Richard Oates

A randomised study of a diet intervention to maintain consistent rectal volume for patients receiving radical radiotherapy to the prostate.

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Automatic tracking of gold seed markers from CBCT image projections in lung and prostate radiotherapy

PURPOSE To construct a method and software to track gold seed implants in prostate and lung patients undergoing radiotherapy using CBCT image projections. METHODS A mathematical model was developed in the MatLab (Mathworks, Natick, USA) environment which uses a combination of discreet cosine transforms and filtering to enhance several edge detection methods for identifying and tracking gold seed fiducial markers in images obtained from Varian (Varian Medical Systems, Palo Alto, USA) and Elekta (Kungstensgatan, Sweden) CBCT projections. RESULTS Organ motion was captured for 16 prostate patients and 1 lung patient. CONCLUSION Image enhancement and edge detection is capable of automatically tracking markers for up to 98% (Varian) and 79% (Elekta) of CBCT projections for prostate and lung markers however inclusion of excessive bony anatomy (LT and RT LAT) inhibit the ability of the model to accurate determine marker location.

Recording a patient diet over the radical course of radiotherapy for prostate cancer using a diet diary: a feasibility study.

Aims: To obtain an estimate of dietary fibre and fluid intake in Australian men undergoing prostate radiotherapy and to establish feasibility and patient compliance with recording normal diet without intervention during the radical course of radiotherapy. Methods: Eleven participants were enrolled and treated with 74 78 Gray (Gy) to the prostate over 8 weeks. Participants were instructed to record a diary of their food and fluid intake and bowel motions for the duration of treatment. Treating radiation therapists were instructed to initial the diet diary daily. Diet diaries were assessed for compliance by analysing the number of days over the treatment period and the number of diary pages submitted. The diet diaries were analysed for nutrient intake of fibre and fluids. Results: A total of 10 of 11 participants submitted a diet record for the full duration of treatment with a median compliance of 100% (range 90.4 100%) of days recorded. The mean (standard deviation) of fibre and fluids recorded in the diets were 21.5 g (5.5) and 2227.1 g (733.1), respectively. Conclusions: It is feasible for patients to record a diet diary over a radical course of prostate radiotherapy. In this study, most patients were highly compliant with submitting a diet record for each day during treatment.

What benefit could be derived from on-line adaptive prostate radiotherapy using rectal diameter as a predictor of motion?

This study investigated a relationship between rectum diameter and prostate motion during treatment with a view to reducing planning target volume (PTV) margins for an adaptive protocol. One hundred and ninety-four cone-beam computed tomography (CBCT) images of 10 patients were used to relate rectum diameter on CBCT to prostate intrafraction displacement. A threshold rectum diameter was used to model the impact of an adaptive PTV margin on rectum and bladder dose. Potential dose escalation with a 6 mm uniform margin adaptive protocol was compared to a PTV margin of 10 mm expansion of the clinical target volume (CTV) except 6 mm posterior. Of 194 fractions, 104 had a maximum rectal diameter of ≤3.5 cm. The prostate displaced ≤4 mm in 102 of those fractions. Changing from a standard to an adaptive PTV margin reduced the volume of rectum receiving 25, 50, 60, and 70 Gy by around 12, 9, 10, and 16%, respectively and bladder by approximately 21, 27, 29, and 35%, respectively. An average dose escalation of 4.2 Gy may be possible with an adaptive prostate radiotherapy protocol. In conclusion, a relationship between the prostate motion and the diameter of the rectum on CBCT potentially could enable daily adaptive radiotherapy which can be implemented from the first fraction.

A study on planning organ at risk volume for the rectum using cone beam computed tomography in the treatment of prostate cancer

In this study, we analyzed planning organ at risk volume (PRV) for the rectum using a series of cone beam computed tomographies (CBCTs) acquired during the treatment of prostate cancer and evaluated the dosimetric effect of different PRV definitions. Overall, 21 patients with prostate cancer were treated radically with 78Gy in 39 fractions had in total 418 CBCTs, each acquired at the end of the first 5 fractions and then every alternate fraction. The PRV was generated from the Boolean sum volume of the rectum obtained from first 5 fractions (PRV-CBCT-5) and from all CBCTs (PRV-CBCT-All). The PRV margin was compared at the superior, middle, and inferior slices of the contoured rectum to compare PRV-CBCT-5 and PRV-CBCT-All. We also compared the dose received by the planned rectum (Rectum-computed tomography [CT]), PRV-CBCT-5, PRV-CBCT-All, and average rectum (CBCT-AV-dose-volume histogram [DVH]) at critical dose levels. The average measured rectal volume for all 21 patients for Rectum-CT, PRV-CBCT-5, and PRV-CBCT-All was 44.3 ± 15.0, 92.8 ± 40.40, and 121.5 ± 36.7cm(3), respectively. For PRV-CBCT-All, the mean ± standard deviation displacement in the anterior, posterior, right, and left lateral directions in centimeters was 2.1 ± 1.1, 0.9 ± 0.5, 0.9 ± 0.8, and 1.1 ± 0.7 for the superior rectum; 0.8 ± 0.5, 1.1 ± 0.5, 1.0 ± 0.5, and 1.0 ± 0.5 for the middle rectum; and 0.3 ± 0.3; 0.9 ± 0.5; 0.4 ± 0.2, and 0.5 ± 0.3 for the inferior rectum, respectively. The first 5 CBCTs did not predict the PRV for individual patients. Our study shows that the PRV margin is different for superior, middle, and the inferior parts of the rectum, it is wider superiorly and narrower inferiorly. A uniform PRV margin does not represent the actual rectal variations during treatment for all treatment fractions. The large variation in interpatient rectal size implies a potential role for adaptive radiotherapy for prostate cancer.

Prostate Bed Radiation Therapy: The Utility of Ultrasound Volumetric Imaging of the Bladder

AIMS To evaluate the effect of incorporating daily ultrasound scanning to reduce variation in bladder filling before prostate bed radiotherapy. The primary aim was to confirm that coverage of the planning target volume (PTV) with the 95% isodose was within tolerance when the ultrasound-determined bladder volume was within individualised patient limits. MATERIALS AND METHODS Cone beam computed tomography (CBCT) images were acquired on 10 occasions during the course of treatment to assess systematic changes in rectal or bladder volume as part of a standard offline image-guided radiotherapy (IGRT) protocol. In addition, through a two-part study an ultrasound scan of the bladder was added to the IGRT protocol. In the Part 1 study, the ultrasound-determined bladder volume at the time of treatment simulation in 26 patients was compared with the simulation computed tomography cranio-caudal bladder length. The relationship between the two was used to establish bladder volume tolerance limits for the interventional component of the Part 2 study. In the Part 2 study, 24 patients underwent ultrasound scanning before treatment. When bladder volumes were outside the specified limits, they were asked to drink more water or void as appropriate until the volume was within tolerance. RESULTS Based on the results of the Part 1 study, a 100 ml tolerance was applied in the Part 2 study. Seventy-six per cent of patients found to have bladder volumes outside tolerance were able to satisfactorily adjust their bladder volumes on demand. Comparing the bladder volumes with the CBCT data revealed that the bladder scanner correctly predicted that the target volume would be accurately targeted (using surrogate end points) in 83% of treatment fractions. CONCLUSION A simple hand-held ultrasound bladder scanner provides a practical, inexpensive, online solution to confirming that the bladder volume is within acceptable, patient-specific limits before treatment delivery, with the potential to improve overall treatment accuracy.

Geographical miss of the prostate during image-guided radiotherapy with a 6-mm posterior expansion margin

Our department commonly uses a planning target volume (PTV) expansion of 6 mm posterior and 1 cm in all other directions when treating prostate cancer patients with image‐guided radiotherapy (IGRT). This study aimed to test the adequacy of this PTV expansion by assessing geographical miss of the prostate on post‐treatment cone‐beam CT (CBCT) and identify those at risk of geographical miss.

Rectal complication probability from composite volumes derived from daily cone beam computed tomography in prostate cancer radiotherapy.

AIM The aim of this study is to investigate the rectal complication probabilities for various rectum volumes with intensity-modulated radiation therapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT) in patients undergoing prostate cancer radiotherapy. MATERIALS AND METHODS Thirteen patients undergoing prostate cancer radiotherapy were consecutively selected for this study. All patients were treated with IMRT to a dose of 78 Gy in 39 fractions. Three different rectum volumes: (i) planned rectum (plan-rectum) (ii) Boolean sum of rectum volume based on the cone-beam computed tomography (CBCT) for first five fractions (planning organ at risk volumes [PRV]-CBCT-5), (iii) Boolean sum of rectum volume from all the CBCTs (PRV-CBCT-All) in addition to an average rectal complication (PRV-CBCT-AV) were used for computing the probabilities of rectal complications. To assess the rectal complications with 3D-CRT, a five-field plan was generated for comparison with IMRT. The Lyman-Kutcher-Burman (LKB) normal tissue complication probability (NTCP) model was used to assess the rectal complications for all of the defined rectal volumes. RESULTS The NTCPs for rectum as assessed from plan-rectum, PRV-CBCT-5, PRV-CBCT-All, and PRV-CBCT-AV with IMRT were 9.71% ±4.69%, 16.34% ±9.51%, 19.39% ±9.71%, and 12.81% ±7.22%, respectively. Similarly, with 3D-CRT, the NTCPs were 17.41% ±10.44%, 19.61% ±11.08%, 21.03% ±11.06%, and 17.72% ±10.29%, respectively. CONCLUSION Our results showed that the rectal complications are reduced significantly with IMRT as compared to 3D-CRT. As such, the analyses of NTCP with various defined composite rectum volumes indicate that IMRT requires image-guided adaptive radiotherapy as opposed to 3D-CRT.

SU‐E‐J‐20: A Study On Rectal Complication Probability From Composite Volumes Derived From Daily CBCT in Prostate Cancer Radiotherapy

PURPOSE Dose escalation improves local control in prostate cancer radiotherapy. However, dose escalation is limited due to late rectal toxicity. Bladder and rectal filling / rectal gas during the course of treatment tend to alter the dose to the target volume and critical structures. In this study, an effort has been made to assess the late rectal complication probability from a serial of cone beam computed tomography (CBCT) scans for prostate cancer with IMRT and 3D conformal radiotherapy. METHODS Twelve patients were selected for this study. All patients were treated with IMRT to a dose of 78 Gy with pre-treatment kV/kV orthogonal imaging matched to gold seed fiducials. CBCT scans were acquired at the end of treatment on fractions 1-5 and then every alternate fraction. Alternatively, five field 3D-CRT plans were generated for the above patients. Three different rectum volumes: (i) Plan rectum (ii) Boolean sum of rectum volume based on the CBCT for first 5 fractions (Rectum-5) and (iii) Boolean sum of rectum volume from all the CBCTs (Rectum-all) were used for computing the rectal complications. The Lyman-Kutcher-Burman normal tissue complication probability (NTCP) model has been used in this study to assess grade-2 rectal toxicity. RESULTS The NTCP for rectum with IMRT as assessed from Plan-Rectum, Rectum-5, Rectum-all and average rectum were 11.03 ± 4.91%, 17.45 ± 9.07%, 21.89 ± 7.66% and 13.83 ± 6.82% respectively whereas for 3D-CRT it is 20.22 ± 9.45%, 21.61 ± 9.56%, 23.81 ± 8.62% and 19.78 ± 8.97% respectively. Statistically significant differences were observed between Plan-Rectum, Rectum-5 and Rectum-All with IMRT. CONCLUSION Our results show that large variation in NTCP for IMRT between Plan-rectum, Rectum-5 and rectum-all indicates a potential role for adaptive radiotherapy for prostate cancer. This could in turn lead to dose escalation with IMRT for prostate cancer.