Clinical Implementation of an Eye Fixing and Monitoring System with Head Mount Display / 의학물리

A system to non-invasively fix and monitor eye by a head mounted display (HMD) with a CCD camera for stereotactic radiotherapy (SRS) of uveal melanoma has been developed and implemented clinically. The eye fixing and monitoring system consists of a HMD showing patient a screen for fixing eyeball, a CCD camera monitoring patient' s eyeball, and an immobilization mask. At first, patient' s head was immobilized with a mask. Then, patient was instructed to wear HMD, to which CCD camera was attached, on the mask and see the given reference point on its screen. While patient stared at the given point in order to fix eyeball, the camera monitored its motion. Four volunteers and one patient of uveal melanoma for SRS came into this study. For the volunteers, setup errors and the motion of eyeball were analyzed. For the patient, CT scans were performed, with patient' s wearing HMD and fixing the eye to the given point. To treat patient under the same condition, daily CT scans were also performed before every treatment and the motion of lens was compared to the planning CT. Setup errors for four volunteers were within 1 mm and the motion of eyeball was fixed within the clinically acceptable ranges. For the patient with uveal melanoma, the motion of lens was fixed within 2 mm from daily CT scans. An eye fixing and monitoring system allowed immobilizing patient as well as monitoring eyeball and was successfully implemented in the treatment of uveal melanoma for SRS.

Preliminary Results of Phase I/II Study of Simultaneous Modulated Accelerated (SMART) for Nasopharyngeal Carcinoma / 대한방사선종양학회지

PURPOSE: To present preliminary results of intensity-modulated radiotherapy (IMRT) using the simultaneous modulated accelerated radiation therapy (SMART) boost technique in patients with nasopharyngeal carcinoma (NPC). MATERIALS AND METHODS: Twenty patients who underwent IMRT for non-metastatic NPC at the Asan Medical Center between September 2001 and December 2003 were prospectively evaluated. IMRT was delivered using the "step and shoot" SMART technique at prescribed doses of 72 Gy (2.4 Gy/day) to the gross tumor volume (GTV), 60 Gy (2 Gy/day) to the clinical target volume (CTV) and metastatic nodal station, and 46 Gy (2 Gy/day) to the clinically negative neck region. Eighteen patients also received concurrent chemotherapy using cisplatin once per week. RESULTS: The median follow-up period was 27 months. Nineteen patients completed the treatment without interruption; the remaining patient interrupted treatment for 2 weeks owing to severe pharyngitis and malnutrition. Five patients (25%) had RTOG grade 3 mucositis, whereas nine (45%) had grade 3 pharyngitis. Seven patients (35%) lost more than 10% of their pretreatment weight, whereas 11 (55%) required intravenous fluids and/or tube feeding. There was no grade 3 or 4 chronic xerostomia. All patients showed complete response. Two patients had distant metastases and loco-regional recurrence, respectively. CONCLUSION: IMRT using the SMART boost technique allows parotid sparing, as shown clinically and by dosimetry, and may also be more effective biologically. A larger population of patients and a longer follow-up period are needed to evaluate ultimate tumor control and late toxicity.

Effectiveness of Breath Hold with a ABC for SRS of Lung Cancer

PURPOSE: It is very important to remove or to reduce the effect of organ motion due to respiration in stereotatic radiosurgery of lung. This study reports the effectiveness of the breath hold technique with a ABC for reducing the breathing effect. MATERIALS AND METHODS: Whole body stereotactic frame (Elekta, Sweden) was used for lung SRS. Patients who have tumor motion range larger than 10 mm from fluoroscopic observation were selected to apply a ABC. Seventeen patients were enrolled in this study. Passive breath hold is possible with our ABC. Automatic breath hold was set at 80% of deep inspiration. Breath hold time was 25~30 seconds depending on the patients. Three consecutive CT scans were performed as indicated in Asan Medical Center SRS procedure for each patients. Lung volume and PTV differences between with breath hold and free breath were examined for 5 patients. RESULTS: The breath hold technique with ABC could be applied for 15 patients. Inter-, intra-treatment organ motion with ABC showed 1.5 mm, while it was 2.3 mm with abdomen compress. When with breath hold technique, PTV and CTV was reduced 33.7% and 45.4%, respectively, and lung volume was increased 32.3 % compared to conventional SRS method. CONCLUSION: Better target localization could be achieved with breath hold technique in lung SRS. Tumor motion could be minimized and relative lung volume irradiation could be reduced

Study of Respiration Simulating Phantom using Thermocouple-based Respiration Monitoring Mask / 대한방사선종양학회지

PURPOSE: To develop the respiration simulating phantom with thermocouple for evaluating 4D radiotherapy such as gated radiotherapy, breathing control radiotherapy and dynamic tumor tracking radiotherapy. MATERIALS AND METHODS: The respiration monitoring mask (ReMM) with thermocouple was developed to monitor the patient's irregular respiration. The signal from ReMM controls the simulating phantom as organ motion of patients in real-time. The organ and the phantom motion were compared with its respiratory curves to evaluate the simulating phantom. ReMM was used to measure patients' respiration, and the movement of simulating phantom was measured by using RPM(R). The fluoroscope was used to monitor the patient's diaphragm motion. RESULTS: Comparing with the curves of respiration measured by thermocouple and those of the organ motion measured by fluoroscope and RPM, the standard deviations between the curves were 9.68% and 8.53% relative to the organ motion, respectively. The standard deviation of discrepancy between the respiratory curve and the organ motion was 8.52% of motion range. CONCLUSION: Patients felt comfortable with ReMM. The relationship between the signal from ReMM and the organ motion shows strong correlation. The phantom simulates the organ motion in real-time according to the respiratory signal from the ReMM. It is expected that the simulating phantom with ReMM could be used to verify the 4D radiotherapy.

Optimum Segment Size for Intensity Modulated Radiation Therapy of Lung Region

PURPOSE: In general, it is possible to generate better leaf sequencing from the ideal fluence map or dose distribution close to the optimized results of the radiation treatment planning (RTP) system, from the filed smaller segment size in Intensity modulated radiation therapy (IMRT). Conversely, an intra-treatment organ motion issue, which prevents the smallest segment size from being chosen, always exists. Furthermore, the question has been raised regarding the proper target margin for IMRT cases with a moving target, as the field itself moves while the target moves, unlike traditional static fields. In this study, the effects of intra-treatment target motion on the segment size have been examined. MATERIALS AND METHODS: Various sizes of rectangular patterns were designed for an IMRT fluence map. A leaf sequence was generated using the step and shoot beam delivery method. The intensity ratios between adjacent segments were 0.2, 0.4 and 0.8. The range of target motion was assumed to be +/-0.3~2.0 cm, in a sinusoidal shape. The dynamic leaf motion that reflected the target motion was calculated to simulate the motion. Film dosimetry was performed to analyze the motion effects. RESULTS: The intensity ratios of the adjacent segments were degraded in all cases. The dose distribution with segment sizes less than half the breathing amplitude showed a significantly degraded intensity map. With a beam irradiation time for a segment greater than two breathing cycles, the dose distribution around the target margin showed a similar tendency as the static fields. CONCLUSION: The minimum size of IMRT segments in the fluence map should be chosen taking the intra-treatment organ motion into consideration. The dose distribution with segment sizes less than half the breathing amplitude was degraded significantly in the intensity map. With a beam irradiation time for a segment greater than two breathing cycles, the target margin can be defined as the same as for a conventional static field

Results of the Definitive Radiation Therapy for the Early Stage (Stage I) Non-small Cell Lung Cancer

PURPOSE: To investigate the effectiveness and safety of definitive radiation therapy for Stage I non-small cell lung cancer patients who were medically inoperable or refused surgery. Material and M ethods: A retrospective study was conducted of 36 patients who received definitive radiation therapy for pathologically proven Stage I non-small cell lung cancer in the Department of Radiation Oncology, Asan Medical Center, between July 1989 and July 2003. Twenty three patients received conventional radiation therapy with a fraction size of 1.2~3.0 Gy, with a total dose of 50.0~70.2 Gy (CRT group). Thirteen patients received stereotactic radiosurgery with a fraction size of 10~12 Gy, with a total dose of 30~48 Gy using a Stereotactic Body Frame (Precision TherapyTM, SRS group). RESULTS: The two- and 5-year overall survival rates (OS) of all the patients were 79 and 44%, respectively. The two- and 5-year OS of the CRT and SRS groups were 43 and 53%, and 7 and 27%, respectively, but showed no statistically significant difference (p=0.5173). The two- and 5-year cause-specific survival rates (CSS) of the SRS group were superior to those of the CRT group (2YCSS: 100 vs. 70%, 5YCSS: 50 vs. 39%), but were not statistically significant (p=0.2086). The two- and 5-year local progressionfree survival rates (LPFS) of all the patients were 67 and 57%, respectively. The 5-year LPFS of the SRS group was superior to that of the CRT group (66 vs. 54%), but was not statistically significant (p=0.3937). The T-stage, tumor size, treatment method (CRT vs. SRS) and tumor dose did not affect the 2-year LPFS. Grade 2~3 radiation pneumonitis developed in 5 patients (14%), all in the CRT group. The omission of elective nodal irradiation (ENI) did not affect the incidence of Grade 2~3 radiation pneumonitis in the CRT group (ENI group 17%, no ENI group 25%, p=0.538). CONCLUSION: Definitive radiation therapy for Stage I non-small cell lung cancer patients that were medically inoperable or who refused surgery was considered effective and safe. Stereotactic radiosurgery was proven to be superior to that of conventional radiation therapy, although no statistically significant difference was shown. To investigate the optimal radiation dose and fractionation scheme of SRS, a prospective study, including more patients, is mandatory

Radioresponse of Hepatocellular Carcinoma-Treatment of Lymph Node Metastasis / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: To analyze the radioresponse of hepatocellular carcinomas (HCC), using accurate measurements of the tumor size in extrahepatic lymph node metastasis, and to obtain information for the future treatment of primary intrahepatic lesions. MATERIALS AND METHODS: Fifty-one extrahepatic lymph node metastases from primary HCCs, which could be treated by external radiotherapy alone, were included in this study. The radiation dose ranged from 30 to 51 Gy with fraction sizes of 2.0~3.0 Gy. Responses were determined by measuring the areas on CT scans 0, 1 and 3 months after the completion of radiotherapy. The median follow-up period of the surviving patients was 10 months. RESULTS: The overall response rate was 76%, and the important factors were; total dose of radiation, time dose fractionation (TDF) value and the biologically effective dose (BED). A dose of 45 Gy or higher showed an objective response rate of 93%, and if the TDF value was higher than 90, a similar result was observed. In about half (47%) of the patients the maximum response was observed at 3 months or later. The response duration was observable in 14 patients surviving 12 months or longer. Regrowth of irradiated lesions were observed in 4 (66.7%) patients among those who received less than 45 Gy, and in 4 (50%) among those who were treated with 45 Gy or more. There was a statistically significant difference in the survivals between the responders and non-responders (p=0.008). Gastrointestinal bleeding or ulceration was observed in 8 patients, including 3 with NCI common toxicity criteria grade III or higher. CONCLUSION: Radiotherapy was an effective palliative modality for extrahepatic metastasis in HCCs. A radiation dose of 45 Gy or higher (or a TDF value > or =90), was required for a major response.

Feasibility Study of the Real-Time IMRT Dosimetry Using a Scintillation Screen / 대한방사선종양학회지

PURPOSE: To study the feasibility of verifying real-time 2-D dose distribution measurement system with the scintillation screen for the quality assurance. MATERIALS AND METHODS: The water phantom consisted of a scintillation screen (LANEX fast screen, Kodak, USA) that was axially located in the middle of an acrylic cylinder with a diameter of 25 cm. The charge-coupled device (CCD) camera was attached to the phantom in order to capture the visible light from the scintillation screen. To observe the dose distribution in real time, the intensity of the light from the scintillator was converted to a dosage. The isodose contours of the calculations from RTP and those of the measurements using the scintillation screen were compared for the arc therapy and the intensity modulated radiation therapy (IMRT). RESULTS: The kernel, expressed as a multiplication of two error functions, was obtained in order to correct the sensitivity of the CCD of the camera and the scintillation screen. When comparing the calculated isodose and measured isodose, a discrepancy of less than 8 mm in the high dose region was observed. CONCLUSIONS: Using the 2-D dosimetry system, the relationship between the light and the dosage could be found, and real-time verification of the dose distribution was feasible.

Impact of the Planning CT Scan Time on the Reflection of the Lung Tumor Motion / 대한방사선종양학회지

PURPOSE: To evaluate the reflection of tumor motion according to the planning CT scan time. MATERIAL AND METHODS: A model of N-shape, which moved along the longitudinal axis during the ventilation caused by a mechanical ventilator, was produced. The model was scanned by planning CT, while setting the relative CT scan time (T; CT scan time/ventilatory period) to 0.33, 0.50, 0.67, 0.75, 1.00, 1.33 T, and 1.53 T. In addition, three patients with non-small cell lung cancer who received stereotactic radiosurgery in the Department of Radiation Oncology, Asan Medical Center from 03/19/2002 to 05/21/2002 were scanned. Slow (IQ Premier, Picker, scan time 2.0 seconds per slice) and fast CT scans (LightSpeed, GE Medical Systems, with a scan time of 0.8 second per slice) were performed for each patient. The magnitude of reflected movement of the N-shaped model was evaluated by measuring the transverse length, which reflected the movement of the declined bar of the model at each slice. For patients' scans, all CT data sets were registered using a stereotactic body frame scale with the gross tumor volumes delineated in one CT image set. The volume and three-dimensional diameter of the gross tumor volume were measured and analyzed between the slow and fast CT scans. RESULTS: The reflection degree of longitudinal movement of the model increased in proportion to the relative CT scan times below 1.00 T, but remained constant above 1.00 T. Assuming the mean value of scanned transverse lengths with CT scan time 1.00 T to be 100%, CT scans with scan times of 0.33, 0.50, 0.67, and 0.75 T missed the tumor motion by 30, 27, 20, and 7.0% respectively. Slow (scan time 2.0 sec) and Fast (scan time 0.8 sec) CT scans of three patients with longitudinal movement of 3, 5, and 10 mm measured by fluoroscopy revealed the increases in the diameter along the longitudinal axis increased by 6.3, 17, and 23% in the slow CT scans. CONCLUSIONS: As the relative CT scan time increased, the reflection of the respiratory tumor movement on planning CT also increased, but remained constant with relative CT scan times above 1.00 T. When setting the planning CT scan time above one respiration period (>1.00 T), only the set-up margin is needed to delineate the planning target volume. Therefore, therapeutic ratio can be increased by reducing the radiation dose delivered to normal lung tissue.

Clinical Results of Stereotactic Body Frame based Fractionated Radiosurgery for Primary or Metastatic Thoracic Tumors

PURPOSE: The aim of the study was to evaluate the treatment outcomes of stereotactic radiosurgery (SRS) using a stereotactic body frame for primary or metastatic thoracic tumors. Methods and Materials: Between January 1998 and December 2003, 101 lesions from 91 patients with primary or metastatic thoracic tumors were treated. The eligible patients included 38 with primary lung cancers and 53 with metastatic tumors from the lung, liver, gastrointestinal and other organs. All patients were immobilized using a stereotactic body frame and permitted to breathe shallowly. The respiratory movement was restricted by a diaphragm controller when the tumor movement was greater than 5 mm. Recently, for further restriction of tumor movement, an active breathing control (ABC) apparatus was used in some trained patients whose tumors located in lower lobe. Three to eight coplanar or non-coplanar photon beams were used to adequately cover the planning target volume. A dose of 10~12 Gy per fraction was given three to four times over consecutive days, to a total dose of 30~48 Gy (median 40 Gy). Local control was assessed as complete or partial responses and by a stable disease, as measured by serial chest CT scans at 1 month, and then every 3-months, and/or 18FDG-PET scans 1 month after treatment. The median follow-up period was 14 months, ranging from 4 to 56 months. RESULTS: The overall response rate was 82%, with twenty (22%) complete and 55 (60%) partial responses. The rate of crude local control in all patients was 86% and the one- and two-year local progression free survival rates were 90 and 81%, respectively. The patients who received 48 Gy showed better local progression free survival than those that received 40 Gy or less (one-year; 100% vs. 86.7%), but this was not statistically significant. Of the 21 patients with primary lung cancer, local progression was observed in 3, at 12, 21 and 26 months after treatment, and the one- and two- year local progression free survival rates were 93 and 81%, respectively. The set-up error, as checked by CT-simulation and portal films, for every treatment was within 5 mm in all directions (X, Y and Z axis). No pulmonary complications greater than RTOG toxicity criteria grade 2 were observed. CONCLUSION: From our experience of the stereotactic body frame based radiosurgery it appears a safe and promising treatment modality for the local management of primary or metastatic lung tumors. The optimal total dose, fractionation schedule and treatment volume should be modified after a longer follow-up of these results. Further study related to the optimal evaluation tools is also necessary to differentiate local tumor progression from radiation-induced pulmonary injury

Phase II Study of 3-D Conformal Radiotherapy and Concurrent MVP (Mitomycin-C+Vinblastine+Cisplatin) Chemotherapy for Unresectable Non-Small Cell Lung Cancer

PURPOSE: To evaluate the feasibility, treatment outcome, and toxicity of hyperfractionated 3-D conformal radiotherapy and concurrent MVP chemotherapy in locally advanced, unresectable stage III non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: From August 1993 to December 1996, 161 patients with unresectable stage III NSCLC were entered into this trial, and 146 (91%) completed the treatment. Hyperfractionated radiotherapy was given to a total dose of 64.8~70 Gy (1.2 Gy/fx, bid) with 2 cycles of concurrent MVP (Mitomycin-C 6 mg/m2 d2 and d29, Vinblastine 6 mg/m2 d2 and d 29, and Cisplatin 60 mg/m2 d1 and d28) chemotherapy. Of the 146 patients who completed the treatment, 78 received noncoplanar 3D conformal radiotherapy using 4~6 fields and 17 received coplanar-segmented conformal radiotherapy. Clinical tumor response was assessed one month after the completion of radiotherapy by a computerized tomography (CT) scan. Toxicity was graded using the SWOG criteria. Normal tissue complication probability (NTCP) for the lung was calculated to determine any the correlation with radiation pneumonitis. Nineteen (13%) had stage IIIa and 127 (87%) had IIIb disease, which included 16 patients with pleural effusion and 20 with supraclavicular lymph node metastasis. RESULTS: The response rate was 75%, composed of 22% complete responders and 53% partial responders. With a minimum follow up of 45 months, overall survival was 51.2% at 1 year, 25.1% at 2 years and 14.8% at 5 years; median survival was 12 months. Patients achieving complete response (n=32) had a 2-year overall survival of 49.8% and a 5 year survival of 39.2%, compared to 22.5% and 11.4% survival for the partial responders (n=78) (p=0.0001). Actuarial local progression free survivals for all patients were 65% at 1 year, 42% at 2 years and 36% at 4 years, and actuarial distant free survival was 58% at 1 year, 49% at 2 years and 41% at 5 years. Severe weight loss (more than 10%) occurred in 20 of the 146 patients (13.7%) during treatment, 42 patients (29%) developed radiation pneumonitis, 29 had grade 1 and 13 showed grade 2. The average NTCP value of the patients who showed radiation pneumonitis was significantly higher than that of patients without pneumonitis (66.0% vs. 26.4%). Four patients died of treatment related toxicity. CONCLUSION: Hyperfractionated 3D conformal radiotherapy and concurrent chemotherapy, as described here, is a well tolerate regimen with acceptable toxicity. More effective treatment scheme will be required to improve on local disease control and overall survival.

Partial Block Technique for Radiation Therapy of Lung Cancer with Dynamic Multi-leaf Collimator

PURPOSE: A spinal cord partial block technique (PBT) with dynamic multileaf collimator (dMLC) for the reduction of the spinal cord dose while keeping the tumor dose unchanged has been developed and its effectiveness has been examined. MATERIALS AND METHODS: Conventional 3-D conformal therapy treatment plan is deigned prior to the PBT application. Beam parameters such as, number of beams, beam directions were determined during 3-D conformal therapy planning process. The shape and the weight of the partial block for optimizing the dose distribution are designed with the forward intensity modulated radiation therapy (fIMRT). Eight cases of lung cancer, in which it was found to be impossible to deliver enough doses to targets with the conventional technique because the doses of the normal lungs or the spinal cords were over the tolerance limit, are used to verify the usefulness of this technique. Comparison of the dose volume histogram (DVH) is performed to compare the treatment plan. RESULTS: PBT plan cauld reduce the maximum dose to the spinal cord up to 29.7% and the mean dose to the lungs up to 11.1%. CONCLUSION: All of the cases showed that the PBT plans are better than the conventional 3-D plans and the spinal cord doses or the normal lung doses can be reduced to tolerance limit

Technical Review of Target Volume Delineation on the Posterior Fossa Tumor:An Optimal Head and Neck Position / 대한방사선종양학회지

PURPOSE: To explore a 3D conformal radiotherapy technique for a posterior fossa boost, and the potential advantages of a prone position for such radiotherapy. MATERIALS AND METHODS: A CT simulator and 3D conformal radiotherapy planning system was used for the posterior fossa boost treatment of a 13-year-old medulloblastoma patient. He was placed in the prone position and immobilized with an aquaplast mask and immobilization mold. CT scans were obtained of the brain from the top of the skull to the lower neck, with IV contrast enhancement. The target volume and normal structures were delineated on each slice, with treatment planning performed using non-coplanar conformal beams. RESULTS: The CT scans, and treatment in the prone position, were performed successfully. In the prone position, the definition of the target volume was made easier due to the well enhanced tentorium. In addition, the posterior fossa was located anteriorly, and with the greater choice of beam arrangements, more accurate treatment planning was possible as the primary beams were not obstructed by the treatment table. CONCLUSION: A posterior fossa boost, in the prone position, is feasible in cooperating patients, but further evaluation is needed to define the optimal and most comfortable treatment positions.

Preliminary Results of Stereotactic Body Frame Based Fractionated Radiosurgery on Consecutive Days for Primary Lung Cancer or Metastatic Lung Tumors

To evaluate the feasibility and treatment outcomes of stereotactic radiosurgery (SRS) using a stereotactic body frame (Precision TherapyTM), we prospectively reviewed 34 tumors of the 28 patients with primary or metastatic intrathoracic lung tumors. Eligible patients included were 9 with primary lung cancer and 19 with metastatic tumors from the lung, liver and many other organs. A single dose of 10 Gy to the clinical target volume (CTV) was delivered to a total dose of 30~40 Gy with 3~4 fractions. Four to 8 coplanar or non-coplanar static fields were generated to adequately cover the planning target volume (PTV) as well as to exclude the critical structures as much as possible. More than 90% of the PTV was delivered the prescribed dose in the majority of cases (average; 96%, range; 74%~100%). The mean PTV was 41.4 cc ranging from 4.4 to 230 cc. Set-up error was within 5 mm in all directions (X, Y, Z axis). The response was evaluated by using a chest CT and or 18FDG-PET scans after SRS treatment, 11 patients (39%) showed complete response, 12 (43%) partial response (decrease of more than 50% of the tumor volume), and 4 patients showed minimally decreased tumor volume or stable disease, but 1 patient showed progressive disease. With a median follow-up period of 18 months, a median local disease progression free interval was 18 months ranging from 7 to 35 months. Although all patients developed grade 1 radiation pneumonitis within 3 months, none had symptomatic or serious late complications after completing SRS treatment. Given these observations, it is concluded that the stereotactic body frame based SRS is a safe and effective treatment modality for the local management of primary or metastatic lung tumors. However, the optimum total dose and fractionation schedule used should be determined after the longer follow-up of these results.

One Click Film (OCF) Dosimetry System for Routine QA / 대한방사선종양학회지

PURPOSE: To develop a practical film dosimetry system for routine Quality Assurance (QA). MATERIALS AND METHODS: An One Click Film (OCF) Dosimetry system was designed to perform swift routine QA with functions including automatic fog value elimination, angle adjustment, automatic symmetry calculation, and realtime profile generation with the ability to display realtime three-dimensional dose distributions. RESULTS: The most frequently used functions for routine QA, such as the elimination of the fog value, conversion into an H&D curve, symmetry, and isodose distribution, can be achieved with only one click. CONCLUSION: Reliable results were achieved with the OCF dosimetry with simpler steps than other commercially available film dosimetry systems for routine QA. More research on the refined user interface will make this system be clinically useful.

Quality Assurance of Patients for Intensity Modulated Radiation Therapy / 대한방사선종양학회지

PURPOSE: To establish and verify the proper and the practical IMRT (Intensity-modulated radiation therapy) patient QA (Quality Assurance). MATERIALS AND METHODS: An IMRT QA which consists of 3 steps and 16 items were designed and examined the validity of the program by applying to 9 patients, 12 IMRT cases of various sites. The three step QA program consists of RTP related QA, treatment information flow QA, and a treatment delivery QA procedure. The evaluation of organ constraints, the validity of the point dose, and the dose distribution are major issues in the RTP related QA procedure. The leaf sequence file generation, the evaluation of the MLC control file, the comparison of the dry run film, and the IMRT field simulate image were included in the treatment information flow procedure QA. The patient setup QA, the verification of the IMRT treatment fields to the patients, and the examination of the data in the Record & Verify system make up the treatment delivery QA procedure. RESULTS: The point dose measurement results of 10 cases showed good agreement with the RTP calculation within 3%. One case showed more than a 3% difference and the other case showed more than 5%, which was out side the tolerance level. We could not find any differences of more than 2 mm between the RTP leaf sequence and the dry run film. Film dosimetry and the dose distribution from the phantom plan showed the same tendency, but quantitative analysis was not possible because of the film dosimetry nature. No error had been found from the MLC control file and one mis-registration case was found before treatment. CONCLUSION: This study shows the usefulness and the necessity of the IMRT patient QA program. The whole procedure of this program should be performed, especially by institutions that have just started to accumulate experience. But, the program is too complex and time consuming. Therefore, we propose practical and essential QA items for institutions in which the IMRT is performed as a routine procedure.

Preliminary Results of Stereotactic Radiosurgery Using Stereotactic Body Frame / 대한방사선종양학회지

PURPOSE: To evaluate efficacy and complication of stereotactic radiosurgery using stereotactic body frame. METHODS AND MATERIALS: From December 1997 to June 1999, 11 patients with primary and metastatic tumors were treated with stereotactic radiosurgery using stereotactic body frame(Precision Therapy(TM)). Three patients were treated with primary hepatoma and seven with metastatic tumor from liver, lung, breast, trachea and one with arteriovenous malformation on neck. We used vacuum pillow for immobilization and made skin marker on sternum and tibia area with chest marker and leg marker. Diaphragm control was used for reducing movement by respiration. CT-simulation and treatment planning were performed. Set-up error was checked by CT-Simulator before each treatment. Dose were calculated on the 80~90% isodose of isocenter dose and given consecutive 3 fractions for total dose of 30 Gy (10 Gy/fraction). RESULTS: Median follow-up was 12 months. One patient (9%) showed complete response and four patients (36%) showed partial response and others showed stable disease. Planning target volumes (PTV) ranged from 3 to 111 cc (mean 18.4 cc). Set-up error was within 5 mm in all directions (X, Y, Z axis). There was no complication in all patients. CONCLUSION: In primary and metastatic tumors, stereotactic radiosurgery using stereotactic body frame is very safe, accurate and effective treatment modality.

A CT Simulator Phantom for Geometrical Test / 대한방사선종양학회지

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.

Options in Intracoronary Radiation Therapy / 대한핵의학회잡지

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.

The Broad-beam CT Image Reconstruction from Simulator Images / 대한방사선종양학회지

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.