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Evaulating the Advantages and Disadvantages Using 4 Degree-of-Freedom (DOF) Versus 6 Degree-of-Freedom (DOF) for Tomotherapy Treatment in Head-and-Neck Cancer
Poster Viewing Abstracts S745
Volume 84 Number 3S Supplement 2012
3401 A Retrospective Analysis of Setup Reproducibility for Anorectal Cancer Patients Treated Prone on a Belly Board A.M. Monjazeb, J. Cui, M. Daly, A.M. Chen, R. Fragoso, J.A. Perks, J. Mayadev, and A.L. Michaud; UC Davis Comprehensive Cancer Center, Sacramento, CA Purpose/Objective(s): Small bowel toxicity is a feared complication of pelvic radiation therapy. Patients with anal anorectal cancer are often treated in the prone position on a belly-board to displace and minimize small bowel toxicity. Studies in prostate, gynecological, and gastrointestinal malignancies suggest that this treatment setup is less reproducible than the supine position. Recently, our institution has adopted the use image guided radiation therapy (IGRT) to account for this variability. We present the results of our experience to assess whether published recommendations for planning target volume (PTV) margins are sufficient to account for this increased variability. Materials/Methods: A total of 301 cone beam CT-guided setup shifts were retrospectively analyzed for 15 consecutive patients treated between 10/ 2010 and 01/2012 in the prone position on a belly board for anal or rectal cancer. Image guided patient alignment was performed using bony structures of the pelvis as landmarks. These were reviewed and compared to 2009 RTOG contouring atlas guidelines of 7-10 mm for PTV delineation in ano-rectal cancer. Results: The mean/median shifts (in mm) for all patients studied in the superior/inferior, left/right, and anterior/posterior directions were 0.6/0.6, 0.2/-0.2, and 0.6/0.7, respectively. One hundred forty-three of the 301 treatments (48%) required shifts exceeding 7mm and 72 of the 301 (24%) required shifts exceeding 10mm. Of the 15 patients studied, 2 patients (13%) did not require any setup shifts > 7mm and 6 patients (40%) did not require any setup shifts > 10mm. 11 patients (73%) required shifts > 7mm in greater than 20% of treatments and 4 patients (27%) required shifts > 10mm in greater than 20% of treatments. The mean shift over the course of treatment for individual patients ranged from 3.1 to 14.2 mm (mean for the cohort: 6.8 mm, median for the cohort: 5.6 mm). Conclusion: Based on the 2009 RTOG contouring atlas guidelines recommending a 7 to 10 mm PTV expansion, in 24-48% of treated fractions would have a portion of the clinical target volume (CTV) outside the high dose region due to setup variability without the use of IGRT. For many patients greater than 20% of treatments would have provided incomplete CTV coverage. This is of particular concern in the context of treatment with intensity modulated radiation therapy with sharp dose gradients beyond the delineated target volume. This data further suggests that there may be a subgroup of patients who will frequently require significant shifts for alignment while others will set-up quite reproducibly. Whether these potential misses could translate into a change in treatment efficacy is unknown. We suggest the use of IGRT to help account for the increased set-up variability in patients treated prone on a belly-board. Author Disclosure: A.M. Monjazeb: None. J. Cui: None. M. Daly: None. A.M. Chen: None. R. Fragoso: None. J.A. Perks: None. J. Mayadev: None. A.L. Michaud: None.
3402 Feasibility Study of Using Iodized Oil as Tumor Motion Surrogate For Liver IGRT B. Cho, I. Cho, J. Kwak, J. Jung, S. Yoon, J. Kim, and S. Ahn; Asan Medical Center, Seoul, Korea, Republic of Korea Purpose/Objective(s): To present the clinical investigation in using a radiopaque contrast, iodized oil as a direct surrogate for image guided radiation therapy (IGRT) of liver cancer patients underwent transcatheter arterial chemoembolization (TACE). Materials/Methods: Ten patients with Hepatocellular carcinoma (HCC) underwent TACE were enrolled for stereotactic body radiation therapy. For each patient, a 4DCT was scanned for delineation of target and iodized oil markers. For the purpose of image guidance CBCT and two orthogonal fluoroscopic images were acquired for each treatment. In order to evaluate
feasibility of iodized oil as a respiratory motion surrogate, Hounsfield unit(HU) of selected iodized oil and the volume of iodized oil markers were evaluated. Results: Total 21 iodized oil markers were contoured and utilized for patient setup. The volume of contoured iodized oil markers were 3.5 cc on average. The average number of iodized oil markers per patient was two(1w3). During the image guidance process, 19 markers were successfully used for 3D CBCT and 2D kV matching. As for 2D kV scans, 6 iodized oil markers were covered with bony anatomic structure. Total 13 iodized oil markers were fully detectable both CBCT and fluoroscopy. The minimum threshold of HU for fully detectable iodized oil marker was 1157 HU. The maximum HU of each marker was 1121738 HU. For nine patients who underwent more than 4 times of TACE procedure IGRT was successfully performed. However, For one patient, the iodized oil markers were washed out and disappeared on CBCT at the 1st fraction of treatment. For the patient the number of TACE procedure was twice and TACE time was prior to five month of radiation therapy. The HU of iodized oil marker was 25966 HU. Conclusions: Iodized oil could be used as a respiratory motion surrogate for liver IGRT. However, one might need to consider HU and TACE procedure time to prevent from iodized oil washout. Author Disclosure: B. Cho: None. I. Cho: None. J. Kwak: None. J. Jung: None. S. Yoon: None. J. Kim: None. S. Ahn: None.
3403 Evaulating the Advantages and Disadvantages Using 4 Degree-ofFreedom (DOF) Versus 6 Degree-of-Freedom (DOF) for Tomotherapy Treatment in Head-and-Neck Cancer G. Chiu and W.K. Fung; Hong Kong Sanatoirum & Hospital, Hong Kong, Hong Kong Purpose/Objective(s): To evaluate the advantages and disadvantages using 4 degree of freedom (DOF) versus 6 degree of freedom (DOF) for tomotherapy treatment in head and neck cancer. Materials/Methods: Evaluation is based on 28 consecutive patients with head and neck tomotherapy treatment with a total of 1064 fractions (i.e., 38 fractions/treatment) and 1064 image registrations. Pretreatment Megavoltage Computed Tomography (MVCT) was acquired for patient alignment to verify shift and residual setup errors. For all patients, 4DOF correction was applied and treatment proceeded afterwards. The residual errors for lateral, longitudinal, vertical and roll were recorded for study in alternate day (i.e., 532 images in 19 days of 28 patients). 6DOF residual errors for lateral, longitudinal, vertical, pitch, roll and yaw were also recorded by re-registration the pretreatment MVCT with the planning CT using 6DOF option right after the treatment. Translational and rotational residual errors from 4DOF and 6DOF were compared. Results: Positioning errors for both 4DOF and 6DOF were small. The systematic errors of 4DOF correction were 1.2 mm, 1.8 mm, 1.3 mm and 0.3 in lateral, longitudinal, vertical and roll. The systematic errors of 6DOF correction were 1.7 mm, 1.8 mm, 1.3 mm, 0.4 , 0.6 and 0.7 in lateral, longitudinal, vertical, pitch, roll and yaw respectively. The random errors of 4DOF correction were 1.7 mm, 1.9 mm, 1.7 mm and 0.5 in lateral, longitudinal, vertical and roll. The systematic errors of 6DOF corrections were 2.2 mm, 1.9 mm, 1.7 mm, 0.8 , 0.9 and 0.9 in lateral, longitudinal, vertical, pitch, roll and yaw respectively. Conclusion: Systematic and random errors in longitudinal and vertical directions from both 4DOF and 6DOF correction were the same. The systematic and random errors in lateral direction from 4DOF and 6DOF correction were different due to the lack of yaw correction in the Tomotherapy system, but the difference of 0.5 mm was still small. The rotational residual errors were below 1 . There is no significant advantage in using 6DOF correction in which 6DOF correction needs extra time and a 6DOF couch which means extra cost, it is suggested 4DOF is good enough for treatment verification in tomotherapy treatment. Author Disclosure: G. Chiu: None. W.K. Fung: None.
Volume 84 Number 3S Supplement 2012
3401 A Retrospective Analysis of Setup Reproducibility for Anorectal Cancer Patients Treated Prone on a Belly Board A.M. Monjazeb, J. Cui, M. Daly, A.M. Chen, R. Fragoso, J.A. Perks, J. Mayadev, and A.L. Michaud; UC Davis Comprehensive Cancer Center, Sacramento, CA Purpose/Objective(s): Small bowel toxicity is a feared complication of pelvic radiation therapy. Patients with anal anorectal cancer are often treated in the prone position on a belly-board to displace and minimize small bowel toxicity. Studies in prostate, gynecological, and gastrointestinal malignancies suggest that this treatment setup is less reproducible than the supine position. Recently, our institution has adopted the use image guided radiation therapy (IGRT) to account for this variability. We present the results of our experience to assess whether published recommendations for planning target volume (PTV) margins are sufficient to account for this increased variability. Materials/Methods: A total of 301 cone beam CT-guided setup shifts were retrospectively analyzed for 15 consecutive patients treated between 10/ 2010 and 01/2012 in the prone position on a belly board for anal or rectal cancer. Image guided patient alignment was performed using bony structures of the pelvis as landmarks. These were reviewed and compared to 2009 RTOG contouring atlas guidelines of 7-10 mm for PTV delineation in ano-rectal cancer. Results: The mean/median shifts (in mm) for all patients studied in the superior/inferior, left/right, and anterior/posterior directions were 0.6/0.6, 0.2/-0.2, and 0.6/0.7, respectively. One hundred forty-three of the 301 treatments (48%) required shifts exceeding 7mm and 72 of the 301 (24%) required shifts exceeding 10mm. Of the 15 patients studied, 2 patients (13%) did not require any setup shifts > 7mm and 6 patients (40%) did not require any setup shifts > 10mm. 11 patients (73%) required shifts > 7mm in greater than 20% of treatments and 4 patients (27%) required shifts > 10mm in greater than 20% of treatments. The mean shift over the course of treatment for individual patients ranged from 3.1 to 14.2 mm (mean for the cohort: 6.8 mm, median for the cohort: 5.6 mm). Conclusion: Based on the 2009 RTOG contouring atlas guidelines recommending a 7 to 10 mm PTV expansion, in 24-48% of treated fractions would have a portion of the clinical target volume (CTV) outside the high dose region due to setup variability without the use of IGRT. For many patients greater than 20% of treatments would have provided incomplete CTV coverage. This is of particular concern in the context of treatment with intensity modulated radiation therapy with sharp dose gradients beyond the delineated target volume. This data further suggests that there may be a subgroup of patients who will frequently require significant shifts for alignment while others will set-up quite reproducibly. Whether these potential misses could translate into a change in treatment efficacy is unknown. We suggest the use of IGRT to help account for the increased set-up variability in patients treated prone on a belly-board. Author Disclosure: A.M. Monjazeb: None. J. Cui: None. M. Daly: None. A.M. Chen: None. R. Fragoso: None. J.A. Perks: None. J. Mayadev: None. A.L. Michaud: None.
3402 Feasibility Study of Using Iodized Oil as Tumor Motion Surrogate For Liver IGRT B. Cho, I. Cho, J. Kwak, J. Jung, S. Yoon, J. Kim, and S. Ahn; Asan Medical Center, Seoul, Korea, Republic of Korea Purpose/Objective(s): To present the clinical investigation in using a radiopaque contrast, iodized oil as a direct surrogate for image guided radiation therapy (IGRT) of liver cancer patients underwent transcatheter arterial chemoembolization (TACE). Materials/Methods: Ten patients with Hepatocellular carcinoma (HCC) underwent TACE were enrolled for stereotactic body radiation therapy. For each patient, a 4DCT was scanned for delineation of target and iodized oil markers. For the purpose of image guidance CBCT and two orthogonal fluoroscopic images were acquired for each treatment. In order to evaluate
feasibility of iodized oil as a respiratory motion surrogate, Hounsfield unit(HU) of selected iodized oil and the volume of iodized oil markers were evaluated. Results: Total 21 iodized oil markers were contoured and utilized for patient setup. The volume of contoured iodized oil markers were 3.5 cc on average. The average number of iodized oil markers per patient was two(1w3). During the image guidance process, 19 markers were successfully used for 3D CBCT and 2D kV matching. As for 2D kV scans, 6 iodized oil markers were covered with bony anatomic structure. Total 13 iodized oil markers were fully detectable both CBCT and fluoroscopy. The minimum threshold of HU for fully detectable iodized oil marker was 1157 HU. The maximum HU of each marker was 1121738 HU. For nine patients who underwent more than 4 times of TACE procedure IGRT was successfully performed. However, For one patient, the iodized oil markers were washed out and disappeared on CBCT at the 1st fraction of treatment. For the patient the number of TACE procedure was twice and TACE time was prior to five month of radiation therapy. The HU of iodized oil marker was 25966 HU. Conclusions: Iodized oil could be used as a respiratory motion surrogate for liver IGRT. However, one might need to consider HU and TACE procedure time to prevent from iodized oil washout. Author Disclosure: B. Cho: None. I. Cho: None. J. Kwak: None. J. Jung: None. S. Yoon: None. J. Kim: None. S. Ahn: None.
3403 Evaulating the Advantages and Disadvantages Using 4 Degree-ofFreedom (DOF) Versus 6 Degree-of-Freedom (DOF) for Tomotherapy Treatment in Head-and-Neck Cancer G. Chiu and W.K. Fung; Hong Kong Sanatoirum & Hospital, Hong Kong, Hong Kong Purpose/Objective(s): To evaluate the advantages and disadvantages using 4 degree of freedom (DOF) versus 6 degree of freedom (DOF) for tomotherapy treatment in head and neck cancer. Materials/Methods: Evaluation is based on 28 consecutive patients with head and neck tomotherapy treatment with a total of 1064 fractions (i.e., 38 fractions/treatment) and 1064 image registrations. Pretreatment Megavoltage Computed Tomography (MVCT) was acquired for patient alignment to verify shift and residual setup errors. For all patients, 4DOF correction was applied and treatment proceeded afterwards. The residual errors for lateral, longitudinal, vertical and roll were recorded for study in alternate day (i.e., 532 images in 19 days of 28 patients). 6DOF residual errors for lateral, longitudinal, vertical, pitch, roll and yaw were also recorded by re-registration the pretreatment MVCT with the planning CT using 6DOF option right after the treatment. Translational and rotational residual errors from 4DOF and 6DOF were compared. Results: Positioning errors for both 4DOF and 6DOF were small. The systematic errors of 4DOF correction were 1.2 mm, 1.8 mm, 1.3 mm and 0.3 in lateral, longitudinal, vertical and roll. The systematic errors of 6DOF correction were 1.7 mm, 1.8 mm, 1.3 mm, 0.4 , 0.6 and 0.7 in lateral, longitudinal, vertical, pitch, roll and yaw respectively. The random errors of 4DOF correction were 1.7 mm, 1.9 mm, 1.7 mm and 0.5 in lateral, longitudinal, vertical and roll. The systematic errors of 6DOF corrections were 2.2 mm, 1.9 mm, 1.7 mm, 0.8 , 0.9 and 0.9 in lateral, longitudinal, vertical, pitch, roll and yaw respectively. Conclusion: Systematic and random errors in longitudinal and vertical directions from both 4DOF and 6DOF correction were the same. The systematic and random errors in lateral direction from 4DOF and 6DOF correction were different due to the lack of yaw correction in the Tomotherapy system, but the difference of 0.5 mm was still small. The rotational residual errors were below 1 . There is no significant advantage in using 6DOF correction in which 6DOF correction needs extra time and a 6DOF couch which means extra cost, it is suggested 4DOF is good enough for treatment verification in tomotherapy treatment. Author Disclosure: G. Chiu: None. W.K. Fung: None.