No abstract available.
Brachytherapy/*methods ; Female ; Humans ; Radiotherapy, Conformal/*methods ; Ultrasonography, Interventional/*methods ; Uterine Cervical Neoplasms/*radiography

BACKGROUNDA novel radioactive 125I seed-loaded biliary stent has been used for patients with malignant biliary obstruction. However, the dosimetric characteristics of the stents remain unclear. Therefore, we aimed to describe the dosimetry of the stents of different lengths - with different number as well as activities of 125I seeds.

METHODSThe radiation dosimetry of three representative radioactive stent models was evaluated using a treatment planning system (TPS), thermoluminescent dosimeter (TLD) measurements, and Monte Carlo (MC) simulations. In the process of TPS calculation and TLD measurement, two different water-equivalent phantoms were designed to obtain cumulative radial dose distribution. Calibration procedures using TLD in the designed phantom were also conducted. MC simulations were performed using the Monte Carlo N-Particle eXtended version 2.5 general purpose code to calculate the radioactive stent's three-dimensional dose rate distribution in liquid water. Analysis of covariance was used to examine the factors influencing radial dose distribution of the radioactive stent.

RESULTSThe maximum reduction in cumulative radial dose was 26% when the seed activity changed from 0.5 mCi to 0.4 mCi for the same length of radioactive stents. The TLD's dose response in the range of 0-10 mGy irradiation by 137Cs γ-ray was linear: y = 182225x - 6651.9 (R2=0.99152; y is the irradiation dose in mGy, x is the TLDs' reading in nC). When TLDs were irradiated by different energy radiation sources to a dose of 1 mGy, reading of TLDs was different. Doses at a distance of 0.1 cm from the three stents' surface simulated by MC were 79, 93, and 97 Gy.

CONCLUSIONSTPS calculation, TLD measurement, and MC simulation were performed and were found to be in good agreement. Although the whole experiment was conducted in water-equivalent phantom, data in our evaluation may provide a theoretical basis for dosimetry for the clinical application.

Brachytherapy ; methods ; Computer Simulation ; Humans ; Monte Carlo Method ; Radiometry ; methods ; Thermoluminescent Dosimetry ; methods

No abstract available.
Brachytherapy/*methods ; Female ; Humans ; Radiotherapy, Conformal/*methods ; Ultrasonography, Interventional/*methods ; Uterine Cervical Neoplasms/*radiography

Soft tissue is one kind of elastic tissue which includes the blood vessel and nerve, and brachytherapy is a radioactive and non-invasive way for the treatment of cancer in which soft tissue is always deformed. Aiming at this soft tissue-induced-problem, the present authors have made a research on the trajectory planning in operation. The 3D artificial potential field of organ is set up by the function definition of cancer attracting force and blood vessel repulsion force, the dynamic finite element model is also built for the important displacement parameters of deformation node in needle invasion process. Moreover, the minimum potential direction in each node, and the static and dynamic trajectory planning are investigated. Finally, the experimental simulation shows the validation and correctness of the above-mentioned method.
Brachytherapy ; methods ; Computer Simulation ; Connective Tissue ; physiology ; Elasticity ; Hardness ; Humans ; Needles ; Punctures ; methods

It is well known that intracavitary radiotherapy (ICR), either alone or in combination with external-beam radiotherapy (EBRT) is an essential component of the radiation treatment of uterine cervical cancer. Although low-dose-rate (LDR) brachytherapy has been successfully applied to the management of such patients, several radiation oncologists have experience of using high-dose-rate (HDR) brachytherapy with promising clinical results over the past 4 decades. However, there has been a considerable reluctance by radiation oncologists and gynecologists in North America to employ the HDR remote afterloading technique instead of the more firmly established LDR treatment modality. In contrast, the HDR-ICR system is rapidly gaining acceptance in Korea since the introduction of the Ralstron, remotely controlled afterloading system using HDR Co-60 sources, at the Yonsei Cancer Center in 1979. According to brachytherapy statistics reported by the Korean Society of Therapeutic Radiology and Oncology, in 1997, brachytherapy was performed upon 1,758 Korean patients with uterine cervical cancer, of whom approximately 83% received HDR brachytherapy. In this review, we present our experiences of HDR-ICR for the treatment of uterine cervical cancer. In addition, we discuss the controversial points, which are raised by those considering the use of HDR-ICR for uterine cervical cancer; these issues include physical and radiobiological considerations, and the prospect of future technical improvements.
Brachytherapy/*methods ; Cervix Neoplasms/*radiotherapy ; Dose Fractionation ; Female ; Human ; Radiotherapy Planning, Computer-Assisted

Commercially available rectal retractors can be used in high dose rate intracavitary brachytherapy (HDR ICR) as one of the methods for reducing the rectal dose in radiotherapy for a uterine cervical cancer. However, the extent of the rectal protection achieved using these rectal retractors has not been reported. The aim of the study was to examine the effect of a rectal retractor on reducing the rectal dose in HDR ICR. Thirty patients were treated with HDR ICR using rectal retractors. Tandem and ovoids were applied in 15 patients and ovoids only were used in the other 15 patients. During the simulation, the rectum was filled with barium, and anteroposterior and lateral radiographs were then taken with and without the rectal retractor. Along the anterior rectal wall outlined, 4 to 8 points (median 6) were chosen to calculate the dose for each patient including the rectal point (RP), which is an author-defined rectal point modified from the definition of the rectal reference point in the ICRU report 38. The length of the measured rectum was 3-7 cm (median 5 cm). The bladder point (BP) dose was measured as recommended by the ICRU. The prescription doses to point A varied from 3.5 to 5 Gy (median 4 Gy). Paired comparisons were made on the individual patients by calculating the normalized mean doses of the RP, the maximal point (MP), and the longitudinal average (LA) with and without the rectal retractor. The doses to the bladder points (BP) were also calculated in parallel to the rectal points. The anterior rectal walls were displaced posteriorly after inserting the rectal retractor. In the tandem and ovoids group, the number of patients with a reduced dose in the RP, MP and LA were 14 (93.3%), 12 (80.0%) and 13 (86.7%), respectively. In the ovoids only group, the corresponding figures were 14 (93.3%), 14 (93.3%) and 14 (93.3%). In the tandem and ovoids group, the reduced dose in the RP, MP, and LA dose were 0.52 Gy (13.0%), 0.50 Gy (12.5%), and 0.39 Gy (9.8%), respectively (p < 0.05). In the ovoids only group, the RP, MP, and LA dose were reduced by 0.62 Gy (15.5%), 0.92 Gy (23.0%), and 0.54 Gy (13.5%), respectively (p < 0.05). There was no significant change in the bladder point doses when the rectal retractor was applied, although the mean BP dose were 0.27 Gy and 0.09 Gy lower for the tandem and ovoids group and for ovoids only group, respectively (p > 0.05). The mean RP, MP, and LA dose reduction rates of the patient subgroup where the RP dose was < 70% of the prescription dose were compared with the subgroup where the RP dose was > 70%. The effect of the rectal dose reduction was significant only in the subgroup of patients who received > 70% of the prescription dose (p < 0.05). The use of the rectal retractor was a simple and an effective method for reducing the rectal dose. It was also considered to be a highly reproducible method, which can replace the time-consuming vaginal gauze packing in HDR-ICR.
Brachytherapy/*instrumentation/methods ; Cervix Neoplasms/*radiotherapy ; Female ; Human ; Radiotherapy Dosage ; *Rectum ; Surgical Instruments ; Vagina

OBJECTIVETo verify the feasibility of setup error verification by observing patents' source-skin distance (SSD) for patients of head tumor.

METHODSFilms for 21 patients with head tumor were recorded using simulator (Varian Acuity 8.6), and comparison with reference digitally reconstructed radiograph (DRR) from Treatment plan system (TPS). The deviation of setup for 21 patients in the left-right, anterior-posterior and superior-inferior directions were measured by using 2D match, and SSD error was recorded when gantry angle was 0 degrees, 45 degrees, 315 degrees. Then setup error and corresponding SSD error were analyzed.

RESULTSThe systematic errors and random errors of 21 patients in the left-right, anterior-posterior and superior-inferior directions were (1.1 +/- 11.6) mm, (0.7 +/- 1.2) mm, (0.9 +/- 1.5) mm, and (1.51 +/- 3.1) mm, (1.05 +/- 3.3) mm, (1.60 +/- 2.3) mm. The systematic SSD errors and random SSD errors were (1.25 +/- 1.3) mm, (1.04 +/- 1.3) mm. (1.10 +/- 2.3) mm, and (2.03 +/- 1.7) mm, (2.81 +/- 2.3) mm, (2.33 +/- 3.0) mm for gantry angle was 0 degrees, 45 degrees, 315 degrees, respectively.

CONCLUSIONSIt is simple and feasible for setup error verification by observing patients' SSD and can be auxiliary to other verification means.

Algorithms ; Brachytherapy ; methods ; Feasibility Studies ; Head and Neck Neoplasms ; radiotherapy ; Humans ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted

OBJECTIVETo investigate the effect on the dose distribution of source position displacement with the target region margin in catheter-based 192Ir line source endovascular brachytherapy.

METHODDose rate distribution along longitudinal axes was estimated by the formula recommended by AAPM No.60 and No. 43.

RESULTSIn the two cases of source displacement (1.1 and 5 mm) doses of target region margin was decreased dramatically (at most 53.9% and 565.8% respectively) were compared to that of no source displacement, and the affected range was 6 mm and 9 mm respectively.

CONCLUSIONSource displacement will lead to the decrease of dose in target region margin.

Animals ; Brachytherapy ; methods ; Coronary Restenosis ; radiotherapy ; Coronary Vessels ; radiation effects ; Iridium Radioisotopes ; therapeutic use ; Radiotherapy Dosage

OBJECTIVETo design a new afterloading brachytherapy simulation system based on CT images.

METHODSThis paper mainly focuses on the anthropomorphic pelvic phantom spiled by three pipelines and the nasopharyngeal carcinoma spiled by two pipelines. Microsoft Visual C++ was used to parse CT images for some information, then to reconstruct pipelines in the body of phantom or the patient and to give the three-dimensional coordinate of dwelling points. The dose distribution displayed on CT images was processed by the dose distribution calculation methods near single afterloading source and the dose optimization methods. VTK technology was used in the 3D display in the system.

RESULTSAccording to the reference points applied by doctors, the system can calculate reversely the dwelling time of dwelling points in pipelines and get satisfying dose distribution on CT images. Besides, it can reflect the 3D relationship between the dose volume and the normal tissues.

CONCLUSIONSThis system overcomes some deficiencies of 2D afterloading brachytherapy simulation system based on X-ray films which are used widely in China. It supplies 3D display of dose distribution for clinical doctors. At present, the system is being tested in clinics.

Brachytherapy ; methods ; Computer Simulation ; Imaging, Three-Dimensional ; Software ; Tomography, X-Ray Computed

BACKGROUNDPercutaneous brachytherapy is a valuable method for the treatment of lung cancer and mediastinal lymph nodes metastasis. However, in some of the metastatic lymph nodes in the middle mediastinum, the percutaneous approach cannot be used safely due to possible damage to surrounding anatomical structures. We established an animal model (group of 12 pigs) to assess the safety and feasibility of computed tomography (CT)-guided vena cava puncture.

METHODSUnder CT guidance, an 18G needle was used to puncture the anterior wall of the anterior vena cava (AVC) in 12 pigs. The 18G needle was chosen as it is similar in size to the needles employed for clinical application in brachytherapy. The incidence of complications and vital signs was monitored during the procedure. Thoracotomy was performed to remove AVC specimens, which were analyzed for histological evidence of vessel wall damage and repair.

RESULTSFollowing postoperative enhanced CT, two animals were found to have a small pneumothorax (one being hemopneumothorax). The intraoperative oxygen saturation of both animals was not significantly decreased and was maintained at 93-100%. No animals developed mediastinal hematoma. Preoperative, intraoperative, and postoperative changes in blood pressure, heart rate, hemoglobin, and blood oxygen saturation were not significant. Histological evaluation of AVC specimens showed that by 7 days following the procedure, the endothelial layer was smooth with notable scar repair in the muscularis layer.

CONCLUSIONSCT performed after the procedure and histological preparations confirmed the safety of the procedure. This indicates that percutaneous brachytherapy for metastatic middle mediastinal lymph nodes can be carried out via the superior vena cava.

Animals ; Brachytherapy ; methods ; Lung Neoplasms ; radiotherapy ; Lymphatic Metastasis ; radiotherapy ; Swine ; Tomography, X-Ray Computed