Real-Time Treatment Planning Optimisation for Brachytherapy

In this paper, we present an integrated system for real-time dose distribution calculation and treatment planning optimisation for brachytherapy of prostate cancer, with a special emphasis on the visual integration of the dosimetry and target images obtained from the open magnetic resonance system. This system involves a fast method to calculate dose distributions of multiple concurrent radioactive sources, based on the combination of elements from a database of pre-calculated dose distribution maps for single sources, combined linearly to provide the final dose distribution map. Simulated annealing, in conjunction with the inverse planning method, is used to determine the source dwell times at pre-selected locations in order to optimally irradiate thetumour while preserving the surrounding healthy tissues. This algorithm, implemented in FORTRAN, is integrated into a computer-assisted treatment planning tool, written in JAVA, using the runtime class and RMI API of Java. The whole system is now under clinical testing at the Geneva University Hospital

High dose rate brachytherapy as monotherapy for localised prostate cancer : a hypofractionated two-implant approach in 351 consecutive patients

BACKGROUND: To report the clinical outcome of high dose rate brachytherapy as sole treatment for clinically localised prostate cancer. METHODS: Between March 2004 and January 2008, a total of 351 consecutive patients with clinically localised prostate cancer were treated with transrectal ultrasound guided high dose rate brachytherapy. The prescribed dose was 38.0 Gy in four fractions (two implants of two fractions each of 9.5 Gy with an interval of 14 days between the implants) delivered to an intraoperative transrectal ultrasound real-time defined planning treatment volume. Biochemical failure was defined according to the Phoenix Consensus and toxicity evaluated using the Common Toxicity Criteria for Adverse Events version 3. RESULTS: The median follow-up time was 59.3 months. The 36 and 60 month biochemical control and metastasis-free survival rates were respectively 98%, 94% and 99%, 98%. Toxicity was scored per event with 4.8% acute Grade 3 genitourinary and no acute Grade 3 gastrointestinal toxicity. Late Grade 3 genitourinary and gastrointestinal toxicity were respectively 3.4% and 1.4%. No instances of Grade 4 or greater acute or late adverse events were reported. CONCLUSIONS: Our results confirm high dose rate brachytherapy as safe and effective monotherapy for clinically organ-confined prostate cancer

Measured dose distributions of iodine-125 sources and the computerised optimisation of their positions in brachytherapy planning

Includes bibliographies.The use of 1-125 seeds in brachytherapy is widespread and becoming increasingly varied. The spatial dose distributions around two types of 1-125 seeds in general use, were measured using a Geiger-Muller chamber. Seeds with the 1-125 adsorbed onto resin spheres had a 10% less anisotropic dose distribution than seeds containing a silver wire with the 1-125 adsorbed onto it. An interpolative method was developed for fast dose calculations taking this anisotropy into account

Verification of Gynaecological Brachytherapy Treatments Using an End-to-End Phantom

High dose rate brachytherapy allows the delivery of radiation internally, with high-dose gradients creating a conformal distribution. The inherent drawback of this treatment exists within small uncertainties producing a large impact on safety and efficacy. Applicator displacement was ret-rospectively simulated for 29 cervical cancer treatments to determine a critical shift in applicator position. A 2 mm shift in the anterior and posterior directions was detrimental to the bladder and rectum, respectively and a 4 mm shift in all directions caused a critical reduction in HR-CTV cover-age. These findings indicate the importance of quality assurance practices that mitigate applicator displacement. Furthermore, the source localisation accuracy required for cervical brachytherapy was quantified. HDR gynaecological brachytherapy relies on 3D imaging, contouring, precise reconstruc-tion of applicator position and transfer of data to the afterloading device. To evaluate this process an end-to-end phantom was developed, which consists of a component that houses gynaecological applicators and the Magic Plate 987 (MP987), created by the Centre of Medical and Radiation Physics, University of Wollongong. The 21 × 22.5 cm2 silicon diode array facilitates source tracking at clinically relevant depths. A characterisation of the MP987 for HDR source tracking has been performed, producing an error in dwell time and position of 0.1s and 0.25 mm respectively, for dwell times greater than 5 s. Source tracking accuracy is a function of both dwell time and distance from detector to source. The End-to-end phantom has verified both vaginal and cervical treatments. For a vaginal treat-ment, the mean residual in dwell position is within (0.24 ± 0.01) mm for all directions, with the difference in dwell time being (0.10 ± 0.01) s. Catheter swap, indexer length and activity miscalibration errors were all detected within the vaginal therapy end-to-end test. Validation of the End-to-end phantom for a cervical brachytherapy treatment produced a mean difference of (3.49 ± 0.57) mm,(4.74 ± 0.77) mm, (6.14± 1) mm in the X, Y and Z directions respectively, with a dwell time differ-ence of (0.19 ± 0.03) s. The localisation accuracy achieved is below the critical displacement value established within the treatment planning study. Improvement in co-registration and Z localisation methodologies will provide better outcomes for cervical cases. The End-to-end phantom successfully verifies the procedure for HDR gynaecological brachytherapy treatments, enabling safe and effective patient care

Does inverse planning improve plan quality in interstitial high-dose-rate breast brachytherapy?

Purpose: To investigate the effect of input parameters for an inverse optimization algorithm, and dosimetrically evaluate and compare clinical treatment plans made by inverse and forward planning in high-dose-rate interstitial breast implants. Material and methods: By using a representative breast implant, input parameters responsible for target coverage and dose homogeneity were changed step-by-step, and their optimal values were determined. Then, effects of parameters on dosimetry of normal tissue and organs at risk were investigated. The role of dwell time modulation restriction was also studied. With optimal input parameters, treatment plans of forty-two patients were re-calculated using an inverse optimization algorithm (HIPO). Then, a pair-wise comparison between forward and inverse plans was performed using dose-volume parameters. Results: To find a compromise between target coverage and dose homogeneity, we recommend using weight factors in the range of 70-90 for minimum dose, and in the range of 10-30 for maximum dose. Maximum dose value of 120% with a weight factor of 5 is recommended for normal tissue. Dose constraints for organs at risk did not play an important role, and the dwell time gradient restriction had only minor effect on target dosimetry. In clinical treatment plans, at identical target coverage, the inverse planning significantly increased the dose conformality (COIN, 0.75 vs. 0.69, p < 0.0001) and improved the homogeneity (DNR, 0.35 vs. 0.39, p = 0.0027), as compared to forward planning. All dosimetric parameters for non-target breast, ipsilateral lung, ribs, and heart were significantly better with inverse planning. The most exposed small volumes for skin were less in HIPO plans, but without statistical significance. Volume irradiated by 5% was 173.5 cm(3) in forward and 167.7 cm(3) in inverse plans (p = 0.0247). Conclusions: By using appropriate input parameters, inverse planning can provide dosimetrically superior dose distributions over forward planning in interstitial breast implants

Innovations in Radiotherapy Technology.

Many low- and middle-income countries, together with remote and low socioeconomic populations within high-income countries, lack the resources and services to deal with cancer. The challenges in upgrading or introducing the necessary services are enormous, from screening and diagnosis to radiotherapy planning/treatment and quality assurance. There are severe shortages not only in equipment, but also in the capacity to train, recruit and retain staff as well as in their ongoing professional development via effective international peer-review and collaboration. Here we describe some examples of emerging technology innovations based on real-time software and cloud-based capabilities that have the potential to redress some of these areas. These include: (i) automatic treatment planning to reduce physics staffing shortages, (ii) real-time image-guided adaptive radiotherapy technologies, (iii) fixed-beam radiotherapy treatment units that use patient (rather than gantry) rotation to reduce infrastructure costs and staff-to-patient ratios, (iv) cloud-based infrastructure programmes to facilitate international collaboration and quality assurance and (v) high dose rate mobile cobalt brachytherapy techniques for intraoperative radiotherapy