A novel and innovative device to retract rectum during radiation therapy of pelvic tumors (original) (raw)
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Clinical effects of rectal retractor application in prostate cancer radiotherapy
Medical Journal of the Islamic Republic of Iran, 2021
Background: Radiation-induced rectal toxicities remain as a major risk during prostate radiotherapy. One approach to the reduction of rectal radiation dose is to physically increase the distance between the rectal wall and prostate. Therefore, the aim of this study was to evaluate whether the application of the rectal retractor (RR) can reduce rectal dose and toxicity in prostate cancer 3-dimensional conformal radiotherapy (3D-CRT). Methods: Overall, 36 patients with localized prostate cancer were randomized into the 2 groups, 18 patients with RR in-place and 18 without RR. All patients underwent planning computed tomography (CT). Patients were treated with 70 Gy in 35 fractions of 3D-CRT. In the RR group, RR was used during cone-down 20 treatment fractions. Acute and late gastrointestinal (GI) toxicities were assessed using EORTC/RTOG scoring system weekly during radiotherapy, 3, and 12 months after treatment. Device-related events were recorded according to CTCAE version 4.0. Pati...
Dynamic modulated brachytherapy (DMBT) for rectal cancer
2013
Purpose: All forms of past and current high-dose-rate brachytherapy utilize immobile applicators during treatment delivery. The only moving part is the source itself. This paradigm misses an important degree of freedom that, if explored, can in some instances produce previously unachievable dose conformality; that is, the dynamic motion of the applicator itself during treatment delivery. Monte Carlo and treatment planning simulations were used to illustrate the potential benefits of moving applicators for rectal cancer applications in particular. This concept is termed dynamic modulated brachytherapy (DMBT). Methods: The DMBT system uses a high-density, 18.0 g/cm 3 , 45 mm long tungsten alloy shield, cylindrical in shape, with a small window on one side to encapsulate a 192 Ir source, to create collimation that results in a highly directional beam profile. This shield can be dynamically translated and rotated, using an attached robotic arm, during treatment to create a volumetric modulated arc therapytype delivery, but from inside the rectal cavity. Monte Carlo simulations and planning optimization algorithms were developed inhouse to evaluate the effectiveness of this new approach using 36 clinical treatment plans comprised of 13 patients each treated using the intracavitary mold applicator (ICMA, Nucletron, The Netherlands) to quantify the potential clinical benefit. The prescription dose was 10 Gy/fx and the group had an average clinical target volume of 9.0 ± 3.5 cm 3 . Ideal phantom geometries were used to evaluate the impact of various shield dimensions and designs on the resulting plan quality. Results: Simulations of ideal phantom geometries found that shields as small as 10 mm in diameter can produce high quality plans. For the clinical patient cases, compared to the ICMA, for equal prescription tumor coverage, the DMBT plans provided >30% decrease in D 5 (high dose volume) resulting in a ∼40% decrease in dose heterogeneity index. In addition, mean dose and D 98 showed a reduction (typically 40%-60%) on all critical structures evaluated. However, for a 10 Gy prescribed dose there was an increase in total treatment time on average from 7.6 to 20.8 min for a source with an air-kerma strength of 40.25 kU (10 Ci). Conclusions: Dosimetric properties of a novel DMBT system have been described and evaluated. Comparison with the ICMA commercial applicator has shown it to be a prospective step forward in high-dose-rate brachytherapy 192 Ir technology. Dynamic motion of an applicator during treatment, for any applicator and site in general, can provide additional degrees of freedom that, if properly considered, can potentially increase the plan quality significantly.
Medical Physics, 2013
Purpose: All forms of past and current high-dose-rate brachytherapy utilize immobile applicators during treatment delivery. The only moving part is the source itself. This paradigm misses an important degree of freedom that, if explored, can in some instances produce previously unachievable dose conformality; that is, the dynamic motion of the applicator itself during treatment delivery. Monte Carlo and treatment planning simulations were used to illustrate the potential benefits of moving applicators for rectal cancer applications in particular. This concept is termed dynamic modulated brachytherapy (DMBT). Methods: The DMBT system uses a high-density, 18.0 g/cm 3 , 45 mm long tungsten alloy shield, cylindrical in shape, with a small window on one side to encapsulate a 192 Ir source, to create collimation that results in a highly directional beam profile. This shield can be dynamically translated and rotated, using an attached robotic arm, during treatment to create a volumetric modulated arc therapytype delivery, but from inside the rectal cavity. Monte Carlo simulations and planning optimization algorithms were developed inhouse to evaluate the effectiveness of this new approach using 36 clinical treatment plans comprised of 13 patients each treated using the intracavitary mold applicator (ICMA, Nucletron, The Netherlands) to quantify the potential clinical benefit. The prescription dose was 10 Gy/fx and the group had an average clinical target volume of 9.0 ± 3.5 cm 3 . Ideal phantom geometries were used to evaluate the impact of various shield dimensions and designs on the resulting plan quality. Results: Simulations of ideal phantom geometries found that shields as small as 10 mm in diameter can produce high quality plans. For the clinical patient cases, compared to the ICMA, for equal prescription tumor coverage, the DMBT plans provided >30% decrease in D 5 (high dose volume) resulting in a ∼40% decrease in dose heterogeneity index. In addition, mean dose and D 98 showed a reduction (typically 40%-60%) on all critical structures evaluated. However, for a 10 Gy prescribed dose there was an increase in total treatment time on average from 7.6 to 20.8 min for a source with an air-kerma strength of 40.25 kU (10 Ci). Conclusions: Dosimetric properties of a novel DMBT system have been described and evaluated. Comparison with the ICMA commercial applicator has shown it to be a prospective step forward in high-dose-rate brachytherapy 192 Ir technology. Dynamic motion of an applicator during treatment, for any applicator and site in general, can provide additional degrees of freedom that, if properly considered, can potentially increase the plan quality significantly.
Urologic Oncology: Seminars and Original Investigations, 2004
Purpose: When Ͼ25% of the rectum is irradiated to Ն70 Gy, the risk of developing Grade 2 or higher rectal complications is significantly increased. This study evaluates the impact on dose to the rectum from the use of an intrarectal (IR) balloon device, previously shown to immobilize the prostate gland and localize the rectum, in patients receiving dose escalated 3-dimentional (3D) conformal radiation therapy. Materials and Methods: From July 2001 through February 2003, 28 consecutive patients with prostate cancer underwent computerized tomography-based simulation with and without the IR balloon in place. Treatment planning was performed for three clinical paradigms in which the IR balloon was not used at all (0 Gy), used during the cone-down for 15 treatments (28.35 Gy), or used for the entire course of 40 treatments (75.6 Gy). The three plans were compared for differences in the percent of rectum receiving Ͼ70 Gy. Results: Dose volume histogram (DVH) analysis revealed that the median(range) of percent rectal volume exceeding 70 Gy was 25% (12.7-41.5%), 7.5% (0.9 -19.5%), and 3.6% (0 -8.7%) for patients in whom the IR balloon was used for 0, 15, and 40 treatments, respectively. The percent of rectum exceeding 70 Gy was significantly different for all treatment plan comparisons (P Ͻ 0.0001). Conclusions: Grade 2 or higher rectal toxicity may be minimized during dose escalated 3D conformal radiation therapy through the use of an IR balloon during the 3-week cone down portion of an 8-week treatment course.
Journal of Cancer Research and Therapeutics, 2014
Purpose: A prospective study was undertaken to evaluate the influence of patient positioning on the set up variations to determine the planning target volume (PTV) margins and to evaluate the clinical relevance volume assessment of the small bowel (SB) within the irradiated volume. Materials and Methods: During the period of months from December 2011 to April 2012, a computed tomography (CT) scan was done either in supine position or in prone position using a belly board (BB) for 20 consecutive patients. All the patients had histologically proven rectal cancer and received either post-or pre-operative pelvic irradiation. Using a three-dimensional planning system, the dose-volume histogram for SB was defined in each axial CT slice. Total dose was 46-50 Gy (2 Gy/fraction), delivered using the 4-field box technique. The set up variation of the study group was assessed from the data received from the electronic portal imaging device in the linear accelerator. The shift along X, Y, and Z directions were noted. Both systematic and random errors were calculated and using both these values the PTV margin was calculated. Results: The systematic errors of patients treated in the supine position were 0.87 (X-mm), 0.66 (Y-mm), 1.6 (Z-mm) and in the prone position were 1.3 (X-mm), 0.59 (Y-mm), 1.17 (Z-mm). The random errors of patients treated in the supine positions were 1.81 (X-mm), 1.73 (Y-mm), 1.83 (Z-mm) and in prone position were 2.02 (X-mm), 1.21 (Y-mm), 3.05 (Z-mm). The calculated PTV margins in the supine position were 3.45 (X-mm), 2.87 (Y-mm), 5.31 (Z-mm) and in the prone position were 4.91 (X-mm), 2.32 (Y-mm), 5.08 (Z-mm). The mean volume of the peritoneal cavity was 648.65 cm 3 in the prone position and 1197.37 cm 3 in the supine position. Conclusion: The prone position using BB device was more effective in reducing irradiated SB volume in rectal cancer patients. There were no significant variations in the daily set up for patients treated in both supine and prone positions.
Dynamic conformal arc radiotherapy with rectum hollow-out technique for localized prostate cancer
Radiotherapy and Oncology, 2009
To report the feasibility of dynamic conformal arc radiotherapy with rectum hollow-out technique (DCAT-HO) for localized prostate cancer. Methods and materials: Between October 2000 and April 2007, 204 patients with clinically localized or locally advanced prostate cancer were treated with DCAT-HO. All patients were given neoadjuvant total androgen deprivation (AD) therapy (median 6 months, range 2-27 months). All patients with T3 or T4 stage received post-irradiation AD for 24 months. A total of 128 patients (63%) were treated with 70 Gy, and 76 patients (37%) were treated with 74 Gy. Acute and late toxicities were scored by the Radiation Therapy Oncology Group morbidity grading scales. PSA relapse was defined as three successive PSA elevations after a post-treatment nadir. The median follow-up was 37 months. Results: Both the acute Grade 2 rectal and urinary toxicities were 1.0%, and no patients experienced acute Grade 3 or higher symptoms. The 3-year rates of both P late Grade 2 rectal and urinary toxicities were 3.4%. The 3-year PSA relapse-free survival for low, intermediate, and high-risk group patients treated with 70 Gy were 54%, 75%, and 87%, respectively. Conclusions: These findings demonstrate the feasibility of DCAT-HO in a large number of patients with short follow-up. DCAT-HO reduced the volume of the rectum exposed to higher doses and this led to an overall reduction in late rectal toxicity.