiographically demonstrated airway obstruction due to gross tumor volume. Each patient also received a SPECT perfusion study within one week of the planning 4D CT, and prior to the initiation of treatment. Deformable image registration was used to map corresponding lung tissue elements between the extreme component phase images, from which quantitative three-dimensional (3D) images representing the local pulmonary specific ventilation were constructed. Semi-automated segmentation of the percentile perfusion distribution was performed to identify regional defects distal to the known obstructing lesion. Semi-automated segmentation was similarly performed by multiple observers to delineate corresponding defect regions depicted on 4D CT ventilation. Normalized Dice similarity coefficient (NDSC) indices were determined for each observer between SPECT perfusion and 4D CT ventilation defect regions to assess spatial overlap agreement. Tidal volumes determined from 4D CT ventilation were evaluated versus measurements obtained from lung parenchyma segmentation. Linear regression resulted in a linear fit with slope = 1.01 (R² = 0.99). Respective values for the average DSC, NDSC(1 mm) and NDSC(2 mm) for all cases and multiple observers were 0.78, 0.88 and 0.99, indicating that, on average, spatial overlap agreement between ventilation and perfusion defect regions was comparable to the threshold for agreement within 1-2 mm uncertainty. Corresponding coefficients of variation for all metrics were similarly in the range: 0.10%-19%. This study is the first to quantitatively assess 3D spatial overlap agreement between clinically acquired SPECT perfusion and specific ventilation from 4D CT. Results suggest high correlation between methods within the sub-population of lung cancer patients with malignant airway stenosis.
Radiotherapy and Oncology, 2013
This study quantifies pulmonary radiation toxicity in patients who received proton therapy for es... more This study quantifies pulmonary radiation toxicity in patients who received proton therapy for esophagus cancer. Materials/methods: We retrospectively studied 100 esophagus cancer patients treated with proton therapy. The linearity of the enhanced FDG uptake vs. proton dose was evaluated using the Akaike Information Criterion (AIC). Pneumonitis symptoms (RP) were assessed using the Common Toxicity Criteria for Adverse Events version 4.0 (CTCAEv4). The interaction of the imaging response with dosimetric parameters and symptoms was evaluated. Results: The RP scores were: 0 grade 4/5, 7 grade 3, 20 grade 2, 37 grade 1, and 36 grade 0. Each dosimetric parameter was significantly higher for the symptomatic group. The AIC winning models were 30 linear, 52 linear quadratic, and 18 linear logarithmic. There was no significant difference in the linear coefficient between models. The slope of the FDG vs. proton dose response was 0.022 for the symptomatic and 0.012 for the asymptomatic (p = 0.014). Combining dosimetric parameters with the slope did not improve the sensitivity or accuracy in identifying symptomatic cases. Conclusions: The proton radiation dose response on FDG PET/CT imaging exhibited a predominantly linear dose response on modeling. Symptomatic patients had a higher dose response slope.
Radiation Oncology, 2014
Background: A retrospective analysis is performed to determine if pre-treatment [ 18 F]-2-fluoro-... more Background: A retrospective analysis is performed to determine if pre-treatment [ 18 F]-2-fluoro-2-deoxyglucose positron emission tomography/computed tomography (FDG PET/CT) image derived parameters can predict radiation pneumonitis (RP) clinical symptoms in lung cancer patients. Methods and Materials: We retrospectively studied 100 non-small cell lung cancer (NSCLC) patients who underwent FDG PET/CT imaging before initiation of radiotherapy (RT). Pneumonitis symptoms were evaluated using the Common Terminology Criteria for Adverse Events version 4.0 (CTCAEv4) from the consensus of 5 clinicians. Using the cumulative distribution of pre-treatment standard uptake values (SUV) within the lungs, the 80th to 95th percentile SUV values (SUV 80 to SUV 95) were determined. The effect of pre-RT FDG uptake, dose, patient and treatment characteristics on pulmonary toxicity was studied using multiple logistic regression. Results: The study subjects were treated with 3D conformal RT (n = 23), intensity modulated RT (n = 64), and proton therapy (n = 13). Multiple logistic regression analysis demonstrated that elevated pre-RT lung FDG uptake on staging FDG PET was related to development of RP symptoms after RT. A patient of average age and V 30 with SUV 95 = 1.5 was an estimated 6.9 times more likely to develop grade ≥ 2 radiation pneumonitis when compared to a patient with SUV 95 = 0.5 of the same age and identical V 30. Receiver operating characteristic curve analysis showed the area under the curve was 0.78 (95% CI = 0.69-0.87). The CT imaging and dosimetry parameters were found to be poor predictors of RP symptoms. Conclusions: The pretreatment pulmonary FDG uptake, as quantified by the SUV 95 , predicted symptoms of RP in this study. Elevation in this pre-treatment biomarker identifies a patient group at high risk for post-treatment symptomatic RP.
Physics in Medicine and Biology, 2013
Rationale and Objectives-Landmark point-pairs provide a strategy to assess deformable image regis... more Rationale and Objectives-Landmark point-pairs provide a strategy to assess deformable image registration (DIR) accuracy in terms of the spatial registration of the underlying anatomy depicted in medical images. In this study, we propose to augment a publicly available database (www.dir-lab.com) of medical images with large sets of manually identified anatomic feature pairs between breath-hold computed tomography (BH-CT) images for DIR spatial accuracy evaluation. Materials and Methods-10 BH-CT image pairs were randomly selected from the COPDgene study cases. Each patient had received CT imaging of the entire thorax in the supine position at 1/4 th dose normal expiration and maximum effort full dose inspiration. Using dedicated in-house software, an imaging expert manually identified large sets of anatomic feature pairs between images. Estimates of inter-and intra-observer spatial variation in feature localization were determined by repeat measurements of multiple observers over subsets of randomly selected features. Results-7298 anatomic landmark features were manually paired between the 10 sets of images. Quantity of feature pairs per case ranged from 447 to 1172. Average 3D Euclidean landmark displacements varied substantially among cases, ranging from 12.29 (SD: 6.39) to 30.90 (SD: 14.05) mm. Repeat registration of uniformly sampled subsets of 150 landmarks for each case yielded estimates of observer localization error, which ranged in average from 0.58 (SD: 0.87) to 1.06 (SD: 2.38) mm for each case. Conclusions-The additions to the online web database (www.dir-lab.com) described in this work will broaden the applicability of the reference data, providing a freely available common dataset for targeted critical evaluation of DIR spatial accuracy performance in multiple clinical settings. Estimates of observer variance in feature localization suggest consistent spatial accuracy for all observers across both 4D CT and COPDgene patient cohorts.
Physics in Medicine and Biology, 2004
The purpose of this work was to develop and validate an automated method for intrathoracic tumour... more The purpose of this work was to develop and validate an automated method for intrathoracic tumour motion estimation from breath-hold computed tomography (BH CT) imaging using the three-dimensional optical flow method (3D OFM). A modified 3D OFM algorithm provided 3D displacement vectors for each voxel which were used to map tumour voxels on expiration BH CT onto inspiration BH CT images. A thoracic phantom and simulated expiration/inspiration BH CT pairs were used for validation. The 3D OFM was applied to the measured inspiration and expiration BH CT images from one lung cancer and one oesophageal cancer patient. The resulting displacements were plotted in histogram format and analysed to provide insight regarding the tumour motion. The phantom tumour displacement was measured as 1.20 and 2.40 cm with full-width at tenth maximum (FWTM) for the distribution of displacement estimates of 0.008 and 0.006 cm, respectively. The maximum error of any single voxel&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s motion estimate was 1.1 mm along the z-dimension or approximately one-third of the z-dimension voxel size. The simulated BH CT pairs revealed an rms error of less than 0.25 mm. The displacement of the oesophageal tumours was nonuniform and up to 1.4 cm, this was a new finding. A lung tumour maximum displacement of 2.4 cm was found in the case evaluated. In conclusion, 3D OFM provided an accurate estimation of intrathoracic tumour motion, with estimated errors less than the voxel dimension in a simulated motion phantom study. Surprisingly, oesophageal tumour motion was large and nonuniform, with greatest motion occurring at the gastro-oesophageal junction.
Medical Physics, 2014
Block matching is a well-known strategy for estimating corresponding voxel locations between a pa... more Block matching is a well-known strategy for estimating corresponding voxel locations between a pair of images according to an image similarity metric. Though robust to issues such as image noise and large magnitude voxel displacements, the estimated point matches are not guaranteed to be spatially accurate. However, the underlying optimization problem solved by the block matching procedure is similar in structure to the class of optimization problem associated with B-spline based registration methods. By exploiting this relationship, the authors derive a numerical method for computing a global minimizer to a constrained B-spline registration problem that incorporates the robustness of block matching with the global smoothness properties inherent to B-spline parameterization. Methods: The method reformulates the traditional B-spline registration problem as a basis pursuit problem describing the minimal l 1-perturbation to block match pairs required to produce a B-spline fitting error within a given tolerance. The sparsity pattern of the optimal perturbation then defines a voxel point cloud subset on which the B-spline fit is a global minimizer to a constrained variant of the B-spline registration problem. As opposed to traditional B-spline algorithms, the optimization step involving the actual image data is addressed by block matching. Results: The performance of the method is measured in terms of spatial accuracy using ten inhale/exhale thoracic CT image pairs (available for download at www.dir-lab.com) obtained from the COPDgene dataset and corresponding sets of expert-determined landmark point pairs. The results of the validation procedure demonstrate that the method can achieve a high spatial accuracy on a significantly complex image set. Conclusions: The proposed methodology is demonstrated to achieve a high spatial accuracy and is generalizable in that in can employ any displacement field parameterization described as a least squares fit to block match generated estimates. Thus, the framework allows for a wide range of image similarity block match metric and physical modeling combinations.
Medical Physics, 2012
ABSTRACT Purpose: An exciting form of ventilation imaging is being developed based on 4-dimension... more ABSTRACT Purpose: An exciting form of ventilation imaging is being developed based on 4-dimensional computed tomography (4DCT) data. Because 4DCTs are routine for thoracic radiation therapy, calculating ventilation maps from 4DCT data does not add extra dosimetric or monetary cost. Studies have discussed designing treatment plans to avoid highly-ventilated areas of the lung. However, the hypothesis that using ventilation in treatment planning can reduce thoracic toxicity remains to be tested. The purpose of our work was to determine whether incorporating ventilation-based functional information could improve prediction for clinical thoracic toxicity. Methods: The study used 96 lung cancer patients, 17 of whom developed radiation pneumonitis (CTCAE 3.0 Grade>=3). Pre-treatment 4DCT data, spatial registration, and a density-change based model were used to compute pre-treatment ventilation maps for each patient. Using dose and ventilation, we calculated dose-volume and dose-function histograms, mean lung doses (MLD), and ventilation-weighted MLD (fMLD). The ventilation-weighted dosimetric values were compared between the pneumonitis group and the non-pneumonitis group using a two-sample t-test. The ventilation-based functional data were incorporated into a predictive dose-response model and maximum likelihood was used to determine whether incorporating functional data could significantly improve the model fit to clinical toxicity data. Results: Specific patient examples illustrate that using functional dose metrics can lead to better estimates of toxicity. The fMLD was higher for patients that developed pneumonitis (20.8 Gy) than for those that did not (18.9 Gy), however, the results were not significant (p=0.251). Although fMLD improved model fit over using MLD, the difference in fits was not found to be significant (p=0.312). Conclusions: This is the first study that has attempted to link irradiating ventilated portions of the lung to clinical outcomes. Although promising data were presented, the results were not statistically significant. Future work will include more patients and further functional information with perfusion imaging.
International Journal of Radiation Oncology*Biology*Physics, 2013
Purpose-Four-dimensional computed tomography (4DCT)-based ventilation is an emerging imaging moda... more Purpose-Four-dimensional computed tomography (4DCT)-based ventilation is an emerging imaging modality that can be used in the thoracic treatment planning process. The clinical benefit of using ventilation images in radiation treatment plans remains to be tested. The purpose of the current work was to test the potential benefit of using ventilation in treatment planning by evaluating whether dose to highly ventilated regions of the lung resulted in increased incidence of clinical toxicity. Methods and Materials-Pretreatment 4DCT data were used to compute pretreatment ventilation images for 96 lung cancer patients. Ventilation images were calculated using 4DCT data, deformable image registration, and a density-change based algorithm. Dose-volume and ventilation-based dose function metrics were computed for each patient. The ability of the dosevolume and ventilation-based dose-function metrics to predict for severe (grade 3+) radiation pneumonitis was assessed using logistic regression analysis, area under the curve (AUC) metrics, and bootstrap methods. Results-A specific patient example is presented that demonstrates how incorporating ventilation-based functional information can help separate patients with and without toxicity. The logistic regression significance values were all lower for the dose-function metrics (range P=. 093-.250) than for their dose-volume equivalents (range, P=.331-.580). The AUC values were all greater for the dose-function metrics (range, 0.569-0.620) than for their dose-volume equivalents (range, 0.500-0.544). Bootstrap results revealed an improvement in model fit using
International Journal of Radiation Oncology*Biology*Physics, 2007
Purpose: To investigate the ability of four-dimensional computed tomography (4D CT)-derived venti... more Purpose: To investigate the ability of four-dimensional computed tomography (4D CT)-derived ventilation images to identify regions of highly functional lung for avoidance in intensitymodulated radiotherapy (IMRT) planning in locally advanced non-small cell lung cancer (NSCLC). Methods and Materials: The treatment planning records from 21 patients with stage III NSCLC were selected. Ventilation images were generated from the 4D CT sets, and each was imported into the treatment-planning system. Ninety percentile functional volumes (PFV90), constituting the 10% of the lung volume where the highest ventilation occurs, were generated. Baseline IMRT plans were generated using the lung volume constraint on V20 (<35%), and two additional plans were generated using constraints on the PFV90 without a volume constraint. Dose-volume (DVH) and dose-function (DFH) histograms were generated and used to evaluate the PTV coverage, lung volume, and functional parameters for comparison of the plans. Results: The mean dose to the PFV90 was reduced by 2.9 Gy, and the DFH at 5 Gy (F5) was reduced by 9.6% (SE=2.03%). The F5, F10, V5, and V10 were all significantly reduced from the baseline values. We identified a favorable subset of patients for whom there was a further significant improvement in the mean lung dose. Conclusions: 4D CT-derived ventilation regions were successfully utilized as avoidance structures to reduce the DVH and DFH at 5 Gy in all the cases. In a subset, there was also a
International Journal of Radiation Oncology*Biology*Physics, 2007
Purpose: To quantify the relationship between the local radiation dose received and the posttreat... more Purpose: To quantify the relationship between the local radiation dose received and the posttreatment positron emission tomography/computed tomography (PET/CT) [ 18 F]2-fluoro-2-deoxyglucose (FDG) uptake in the lung. Methods and Materials: The data from 36 patients treated for esophageal cancer with thoracic radiotherapy who underwent restaging PET/CT imaging between 4 and 12 weeks after radiotherapy completion were evaluated. Their treatment planning CT was registered with the restaging PET/CT. Using histogram analysis, the voxel average FDG-PET uptake vs. radiation dose was obtained for each case. Hierarchical linear regression models for each patient were applied to study the variation in the linear trends between cases. Deviation of the dose-response curve from a linear model was tested. Results: The median time between radiotherapy completion and FDG-PET imaging was 40 days (range, 26-70 days). The median of the mean standard uptake value in the lung that received 0-5 Gy was 0.63 (range, 0.36-1.27), 5-10 Gy was 0.77 (range, 0.40-1.35), 10-20 Gy was 0.80 (range, 0.40-1.72), and >20 Gy was 1.08 (range, 0.44-2.63). A hierarchical linear regression model of the radiation dose and normalized FDG uptake per case found an adequate fit with the linear model, and the addition of quadratic and logarithmic functions did not improve the fit. The 36 cases had a posterior mean of slopes range of 0.0048-0.069. Conclusion: The regional dose vs. radiation pneumonitis response was evaluated with FDG-PET/CT imaging. Statistical modeling found a linear relationship. The slope of this relationship varied over an order of magnitude, reflecting the range of the underlying biological response to radiation among the study population.
International Journal of Radiation Oncology*Biology*Physics, 2007
Purpose: To assess quantitatively the impact of incorporating functional lung imaging into intens... more Purpose: To assess quantitatively the impact of incorporating functional lung imaging into intensity-modulated radiation therapy planning for locally advanced non-small cell lung cancer (NSCLC). Methods and Materials: Sixteen patients with advanced-stage NSCLC who underwent radiotherapy were included in this study. Before radiotherapy, each patient underwent lung perfusion imaging with single-photonemission computed tomography and X-ray computed tomography (SPECT-CT). The SPECT-CT was registered with simulation CT and was used to segment the 50-and 90-percentile hyperperfusion lung (F50 lung and F90 lung). Two IMRT plans were designed and compared in each patient: an anatomic plan using simulation CT alone and a functional plan using SPECT-CT in addition to the simulation CT. Dosimetric parameters of the two types of plans were compared in terms of tumor coverage and avoidance of normal tissues. Results: In incorporating perfusion information in IMRT planning, the median reductions in the mean doses to the F50 and F90 lung in the functional plan were 2.2 and 4.2 Gy, respectively, compared with those in the anatomic plans. The median reductions in the percentage of volume irradiated with >5 Gy, >10 Gy, and >20 Gy in the functional plans were 7.1%, 6.0%, and 5.1%, respectively, for F50 lung, and 11.7%, 12.0%, and 6.8%, respectively, for F90 lung. A greater degree of sparing of the functional lung was achieved for patients with large perfusion defects compared with those with relatively uniform perfusion distribution. Conclusion: Function-guided IMRT planning appears to be effective in preserving functional lung in locally advanced-stage NSCLC patients.
International Journal of Radiation Oncology*Biology*Physics, 2008
Purpose-To compare three-dimensional (3D) and 4D computed tomography (CT)-based treatment plans f... more Purpose-To compare three-dimensional (3D) and 4D computed tomography (CT)-based treatment plans for proton therapy or intensity-modulated radiation therapy (IMRT) for esophageal cancer in terms of doses to the lung, heart, and spinal cord and variations in target coverage and normal tissue sparing. Materials and Methods-IMRT and proton plans for 15 patients with distal esophageal cancer were designed from the 3D average CT scans and then recalculated on 10 4D CT data sets. Dosimetric data were compared for tumor coverage and normal tissue sparing. Results-Compared with IMRT, median lung volumes exposed to 5,10, and 20 Gy and mean lung dose were reduced by 35.6%, 20.5%,5.8%, and 5.1 Gy for a two-beam proton plan and by 17.4%, 8.4%,5%, and 2.9 Gy for a three-beam proton plan. The greater lung sparing in the two-beam proton plan was achieved at the expense of less conformity to the target (conformity index CI=1.99) and greater irradiation of the heart (heart-V40=41.8%) compared with the IMRT plan(CI=1.55, heart-V40=35.7%) or the three-beam proton plan (CI=1.46, heart-V40=27.7%). Target coverage differed by more than 2% between the 3D and 4D plans for patients with substantial diaphragm motion in the three-beam proton and IMRT plans. The difference in spinal cord maximum dose between 3D and 4D plans could exceed 5 Gy for the proton plans partly owing to variations in stomach gas-filling. Conclusions-Proton therapy provided significantly better sparing of lung than did IMRT. Diaphragm motion and stomach gas-filling must be considered in evaluating target coverage and cord doses.
International Journal of Radiation Oncology*Biology*Physics, 2007
Purpose: To demonstrate that high-resolution computed tomography (CT) can be used to quantify los... more Purpose: To demonstrate that high-resolution computed tomography (CT) can be used to quantify loss of pulmonary compliance in irradiated mice. Methods and Materials: Computed tomography images of three nonirradiated (controls) and three irradiated mice were obtained 200 days after a single dose of 16-Gy Co (60) thoracic irradiation. While intubated, each animal was imaged at static breath-hold pressures of 2, 10, and 18 cm H 2 O. A deformable image registration algorithm was used to calculate changes in air volume between adjacent-pressure CT image pairs (e.g., 2 and 10 cm H 2 O), and functional images of pulmonary compliance were generated. The mass-specific compliance was calculated as the change in volume divided by the pressure difference between the 2 image sets and the mass of lung tissue. Results: For the irradiated mice, the lung parenchyma mean CT values ranged from ؊314 (؎ 11) Hounsfield units (HU) to ؊378 (؎ 11) HU. For the control mice, the mean CT values ranged from ؊549 (؎ 11) HU to ؊633 (؎ 11) HU. Irradiated mice had a 60% (45, 74%; 95% confidence interval) lower mass-specific compliance than did the controls (0.039 [؎ 0.0038] vs. 0.106 [؎ 0.0038] mL air per cm H 2 O per g lung) from the 2-cm to 10-cm H 2 O CT image pair. The difference in compliance between groups was less pronounced at the higher distending pressures. Conclusion: High-resolution CT was used to quantify a reduction in mass-specific compliance following whole lung irradiation in mice. This small animal radiation injury model and assay may be useful in the study of lung injury.
International Journal of Radiation Oncology*Biology*Physics, 2003
respiratory motion, was determined such that the dose reduction in the CTV due to respiratory mot... more respiratory motion, was determined such that the dose reduction in the CTV due to respiratory motion was Յ 0.1% of the prescription dose. The influence of the planning dose distribution on the target margin was examined, and incorporated in the margin minimization. To achieve mean target position during the pre-planning imaging, the active breathing control (ABC) device is currently used during the CT scanning. However, CT images acquired using respiratory gating or respiratory correlated CT imaging, which have been developed for radiotherapy, can also be applied to extrapolate the treatment target at the mean position. S234