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His W.C.,Shanghai Proton and Heavy Ion Center | Schreuder A.N.,Proton Therapy | Zeidan O.,Health Cancer Center Orlando Health
Journal of Applied Clinical Medical Physics | Year: 2015

We present a quantitative methodology to measure head interfraction movements within intracranial masks of commercial immobilization devices used for proton radiotherapy. A three-points tracking (3PtTrack) method was developed to measure the mask location for each treatment field over an average of 10 fractions for seven patients. Five patients were treated in supine with the Qfix Base-of-Skull (BoS) headframe, and two patients were treated in prone with the CIVCO Uni-frame baseplate. Patients were first localized by an in-room, image-guidance (IG) system, and then the mask location was measured using the 3PtTrack method. Measured mask displacements from initial location at the first fraction are considered equivalent to the head interfraction movement within the mask. The trends of head movements and couch displacements and rotation were analyzed in three major directions. The accuracy of 3PtTrack method was shown to be within 1.0mm based on daily measurements of a QA device after localization by the IG system for a period of three months. For seven patients, mean values of standard deviation (SD) in anterior-posterior, lateral, and superior-inferior directions were 1.1mm, 1.4 mm, and 1.6 mm for head movements, and were 1.4 mm, 1.8 mm, and 3.4mm for couch displacements. The mean SD values of couch rotations were 1.1o, 0.9o, and 1.1o for yaw, pitch, and roll, respectively. The overall patterns of head movements and couch displacements were similar for patients treated in either supine or prone, with larger deviations in the superior-inferior (SI) direction. A suboptimal mask fixation to the frame of the mask to the H&N frame is likely the cause for the observed larger head movements and couch displacements in the SI direction compared to other directions. The optical-tracking methodology provided a quantitative assessment of the magnitude of head motion.

Rana S.,Proton Therapy | Cheng C.,Vantage Oncology | Zheng Y.,Proton Therapy | Hsi W.,McLaren | And 4 more authors.
Journal of Applied Clinical Medical Physics | Year: 2014

The main purposes of this study were to 1) investigate the dosimetric quality of uniform scanning proton therapy planning (USPT) for prostate cancer patients with a metal hip prosthesis, and 2) compare the dosimetric results of USPT with that of volumetric-modulated arc therapy (VMAT). Proton plans for prostate cancer (four cases) were generated in XiO treatment planning system (TPS). The beam arrangement in each proton plan consisted of three fields (two oblique fields and one lateral or slightly angled field), and the proton beams passing through a metal hip prosthesis was avoided. Dose calculations in proton plans were performed using the pencil beam algorithm. From each proton plan, planning target volume (PTV) coverage value (i.e., relative volume of the PTV receiving the prescription dose of 79.2 CGE) was recorded. The VMAT prostate planning was done using two arcs in the Eclipse TPS utilizing 6 MV X-rays, and beam entrance through metallic hip prosthesis was avoided. Dose computation in the VMAT plans was done using anisotropic analytical algorithm, and calculated VMAT plans were then normalized such that the PTV coverage in the VMAT plan was the same as in the proton plan of the corresponding case. The dose-volume histograms of calculated treatment plans were used to evaluate the dosimetric quality of USPT and VMAT. In comparison to the proton plans, on average, the maximum and mean doses to the PTV were higher in the VMAT plans by 1.4% and 0.5%, respectively, whereas the minimum PTV dose was lower in the VMAT plans by 3.4%. The proton plans had lower (or better) average homogeneity index (HI) of 0.03 compared to the one for VMAT (HI = 0.04). The relative rectal volume exposed to radiation was lower in the proton plan, with an average absolute difference ranging from 0.1% to 32.6%. In contrast, using proton planning, the relative bladder volume exposed to radiation was higher at high-dose region with an average absolute difference ranging from 0.4% to 0.8%, and lower at low- and medium-dose regions with an average absolute difference ranging from 2.7% to 10.1%. The average mean dose to the rectum and bladder was lower in the proton plans by 45.1% and 22.0%, respectively, whereas the mean dose to femoral head was lower in VMAT plans by an average difference of 79.6%. In comparison to the VMAT, the proton planning produced lower equivalent uniform dose (EUD) for the rectum (43.7 CGE vs. 51.4 Gy) and higher EUD for the femoral head (16.7 CGE vs. 9.5 Gy), whereas both the VMAT and proton planning produced comparable EUDs for the prostate tumor (76.2 CGE vs. 76.8 Gy) and bladder (50.3 CGE vs. 51.1 Gy). The results presented in this study show that the combination of lateral and oblique fields in USPT planning could potentially provide dosimetric advantage over the VMAT for prostate cancer involving a metallic hip prosthesis.

Hsi W.C.,Proton Therapy | Hsi W.C.,Shanghai Proton and Heavy Ion Center | Law A.,ProCure Training and Development Center | Schreuder A.N.,ProCure Training and Development Center | And 2 more authors.
Medical Physics | Year: 2014

Purpose: An optical tracking and positioning system (OTPS) was developed to validate the software-driven isocentric (SDI) approach to control the six-degrees-of-freedom movement of a robotic couch. Methods: The SDI approach to movements rotating around a predefined isocenter, referred to as a GeoIso, instead of a mechanical pivot point was developed by the robot automation industry. With robotic couch-sag corrections for weight load in a traditional SDI approach, movements could be accurately executed for a GeoIso located within a 500 mm cubic volume on the couch for treatments. The accuracy of SDI movement was investigated using the OTPS. The GeoIso was assumed to align with the proton beam isocenter (RadIso) for gantry at the reference angle. However, the misalignment between GeoIso and RadIso was quantitatively investigated by measuring the displacements at various couch angles for a target placed at the RadIso at an initial couch angle. When circular target displacements occur on a plane, a relative isocenter shift (RIS) correction could be applied in the SDI movement to minimize target displacements. Target displacements at a fixed gantry angle without and with RIS correction were measured for 12 robotic couches. Target displacements for various gantry angles were performed on three couches in gantry rooms to study the gantry-induced RadIso shift. The RIS correction can also be applied for the RadIso shift. A new SDI approach incorporating the RIS correction with the couch sag is described in this study. In parallel, the accuracy of SDI translation movements for various weight loads of patients on the couch was investigated during positioning of patients for proton prostate treatments. Results: For a fixed gantry angle, measured target displacements without RIS correction for couch rotations in the horizontal plane varied from 4 to 20 mm. However, measured displacements perpendicular to couch rotation plane were about 2 mm for all couches. Extracted misalignments of GeoIso and RadIso in the horizontal plane were about 10 mm for one couch and within 3 mm for the rest of couches. After applying the RIS correction, the residual target displacements for couch rotations were within 0.5 mm to RadIso for all couches. For various gantry angles, measured target location for each angle was within 0.5 mm to its excepted location by the preset RadIso shift. Measured target displacements for ±30° of couch rotations were within 0.5 mm for gantry angles at 0° and 180°. Overall, nearly 85% of couch movements were within 0.5 mm in the horizontal plane and 0.7 mm vector distance from required displacements. Conclusions: The authors present an optical tracking methodology to quantify for software-driven isocentric movements of robotic couches. By applying proper RIS correction for misaligned GeoIso and RadIso for each couch, and the RadIso shifts for a moving gantry, residual target displacements for isocentric couch movements around the actual RadIso can be reduced to submillimeter tolerance. © 2014 American Association of Physicists in Medicine.

Wong A.T.,SUNY Downstate Medical Center | Safdieh J.J.,SUNY Downstate Medical Center | Rineer J.,Health Cancer Center Orlando Health | Weiner J.,SUNY Downstate Medical Center | And 2 more authors.
International Urology and Nephrology | Year: 2015

Purpose: To analyze patterns of care in younger patients (<60 years old) with localized prostate cancer and to identify factors associated with selection of therapy using a large, population-based database. Methods: The Surveillance, Epidemiology, and End Results database was queried to identify men <60 years old diagnosed with localized prostate cancer between 2010 and 2011. Patients were determined to have undergone no active treatment, local therapy, radiation therapy (RT), or radical prostatectomy (RP). Univariate and multivariate logistic regression analyses were performed to identify factors associated with the use of definitive therapy. Results: A total of 12,732 men were included in this analysis. For the entire cohort, 12.5 % received no definitive treatment, 61.6 % RP, 22.0 % RT, and 3.3 % RP with adjuvant RT. Among men with low-, intermediate-, and high-risk prostate cancer, 17.2, 7.1, and 15.9 %, respectively, received no definitive therapy. RP was the most common choice of definitive therapy, utilized in 74.6 % of patients. Adjuvant RT after RP was utilized in 16.2 % of cases with positive margin and/or pT3/pT4 disease. African-American race, single marital status, and Medicaid/no insurance were associated with a decreased likelihood of receiving definitive treatment. Conclusions: A significant proportion of younger men diagnosed with localized prostate cancer, particularly with low- or high-risk disease, are not receiving definitive therapy. African-American men, uninsured men, and patients with Medicaid or no medical insurance are less likely to receive definitive treatment. © 2015, Springer Science+Business Media Dordrecht.

Sharon Qi X.,University of California at Los Angeles | Neylon J.,University of California at Los Angeles | Can S.,University of California at Los Angeles | Staton R.,Health Cancer Center Orlando Health | And 3 more authors.
Current Cancer Therapy Reviews | Year: 2014

Purposes: To improve normal tissue sparing for head-and-neck (H&N) image-guided radiotherapy (IGRT) by employing treatment plans with tighter margins for CTV 2 and 3, and documenting the delivered dose throughout the entire treatment course. Methods: Ten H&N cases treated with simultaneous integrated boost on a TomoTherapy unit (Accuray Inc.) were analyzed. Dose-limiting critical structures included brainstem, spinal cord, cochleae, parotid glands and mandible. The targets include the PTV1 (gross disease volume), PTV2 (next echelon nodal regions) and PTV3 (areas harboring subclinical disease). The standard margin plans (plan_ref) were generated using the standard margin of 3 mm to CTV1-3. Reduced margin plans (plan_0margin) using the CTV-to-PTV margin of zero for CTV2 and 3 were compared with plan_ref. All patients went through daily pre-treatment megavoltage CT (MVCT) and weekly kilovoltage CT (kVCT) scans. A GPU-based 3D image deformation/ visualization tool was developed to register the weekly kVCT scans with the planning CT scan. The deformation of each contoured structures was computed to account for non-rigid change in the patient setup. Calculation of the dose accumulation was performed to determine the delivered mean/minimum/maximum dose, dose volume histograms (DVHs), etc. Results: The averaged planned cord maximum doses in Plan_0margin were 7.6% lower, and the parotid mean doses were 18.9% lower than plan_Ref. No significant changes in D95 and D90 for the CTV2/3 cumulative doses in both reference and Plan_0margin were observed during the planning stage. Under kVCT guidance on TomoTherapy, for the reference plans, the averaged cumulative mean dose ratios during the entire treatment course were consistent within 5% and 1.5% of the planned mean doses for PTVs and CTVs, respectively. Interfraction anatomical changes introduced variations in delivered target doses that reduced the improved normal structure sparing observed in plan_0margin during the planning stage. For the tighter margin plans, the cumulative mean dose ratios were consistent within 4.3% and 2.3% of the planned mean doses for CTV2 and CTV3, respectively. Similar dose variations of the delivered dose were seen for the reference and tighter margin plans. However, the delivered maximum and mean doses for the cord were 20% and 10% higher than the planned doses; a 3.6% higher cumulative mean dose for the parotids was also observed for the delivered dose than the planned doses in both plans. Conclusions: The GPU-based image framework enables real-time dose verification, accumulation and documentation. By imposing tighter CTV margins for level 2 and 3 targets for H&N irradiation, acceptable cumulative doses were achievable when coupled with weekly kVCT guidance while improving normal structure sparing. © 2014 Bentham Science Publishers.

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