Image guided radiotherapy Research Papers (original) (raw)

This study investigates the dose from the 1 mm collimator width megavoltage fan-beam CT (fine, normal and coarse pitch) available on tomotherapy as well as for whole-breast tomotherapy treatments. The BEIR VII lifetime attributable risk... more

- by
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- Cancer, Risk, Risk assessment, Image guided radiotherapy

Radiation therapy (RT) is a crucial component of cancer care, used in the treatment of over 50% of cancer patients. Patients undergoing image guided RT or brachytherapy routinely have inert RT biomaterials implanted into their tumors. The single function of these RT biomaterials is to ensure geometric accuracy during treatment. Recent studies have proposed that the inert biomaterials could be upgraded to "smart" RT biomaterials, designed to do more than 1 function. Such smart biomaterials include next-generation fiducial markers, brachytherapy spacers, and balloon applicators, designed to respond to stimuli and perform additional desirable functions like controlled delivery of therapy-enhancing payloads directly into the tumor subvolume while minimizing normal tissue toxicities. More broadly, smart RT biomaterials may include functionalized nanoparticles that can be activated to boost RT efficacy. This work reviews the rationale for smart RT biomaterials, the state of the ...

- by Twalib Ngoma
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- Artificial Intelligence, Brachytherapy, Nanoparticles, Image guided radiotherapy

Radiotherapy has become an essential part of breast cancer treatment as it reduces the chances of recurrence of the cancer. But long-term follow-up of the patients receiving breast irradiation showed an increase in mortality rate due to cardiovascular issues. Many new dose delivery techniques have been developed for of better localization of the target and maximum sparing of normal tissues. Three of such techniques are reviewed in this paper. An article studying the advantage of moderate deep inspiration breath hold (a technique used to immobilize the target) showed a reduction from 2.3 mL to 0.79 mL in the irradiated heart volume and from 4.2 Gy to 2.5 Gy in the mean dose to the heart. Another article reviewed in this paper is the about prone positioning of patient during irradiation that showed a mean reduction of 7.5 cm3 in irradiated heart volume with prone position for 85% of the patients. Last technique reviewed in this article is intensity modulated radiotherapy. The article reviewed for post-lumpectomy radiotherapy showed a reduction of 10.7% in mean dose to left ventricle and from 45 cm3 to 5.84 cm3 in the heart volume receiving dose greater than 30 Gy. The article reviewed for post-mastectomy radiotherapy showed 46% reduction in heart volume receiving dose higher than 35 Gy and a mean dose reduction of 20%.

Purpose: Flattening filter free (FFF) beams generated by medical linear accelerators have recently started to be used in radiotherapy clinical practice. Such beams present fundamental differences with respect to the standard filter flattened (FF) beams, making the generally used dosimetric parameters and definitions not always viable. The present study will propose possible definitions and suggestions for some dosimetric parameters for use in quality assurance of FFF beams generated by medical linacs in radiotherapy.

- by Tommy Knöös
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- Biomedical Engineering, Radiosurgery, Medical Physics, Radiotherapy

The purpose of this study was to evaluate helical tomotherapy dosimetry in postmastectomy patients
undergoing treatment for chest wall and positive nodal regions with simultaneous integrated boost (SIB) in
the scar region using strip bolus. Six postmastectomy patients were scanned with a 5-mm-thick strip bolus
covering the scar planning target volume (PTV) plus 2-cm margin. For all 6 cases, the chest wall received a
total cumulative dose of 49.3–50.4 Gy with daily fraction size of 1.7–2.0 Gy. Total dose to the scar PTV was
prescribed to 58.0–60.2 Gy at 2.0–2.5 Gy per fraction. The supraclavicular PTV and mammary nodal PTV
received 1.7–1.9 dose per fraction. Two plans (with and without bolus) were generated for all 6 cases. To
generate no-bolus plans, strip bolus was contoured and overrode to air density before planning. The setup
reproducibility and delivered dose accuracy were evaluated for all 6 cases. Dose-volume histograms were
used to evaluate dose-volume coverage of targets and critical structures. We observed reduced air
cavities with the strip bolus setup compared with what we normally see with the full bolus. The
thermoluminescence dosimeters (TLD) in vivo dosimetry confirmed accurate dose delivery beneath the
bolus. The verification plans performed on the first day megavoltage computed tomography (MVCT)
image verified that the daily setup and overall dose delivery was within 2% accuracy compared with
the planned dose. The hotspot of the scar PTV in no-bolus plans was 111.4% of the prescribed dose
averaged over 6 cases compared with 106.6% with strip bolus. With a strip bolus only covering the
postmastectomy scar region, we observed increased dose uniformity to the scar PTV, higher setup
reproducibility, and accurate dose delivered beneath the bolus. This study demonstrates the feasibility of using
a strip bolus over the scar using tomotherapy for SIB dosimetry in postmastectomy treatments.

- by Yi Rong and +1
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- Breast Cancer, TomoTherapy, Radiotherapy, Image guided radiotherapy

Purpose: To compare imaging doses from MV images, kV radiographs, and kV-CBCT and describe methods to reduce the dose to patient's organs using existing on-board imaging devices. Method and materials: Monte Carlo techniques were used to simulate kV X-ray sources. The kV image doses to a variety of patient anatomies were calculated by using the simulated realistic sources to deposit dose in patient CT images. For MV imaging, the doses for the same patients were calculated using a commercial treatment planning system. Results: Portal imaging results in the largest dose to anatomic structures, followed by Varian OBI CBCT, Varian TrueBeam CBCT and then kV radiographs. The imaging doses for the 50% volume from the DVHs, D50, to the eyes for representative head images are 4.3-4.8 cGy; 0.05-0.06 cGy; 0.04-0.05 cGy; and, 0.12 cGy; D50 to the bladder for representative pelvis images are 3.3 cGy; 1.6 cGy; 1.0 cGy; and, 0.07 cGy; while D50 to the heart for representative thorax images are 3.5 cGy; 0.42 cGy; 0.2 cGy; and, 0.07 cGy; when using portal imaging, OBI kV-CBCT scans, TrueBeam kV-CBCT scans and kV radiographs, respectively. The orientation of the kV beam can affect organ dose. For example, D50 to the eyes can be reduced from 0.12 cGy using AP and right lateral radiographs to 0.008-0.017 cGy when using PA and right lateral radiographs. In addition, organ exposures can be further reduced to 15-70% of their original values with the use of a full-fan, bow-tie filter for kV radiographs. In contrast, organ doses increase by a factor of $2-4 if bow-tie filters are not used during kV-CBCT acquisitions. Conclusion: Current on-board kV imaging devices result in much lower imaging doses compared to MV imagers even taking into account of higher bone dose from kV X-rays. And a variety of approaches are available to significantly reduce the image doses.

- by Peter Munro
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- Image guided radiotherapy, Thorax, Pelvis, Monte Carlo Method
- by William Yuh
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- Radiation Oncology, Forecasting, Quality Improvement, Image guided radiotherapy

We prospectively utilized the Dose Verification System with radiopaque MOSFET dosimeters in twenty patients undergoing IMRT with daily image guidance. Dose measurements consistently higher than 6% above predicted values were observed for 3 of 20 patients and while review of daily IGRT revealed acceptable alignment of the prostate target volumes and implanted dosimeters, significant anatomic changes within the treated region were detected. Repeat CT simulation and radiation planning resulted in resolution of the discrepancy.

- by Timothy Showalter and +2
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- Prostate Cancer, Movement, Image guided radiotherapy, IGRT

Purpose: To have an initial assessment of the Vero Dynamic Tracking workflow in clinical circumstances and quantify the performance of the tracking system, a simulation study was set up on 5 lung and liver patients. Methods and materials: The preparatory steps of a tumor tracking treatment, based on fiducial markers implanted in the tumor, were executed allowing pursuit of the tumor with the gimbaled linac and monitoring X-rays acquisition, however, without activating the 6 MV beam. Data were acquired on workflow time-efficiency, tracking accuracy and imaging exposure. Results: The average time between the patient entering the treatment room and the first treatment field was about 9 min. The time for building the correlation model was 3.2 min. Tracking errors of 0.55 and 0.95 mm (1r) were observed in PAN/TILT direction and a 2D range of 3.08 mm. A skin dose was determined of 0.08 mGy/image, with a source-to-skin distance of 900 mm and kV exposure of 1 mAs. On average 1.8 mGy/min kV skin dose was observed for 1 Hz monitoring. Conclusion: The Vero tracking solution proved to be fully functional and showed performance comparable with other real-time tracking systems.

- by Dirk Verellen and +3
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- Movement, Image guided radiotherapy, Neoplasms, Patient Simulation

The purpose of this study was to investigate the feasibility of using a single QA device for comprehensive, efficient daily QA of a linear accelerator (Linac) and three image-guided stereotactic positioning systems (IGSPSs). The Sun Nuclear Daily QA 3 (DQA3) device was used to perform daily dosimetry and mechanical accuracy tests for an Elekta Linac, as well as daily image geometric and isocenter coincidence accuracy tests for three IGSPSs: the AlignRT surface imaging system; the frameless SonArray optical tracking System (FSA) and the Elekta kV CBCT. The DQA3 can also be used for couch positioning, repositioning, and rotational tests during the monthly QA. Based on phantom imaging, the Linac coordinate system determined using AlignRT was within 0.7 mm/0.6° of that of the CBCT system. The difference is attributable to the different calibration methods that are utilized for these two systems. The laser alignment was within 0.5 mm of the isocenter location determined with the three IG...

- by Jean Peng
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- Algorithms, Image guided radiotherapy, Feasibility Studies, Time Factors

Purpose: To investigate the effects of using volumetric modulated arc therapy (VMAT) and/or voluntary moderate deep inspiration breath-hold (vmDIBH) in the radiation therapy (RT) of left-sided breast cancer including the regional lymph nodes. Materials and methods: For 13 patients, four treatment combinations were compared; 3D-conformal RT (i.e., forward IMRT) in free-breathing 3D-CRT(FB), 3D-CRT(vmDIBH), 2 partial arcs VMAT(FB), and VMAT(vmDIBH). Prescribed dose was 42.56 Gy in 16 fractions. For 10 additional patients, 3D-CRT and VMAT in vmDIBH only were also compared. Results: Dose conformity, PTV coverage, ipsilateral and total lung doses were significantly better for VMAT plans compared to 3D-CRT. Mean heart dose (D mean,heart ) reduction in 3D-CRT(vmDIBH) was between 0.9 and 8.6 Gy, depending on initial D mean,heart (in 3D-CRT(FB) plans). VMAT(vmDIBH) reduced the D mean,heart further when D mean,heart was still >3.2 Gy in 3D-CRT(vmDIBH). Mean contralateral breast dose was higher for VMAT plans (2.7 Gy) compared to 3DCRT plans (0.7 Gy). Conclusions: VMAT and 3D-CRT(vmDIBH) significantly reduced heart dose for patients treated with locoregional RT of left-sided breast cancer. When D mean,heart exceeded 3.2 Gy in 3D-CRT(vmDIBH) plans, VMAT(vmDIBH) resulted in a cumulative heart dose reduction. VMAT also provided better target coverage and reduced ipsilateral lung dose, at the expense of a small increase in the dose to the contralateral breast. (M. Essers).

- by Sarah Osman and +1
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- Treatment Outcome, Image guided radiotherapy, Lung Diseases, Radiometry

Imaging techniques are increasingly integrated into modern radiotherapy (RT). Multimodal imaging is used to define the target for RT planning and imaging technology is also being integrated into linear accelerators, with the purpose to ensure delivery of radiation with high geometric accuracy. The integration of imaging in RT calls for a stronger collaboration between diagnostic radiologists and the professions involved in RT.

Radiotherapy for rectal cancer is becoming more conformal. Both the rectum and the mesorectum are mobile structures and the use of image-guided radiotherapy techniques may improve treatment delivery. Studies up to 2008 have previously been reviewed; rectal motion was mostly studied in bladder and prostate cancer cases. Large variations were seen in both the rectal volume and rectal wall displacement during the treatment course. We reviewed the literature on primary rectal cancer. A systematic review was conducted using Medline and Embase databases using the keywords 'rectal, radiotherapy, IGRT, image guided, organ motion, internal margin, target shape/volume'. Nine studies looked at both inter-and intrafractional motion of the gross tumour volume, rectum, mesorectum and the clinical target volume using a variety of imaging modalities. There was significant movement in the upper mesorectum. There was a strong relationship between rectal filling and mesorectal motion. Differences according to gender and body mass index have been reported. One study showed adequate dose to the rectum despite rectal motion and deformation. Current margin recipes may not apply to deformable structures. Suggested margins for the clinical target volume to planning target volume expansion are between 1 and 3.5 cm. There may be a role for re-imaging and re-planning during a treatment course. From the available data, electronic portal imaging devices should continue to be used to match for bony anatomy. Additional information on internal motion can be obtained by cone beam computer tomography or tomotherapy and if available its use should be considered. Individualised anisotropic margins may be required. Further work is required to assess the optimal imaging modality, whether to match to bone or soft tissue, and to assess if internal motion affects treatment outcome.

- by Bernadette Coles
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- Treatment Outcome, Prostate Cancer, Image guided radiotherapy, Clinical oncology

Brachytherapy has consistently provided a very conformal radiation therapy modality. Over the last two decades this has been associated with significant improvements in imaging for brachytherapy applications (prostate, gynecology), resulting in many positive advances in treatment planning, application techniques and clinical outcome. This is emphasized by the increased use of brachytherapy in Europe with gynecology as continuous basis and prostate and breast as more recently growing fields. Image guidance enables exact knowledge of the applicator together with improved visualization of tumor and target volumes as well as of organs at risk providing the basis for very individualized 3D and 4D treatment planning. In this commentary the most important recent developments in prostate, gynecological and breast brachytherapy are reviewed, with a focus on European recent and current research aiming at the definition of areas for important future research. Moreover the positive impact of GE...

- by Frank-André Siebert
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- Brachytherapy, Radiation Therapy, Translational Research, Clinical research

Conventional treatment options for clinically localized, low-risk prostate cancer include radical prostatectomy, external-beam radiotherapy (EBRT) and low-dose-rate brachytherapy. Advances in image-guided radiotherapy (IGRT) since the 1980s, the development of intensity-modulated radiotherapy (IMRT) during the 1990s and evidence from radiobiological models-which support the use of high doses per fraction-have developed alongside novel advanced radiotherapy modalities that include high-dose-rate brachytherapy (HDR-BT), stereotactic body radiotherapy (SBRT) and proton beam therapy. The relationship between the outcomes of and toxicities experienced by patients with prostate cancer treated with HDR-BT, SBRT and particle-beam therapy should provide urologists and oncologists an understanding of the continually evolving technology in prostate radiotherapy. On the basis of published evidence, conventionally fractionated EBRT with IMRT is considered the standard of care over conventional 3...

- by Timothy Showalter and +2
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- Radiosurgery, Image guided radiotherapy, Clinical Sciences

Introduction: Current treatment options for prostate cancer, other than active surveillance, are limited to entire prostate gland destruction through removal (radical prostatectomy), radiation (external beam, brachytherapy, or a combination of both), or thermal ablation (cryoablation, high-intensity focused ultrasound, or radiofrequency). There has been a demand to develop ablative therapies that attempt to reduce treatment burden while retaining cancer control and avoiding the psychological morbidity associated with surveillance.

Purpose: To evaluate use of breath-hold CTs and implanted fiducials for definition of the internal target volume (ITV) margin for upper abdominal stereotactic body radiation therapy (SBRT). To study the statistics of inter-and intra-fractional motion information. Methods and materials: 11 patients treated with SBRT for locally advanced pancreatic cancer (LAPC) or liver cancer were included in the study. Patients underwent fiducial implantation, free-breathing CT and breath-hold CTs at end inhalation/exhalation. All patients were planned and treated with SBRT using volumetric modulated arc therapy (VMAT). Two margin strategies were studied: Strategy I uses PTV = ITV + 3 mm; Strategy II uses PTV = GTV + 1.5 cm. Both CBCT and kV orthogonal images were taken and analyzed for setup before patient treatments. Tumor motion statistics based on skeletal registration and on fiducial registration were analyzed by fitting to Gaussian functions.

- by Nicholas Nissen and +1
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- Radiation Oncology, Radiosurgery, Image guided radiotherapy, Motion

Background and purpose: To investigate critical structure movement and subsequent dose received during conformal MR-guided cervix brachytherapy. Materials and methods: 21 patients (36 HDR fractions) undergoing brachytherapy for cervical cancer underwent a second MR immediately prior to treatment (pre-treatment MR). Bowel (including sigmoid), bladder and rectum were outlined on both planning and pre-treatment MR scans and dosimetry compared. Results: No statistically significant differences were found between the volumes of the OAR doses across the two scans but there were large variations between patients with differences of up to 3.3 Gy observed. The percentage of fractions for which D 2cc was within 10% of that planned was 61.1%, 41.7% and 47.2% for bladder, rectum and bowel, respectively. The average time between MR scans was found to be 4.75 h (SD ± 1.2; range 3.2-9.9 h), with no correlation found with critical structure movement within this range. Conclusions: OAR movement is difficult to predict though significant changes occur in individual patients. In 61% of cases in our sample the D 2cc dose changed by at least 10% for at least one OAR from that planned. Pre-treatment imaging with subsequent adjustment of dosimetry will minimise the impact of organ movement on delivered dose.

- by Linda Bryant
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- Brachytherapy, MRI, Movement, Image guided radiotherapy

optimization of scanned ion beam tracking therapy for moving tumors. Phys. Med. Biol. 59 3431-52.

- by Christoph Bert
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- Biomedical Engineering, Water, Movement, Image guided radiotherapy

A commercially-available device for magnetic resonance image guided radiation therapy (MR-IGRT) using Cobalt-60 (Co-60) sources can create highly-conformal IMRT treatment plans. Pair-wise Comparisons between Co-60 and linac plans show similar target coverage and heterogeneity and comparable organ-at-risk (OAR) sparing for organs with mean doses > 20 Gy. We expect that the benefits of soft-tissue localization, real-time MR image guidance, and advanced motion management techniques will outweigh increases in mean dose to OARs.

Background and purpose: To develop a class solution for prostate Stereotactic Ablative Radiotherapy (SABR) using Volumetric Modulated Arc Therapy (VMAT). Materials and methods: Seven datasets were used to compare plans using one 360°arc (1FA), one 210°arc (1PA), two full arcs and two partial arcs. Subsequently using 1PA, fifteen datasets were compared using (i) 6 mm CTV-PTV margins, (ii) 8 mm CTV-PTV margins and (iii) including the proximal SV within the CTV. Monaco™ 3.2 (Elekta™) was used for planning with the Agility™ MLC system (Elekta™). Results: Highly conformal plans were produced using all four arc arrangements. Compared to 1FA, 1PA resulted in significantly reduced rectal doses, and monitor units and estimated delivery times were reduced in six of seven cases. Using 6 mm CTV-PTV margins, planning constraints were met for all fifteen datasets. Using 8 mm margins required relaxation of the uppermost bladder constraint in three cases to achieve adequate coverage, and, compared to 6 mm margins, rectal and bladder doses significantly increased. Including the proximal SV required relaxation of the uppermost bladder and rectal constraints in two cases, and rectal and bladder doses significantly increased. Conclusions: Prostate SABR VMAT is optimal using 1PA. 6 mm CTV-PTV margins, compatible with daily fiducial-based IGRT, are consistently feasible in terms of target objectives and OAR constraints.

- by Jonathan M Sykes
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- Radiosurgery, Image guided radiotherapy

Purpose-Toxicity concerns have limited pelvic nodal prescriptions to doses that may be suboptimal for controlling microscopic disease. In a prospective trial, we tested whether imageguided IMRT can safely deliver escalated nodal doses... more

Traditional oncology distinguishes between two separate and incommensurable states in the evolution of solid malignancies: the localized disease, which is curable; and the disseminated status, which is per se palliative. Recently, a huge body of evidence suggests a fundamental change in the understanding of cancer, indicating an intermediate state in the trajectory of solid malignancies: the oligometastatic state. The following review will critically analyse existing hypotheses and facts from the basic sciences and try to contextualize it in regard to the clinical evidence available to date. Consecutively, it will try to draw possible clinical consequences for application of radiotherapy in this specific clinical scenario.

- by Dr. Harun Badakhshi
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- Cancer Biology, Radiotherapy, Image guided radiotherapy, Brain Metastases

Even in the current era of dose-escalated radiotherapy for prostate cancer, biochemical recurrence is not uncommon. Furthermore, biochemical failure is not specific to the site of recurrence. One of the major challenges in the management of prostate cancer patients with biochemical failure after radiotherapy is the early discrimination between those with locoregional recurrence only and those with metastatic disease. While the latter are generally considered incurable, patients with locoregional disease may benefit from emerging treatment options. Ultimately, the objective of salvage therapy is to control disease while ensuring minimal collateral damage, thereby optimizing both cancer and toxicity outcomes. Advances in functional imaging, including multiparametric prostate MRI, abdominopelvic lymphangio-MRI, sentinel node SPECT-CT and/or whole-body PET/CT have paved the way for salvage radiotherapy in patients with local recurrence, microscopic nodal disease limited to the pelvis or...

- by Etienne Martin
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- Palliative Care, Radiosurgery, Brachytherapy, Quality Control

It was our purpose to analyze long-term clinical outcome and to identify prognostic factors after Linac-based fractionated stereotactic radiotherapy (Linac-based FSRT) and stereotactic radiosurgery (SRS) in patients with intracranial... more

- by Dr. Harun Badakhshi
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- Brain Imaging, Neurooncology, Image guided radiotherapy, Primary brain tumors

Small bowel (SB) is an organ at risk (OAR) that may potentially develop toxicity after radiotherapy for cervix cancer. However, its dose from brachytherapy (BT) is not systematically reported as in other OARs, even with image-guided brachytherapy (IGBT). This study aims to introduce consideration of quantified objectives for SB in BT plan optimization and to evaluate the feasibility of sparing SB while maintaining adequate target coverage. In all, 13 patients were included in this retrospective study. All patients were treated with external beam radiotherapy (EBRT) 45 Gy in 25 fractions followed by high dose rate (HDR)-BT boost of 28 Gy in 4 fractions using tandem/ring applicator. Magnetic resonance imaging (MRI) and computed tomographic (CT) images were obtained to define the gross tumor volume (GTV), high-risk clinical target volume (HR-CTV) and OARs (rectum, bladder, sigmoid colon, and SB). Treatment plans were generated for each patient using GEC-ESTRO recommendations based on the first CT/MRI. Treatment plans were revised to reduce SB dose when the D 2 cm 3 dose to SB was 4 5 Gy, while maintaining other OAR constraints. For the 7 patients with 2 sets of CT and MRI studies, the interfraction variation of the most exposed SB was analyzed. Plan revisions were done in 6 of 13 cases owing to high D 2 cm 3 of SB. An average reduction of 19% in D 2 cm 3 was achieved. Meeting SB and other OAR constraints resulted in less than optimal target coverage in 2 patients (D 90 of HR-CTV o 77 Gy αβ10 ). The highest interfraction variation was observed for SB at 16 Ϯ 59%, as opposed to 28 Ϯ 27% for rectum and 21 Ϯ 16% for bladder. Prospective reporting of SB dose could provide data required to establish a potential correlation with radiation-induced late complication for SB. Medical Dosimetry ] (2015) ]]]-]]]

- by Julius Turian
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- Brachytherapy, Image guided radiotherapy, Clinical Sciences

and sharing with colleagues.

- by G. Hanna and +1
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- Image guided radiotherapy, Clinical oncology

Introduction. Incidence of meningioma increases with age. Surgery has been the mainstay treatment. Elderly patients, however,
are at risk of severe morbidity. Therefore, we conducted this study to analyze long-term outcomes of linac-based fractionated
stereotactic radiotherapy (FSRT) for older adults (aged ≥65 years) with meningioma and determine prognostic factors. Materials
and Methods. Between October 1998 and March 2009, 100 patients (≥65, median age, 71 years) were treated with FSRT for
meningioma. Two patients were lost to follow-up. Eight patients each had grade I and grade II meningiomas, and five patients
had grade III meningiomas.The histology was unknown in 77 cases (grade 0). Results.The median follow-up was 37 months, and
3-year, 5-year, and 10-year progression-free survival (PFS) rates were 93.7%, 91.1%, and 82%. Patients with grade 0/I meningioma
showed 3- and 5-year PFS rates of 98.4% and 95.6%. Patients with grade II or III meningiomas showed 3-year PFS rates of 36%.
93.8% of patients showed local tumor control.Multivariate analysis did not indicate any significant prognostic factors. Conclusion.
FSRT may play an important role as a noninvasive and safemethod in the clinical management of older patients withmeningioma.

- by Dr. Harun Badakhshi
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- Oncology, Radiation Oncology, Brain Tumor, Brain

Tumor positional uncertainty has been identified as a major issue that deteriorates the efficacy of radiation therapy. Tumor rotational movement, which is not well understood, can result in significant geometric and dosimetric inaccuracies. The objective of this study was to measure 6 degrees-of-freedom (6 DoF) prostate and lung tumor motion, focusing on the more novel rotation, using kilovoltage intrafraction monitoring (KIM). Continuous kilovoltage (kV) projections of tumors with gold fiducial markers were acquired during radiation therapy for 267 fractions from 10 prostate cancer patients and immediately before or after radiation therapy for 50 fractions from 3 lung cancer patients. The 6 DoF motion measurements were determined from the individual 3-dimensional (3D) marker positions, after using methods to reject spurious and smooth noisy data, using an iterative closest point algorithm. There were large variations in the magnitude of the tumor rotation among different fractions ...

- by Jeremy Booth and +1
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- Algorithms, Movement, Image guided radiotherapy, Three Dimensional Imaging

Background: The α/β ratio for prostate cancer is postulated being in the range of 0.8 to 2.2 Gy, giving rise to the hypothesis that there may be a therapeutic advantage to hypofractionation. To do so, we carried out a randomized trial comparing hypofractionated and conventionally fractionated image-guided intensity modulated radiotherapy (IG-IMRT) in high-risk prostate cancer. Here, we report on acute toxicity and quality of life (QOL) for the first 124 randomized patients. Methods: The trial compares 76 Gy in 38 fractions (5 fractions/week) (Arm 1) to 63 Gy in 20 fractions (4 fractions/week) (Arm 2) (IG-IMRT). Prophylactic pelvic lymph node irradiation with 46 Gy in 23 fractions sequentially (Arm 1) and 44 Gy in 20 fractions simultaneously (Arm 2) was applied. All patients had long term androgen deprivation therapy (ADT) started before RT. Both physician-rated acute toxicity and patient-reported QOL using EPIC questionnaire are described.

- by Eduardas Aleknavicius
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- Radiation Oncology, Quality of life, Image guided radiotherapy, Aged

and sharing with colleagues.

- by Glenn Bauman and +2
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- Femur, Image guided radiotherapy, Prostate, Clinical Sciences

Proton treatment monitoring with Positron-Emission-Tomography (PET) is based on comparing measured and Monte Carlo (MC) predicted β(+) activity distributions. Here we present PET β(+) activity data and MC predictions both during and after proton irradiation of homogeneous PMMA targets, where protons were extracted from a cyclotron. PMMA phantoms were irradiated with 62 MeV protons extracted from the CATANA cyclotron. PET activity data were acquired with a 10 × 10 cm(2) planar PET system and compared with predictions from the FLUKA MC generator. We investigated which isotopes are produced and decay during irradiation, and compared them to the situation after irradiation. For various irradiation conditions we compared one-dimensional activity distributions of MC and data, focussing on Δw50%, i.e., the distance between the 50% rise and 50% fall-off position. The PET system is able to acquire data during and after cyclotron irradiation. For PMMA phantoms the difference between the FLUKA...

Background and purpose: This study evaluates the impact of MRI guided adaptive brachytherapy (BT) on uterine corpus dose. Material and methods: 84 patients with median follow-up of 18 months were analysed. MRI based BT was done according to GEC-ESTRO guidelines. Non-involved uterine corpus at the time of BT was contoured and the uterine corpus dose (D90 and D98) was evaluated for (1) standard loading pattern with source loading to the tip of the tandem and (2) optimised dose plan. Tandem lengths and heights of the 85 Gy isodose were recorded. Results: Dose optimisation resulted in a reduction of active tandem length of 0.4 ± 0.4 cm leading to lowering the D90 to the non-involved uterine corpus from 63.8 ± 9.5 Gy to 56.7 ± 7.5 Gy EQD2 (p < 0.0001). Mean active tandem length was 5.0 ± 1.0 cm, and the height of the 85 Gy isodose was 5.7 ± 1.0 cm in optimised plans. Conclusions: MRI guided dose optimisation lowered the dose to the uterine corpus. However, a total EBRT + BT dose larger than 50 Gy was obtained in 99% of patients. Assuming that 45-50 Gy is sufficient to eradicate microscopic disease, the lowering of uterus corpus dose is not expected to induce additional uterine corpus recurrences in the setting of MRI guided adaptive BT. This hypothesis should be tested in a larger number of patients as e.g. the EMBRACE study.

- by Christian Kirisits
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- Brachytherapy, Image guided radiotherapy, Follow-up studies, Aged

Dosimetry of eye plaques for ocular tumors presents unique challenges in brachytherapy. The challenges in accurate dosimetry are in part related to the steep dose gradient in the tumor and critical structures that are within millimeters of radioactive sources. In most clinical applications, calculations of dose distributions around eye plaques assume a homogenous water medium and full scatter conditions. Recent Monte Carlo (MC)-based eye-plaque dosimetry simulations have demonstrated that the perturbation effects of heterogeneous materials in eye plaques, including the gold-alloy backing and Silastic insert, can be calculated with reasonable accuracy. Even additional levels of complexity introduced through the use of gold foil "seed-guides" and custom-designed plaques can be calculated accurately using modern MC techniques. Simulations accounting for the aforementioned complexities indicate dose discrepancies exceeding a factor of ten to selected critical structures compared to conventional dose calculations. Task Group 129 was formed to review the literature; re-examine the current dosimetry calculation formalism; and make recommendations for eye-plaque dosimetry, including evaluation of brachytherapy source dosimetry parameters and heterogeneity correction factors. A literature review identified modern assessments of dose calculations for Collaborative Ocular Melanoma Study (COMS) design plaques, including MC analyses and an intercomparison of treatment planning systems (TPS) detailing differences between homogeneous and heterogeneous plaque calculations using the American Association of Physicists in Medicine (AAPM) TG-43U1 brachytherapy dosimetry formalism and MC techniques. This review identified that a commonly used prescription dose of 85 Gy at 5 mm depth in homogeneous medium delivers about 75 Gy and 69 Gy at the same 5 mm depth for specific 125 I and 103 Pd sources, respectively, when accounting for COMS plaque heterogeneities. Thus, the adoption of heterogeneous dose calculation methods in clinical practice would result in dose differences >10% and warrant a careful evaluation of the corresponding changes in prescription doses. Doses to normal ocular structures vary with choice of radionuclide, Chiu-Tsao et al.: Dosimetry of 125 I and 103 Pd COMS eye plaques 6162

- by F. Mourtada
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- Biomedical Engineering, Brachytherapy, Medical Physics, Image guided radiotherapy

PURPOSE: Postplan quality assurance using CT shows considerable interobserver contour variability. We examined CT postplans of four experienced brachytherapists for comparison with MR-determined prostate volumes. METHODS AND MATERIALS: Seventy-five patients had CT and MR scans 1 month post-125 I prostate brachytherapy. CT scans were contoured by the treating physician and dosimetry calculated. The prostate was contoured independently on MR by one observer with extensive MR experience, the scans were fused and dosimetric parameters compared. RESULTS: The mean prostate volume on CT was 38.3 cc (17.5e78.6 cc), on MR 33.3 cc (16.3e66.1 cc). On average, the volume on CT was 16.1% larger than on MR (range, 8% smaller to 64% larger). Craniocaudal discordance of the CT vs. MR prostate contours ranged from 4 mm cranial to 10 mm caudal to MR base and from 6 mm cranial to 14 mm caudal to MR apex. The CT prostate volume not only included an average of 90% of the MR prostate (range, 75e99%) but also included normal tissue (mean, 8.3 cc; range, 2.9e17.1 cc). The average difference between the calculated D 90 from CT contours vs. MR contours was 10.0 Gy (standard deviation, 8.8; range, À37.6 to þ41.6 Gy). CONCLUSIONS: On average, only 90% of the MR-defined prostate is included in CT contours, while a volume of normal tissue is erroneously designated as prostate. Lack of awareness of this deficiency in planning and/or operative technique gives a false sense of appreciation of the true conformality, delays implementation of corrective measures, and risks unnecessary side effects.

- by Cynthia Araujo and +1
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- Magnetic Resonance Imaging, Brachytherapy, Treatment Outcome, Quality Assurance

The cone-beam computed tomography (CBCT) imaging modality is an integral component of image-guided adaptive radiation therapy (IGART), which uses patient-specific dynamic/temporal information for potential treatment plan modification. In this study, an offline process for the integral component IGART framework has been implemented that consists of deformable image registration (DIR) and its validation, dose reconstruction, dose accumulation and dose verification. This study compares the differences between planned and estimated delivered doses under an IGART framework of five patients undergoing prostate cancer radiation therapy. The dose calculation accuracy on CBCT was verified by measurements made in a Rando pelvic phantom. The accuracy of DIR on patient image sets was evaluated in three ways: landmark matching with fiducial markers, visual image evaluation and unbalanced energy (UE); UE has been previously demonstrated to be a feasible method for the validation of DIR accuracy at a voxel level. The dose calculated on each CBCT image set was reconstructed and accumulated over all fractions to reflect the 'actual dose' delivered to the patient. The deformably accumulated (delivered) plans were then compared to the original (static) plans to evaluate tumor and normal tissue dose discrepancies. The results support the utility of adaptive planning, which can be used to fully elucidate the dosimetric impact based on the simulated delivered dose to achieve the desired tumor control and normal tissue sparing, which may be of particular importance in the context of hypofractionated radiotherapy regimens.

- by Dezhi Liu
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- Biomedical Engineering, Radiation Therapy, Prostate Cancer, Adaptive Radiation

Purpose: We compared acute and late genitourinary (GU) and gastrointestinal (GI) toxicities in prostate cancer patients treated with three different high-dose radiation techniques. Methods and Materials: A total of 1,903 patients with localized prostate cancer were treated with definitive RT at William Beaumont Hospital from 1992 to 2006: 22% with brachytherapy alone (BT), 55% with image-guided external beam (EB-IGRT), and 23% external beam with high-dose-rate brachytherapy boost (EBRT+HDR). Median dose with BT was 120 Gy for LDR and 38 Gy for HDR (9.5 Gy Â 4). Median dose with EB-IGRT was 75.6 Gy (PTV) to prostate with or without seminal vesicles. For EBRT+HDR, the pelvis was treated to 46 Gy with an additional 19 Gy (9.5 Gy Â 2) delivered via HDR. GI and GU toxicity was evaluated utilizing the NCI-CTC criteria (v.3.0). Median follow-up was 4.8 years.

- by Hong Ye
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- Quality of life, Brachytherapy, Prostate Cancer, Image guided radiotherapy

Background: Image-guided radiotherapy (IGRT) increases the accuracy of treatment delivery through daily target localisation. We report on toxicity symptoms experienced during radiotherapy treatment, with and without IGRT in prostate... more

- by Tomas Kron
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- Radiation, Radiation Oncology, Treatment Outcome, Radiotherapy

Image guided adaptive brachytherapy MRI-based brachytherapy a b s t r a c t Purpose: To investigate and test the feasibility of adaptive 3D image based BT planning for cervix cancer patients in settings with limited access to MRI, using a combination of MRI for the first BT fraction and planning of subsequent fractions on CT. Material and methods: For 20 patients treated with EBRT and HDR BT with tandem/ring applicators two sets of treatment plans were compared. Scenario one is based on the ''gold standard'' with individual MRI-based treatment plans (applicator reconstruction, target contouring and dose optimization) for two BT applications with two fractions each. Scenario two is based on one initial MRI acquisition with an applicator in place for the planning of the two fractions of the first BT application and reuse of the target contour delineated on MRI for subsequent planning of the second application on CT. Transfer of the target from MRI of the first application to the CT of the second one was accomplished by use of an automatic applicator-based image registration procedure. Individual dose optimization of the second BT application was based on the transferred MRI target volume and OAR structures delineated on CT.

- by Richard Pötter and +1
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- Brachytherapy, Image guided radiotherapy, X ray Computed Tomography

Background
18 F-fluoro-ethyl-tyrosine PET is gaining more indications in the field of oncology. We
investigated the potentials of usage of FET-PET/CT in addition to MRI for definition of gross
tumor volume (GTV) in stereotactic radiotherapy of lesions of skull base.
Methods
We included in a prospective setting 21 cases. An MRI was performed, completed by FET
PET/CT. Different GTV’s were defined based on respective imaging tools: 1. GTVMRI, 2.
GTV MRI /CT, 3. GTV composit (1 + 2), and GTVPET = GTV Boost. Lesions could be
visualised by MRI and FET-PET / CT in all patients.
Results
FET tracer enhancement was found in all cases. Skull base infiltration by these lesions was
observed by MRI, CT (PET/CT) and FET-PET (PET/CT) in all patients. Totally, brain tissue
infiltration was seen in 10 patients. While, in 7 (out 10) cases, MRI and CT (from PET/CT)
were indicating brain infiltration, FET-PET could add additional information regarding
infiltrative behaviour: in 3 (out 10) patients, infiltration of the brain was displayed merely in
FET-PET. An enlargement of GTVMRI/CT due to the FET-PET driven information, which
revealed GTVcomposite , was necessary in 7 cases,. This enlargement was significant by definition (> 10% of GTVMRI/CT). The mean PET-effect on GTV counted for 1 ± 4 cm3.
The restricted boost fields were based mainly on the GTVPET volume. In mean, about 8.5
cm3 of GTVMRI/CT, which showed no FET uptake, were excluded from target volume.
GTVboost driven by only-PET-activity, was in mean by 33% smaller than the initial large
treatment field, GTVcomposite , for those cases received boost treatment. FET-PET lead to
significant (>10%) changes in the initial treatment fields in 11/21 patients and showed
additional tumour volume relevant for radiation planning in 6/21 cases, and led to a
subsequent decrease of more than 10% of the initial volumes for the boost fields.
Conclusion
The implementation of FET PET into the planning procedures showed a benefit in terms of
accurate definition of skull base lesions as targets for Image-guided stereotactic
Radiotherapy. This has to be investigated prospectively in larger cohorts.
Keywords
FET-PET, Skull base, Image-guided, Stereotactic radiotherapy

- by Dr. Harun Badakhshi
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- Evidence Based Medicine, PET, Image guided radiotherapy, Image-guided therapy

Stereotactic radiosurgery using frame-based positioning is a well-established technique for the treatment of benign and malignant lesions. By contrast, a new trend toward frameless systems using image-guided positioning techniques is gaining mainstream acceptance. This study was designed to measure the detection and positioning accuracy of the ExacTrac/Novalis Body (ET/NB) for rotations and to compare the accuracy of the frameless with the frame-based radiosurgery technique.A program was developed in house to rotate reference computed tomography images. The angles measured by the system were compared with the known rotations. The accuracy of ET/NB was evaluated with a head phantom with seven lead beads inserted, mounted on a treatment couch equipped with a robotic tilt module, and was measured with a digital water level and portal films. Multiple hidden target tests (HTT) were performed to measure the overall accuracy of the different positioning techniques for radiosurgery (i.e., frameless and frame-based with relocatable mask or invasive ring, respectively).The ET/NB system can detect rotational setup errors with an average accuracy of 0.09° (standard deviation [SD] 0.06°), 0.02° (SD 0.07°), and 0.06° (SD 0.14°) for longitudinal, lateral, and vertical rotations, respectively. The average positioning accuracy was 0.06° (SD 0.04°), 0.08° (SD 0.06°), and 0.08° (SD 0.07°) for longitudinal, lateral and vertical rotations, respectively. The results of the HTT showed an overall three-dimensional accuracy of 0.76 mm (SD 0.46 mm) for the frameless technique, 0.87 mm (SD 0.44 mm) for the relocatable mask, and 1.19 mm (SD 0.45 mm) for the frame-based technique.The study showed high detection accuracy and a subdegree positioning accuracy. On the basis of phantom studies, the frameless technique showed comparable accuracy to the frame-based approach.

- by Tom Depuydt
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- Radiosurgery, Software, Image guided radiotherapy, Clinical Sciences

The aim of this work is to evaluate the geometric accuracy of a prerelease version of a new six degrees of freedom (6DoF) couch. Additionally, a quality assurance method for 6DoF couches is proposed. Methods: The main principle of the performance tests was to request a known shift for the 6DoF couch and to compare this requested shift with the actually applied shift by independently measuring the applied shift using different methods (graph paper, laser, inclinometer, and imaging system). The performance of each of the six axes was tested separately as well as in combination with the other axes. Functional cases as well as realistic clinical cases were analyzed. The tests were performed without a couch load and with a couch load of up to 200 kg and shifts in the range between −4 and +4 cm for the translational axes and between −3 • and +3 • for the rotational axes were applied. The quality assurance method of the new 6DoF couch was performed using a simple cube phantom and the imaging system. Results: The deviations (mean ± one standard deviation) accumulated over all performance tests between the requested shifts and the measurements of the applied shifts were −0.01 ± 0.02, 0.01 ± 0.02, and 0.01 ± 0.02 cm for the longitudinal, lateral, and vertical axes, respectively. The corresponding values for the three rotational axes couch rotation, pitch, and roll were 0.03 • ± 0.06 • , −0.04 • ± 0.12 • , and −0.01 • ± 0.08 • , respectively. There was no difference found between the tests with and without a couch load of up to 200 kg. Conclusions: The new 6DoF couch is able to apply requested shifts with high accuracy. It has the potential to be used for treatment techniques with the highest demands in patient setup accuracy such as those needed in stereotactic treatments. Shifts can be applied efficiently and automatically. Daily quality assurance of the 6DoF couch can be performed in an easy and efficient way. Long-term stability has to be evaluated in further tests.

- by Michael Fix and +2
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- Biomedical Engineering, Radiosurgery, Medical Physics, Radiotherapy

Purpose: High dose rate (HDR) brachytherapy is a form of radiation therapy for treating prostate cancer whereby a high activity radiation source is moved between predefined positions inside applicators inserted within the treatment volume. Accurate positioning of the source is essential in delivering the desired dose to the target area while avoiding radiation injury to the surrounding tissue. In this paper, HDR BrachyView, a novel inbody dosimetric imaging system for real time monitoring and verification of the radioactive seed position in HDR prostate brachytherapy treatment is introduced. The current prototype consists of a 15 × 60 mm 2 silicon pixel detector with a multipinhole tungsten collimator placed 6.5 mm above the detector. Seven identical pinholes allow full imaging coverage of the entire treatment volume. The combined pinhole and pixel sensor arrangement is geometrically designed to be able to resolve the three-dimensional location of the source. The probe may be rotated to keep the whole prostate within the transverse plane. The purpose of this paper is to demonstrate the efficacy of the design through computer simulation, and to estimate the accuracy in resolving the source position (in detector plane and in 3D space) as part of the feasibility study for the BrachyView project. Methods: Monte Carlo simulations were performed using the GEANT4 radiation transport model, with a 192 Ir source placed in different locations within a prostate phantom. A geometrically accurate model of the detector and collimator were constructed. Simulations were conducted with a single pinhole to evaluate the pinhole design and the signal to background ratio obtained. Second, a pair of adjacent pinholes were simulated to evaluate the error in calculated source location. Results: Simulation results show that accurate determination of the true source position is easily obtainable within the typical one second source dwell time. The maximum error in the estimated projection position was found to be 0.95 mm in the imaging (detector) plane, resulting in a maximum source positioning estimation error of 1.48 mm. Conclusions: HDR BrachyView is a feasible design for real-time source tracking in HDR prostate brachytherapy. It is capable of resolving the source position within a subsecond dwell time. In combination with anatomical information obtained from transrectal ultrasound imaging, HDR BrachyView adds a significant quality assurance capability to HDR brachytherapy treatment systems.

- by Michael Lerch and +3
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- Biomedical Engineering, Monte Carlo Simulation, Brachytherapy, Medical Physics

"Image-guided intensity-modulated radiotherapy for patients with locally advanced gastric cancer: a clinical feasibility study.
Badakhshi H, Gruen A, Graf R, Boehmer D, Budach V.
Source: Gastric Cancer. 2013 Oct 11.
Department for Radiation Oncology, Charité School of Medicine and University Hospital Berlin, Augustenburger Platz 1, 13353, Berlin, Germany, Harun.Badakhshi@charite.de.
Abstract
BACKGROUND:
The aim of this study was to determine the medical and technical feasibility of intensity-modulated radiotherapy (IMRT) in high-risk nonmetastatic gastric cancer stage II and III after primary gastrectomy and D2 lymphadenectomy.
METHODS AND MATERIALS:
A prospective nonrandomized phase II trial was performed on 25 consecutive patients with gastric cancer with high risk (T3-4, N1-3, G2-3, R0-1). The dose delivered was 45 Gy (1.80 Gy per fraction) in IMRT technique. Concurrent 5-fluorouracil-based chemotherapy at 225 mg/m2 was administered as a continuous intravenous infusion. Primary endpoints were acute gastrointestinal toxicity (CTC 4.0) and technical feasibility of IMRT in regard to dose planning and radiation delivery.
RESULTS:
Early acute events were defined as clinical and chemical adverse effects of IMRT and concurrent chemotherapy during treatment. By definition, 90 days after the end of IMRT has been evaluated as acute-phase toxicity. No patient had grade 4 or higher acute adverse events. Clinical grade 3 toxicity occurred in two patients (8 %) with diarrhea and in one case (4 %) with nausea. Hematological changes with grade 3 occurred in three cases (12 %) with hemoglobin decrease, in five cases (25 %) as leukopenia, and in one case (4 %) with thrombocytopenia. The mean dose for liver was 16 Gy and the percentage volume exceeding 30 Gy (V30) was 21 %. Mean dose for right and left kidney was 9 and 13 Gy, respectively, and V20 was 9 % and 13 %, respectively. Heart received a median dose of 15 Gy and V40 was 17 %. The mean dose to the bowel was 11 Gy and V40 was 6 %. Spinal cord had at maximum 33 Gy in median. Specifics of dose distribution, including the coverage, for the target region were as follows: minimum was 33 Gy, maximum 48.6 Gy, and mean dose 44.6 Gy. The prescribed dose (45 Gy) covered 99 % and 95 % of planning target volume (OTV) in 66 % and 92 % of cases, respectively. Median PTV was 15.77 ml (range, 805-3,604 ml).
CONCLUSIONS:
The data support the practical feasibility of IMRT in adjuvant treatment in high-risk gastric cancer in the postoperative setting as a proof of principle. Acute toxicity has been tolerable."

- by Dr. Harun Badakhshi
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- Image guided radiotherapy, IMRT, Gastric Cancer, Digital Story Telling

Compensation for respiratory motion is important during abdominal cancer treatments. In this work we report the results of the 2015 MICCAI Challenge on Liver Ultrasound Tracking and extend the 2D results to relate them to clinical relevance in form of reducing treatment margins and hence sparing healthy tissues, while maintaining full duty cycle. We describe methodologies for estimating and temporally predicting respiratory liver motion from continuous ultrasound imaging, used during ultrasound-guided radiation therapy. Furthermore, we investigated the trade-off between tracking accuracy and runtime in combination with temporal prediction strategies and their impact on treatment margins. Based on 2D ultrasound sequences from 39 volunteers, a mean tracking accuracy of 0.9 mm was achieved when combining the results from the 4 challenge submissions (1.2 to 3.3 mm). The two submissions for the 3D sequences from 14 volunteers provided mean accuracies of 1.7 and 1.8 mm. In combination wit...

- by Andre Hallack
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- Algorithms, Biomedical Engineering, Medical Physics, Medicine

Purpose: Glioblastoma Multiforme (GBM) is the most common malignant brain tumor and frequently recurs in the same location after radiotherapy. Intensive treatment targeting localized lesion is required to improve GBM outcome, but dose escalation using conventional methods is limited by healthy tissue tolerance. Helical Tomotherapy (HT) Dose Painting (DP) treatments were simulated to safely deliver high doses in the recurrent regions. Materials and methods: Apparent Diffusion Coefficient (ADC) data from five recurrent GBM were retrospectively considered for planning. Hypo-fractionated (25À50 Gy, 5 fractions) voxel-based prescriptions were opportunely converted to personalized structured-based dose maps to create DP plans with a commercial Treatment Planning System. Optimized plans were generated and analyzed in terms of plan conformity to dose prescription (Q 0.90–1.10), tolerance of the healthy tissues (D MAX), and dosimetry accuracy of the deliverable plans (c-index). Results: Only three of the five cases could receive a safe retreatment without violating the maximum critical organs dose constraints. The conformity of the simulated plans was between 40.9% and 79.9% (Q 0.90–1.10), their delivery time was in the range of 38.3–63.6 min, while the dosimetry showed c-index of 82.4–92.4%. Conclusions: This study proved the ability of our method to simulate personalized, deliverable and dosi-metrically accurate DPBN plans. HT hypo-fractionated treatments guided by ADC maps can be realized and applied to deliver high doses in the GBM recurrent regions, although there are some critical issues related to low Q 0.90–1.10 values, to exceeding of healthy-tissue dose constraints for some patients and long delivery times.

- by Matteo Orlandi
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- TomoTherapy, Radiotherapy, Image guided radiotherapy, IMRT