Thomas Brun1, Jean-Marc Bachaud2, Pierre Graff-Cailleaud2, Bernard Malavaud3, Daniel Portalez4, Christian Popotte5, Richard Aziza6, Amélie Lusque7, Thomas Filleron7, Soléakhéna Ken8. 1. Institut Claudius Regaud, Institut Universitaire du Cancer de Toulouse - Oncopôle, Department of Engineering and Medical Physics, Toulouse, France. Electronic address: brun.thomas@iuct-oncopole.fr. 2. Institut Claudius Regaud, Institut Universitaire du Cancer de Toulouse - Oncopôle, Department of Radiotherapy, Toulouse, France. 3. Centre Hospitalier Universitaire de Rangueil, Department of Urology, Toulouse, France. 4. Centre Hospitalier Universitaire de Rangueil, Department of Urology, Toulouse, France; Institut Claudius Regaud, Institut Universitaire du Cancer de Toulouse - Oncopôle, Department of Medical Imaging, Toulouse, France. 5. Université Paul Sabatier, Toulouse III, Toulouse, France. 6. Institut Claudius Regaud, Institut Universitaire du Cancer de Toulouse - Oncopôle, Department of Medical Imaging, Toulouse, France. 7. Institut Claudius Regaud, Institut Universitaire du Cancer de Toulouse - Oncopôle, Clinical Trials Office, Toulouse, France. 8. Institut Claudius Regaud, Institut Universitaire du Cancer de Toulouse - Oncopôle, Department of Engineering and Medical Physics, Toulouse, France.
Abstract
PURPOSE: To present the feasibility study of optimal dose coverage in ultra-focal brachytherapy (UFB) with multiparametric MRI for low- and intermediate-risk prostate cancer. METHODS AND MATERIALS: UFB provisional dose plans for small target volumes (<7 cc) were calculated on a prostate training phantom to optimize the seeds number and strength. Clinical UFB consisted in a contour-based nonrigid registration (MRI/Ultrasound) to implant a fiducial marker at the location of the tumor focus. Dosimetry was performed with iodine-125 seeds and a prescribed dose of 160 Gy. On CT scans acquired at 1 month, dose coverage of 152 Gy to the ultra-focal gross tumor volume was evaluated. Registrations between magnetic resonance and CT scans were assessed on the first 8 patients with three software solutions: VariSeed, 3D Slicer, and Mirada, and quantitative evaluations of the registrations were performed. Impact of these registrations on the initial dose matrix was performed. RESULTS: Mean differences between simulated dose plans and extrapolated Bard nomogram for UFB volumes were 36.3% (26-56) for the total activity, 18.3% (10-30) for seed strength, and 22.5% (16-38) for number of seeds. Registration method implemented in Mirada performed significantly better than VariSeed and 3D Slicer (p = 0.0117 and p = 0.0357, respectively). For dose plan evaluation between Mirada and VariSeed, D100% (Gy) for ultra-focal gross tumor volume had a mean difference of 28.06 Gy, mean values being still above the objective of 152 Gy. D90% for the prostate had a mean difference of 1.17 Gy. For urethra and rectum, dose limits were far below the recommendations. CONCLUSIONS: This UFB study confirmed the possibility to treat with optimal dose coverage target volumes smaller than 7 cc.
PURPOSE: To present the feasibility study of optimal dose coverage in ultra-focal brachytherapy (UFB) with multiparametric MRI for low- and intermediate-risk prostate cancer. METHODS AND MATERIALS: UFB provisional dose plans for small target volumes (<7 cc) were calculated on a prostate training phantom to optimize the seeds number and strength. Clinical UFB consisted in a contour-based nonrigid registration (MRI/Ultrasound) to implant a fiducial marker at the location of the tumor focus. Dosimetry was performed with iodine-125 seeds and a prescribed dose of 160 Gy. On CT scans acquired at 1 month, dose coverage of 152 Gy to the ultra-focal gross tumor volume was evaluated. Registrations between magnetic resonance and CT scans were assessed on the first 8 patients with three software solutions: VariSeed, 3D Slicer, and Mirada, and quantitative evaluations of the registrations were performed. Impact of these registrations on the initial dose matrix was performed. RESULTS: Mean differences between simulated dose plans and extrapolated Bard nomogram for UFB volumes were 36.3% (26-56) for the total activity, 18.3% (10-30) for seed strength, and 22.5% (16-38) for number of seeds. Registration method implemented in Mirada performed significantly better than VariSeed and 3D Slicer (p = 0.0117 and p = 0.0357, respectively). For dose plan evaluation between Mirada and VariSeed, D100% (Gy) for ultra-focal gross tumor volume had a mean difference of 28.06 Gy, mean values being still above the objective of 152 Gy. D90% for the prostate had a mean difference of 1.17 Gy. For urethra and rectum, dose limits were far below the recommendations. CONCLUSIONS: This UFB study confirmed the possibility to treat with optimal dose coverage target volumes smaller than 7 cc.
Authors: Tae Heon Kim; Jong Nyeong Kim; Young Dong Yu; Seung Ryeol Lee; Young Kwon Hong; Hyun Soo Shin; Dong Soo Park Journal: J Contemp Brachytherapy Date: 2020-10-30