PURPOSE: To develop a method for verifying a treatment setup in stereotactic radiotherapy by matching portal images to DRRs. MATERIALS AND METHODS: Four pairs of orthogonal portal images of one patient immobilized by a thermoplastic mask frame for fractionated stereotactic radiotherapy were compared with DRRs. Portal images are obtained in AP (anterior/posterior) and lateral directions with a target localizer box containing fiducial markers attached to a stereotactic frame. DRRs superimposed over a planned isocenter and fiducial markers are printed out on transparent films. And then, they were overlaid over orthogonal portal images by matching anatomical structures. From three different kind of objects (isocenter, fiducial markers, anatomical structure) on DRRs and portal images, the displacement error between anatomical structure and isocenters (overall setup error), the displacement error between anatomical structure and fiducial markers (immobilization error), and the displacement error between fiducial markers and isocenters (localization error) were measured. RESULTS: Localization errors were 1.5+/-0.3 mm (AP), 0.9+/-0.3 mm (lateral), and immobilization errors were 1.9+/-0.5 mm (AP), 1.9+/-0.4 mm (lateral). In addition, overall setup errors were 1.6+/-0.9 mm (AP), 1.3+/-0.4 mm (lateral). From these orthogonal displacement errors, maximum 3D displacement errors(sqrt{(Delta AP)^2 +(Delta Lat)^2}) were found to be 1.7+/-0.4 mm for localization, 2.6+/-0.6 mm for immobilization, and 2.3+/-0.7 mm for overall treatment setup. CONCLUSION: By comparing orthogonal portal images with DRRs, we find out that it is possible to verify treatment setup directly in stereotactic radiotherapy.
Fiducial Markers ; Humans ; Immobilization ; Masks ; Radiotherapy*

PURPOSE: We have compared the characteristics of Siemens virtual wedge device with physical wedges for clinical application. MATERIALS AND METHODS: We investigated the characteristics and physical wedges for various wedge angles (15,30,45,and 60 degrees)using 6- and 15MV photon beams. Wedge factors were measured in water using an ion chamber for various field sizes and depths. In case of virtual wedge device, as upper jaw moves during irradiation, wedge angles were estimated by accumulated doses. These measurements were performed at off-axis points perpendicular to beam central axis in water for a 15Cm x20Cm radiation field size at the depth of 10Cm. Surface doses without and with virtual or physical wedges were measured using a parallel plate ion chamber at surface. Field size was15Cmx20Cm and a polystyrene phantom was used. RESULT: For various field sizes, virtual and physical wedge factors were changed by maximum 2.1%and 3.9%, respectively. For various depths, virtual and physical wedge factors were changed by maximum 1.9% and 2.9%, respectively. No major difference was found between the virtual and physical wedge angles and the difference was within 0.5 degrees. Surface dose with physical wedge was reduced by maximum 20% (x-ray beam : 6 MV, Wedge angle: 45 degrees, SSD; 80 Cm) relative to one with virtual wedge or without wedge. CONCLUSION: comparison of the characteristics of Siemens virtual wedge device with physical wedges was performed.Depth dependence of virtual wedge factor was smaller than of physical wedge factor. Virtual and physical wedge factors were nearly independent of field size. The accuracy of virtual and physical wedge angles was excellent. Surface dose was found to be reduced using physical wedge.
Axis, Cervical Vertebra ; Jaw ; Polystyrenes ; Silver Sulfadiazine ; Water

PURPOSE:The expression of p53, p21/WAF/CIP, Bcl-2, and Bax underlying the radiation-induced apoptosis in different pH environments using SCK mammary adenocarcinoma cell line was investigated. MATERIALS AND METHODS: Mammary adenocarcinoma cells of A/J mice (SCK cells) in exponential growth phase were irradiated with a linear accelerator at room temperature. The cells were irradiated with 12 Gy and one hour later, the media was replaced with fresh media at a different pHs. After incubation at 37 degrees C for 0-48 h, the extent of apoptosis was determined using agarose gel electrophoresis and flow cytometry. The progression of cells through the cell cycle after irradiation in different pHs was also determined with flow cytometry. Western blot analysis was used to monitor p53, p21/WAF/CIP, Bcl-2, and Bax protein levels. RESULTS:The induction of apoptosis by irradiation in pH 6.6 medium was markedly less than that in pH 7.5 medium. The radiation-induced G2/M arrest in pH 6.6 medium lasted markedly longer than that in pH 7.5 medium. Considerable amounts of p53 and p21 proteins already existed at pH 7.5 and increased the level of p53 and p21 significantly after 12 Gy X-irradiation. An incubation at pH 6.6 after 12 Gy X-irradiation did not change the level of p53 and p21 protein levels significantly. Bcl-2 proteins were not significantly affected by radiation and showed no correlation with cell susceptibility to radiation-induced apoptosis in different pHs. An exposure to 12 Gy of X-rays increased the level of Bax protein at pH 7.5 but at pH 6.6, it was slight. CONCLUSION: The molecular mechanism underlying radiation-induced apoptosis in different pH environments using SCK mammary adenocarcinoma cell line was dependent of the expression p53 and p21/WAF/CIP proteins. We may propose following hypothesis that an acidic stress augments the radiation-induced G2/M arrest, which inhibiting the irradiated cells undergo post-mitotic apoptosis. The effects of environmental acidity on anti-apoptotic and pro-apoptotic function of Bcl-2 family was unclear in SCK mammary adenocarcinoma cell line.
Adenocarcinoma* ; Animals ; Apoptosis* ; bcl-2-Associated X Protein ; Blotting, Western ; Cell Cycle ; Cell Line* ; Electrophoresis, Agar Gel ; Flow Cytometry ; Humans ; Hydrogen-Ion Concentration ; Mice ; Oncogenes* ; Particle Accelerators

PURPOSE: It has been well established that response of cells and tissues to low LET radiations(X- or grmma-ray) can enhanced by comdining with hyperthermia. However, There has been relatively little of hyperthermia on the possible modification of either cellular or tissue responses to other types of radiation. So, We investigated the combined effect of fast neutron irradiation and hyperthermia according to the sequence and time interval of the two MATERIALS AND METHODS: In MKN-45 cells, a human stomach cancer cell line, Surviving fractions were measured according to the sequence treatment of 6,4,2,0 hour interval for fast neutron irradiation(1.5Gy) combined with hyperthermia(41 degrees C for 30 min or 43 degrees C for 30 min). RESULTS: D(0) and n of MKN-45 for neutron were 0.8Gy and 2.5, respectively. The surviving fraction by 1.5 Gy of neutron was 0.36+/-0.34. Interacting powers were mostly. The surviving fraction by 1.5 Gy of neutron was 0.36+/-0.34. Interacting powers were mostly ranged between 1 and 2, bur they were 3.0Gy 2.7, respectively for hyperthermia (41 degrees C for 30 min) followed by neutron irradiation 6 and 4 hours later. CONCLUSION: The combined effect of fast neutron (1.5Gy) and hyperthermia (41 degrees C or 43 degrees C for 30min) is largely independently additive. Preceding mild hyperthermia (41 degrees C for 30 min) 4 or 6 hours before neutron may cause decreased sensitivity to subsequent neutron irradiation.
Cell Line ; Fast Neutrons* ; Fever* ; Humans ; Linear Energy Transfer ; Neutrons ; Stomach Neoplasms

PURPOSE: The purpose of this study is to develop a practical method for determining accurate marker positions for prostate cancer radiotherapy using CT images and kV x-ray images obtained from the use of the on-board imager (OBI). MATERIALS AND METHODS: Three gold seed markers were implanted into the reference position inside a prostate gland by a urologist. Multiple digital image processing techniques were used to determine seed marker position and the center-of-mass (COM) technique was employed to determine a representative reference seed marker position. A setup discrepancy can be estimated by comparing a computed COMOBI with the reference COMCT. A proposed algorithm was applied to a seed phantom and to four prostate cancer patients with seed implants treated in our clinic. RESULTS: In the phantom study, the calculated COMCT and COMOBI agreed with COMactual within a millimeter. The algorithm also could localize each seed marker correctly and calculated COMCT and COMOBI for all CT and kV x-ray image sets, respectively. Discrepancies of setup errors between 2D-2D matching results using the OBI application and results using the proposed algorithm were less than one millimeter for each axis. The setup error of each patient was in the range of 0.1+/-2.7~1.8+/-6.6 mm in the AP direction, 0.8+/-1.6~2.0+/-2.7 mm in the SI direction and -0.9+/-1.5~2.8+/-3.0 mm in the lateral direction, even though the setup error was quite patient dependent. CONCLUSION: As it took less than 10 seconds to evaluate a setup discrepancy, it can be helpful to reduce the setup correction time while minimizing subjective factors that may be user dependent. However, the on-line correction process should be integrated into the treatment machine control system for a more reliable procedure.
Axis, Cervical Vertebra ; Humans ; Prostate ; Prostatic Neoplasms ; Radiotherapy

PURPOSE: LiF TLD has a problem to be used in vivo dosimetry because of the toxic property of LiF. The aim of this study is to develop new dosimeter with LiF TLD to be used in vivo dosimetry. MATERIALS AND METHODS: We designed and manufactured the teflon box(here after TLD holder) to put TLD in. The external size of TLD holder is 4x4x1 mm3. To estimate the effect of TLD holder on TLD response for radiation, the linearity of TLD response to nominal dose were measured for TLD in TLD holder. Measurement were performed in the 10 MV x-ray beam with LiF TLD using a solid water phantom at SSD of 100 cm. Percent Depth Dose (PDD) and Tissue-Maximum Ratio (TMR) with varying phantom thickness on TLD were measured to find the effect of TLD holder on the dose coefficient used for dose calculation in radiation therapy. RESULTS: The linearity of response of TLD in TLD holder to the nominal dose was improved than TLD only used as dosimeter. And in various measurement conditions, it makes a marginnal difference between TLD in TLD holder and TLD only in their responses. CONCLUSION: It was proven that the TLD in TLD holder as a new dosimetry could be used in vivo dosimetry.
Polytetrafluoroethylene ; Silver Sulfadiazine ; Water

PURPOSE: We analyzed setup errors induced by using air-vacuum cushion as immobilization device in patients with rectal cancer. MATERIALS AND METHODS: We had treated the twenty patients with rectal cancer by 6 MV, 10 MVx-ray from Aug. 1998 to Aug. 1999 at Chungnam National University Hospital. All patients were treated at prone position. They were separated to two groups, control group, 10 patients using styrofoam, and test group, 10 patients using styrofoam and air-vacuum cushion. We measured errors of posterior field forx, y axis and lateral field for z, y axis with simulation film and EPID image using a matching technique. RESULTS: In control group, the mean displacement values of pelvic bone landmark forx axis and y axis were 0.02 mm. 0.78 mm, respectively and the standard deviations of systematic error were 2.13 mm, 2.40 mm, respectively and the standard deviation of random error were 1.46 mm. 1.51 mm, respectively. In test group, the mean displacement values ofx axis and y axis were -0.33 mm. 0.81 mm, respectively and the standard deviations of systematic error were 1.71 mm, 3.08 mm, respectively and the standard deviations of random errors were 1.40 mm. 1.88 mm, respectively. The mean displacement values of z axis and y axis were 2.98 mm. 0.74 mm, respectively and the standard deviations of systematic error were 4.75 mm, 2.65 mm, respectively and standard deviations of random error were 2.69 mm. 1.86 mm, respectively. The statistical difference of field size by using air vacuum cushion between two groups in posterior direction and lateral direction was not shown. CONCLUSION: We think that use of air-vacuum cushion may not be an advantage for improving setup accuracy in rectal cancer patients.
Axis, Cervical Vertebra ; Chungcheongnam-do ; Control Groups ; Humans ; Immobilization ; Pelvic Bones ; Prone Position ; Rectal Neoplasms* ; Vacuum

PURPOSE: To setup procedures of quality assurance (QA) for implementing intensity modulated radiation therapy (IMRT) clinically, report QA procedures performed for one patient with prostate cancer. MATERIALS AND METHODS: P3IMRT (ADAC) and linear accelerator (Siemens) with multileaf collimator are used to implement IMRT. At first, the pos itional accuracy, reproducibility of MLC, and leaf transmission factor were evaluated. RTP commissioning was performed again to considers mall field effect. After RTP recommissioning, a test plan of a C-s haped PTV was made using 9 intensity modulated beams, and the calculated isocenter dose was compared with the measured one insolid water phantom. As a patient-specific IMRT QA, one patient with prostate cancer was planned us ing 6 beams of total 74 segmented fields. The same beams were used to recalculate dose in a solid water phantom. Dose of these beams were meas ured with a 0.015cc microionization chamber, a diode detector, films, and a narray detector and compared with calculated one. RESULTS: The pos itioning accuracy of MLC was about 1 mm, and the reproducibility was around 0.5 mm. For leaf transmission factor for 10 MV photon beams, interleaf leakage was measured 1.9% and midleaf leakage 0.9% relative to 10x10 cm2 open filed. Penumbra meas ured with film, diode detector, microionization chamber, and conventional 0.125 cc chambers howed that 80~20% penumbra width meas ured with a 0.125cc chamber was 2 mm larger than that of film, which means a 0.125 ccionization chamber was unacceptable for meas urings mall fields uch like 0.5 cm beamlet. After RTP recommissioning, the discrepancy between the meas ured and calculated dose profile for a small field of 1x1 cm2 size was less than 2%. The isocenter dose of the test plan of C-s haped PTV was meas ured two times with microionization chamber in solid phantom showed that the errors upto 12% for individual beam, but total dose delivered were agreed with the calculated within 2%. The transverse dose distribution meas ured with EC-L film was agreed with the calculated one ingeneral. The isocenter dose for the patient meas ured in solid phantom was agreed within 1.5%. Off-axis dose profiles of each individual beam at the position of the central leaf measured with film and array detector were found that at out-of-the-field region, the calculated dose underestimates about 2%, at inside-the-field the meas ured one was agreed within 3%, except some position. CONCLUSION: It is necessary more tight quality control of MLC for IMRT relative to conventional large field treatment and to develop QA procedures to check intensity pattern more efficiently. At the conclusion, we did setup an appropriate QA procedures for IMRT by a series of verifications including the measurement of absolute dose at the isocenter with a microionization chamber, film dosimetry for verifying intensity pattern, and another meas urement with an array detector for comparing off-axis dose profile.
Film Dosimetry ; Humans ; Particle Accelerators ; Prostatic Neoplasms ; Quality Control ; Water

PURPOSE: Proctitis is one of acute complications encountered when radiotherapy was applied to the pelvis. Radiation-induced proctitis represents similar microscopic findings that are observed in inflammatory bowel disease (IBD). Nitric oxide (NO) plays an important role in the inflammatory process and many data suggest a close relationship between NO production and gastrointestinal inflammation. This study was aimed to establish the optimal radiation dose for radiation-induced proctitis in rat and to find a relationship between radiation proctitis and NO production. MATERIALS AND METHODS: Female Wistar rats, weighing from 150 to 220 g, received various doses(10-30 Gy) of radiation to the rectum. On the 5th and 10th day after irradiation, rectal specimens were evaluated grossly and microscopically. In addition, the degree of NO production by irradiation dose was evaluated by study with NOS expression and nitrite production in the irradiated rectal tissue. To evaluate relationship between radiation proctitis and NO, we administered aminoguanidine, iNOS inhibitor and L-arginine, substrate of NOS to rats from 2 days before to 7 days after the irradiation. RESULTS: There were obvious gross and histological changes after 17.5 Gy or higher radiation dose but not with 15 Gy or less radiation dose. Twenty Gy or higher dose of radiation caused Grade 4 damage in most of rectal specimens which were more likely to be related to the late complications such as fibrosis, rectal bleeding and rectal obstruction. A single fraction of 17.5 Gy to the rat rectum is considered to be an optimal dose to produce commonly experienced proctitis in the clinic. The result demonstrated that severity of microscopic damage of rectal mucosa from irradiation significantly correlated with iNOS overexpression. However, administration of iNOS inhibitor or substrate of iNOS did not influence the degree of rectal damage. CONCLUSION: A single fraction of 17.5 Gy irradiation to the rat rectum considered to be an optimal dose for radiation induced proctitis model. These results indicated that an excess production of NO contributes to pathogenesis of radiation-induced proctitis in part but was not the direct cause of rectal damage.
Animals ; Arginine ; Female ; Fibrosis ; Hemorrhage ; Humans ; Inflammation ; Inflammatory Bowel Diseases ; Models, Animal ; Mucous Membrane ; Nitric Oxide Synthase ; Nitric Oxide* ; Pelvis ; Proctitis* ; Radiotherapy ; Rats* ; Rats, Wistar ; Rectum

PURPOSE: We investigated the temporal alterations of apoptosis and mitotic death followingirradiation in the rat's small intestinal crypts. MATERIALS AND METHODS: Male Sprague-Dawley rats were irradiated 2 Gy by 6 MV linear accelerator and sacrified at 2, 4, 8, 24, 48 hours after irradiation. The mean numbers of the apoptotic cells and mitotic cells per their small intestinal crypts were measured in the unirradiated control and irradiated groups. To compare with H & E staining, ISEL (In Situ End Labelling) were performed in the group having the highest apoptotic count. RESULTS: The mean number of the apoptosis per crypt in the control group was 0.14 and those at 2, 4, 8, 24, 48 hours after irradiation were 1.43, 3.19, 1.15, 0.26, 0.17, respectively. So the apoptosis development was increased upto 4 hours and then normalized around 24 hours following irradiation. The mean number of the mitotic cells per crypt in the control group was 1.29 and those at 2, 4, 8, 24, 48 hours after irradiation were 0.56, 0.47, 0.23, 0.65, 1.19, respectively. The mitotic cell counts following irradiation was decreased to 8 hours and recovered to the normal level about 48 hours. So the increment of apoptotic cell count was occurred earlier and more remarkable than the decrement of mitotic cell count after irradiation. According to the staining time, false positivity was found in the ISEL staining. CONCLUSIONS: The cell death in the small intestinal crypt developed by acute radiation damage was usually decreased to the normal level within 24~48 hours after irradiation and the apoptosis was thought to be more important process than the mitotic death.
Animals ; Apoptosis* ; Cell Count ; Cell Death ; Humans ; Intestine, Small ; Male ; Mitosis ; Particle Accelerators ; Rats* ; Rats, Sprague-Dawley