Estimated Incidence and Projections of Treatment Cost for Vision-threatening Diabetic Retinopathy in Korea

Purpose@#To analyze the incidence and treatment costs associated with vision-threatening diabetic retinopathy (VTDR) in type 2 diabetes and to predict future VTDR populations and treatment expenditures. @*Methods@#Using the data from the National Health Insurance Service from 2006 to 2017, we analyzed VTDR treatment costs by year, sex, and age. Based on the results and changes in future population distributions, we estimated the future number and cost of treatments for VTDR. @*Results@#The number of treatments increased by 2.5-fold from 37,634 in 2006 to 96,214 in 2017, and treatment costs increased 3.4-fold from $13,528,587 in 2006 to $45,643,561 in 2017. When analyzed by year, age, and sex, all showed an increasing trend. Future number of treatments was estimated to increase from approximately 96,000 in 2017 to 220,000 by 2030 and treatment costs were projected to increase by 129% from about $45,643,561 in 2017 to about $1,043,055,262 by 2030. @*Conclusions@#As the incidence of VTDR rises due to an aging population and the frequency of intravitreal injections increases due to insurance reimbursement, future treatment expenditures for VTDR are expected to increase as well. Therefore, appropriate policies must be put in place now to secure medical and financial resources to manage VTDR and reduce medical expenditures in the future.

Evaluation of the Secondary Particle Effect in Inhomogeneous Media for Proton Therapy Using Geant4 Based MC Simulation / 의학물리

In proton therapy, the analysis of secondary particles is important due to delivered dose outside the target volume and thus increased potential risk for the development of secondary cancer. The purpose of this study is to analyze the influence of secondary particles from proton beams on fluence and energy deposition in the presence of inhomogeneous material by using Geant4 simulation toolkit. The inhomogeneity was modeled with the condition that the adipose tissue, bone and lung equivalent slab with thickness of 2 cm were inserted at 30% (Plateau region) and 80% (Bragg peak region) dose points of maximum dose in Bragg curve. The energy of proton was varied with 100, 130, 160 and 190 MeV for energy dependency. The results for secondary particles were presented for the fluence and deposited energy of secondary particles at inhomogeneous condition. Our study demonstrates that the fluence of secondary particles is neither influenced insertion of inhomogeneties nor the energy of initial proton, while there is a little effect by material density. The deposited energy of secondary particles has a difference in the position placed inhomogeneous materials. In the Plateau region, deposited energy of secondary particles mostly depends on the density of inserted materials. Deposited energy in the Bragg region, in otherwise, is influenced by both density of inserted material and initial energy of proton beams. Our results suggest a possibility of prediction about the distribution of secondary particles within complex heterogeneity.

Precision Validation of Electromagnetic Physics in Geant4 Simulation for Proton Therapy / 의학물리

Geant4 (GEometry ANd Tracking) provides various packages specialized in modeling electromagnetic interactions. The validation of Geant4 physics models is a significant issue for the applications of Geant4 based simulation in medical physics. The purpose of this study is to evaluate accuracy of Geant4 electromagnetic physics for proton therapy. The validation was performed both the Continuous slowing down approximation (CSDA) range and the stopping power. In each test, the reliability of the electromagnetic models in a selected group of materials was evaluated such as water, bone, adipose tissue and various atomic elements. Results of Geant4 simulation were compared with the National Institute of Standards and Technology (NIST) reference data. As results of comparison about water, bone and adipose tissue, average percent difference of CSDA range were presented 1.0%, 1.4% and 1.4%, respectively. Average percent difference of stopping power were presented 0.7%, 1.0% and 1.3%, respectively. The data were analyzed through the kolmogorov-smirnov Goodness-of-Fit statistical analysis test. All the results from electromagnetic models showed a good agreement with the reference data, where all the corresponding p-values are higher than the confidence level alpha=0.05 set.

A Monte Carlo Simulation Study of a Therapeutic Proton Beam Delivery System Using the Geant4 Code / 의학물리

We studied a Monte Carlo simulation of the proton beam delivery system at the National Cancer Center (NCC) using the Geant4 Monte Carlo toolkit and tested its feasibility as a dose verification framework. The Monte Carlo technique for dose calculation methodology has been recognized as the most accurate way for understanding the dose distribution in given materials. In order to take advantage of this methodology for application to externalbeam radiotherapy, a precise modeling of the nozzle elements along with the beam delivery path and correct initial beam characteristics are mandatory. Among three different treatment modes, double/single.scattering, uniform scanning and pencil beam scanning, we have modeled and simulated the double.scattering mode for the nozzle elements, including all components and varying the time and space with the Geant4.8.2 Monte Carlo code. We have obtained simulation data that showed an excellent correlation to the measured dose distributions at a specific treatment depth. We successfully set up the Monte Carlo simulation platform for the NCC proton therapy facility. It can be adapted to the precise dosimetry for therapeutic proton beam use at the NCC. Additional Monte Carlo work for the full proton beam energy range can be performed.