Research progress of 125I radioactive seed interstitial brachytherapy in the treatment for pelvic malignancies / 中华放射医学与防护杂志

Brachytherapy with 125I radioactive seed has the advantages of low dose-rate,comtinuous irradiation and repeated implantation to inhibit the replication of tumor cells,and the repeatable implantation.It has been widely used in the treatment for cervial cancer,and can also be applied to pelvic malignancies,including ovarian cancer,colorectal cancer,bladder cancer.Compared with external beam radiotherapy,it can improve the dose of target region to control tumor effectively.At the same time,it can protect the normal tissues and reduce the occurrence of complications.In this paper,we summarized the speciahy,function mechanism,complications and application status of radioactive 125I seed interstitial implantation in the treatment of pelvic malignancies.The application of three dimensional printing in brachytherapy with radioactive 125I seed was also introduced.This review can provide a reliable basis for future standardized seed implantation treatment for pelvic malignancies.

Influence of Couch and Collimator on Dose Distribution of RapidArc Treatment Planning for Prostate Cancer in Radiation Therapy / 의학물리

We investigated the influence of photon energy, couch and collimator angle differences between arcs on dose distribution of RapidArc treatment planning for prostate cancer. RapidArc plans were created for 6 MV and 10 MV photons using 2 arcs coplanar and noncoplanar fields. The collimator angle differences between two arcs were 0degrees, 15degrees, 30degrees, 45degrees, 60degrees, 75degrees and 90degrees. The plans were optimized using same dose constrains for target and OAR (organ at risk). To evaluate the dose distribution, plans were analyzed using CI (conformity index), HI (homogeneity index), QOC (quality of coverage), etc. Photon energy, couch and collimator angle differences between arcs had a little influence on the target and OAR. The difference of dosimetric indices was less than 3.6% in the target and OAR. However, there was significant increase in the region exposed to low dose. The increase of V15% in the femur was 6.4% (left) and 5.5% (right) for the 6 MV treatment plan and 23.4% (left), 24.1% (right) for the noncoplanar plan. The increase of V10% in the Far Region distant from target was 54.2 cc for the 6 MV photon energy, 343.4 cc for the noncoplanar and 457.8 cc for the no collimator rotation between arcs.

Quality Assurance in Intensity Modulated Radiation Theray / 영남의대학술지

Intensity-modulated radiation therapy (IMRT) is believed to be one of the best radiation treatment techniques. IMRT is able to deliver fatal doses of radiation to the tumor region with minimal exposure of critical organs. It is essential to have a comprehensive quality assurance program to assure precision and accuracy in treatment, due to the character of IMRT. We applied quality assurance technique to the Eclipse treatment planning system and sought to determine its effectiveness in patient treatment planning. An acrylic phantom, film, and an ionization chamber were used in this study.

A Comprehensive Computer Program for Monitor Unit Calculation and Beam Data Management: Independent Verification of Radiation Treatment Planning Systems / 의학물리

We developed a user-friendly program to independently verify monitor units (MUs) calculated by radiation treatment planning systems (RTPS), as well as to manage beam database in clinic. The off-axis factor, beam hardening effect, inhomogeneity correction, and the different depth correction were incorporated into the program algorithm to improve the accuracy in calculated MUs. A beam database in the program was supposed to use measured data from routine quality assurance (QA) processes for timely update. To enhance user's convenience, a graphic user interface (GUI) was developed by using Visual Basic for Application. In order to evaluate the accuracy of the program for various treatment conditions, the MU comparisons were made for 213 cases of phantom and for 108 cases of 17 patients treated by 3D conformal radiation therapy. The MUs calculated by the program and calculated by the RTPS showed a fair agreement within +/-3% for the phantom and +/-5% for the patient, except for the cases of extreme inhomogeneity. By using Visual Basic for Application and Microsoft Excel worksheet interface, the program can automatically generate beam data book for clinical reference and the comparison template for the beam data management. The program developed in this study can be used to verify the accuracy of RTPS for various treatment conditions and thus can be used as a tool of routine RTPS QA, as well as independent MU checks. In addition, its beam database management interface can update beam data periodically and thus can be used to monitor multiple beam databases efficiently.

Determination of Tumor Volume in PET for the Radiation Treatment Planning : Computer Simulation / 의학물리

The utilization of PET has been increased so fast since the usefulness of the PET has been proved in various clinical and research fields. Among the many applications, the PET is especially useful in oncology and most of the clinical PET scans are performed for the oncologic examination including the different diagnosis of malignant and benign tumors and assessment of the treatment effects and recurrent tumors. As the PET-CT scanners are widely available, there is increasing interest in the application of the PET images to the radiation treatment planning. Although the CT images are conventionally used for the target volume determination in the radiation treatment planning, there are fundamental limitation in use of only the anatomical information. Therefore, the volume determination of the functionally active tumor region using the PET would be important for the treatment planning. However, the accurate determination of the tumor boundary is not simple in PET due to the relatively low spatial resolution of the currently available PET scanners. In this study, computer simulations were performed to study the relationship between the lesion size, PET resolution, lesion to background ratio and the threshold of image intensity to determine the true tumor volume.

Reduction of postradiation xerostomia in patients with head and neck cancer by superior technology using 3D-RTPS / 实用口腔医学杂志

Objective: To observe the effect of superior technology using three dimension radiation treatment plans (3D-RTPS) in the reduction of postradiation xerostomia in patients with head and neck cancer. Methods: 3D-RTPS of conventional radiation and new superior technique were applied in the patients of 3 kinds of head and neck cancer (tumor in middle, lateral, between middle and lateral area of head and neck). Superior technology including superior ray entrance, multi fields, conformal irradiation and application of wedges. Analysis of 3D dose distributions and dose volume histograms (DVH) was used to evaluate the dose and volume in tumor, parotids and spinal cord in the patients. Tumor dose of 55.6～68.6 Gy (average 58.8 Gy) was given to the patients in conventional radiation group in 8 patients, 53.5～68.5 Gy (average 58.3 Gy) to new radiation technique group in 12 patients. Whole saliva flow rate and subjective xerostomia scores were assessed in patients during radiation course and follow-up. Results: The dose in contralateral parotids in patients with tumor in lateral area, between lateral and middle area in conventional radiation and new radiation technique groups were 51.8～64.3 Gy and 0.4～1.4 Gy, respectively. The dose in parotids in patients with tumor in middle area in conventional radiation and new radiation technique groups were 51.8 and 24.7 Gy respectively. The rate of xerostomia at the end of radiotherapy and in 4～6 months follow-up after radiotherapy in patients of new radiation technique group were 8.3 % (1/12) and 0 respectively. Those in patients in conventional radiation group were 87.5 % (7/8) and 50 % (4/8) respectively. Conclusion: Superior technology using 3D-RTPS can reduce the rate of postradiation xerostomia in patients with head and neck cancer.