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.
Proton Therapy ; Protons* ; Radiotherapy

This study examined the dosimetric influence of implanted gold markers in proton therapy and the effects of their positions in the spread-out Bragg peak (SOBP) proton beam. The implanted cylindrical gold markers were 3 mm long and 1.2 mm in diameter. The dosimetric influence of the gold markers was determined with markers at various locations in a proton-beam field. Spatial dose distributions were measured using a three-dimensional moving water phantom and a stereotactic diode detector with an effective diameter of 0.5 mm. Also, a film dosimetry was performed using Gafchromic External Beam Treatment (EBT) film. The GEANT4 simulation toolkit was used for Monte-Carlo simulations to confirm the measurements and to construct the dose-volume histogram with implanting markers. Motion data were obtained from the portal images of 10 patients to investigate the effect of organ motions on the dosimetric influence of markers in the presence of a rectal balloon. The underdosed volume due to a single gold marker, in which the dose was less than 95% of a prescribed amount, was 0.15 cc. The underdosed volume due to the presence of a gold marker is much smaller than the target volume. However, the underdosed volume is inside the gross tumor volume and is not smeared out due to translational prostate motions. The positions of gold markers and the conditions of the proton-beam field give different impacts on the dose distribution of a target with implanted gold markers, and should be considered in all clinical proton-based therapies.
Film Dosimetry ; Humans ; Prostate ; Prostatic Neoplasms ; Proton Therapy ; Protons ; Tumor Burden ; Water

TomoTherapy has a merit to treat cancer with Intensity modulated radiation and combines precise 3-D imaging from computerized tomography (CT scanning) with highly targeted radiation beams and rotating beamlets. In this paper, we comparing the dose distribution between TomoTherapy and linear accelerator based intensity modulated radiotherapy (IMRT) for 10 Head & Neck patients using TomoTherapy which is newly installed and operated at National Cancer Center since Sept. 2006. Furthermore, we estimate how the homogeneity and Normal Tissue Complication Probability (NTCP) are changed by motion of target. Inverse planning was carried out using CadPlan planning system (CadPlan R.6.4.7, Varian Medical System Inc. 3100 Hansen Way, Palo Alto, CA 94304-1129, USA). For each patient, an inverse IMRT plan was also made using TomoTherapy Hi-Art System (Hi-Art2_2_4 2.2.4.15, TomoTherapy Incorporated, 1240 Deming Way, Madson, WI 53717-1954, USA) and using the same targets and optimization goals. All TomoTherapy plans compared favorably with the IMRT plans regarding sparing of the organs at risk and keeping an equivalent target dose homogeneity. Our results suggest that TomoTherapy is able to reduce the normal tissue complication probability (NTCP) further, keeping a similar target dose homogeneity.
Head ; Humans ; Imaging, Three-Dimensional ; Neck ; Organs at Risk ; Particle Accelerators ; Radiotherapy, Intensity-Modulated

The main benefit of proton therapy over photon beam radiotherapy is the absence of exit dose, which offers the opportunity for highly conformal dose distributions to target volume while simultaneously irradiating less normal tissue. For proton beam therapy two patient specific beam modifying devices are used. The aperture is used to shape the transverse extension of the proton beam to the shape of the tumor target and a patient-specific compensator attached to the block aperture when required and used to modify the beam range as required by the treatment plan for the patient. A block of range shifting material, shaped on one face in such a way that the distal end of the proton field in the patient takes the shape of the distal end of the target volume. The mechanical quality assurance of range compensator is an essential procedure to confirm the 3 dimensional patient-specific dose distributions. We proposed a new quality assurance method for range compensator based on image processing using X-ray tube of proton therapy treatment room. The depth information, boundaries of each depth of plan compensatorfile and x-ray image of compensator were analyzed and presented over 80% matching results with proposed QA program.
Humans ; Proton Therapy ; Protons

Hemorrhage into the esophagus due to aortoesophageal communication is very rare but life-threatening with high morbidity and mortality. Because of this, most cases of aortoesophageal fistula are confirmed by autopsy. However, we report herein a case of a 62-year-old male with an aortoesophageal fistula who was successfully treated with endovascular stent-grafting. The patient had undergone esophageal stent insertion due to esophageal cancer and experienced hematemesis and hemodynamic shock due to an aortoesophageal fistula. Emergency endoscopy was unable to identify the source of the hemorrhage due to massive bleeding. Computed tomography of the chest revealed a focal pseudoaneurysm at the descending aorta and diffuse thinning of the esophageal wall, which were treated with endovascular stent-grafting. Although aortoesophageal fistulas are usually fatal, implantation of a covered stent into the esophagus may help prevent massive bleeding, providing valuable time to treat the patient.
Aneurysm, False ; Aorta, Thoracic ; Autopsy ; Blood Vessel Prosthesis* ; Emergencies ; Endoscopy ; Esophageal Neoplasms* ; Esophagus ; Fistula* ; Hematemesis ; Hemodynamics ; Hemorrhage ; Humans ; Male ; Middle Aged ; Mortality ; Shock ; Stents ; Thorax

Purpose: Since the introduction of robotic surgery, robots for colorectal cancer have replaced laparoscopic surgery, and a single-port robot (SPR) platform has been launched and is being used to treat patients. We analyzed the learning curve and initial complications of using an SPR platform in colorectal cancer surgery. Methods: We reviewed 39 patients who underwent SPR colectomy from April to October 2019. All surgeries were performed by the same surgeon using an SPR device. A learning curve was generated using the cumulative sum methodology to assess changes in total operation time, docking time, and surgeon console time. We grouped the patients into 3 groups according to the time period: the first 11 were phase 1, the next 11 were phase 2, and the last 17 were phase 3. Results: The mean age of the patients was 61.28±13.03 years, and they had a mean body mass index of 23.79±2.86 kg/m2. Among the patients, 23 (59.0%) were male, and 16 (41.0%) were female. The average operation time was 186.59±51.30 minutes, the average surgeon console time was 95.49±35.33 minutes, and the average docking time (time from skin incision to robot docking) was 14.87±10.38 minutes. The surgeon console time differed significantly among the different phases (P<0.001). Complications occurred in 8 patients: 2 ileus, 2 postoperation hemoglobin changes, 3 urinary retentions, and 1 complicated fluid collection. Conclusion In our experience, the learning curve for SPR colectomy was achieved after the 18th case.

Proton therapy facility, which is recently installed at National Cancer Center in Korea, generally produces a large amount of radiation near cyclotron due to the secondary particles and radioisotopes caused by collision between proton and nearby materials during the acceleration. Although the level of radiation by radioisotope decreases in length of time, radiation exposure problem still exists since workers are easily exposed by a low level of radiation for a long time due to their job assignment for maintenance or repair of the proton facility. In this paper, the working environment near cyclotron, where the highest radiation exposure is expected, was studied by measuring the degree of radiation and its duration for an appropriate level of protective action guide. To do this, we measured the radiation change in the graphite based energy degrader, the efficiency of transmitted beam and relative activation degree of the transmission beam line. The results showed that while the level of radiation exposure around cyclotron and beam line during the operation is much higher than the other radiation therapy facilities, the radiation exposure rate per year is under the limit recommended by the law showing 1~3 mSv/year.
Acceleration ; Cyclotrons ; Gamma Rays ; Graphite ; Jurisprudence ; Korea ; Proton Therapy ; Protons ; Radioisotopes