HIPO model

Abstract: In this work the problem of determination of the optimal catheter position and source loading in HDR prostate brachytherapy is modeled as a Mixed Integer Linear Programming (MILP) problem and solved by ILOG CPLEX. The results are compared to those of HIPO, a state of the art inverse treatment plan optimization algorithm. Given that MILP is guaranteed to find the global optimum, it provides the baseline for the evaluation of HIPO solutions. The quality of 12 clinical HDR brachytherapy implants for prostate utilizing HIPO, for dwell time optimization only, has been compared to alternative plans with Linear Programming (LP). All common dose-volume indices for the prostate and the organs at risk have been considered. Our results demonstrate that in the case of dwell time optimization, HIPO delivers high quality plans and the differences to the LP solutions are statistically insignificant (p > 0.05) for all indices examined. In the case of combined catheter position and dwell time optimization, the results for 3 clinical cases have been compared. MILP was able to deliver the optimal solution only for one simple case and upper- lower bounds for the rest. The plans produced by HIPO were clinically acceptable, close and clinically equivalent to the global optimum or the upper bounds delivered by MILP for all 3 cases.

Abstract: Seven patients with intractable hiccups were treated with a calcium channel blocker, nifedipine. A daily dose of 30 to 60 mg of this drug stopped hiccups in 4 patients and improved them in a 5th patient. In 2 patients hiccups recurred within 24 hours after stopping nifedipine. Nifedipine can be effective against intractable hiccups in some patients.

Abstract: Publications have reported the benefits of using high-dose-rate brachytherapy (HDRB) for the treatment of prostate cancer, since it provides similar biochemical control as other treatments while showing lowest long-term complications to the organs at risk (OAR). With the inclusion of anatomy-based inverse planning opti- mizers, HDRB has the advantage of potentially allowing dose escalation. Among the algorithms used, the Inverse Planning Simulated Annealing (IPSA) optimizer is widely employed since it provides adequate dose coverage, minimizing dose to the OAR, but it is known to generate large dwell times in particular positions of the catheter. As an alternative, the Hybrid Inverse treatment Planning Optimization (HIPO) algorithm was recently implemented in Oncentra Brachytherapy V. 4.3. The aim of this work was to compare, with the aid of radiobiological models, plans obtained with IPSA and HIPO to assess their use in our clinical practice. Thirty patients were calculated with IPSA and HIPO to achieve our department's clinical constraints. To evaluate their performance, dosimetric data were collected: Prostate PTV D90(%), V100(%), V150(%), and V200(%), Urethra D10(%), Rectum D2cc(%), and conformity indices. Additionally tumor control probability (TCP) and normal tissue complication probability (NTCP) were calculated with the BioSuite software. The HIPO optimization was performed firstly with Prostate PTV (HIPOPTV) and then with Urethra as priority 1 (HIPOurethra). Initial optimization constraints were then modified to see the effects on dosimetric parameters, TCPs, and NTCPs. HIPO optimizations could reduce TCPs up to 10%-20% for all PTVs lower than 74 cm3. For the urethra, IPSA and HIPOurethra provided similar NTCPs for the majority of volume sizes, whereas HIPOPTV resulted in large NTCP values. These findings were in agreement with dosimetric values. By increasing the PTV maximum dose constraints for HIPOurethra plans, TCPs were found to be in agreement with IPSA without affecting the urethral NTCPs.