Dose tracking assessment for image-guided radiotherapy of the prostate bed and the impact on clinical workflow (original) (raw)
Related papers
Radiotherapy and Oncology, 2011
Purpose: To assess the accuracy of the initial CT plan dose-volume histograms (DVH's) for prostate, rectum and bladder by comparison to delivered doses determined from cone beam CT (CBCT) scans acquired during image-guided treatment. Materials and methods: Twelve prostate patients were treated using daily implanted fiducial guidance and following local protocol for bladder and rectal preparation. CBCT scans were acquired twice weekly and contoured for prostate, rectum and bladder. The planned beams were applied to all CBCT scans to determine the delivered doses. Prostate dose coverage was assessed by the proportion of the CTV fully encompassed by the 95% and 98% isodose lines. Rectal and bladder volumes receiving 40 Gy, 60 Gy and 70 Gy at treatment were compared to the initial plan, with significance determined using the onesample t-test. Results: Four patients showed marginally compromised CTV coverage by the 95% isodose at all CBCT plans. For nine patients the initial plan rectal DVH was significantly outside the range of the treatment DVH's. Conclusions: Dose coverage of the prostate was not achieved for all patients. Observed rectal and bladder doses were higher than predicted. The initial treatment plan cannot be assumed to represent accurate normal tissue doses. Crown
2017
Purpose: The purpose of this study was to identify the best performing algorithm option for deformable registrations between planning computed tomography (pCT and conebeam CT (CBCT) in Velocity using image sets from prostate cancer patients receiving radiation therapy after prostatectomy. Different parameters were studied in an attempt to find parameters related to the success of a deformable registration. Differences between planned dose distributions and new estimations of delivered dose distributions based on weekly CBCTs were investigated. Method: The pCT was registered and deformed into the CBCT geometry, and a calculation of the absorbed dose was performed for each treatment occasion using Velocity Advanced Imaging (AI) which is a deformable image registration (DIR) software. Velocity AI offers several different options for the deformable registration e.g. grid size. 28 patients were included in the study and had weekly CBCTs taken. Deformable registrations were made between t...
Journal of Medical Radiation Sciences, 2020
An automated dose accumulation and contour propagation workflow using daily cone beam computed tomography (CBCTs) images for prostate cases that require pelvic lymph nodes irradiation (PLNs) was developed. This workflow was constructed using MIM® software with the intention to provide accurate dose transformations for plans with two different isocentres, whereby two sequential treatment phases were prescribed. The pre‐processing steps for data extractions from treatment plans, CBCTs, determination of couch shift information and management of missing CBCTs are described. To ensure that the imported translational couch shifts were in the correct orientation and readable in MIM, phantom commissioning was performed. For dose transformation, rigid registration with corrected setup shifts and scaled fractional dose was performed for pCT to daily CBCTs, which were then deformed onto CBCT1. Fractional dose summation resulted in the final accumulated dose for the patient allowing differences...
Rectal dose variation during the course of image-guided radiation therapy of prostate cancer
Radiotherapy and Oncology, 2010
Background and purpose: To investigate the change in rectal dose during the treatment course for intensity-modulated radiotherapy (IMRT) of prostate cancer with image-guidance. Materials and methods: Twenty prostate cancer patients were recruited for this retrospective study. All patients have been treated with IMRT. For each patient, MR and CT images were fused for target and critical structure delineation. IMRT treatment planning was performed on the simulation CT images. Interfractional motion during the course of treatment was corrected using a CT-on-rails system. The rectum was outlined on both the original treatment plan and the subsequent daily CT images from the CT-onrails by the same investigator. Dose distributions on these daily CT images were recalculated with the isocenter shifts relative to the simulation CT images using the leaf sequences/MUs based on the original treatment plan. The rectal doses from the subsequent daily CTs were compared with the original doses planned on the simulation CT using our clinical acceptance criteria. Results: Based on 20 patients with 139 daily CT sets, 28% of the subsequent treatment dose distributions did not meet our criterion of V 40 < 35%, and 27% did not meet our criterion of V 65 < 17%. The inter-fractional rectal volume variation is significant for some patients. Conclusions: Due to the large inter-fractional variation of the rectal volume, it is more favorable to plan prostate IMRT based on an empty rectum and deliver treatment to patients with an empty rectum. Over 70% of actual treatments showed better rectal doses than our clinical acceptance criteria. A significant fraction (27%) of the actual treatments would benefit from adaptive image-guided radiotherapy based on daily CT images.
Radiology and Oncology, 2009
We compare the dosimetry of daily patient positioning based on prostate matching versus bone matching for patients treated with helical tomotherapy. Methods. Ninety-nine pre-treatment 3D megavoltage (MV) CT images of four high risk prostate patients were registered to their respective planning images using two automatic registration algorithms, one achieving bone matching and the other prostate matching. Dose distributions that would have been delivered had patient positioning been based on each matching method were evaluated. Contours were delineated on each MVCT image and prostate, bladder, and rectum dose volume histograms were compared for each image guidance strategy using endpoints adapted from inverse planning constraints. Results. The standard deviation of per fraction prostate ΔD95 values, defined as prostate matching D95 minus bone matching D95, was 0.01 Gy (Range: -0.02 to 0.02 Gy). Defined analogously, bladder ΔD45 and rectum ΔD30 values were 0.12 Gy (Range: -0.22 to 0.52 Gy) and 0.14 Gy (Range: -0.40 to 0.34 Gy), respectively. Conclusions. Bladder ΔD45 and rectum ΔD30 standard deviation values corresponding to 6.1% and 7.5% of their respective planning constraints suggesting critical structure doses are dependent on positioning method. A relationship between critical structure dosimetry and the direction of daily prostate motion was also observed.
2006
Purpose: The aim of this work was to study the variations in delivered doses to the prostate, rectum, and bladder during a full course of image-guided external beam radiotherapy. Methods and Materials: Ten patients with localized prostate cancer were treated with helical tomotherapy to 78 Gy at 2 Gy per fraction in 39 fractions. Daily target localization was performed using intraprostatic fiducials and daily megavoltage pelvic computed tomography (CT) scans, resulting in a total of 390 CT scans. The prostate, rectum, and bladder were manually contoured on each CT by a single physician. Daily dosimetric analysis was performed with dose recalculation. The study endpoints were D95 (dose to 95% of the prostate), rV2 (absolute rectal volume receiving 2 Gy), and bV2 (absolute bladder volume receiving 2 Gy). Results: For the entire cohort, the average D95 (؎SD) was 2.02 ؎ 0.04 Gy (range, 1.79 -2.20 Gy). The average rV2 (؎SD) was 7.0 ؎ . The average bV2 (؎SD) was 8.7 ؎ 6.8 cc (range, 0.3-36.8 cc). Unlike doses for the prostate, there was significant daily variation in rectal and bladder doses, mostly because of variations in volume and shape of these organs. Conclusion: Large variations in delivered doses to the rectum and bladder can be documented with daily megavoltage CT scans. Image guidance for the targeting of the prostate, even with intraprostatic fiducials, does not take into account the variation in actual rectal and bladder doses. The clinical impact of techniques that take into account such dosimetric parameters in daily patient set-ups should be investigated.
The British journal of radiology, 2014
To investigate whether planning target volume (PTV) margins may be safely reduced in radiotherapy of localized prostate cancer incorporating daily online tube potential-cone beam CT (CBCT) image guidance and the anticipated benefit in predicted rectal toxicity. The prostate-only clinical target volume (CTV2) and rectum were delineated on 1 pre-treatment CBCT each week in 18 randomly selected patients. By transposing these contours onto the original plan, dose-volume histograms (DVHs) for CTV2 and the rectum were each calculated and combined, for each patient, to produce a single mean DVH representative of the dose delivered over the treatment course. Plans were reoptimized using reduced CTV2 to PTV2 margins and the consequent radiobiological impact modelled by the tumour control probability (TCP) and normal tissue complication probability (NTCP) of the rectum. All CBCT images were deemed of sufficient quality to identify the CTV and rectum. No loss of TCP was observed when plans usi...
Journal of Applied Clinical Medical Physics, 2006
Using internal fiducial markers and electronic portal imaging (EPI) to realign patients has been shown to significantly reduce positioning uncertainties in prostate radiation treatment. This creates the possibility of decreasing the planning target volume (PTV) margin added on the clinical target volume (CTV), which in turn may allow for dose escalation. We compared the outcome of two plans: 70 Gy/35 fx, 10-mm PTV margin without patient realignment (Reference Plan) and 78 Gy/ 39 fx, 5-mm PTV margin with patient realignment (Escalated Plan). Four-fieldoblique (gantry angles 35°, 90°, 270°, 325°) beam arrangement was used. Monte Carlo code was used to simulate the daily organ motion. Dose to each organ was calculated. Tumor control probability (TCP) and the effective dose to critical organs (D eff ) were calculated using the biologically normalized dose-volume histograms. By comparing the biological factors, we found that the prescription dose can be escalated to 78 Gy/39 fx with a 5-mm PTV margin when using internal fiducial markers and EPI. Based on the available dose-response data for intermediate risk prostate patients, this will result in a 20% increase of local control and significantly reduced rectal complications provided that less serial dose-volume behavior of rectum is proven.