PURPOSE: To generate the axial, coronal and sagittal images from conventional simulation images, as a preliminary study of broad-beam simulator CT. METHODS AND MATERIALS: Volumetric filtered back-projection was performed using 90 sheets of films from conventional simulator for every 4. gantry angle. Two mAs exposure condition for 120kVp beam quality at SFD 140cm was given to each film. Outside the silhouette portion was removed and scatter component was deconvolved before back-projection. RESULTS: The axial, the sagittal and the coronal images with same spatial resolutions over all direction could be obtained. But image quality was very poor. CONCLUSION: CT images could be obtained using broad-beam. Scatter deconvolution technique was effective for this reconstruction. The fact that same spatial resolutions over all direction tells us the possiblility of application of this technique to DRR or Simulator-CT. But the quality of image should be improved for clinical application practicaly.
Image Processing, Computer-Assisted*

The beam characteristics and dosimetric measurements of the 10 MV X-ray beam from a Mevatron KD linear accelerator are examined. The Percent Depth Dose (PDD) table and the Tissue Maximum Ratio (TMR) table are taken from measurement as a function of the field size and the depth. The calculated TMR table from PDD table is compared with those from measurement. Other beam characteristics such as output factor, beam profile (including flatness, symmetry and penumbra), wedge, and the variation of Dmax are presented.
Particle Accelerators*

PURPOSE: To evaluate the clinical implications of scallp penumbra width that comes from multileaf collimator(MLC) effect by the daily routine patient setup error. MATERIALS AND METHODS: The angles of 0degree, 15degree, 30degree, 45degree, 60degree and 75degree inclined-radiation blocked fields were generated using the both conventional cerrobend block and the MLC. Film dosimetry in the phantom were performed to measure penumbral widths of differences between the dose distributions from the cerrobend block and those of respect the MLC. The patient setup error effect on scallop penumbra was simulated with respect to the table of setup error distribution. Same Procedures are repeated for the cerrobend block generated field. RESULTS: There are penumbral widths of to 3mm difference between the dose distributions from two kinds of field shaping tools, the conventional block and the MLC with 4mm setup error model and resolution of 1cm leaf at the isocenter. CONCLUSION: We need not additive margin for MLC, if planning target bolume is selected according to the recommendation of ICRU 50. For particular cases, we can include the target volume with less than 3mm additive margin.
Film Dosimetry ; Humans ; Pectinidae*

The Comparison of the KAPM Dosimetric Protocol (1990) with the TG-21 and Clambda/C(E) (ICRU-21 and SCRAD protocol) method is studied. The therapetutic range of radiation (photon 4MV-15MV and electron 6MeV-20MeV)and three kinds of the chambers were used in the water phantom. The Results from TG-21 and KAPM Protocol did not show much differences (less than 1%) throughout the whole energy range; N(D) from KAPM protocol and Ngas from TG-21 showed 0.2% deviation mainly from W/e difference between two protocols. But the results from KAPM protocol (1990) and those from Clambda/C(E) Method showed -1.9+/-0.6%(KAPM protocol is higher) deviation for photom beam and +3.3+/-1% (KAPM protocol is lower) deviation for electron beams.
Water

In breast cancer, the treatment volume presents a relatively complex three dimensional structure. Effective radiation therapy requires the delivery of adequate dose to a large target volume using complex beam arrangements. The technique proposed here is our department's method using asymmetric jaw with appropriate couch, collimator and gantry rotation. This technique has the following advantages: 1) all treatments are given in a single clinical set up 2) it dose not require half beam blocks 3) it produces exact geometric match 4) it is very convenient and easy to use 5) it has daily reproducibility.
Breast Neoplasms* ; Breast* ; Jaw

Authors have developed highly reproducible calibration method for the Micro-Selection HDR Ir-192 system(Nucletron, Netherland). The new jig has a 10cm radius circular hole in the 30cm x 30cm x 0.2cm acrylic plate, and 5F flexible bronchial tubes are attached around the hole. The source moves along the circle in the tubes an? the ionization chamber is placed vertically at the center of the circular hole(center of the jig). Dose distribution near the center was derived theoretically, and measured with the film dosimetry system. Theoretical calculation and measurement show the error margin below 0.1% for 1mm or 2mm position deviation. We have measured at 12 and 24 points of circle with 1, 6, 11 and 21 second dwell time of source in order to calculate the activity of the source. Measurements have been repeated daily for 50 days. The accuracy and the reproducibility are below 1% error margin. The half life of the source from our measurement is estimated 73.4+/-0.4 days.
Calibration* ; Film Dosimetry ; Half-Life ; Radius

Coronary restenosis is still regarded as Achilles' Hill of interventional cardiology despite relentless efforts of many investigators. Recent experimental and clinical studies have suggested that both gamma and beta radiation can be reduce restenosis after angioplasty. Currently, intracoronary brachytherapy for the prevention of restenosis has become a new evolving treatment modality in interventional cardiology. This report discusses a physical aspect of gamma and beta radiation, initial clinical results and delivery systems used in intracoronary brachytherapy. We shall take a brief overview of methods and their advantages in intracoronary brachytherapy. Future work should provide further insight for the best way of treating restenosis.
Angioplasty ; Beta Particles ; Brachytherapy ; Cardiology ; Coronary Restenosis ; Humans ; Research Personnel

The patterns of the conventional radiation treatment fields and their shielding blocks are analysed to determine the optimal dimension of the MultiLeaf Collimator (MLC) which is considered as an essential tool for conformal therapy. Total 1169 radiation fields from 303 patients (203 from Asan Medical center, 50 from Baek Hosp and 50 from Hanyang Univ. Hosp.) were analysed for this study. Weighted case selection treatment site (from The Korean Society of Therapeutic Radiology 1003). Ninety one percent of total fields have shielding blocks. Y axis is defined as leaf movement direction and it is assumed that MLC is installed on the cranial-caudal direction. The length of X axis were distributed from 4cm to 40cm (less than 21cm for 95% of cases), and Y axis from 5cm to 38cm (less than 22cm for 95% of cases). The shielding blocks extended to less than 6cm from center of the filed for 95% of the cases. Start length for ninety five percent of block is less than 10cm for X axis and 11cm for Y axis. Seventy six percent of shielding blocks could be placed by either X or Y axis direction, 7.9% only by Y axis, 5.1% only by X axis and it is reasonable to install MLC for Y direction. Ninety five percent of patients can be treated with coplanar rotation therapy without changing the collimator angle. Eleven percent of cases of cases were impossible to replace with MLC. Futher study of shielding should be larger than 21cm X 22cm. The MLC should be designed as a pair of 21 leaves with 1cm wide for an acceptable resolution and 17cm long to enable the leaf to overtravel at least 6cm from the treatment field center.
Axis, Cervical Vertebra ; Chungcheongnam-do ; Humans ; Radiation Oncology

Remote afterloading high dose rate brachytherapy(HDRB) is a new technology and needs new biological principle for time and dose schedule. Here, authors attempt to evaluate the technique and clinical outcome in 116 patients, 590 procedures performed at Asan Medical Center for 3 years. From Sep. 1985 to Aug 1992, 471 procedures of intracavitary radiation in 55 patients of cervical cancer and 26 of nasopharyngeal cancer, 79 intraluminal radiation in 12 of esophageal cancer, 11 of endobronchial cancer and 1 Klatskin tumor and 40 interstitial brachytherapy in 4 of breast cancer, 1 sarcoma and 1 urethral cancer were performed. Median follow-up was 7 months with range 1~31 months. All procedures except interstitial were performed under the local anesthesia and they were all well tolerated and completed the planned therapy except 6 patients. 53/58 patients with cervical cancer and 22/26 patients with nasopharynx cancer achieved CR. Among 15 patients with palliative therapy, 80% achieves palliation. We will describe the details of the technique and results in the text. To evaluate biologic effects of HDRB and optimal time/dose/fractionation schedule, we need longer follow-up. But authors feel that HDRB with proper fractionation schedule may yield superior results compared to the low dose rate brachytherapy considering the advantages of HDRB in safety factor for operator, better control of radiation dose and volume and patients comfort over the low dose brachytherapy.
Anesthesia, Local ; Appointments and Schedules ; Brachytherapy* ; Breast Neoplasms ; Chungcheongnam-do ; Esophageal Neoplasms ; Follow-Up Studies ; Humans ; Klatskin's Tumor ; Nasopharyngeal Neoplasms ; Palliative Care ; Sarcoma ; Urethral Neoplasms ; Uterine Cervical Neoplasms

PURPOSE: To design and test the CT simulator phantom for geometrical test. MATERIAL AND METHODS: The PMMA phantom was designed as a cylinder which is 20 cm in diameter and 24 cm in length, along with a 25x25x31 cm3 rectangular parallelepiped. Radio-opaque wires of which diameter is 0.8 mm are attached on the other surface of the phantom as a spiral. The rectangular phantom was made of four 24x24x0.5 cm3 square plates and each plate had a 24x24 cm2, 12x12 cm2, 6x6 cm2 square line. The squares were placed to face the cylinder at angles 0degrees, 15degrees, 30degrees, respectively. The rectangular phantom made it possible to measure the field size, couch angle, the collimator angle, the isocenter shift and the SSD, the measurements of the gantry angle from the cylindrical part. A virtual simulation software, AcQSimTM, offered various conditions to perform virtual simulations and these results were used to perform the geometrical quality assurance of CT simulator. RESULTS: A 0.3~0.5 mm difference was found on the 24 cm field size which was created with the DRR measurements obtained by scanning of the rectangular phantom. The isocenter shift, the collimator rotation, the couch rotation, and the gantry rotation test showed 0.5~1 mm, 0.5~1degrees0.5~1degrees, and 0.5~ 1degreesdifferences, respectively. We could not find any significant differences between the results from the two scanning methods. CONCLUSION: The geometrical test phantom developed in the study showed less than 1 mm (or 1degrees) differences. The phantom could be used as a routine geometrical QC/QA tools, since the differences are within clinically acceptable ranges.
Polymethyl Methacrylate ; Silver Sulfadiazine