Dose-Response Relationship between Radiation Dose and Loco-regional Control in Patients with Stage II-III Esophageal Cancer Treated with Definitive Chemoradiotherapy / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: The correlation between radiation dose and loco-regional control (LRC) was evaluated in patients with stage II-III esophageal cancer treated with definitive concurrent chemoradiotherapy (CRT). MATERIALS AND METHODS: Medical records of 236 stage II-III esophageal cancer patients treated with definitive CRT at Yonsei Cancer Center between 1994 and 2013 were retrospectively reviewed. Among these, 120 received a radiation dose of 60 Gy) is associated with increased LRC, PFS, and OS in patients with stage II-III esophageal cancer treated with definitive CRT.

Is Total Knee Arthroplasty a Viable Treatment Option in Octogenarians with Advanced Osteoarthritis?

PURPOSE: This study directly compared clinical assessment scores and short-term systemic complications after total knee arthroplasty (TKA) between a group of patients aged 80 or older (141 patients) and another group of patients aged between 65 and 70 years (616 patients) with advanced osteoarthritis. MATERIALS AND METHODS: We retrospectively investigated 757 osteoarthritic patients who underwent primary TKA from January 2007 to January 2011 with a follow-up of 1 year. The surgery was performed using an extramedullary alignment guide instrument without invasion of the intramedullary canal to decrease embolic load and blood loss. RESULTS: At 1 year after surgery, the mean Knee Society knee score was improved in both groups (from 63.6 to 83.2 in octogenarians and from 68.3 to 89.0 in the younger group) and the level of satisfaction was excellent in both groups (8 in octogenarians and 8.3 in the younger group), even though there was no notable change in function score in the octogenarians (from 61.0 to 61.9 in the octogenarians and from 62.3 to 73.6 in the younger group). The total incidence of systemic complications (3.4% vs. 1.2%, p=0.400) and surgical complications (2.1% vs. 0.5%, p=0.229) showed no significant difference between groups. CONCLUSIONS: TKA yielded favorable clinical outcomes with a comparatively low postoperative complication rate in octogenarians despite the negligible functional improvement.

Our Experiences with Robot-Assisted Laparoscopic Radical Cystectomy: Orthotopic Neobladder by the Suprapubic Incision Method

PURPOSE: To report our technique for and experience with robot-assisted laparoscopic radical cystectomy (RARC) with orthotopic neobladder (ON) formation in a cohort of bladder cancer patients. MATERIALS AND METHODS: Between December 2007 and December 2011, a total of 35 patients underwent RARC. The patients' mean age was 63.3 years and their mean body mass index was 23.7 kg/m2. Thirty patients had a clinical stage of T2 or higher. Postoperative mean follow-up duration was 25.5 months. In 5 patients, a 4-cm midline infraumbilical skin incision was made for an ileal conduit (IC) and the stoma formation was similar to the open procedure. In 30 patients undergoing the ON procedure, the skin for specimen removal and extracorporeal enterocystoplasty was incised infraumbilically in the early 5 cases with redocking (ON-I) and suprapubically in the latter 25 cases without redocking (ON-S). RESULTS: The mean operative times of the IC, ON-I, and ON-S groups were 442.5, 646.0, and 531.3 minutes, respectively (p=0.001). Mean console and lymph node dissection time were not significantly different between the groups. Mean urinary diversion times in each group were 68.8, 125.0, and 118.8 minutes, respectively (p=0.001). In the comparison between the ON-I and ON-S group, only operative time was significant. Four patients required a blood transfusion. We had no cases of intraabdominal organ injury or open conversion. Thiry-three patients (94.2%) had a pathologic stage of T2 or higher. Two patients (5.7%) had lymph node-positive disease. Postoperative complications included ileus (n=4), stricture in the uretero-ileal junction (n=2), and vesicovaginal fistula (n=1). CONCLUSIONS: Our robotic neobladder-suprapubic incision without redocking procedure is easier and more rapid than that of infraumbilical incision with redocking.

Our Experiences with Robot-Assisted Laparoscopic Radical Cystectomy: Orthotopic Neobladder by the Suprapubic Incision Method

PURPOSE: To report our technique for and experience with robot-assisted laparoscopic radical cystectomy (RARC) with orthotopic neobladder (ON) formation in a cohort of bladder cancer patients. MATERIALS AND METHODS: Between December 2007 and December 2011, a total of 35 patients underwent RARC. The patients' mean age was 63.3 years and their mean body mass index was 23.7 kg/m2. Thirty patients had a clinical stage of T2 or higher. Postoperative mean follow-up duration was 25.5 months. In 5 patients, a 4-cm midline infraumbilical skin incision was made for an ileal conduit (IC) and the stoma formation was similar to the open procedure. In 30 patients undergoing the ON procedure, the skin for specimen removal and extracorporeal enterocystoplasty was incised infraumbilically in the early 5 cases with redocking (ON-I) and suprapubically in the latter 25 cases without redocking (ON-S). RESULTS: The mean operative times of the IC, ON-I, and ON-S groups were 442.5, 646.0, and 531.3 minutes, respectively (p=0.001). Mean console and lymph node dissection time were not significantly different between the groups. Mean urinary diversion times in each group were 68.8, 125.0, and 118.8 minutes, respectively (p=0.001). In the comparison between the ON-I and ON-S group, only operative time was significant. Four patients required a blood transfusion. We had no cases of intraabdominal organ injury or open conversion. Thiry-three patients (94.2%) had a pathologic stage of T2 or higher. Two patients (5.7%) had lymph node-positive disease. Postoperative complications included ileus (n=4), stricture in the uretero-ileal junction (n=2), and vesicovaginal fistula (n=1). CONCLUSIONS: Our robotic neobladder-suprapubic incision without redocking procedure is easier and more rapid than that of infraumbilical incision with redocking.

Intensity Modulated Radiation Therapy Commissioning and Quality Assurance: Implementation of AAPM TG119 / 의학물리

The purpose of this study is to evaluate the accuracy of IMRT in our clinic from based on TG119 procedure and establish action level. Five IMRT test cases were described in TG119: multi-target, head&neck, prostate, and two C-shapes (easy&hard). There were used and delivered to water-equivalent solid phantom for IMRT. Absolute dose for points in target and OAR was measured by using an ion chamber (CC13, IBA). EBT2 film was utilized to compare the measured two-dimensional dose distribution with the calculated one by treatment planning system. All collected data were analyzed using the TG119 specifications to determine the confidence limit. The mean of relative error (%) between measured and calculated value was 1.2+/-1.1% and 1.2+/-0.7% for target and OAR, respectively. The resulting confidence limits were 3.4% and 2.6%. In EBT2 film dosimetry, the average percentage of points passing the gamma criteria (3%/3 mm) was 97.7+/-0.8%. Confidence limit values determined by EBT2 film analysis was 3.9%. This study has focused on IMRT commissioning and quality assurance based on TG119 guideline. It is concluded that action level were +/-4% and +/-3% for target and OAR and 97% for film measurement, respectively. It is expected that TG119-based procedure can be used as reference to evaluate the accuracy of IMRT for each institution.

Division of the N2 Stage According to the Multiplicity of the Involved Nodal Stations May be Necessary in the N2-NSCLC Patients Who are Treated with Postoperative Radiotherapy / 대한방사선종양학회지

PURPOSE: We wanted to evaluate the prognostic factors for the pathologic N2 non-small cell lung cancer (NSCLC) patients who were treated by postoperative radiotherapy. MATERIALS AND METHODS: We retrospectively reviewed 112 pN2 NSCLC patients who underwent surgery and postoperative radiotherapy (PORT) From January 1999 to February 2008. Seventy-five (67%) patients received segmentectomy or lobectomy and 37 (33%) patients received pneumonectomy. The resection margin was negative in 94 patients, and it was positive or close in 18 patients. Chemotherapy was administered to 103 (92%) patients. Nine (8%) patients received PORT alone. The median radiation dose was 54 Gy (range, 45 to 66), and the fraction size was 1.8~2 Gy. RESULTS: The 2-year overall survival (OS) rate was 60.2% and the disease free survival (DFS) rate was 44.7% for all the patients. Univariate analysis showed that the patients with multiple-station N2 disease had significantly reduced OS and DFS (p=0.047, p=0.007) and the patients with an advanced T stage (> or =T3) had significantly reduced OS and DFS (p or =5 cm) and positive lymphovascular invasion reduced the OS (p=0.035, 0.034). Using multivariate analysis, we found that multiple-station N2 disease and an advanced T stage (> or =T3) significantly reduced the OS and DFS. Seventy one patients (63.4%) had recurrence of disease. The patterns of failure were loco-regional in 23 (20.5%) patients, distant failure in 62 (55.4%) and combined loco-regional and distant failure in 14 (12.5%) patients. CONCLUSION: Multiple involvement of mediastinal nodal stations for the pN2 NSCLC patients with PORT was a poor prognostic factor in this study. A prospective study is necessary to evaluate the N2 subclassification and to optimize the adjuvant treatment.

Development of an Automatic Seed Marker Registration Algorithm Using CT and kV X-ray Images / 대한방사선종양학회지

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.

Evaluation of Geometric Correspondence of kV X-ray Images, Electric Portal Images and Digitally Reconstructed Radiographic Images / 의학물리

In this study we estimated a geometric correlation among digitally reconstructed radiographic image (DRRI), kV x-ray image (kVXI) from the On-Board Imager (OBI) and electric portal image (EPI). To verify geometric correspondence of DRRI, kVXI and EPI, specially designed phantom with indexed 6 ball bearings (BBs) were employed. After accurate setup of the phantom on a treatment couch using orthogonal EPIs, we acquired set of orthogonal kVXIs and EPIs then compared the absolute positions of the center of the BBs calculated at each phantom plane for kVXI and EPI respectively. We also checked matching result for obliquely incident beam (gantry angle of 315 degrees) after 2D-2D matching provided by OBI application. A reference EPI obtained after initial setup of the phantom was compared with 10 series of EPIs acquired after each 2D-2D matching. Imaginary setup errors were generated from -5 mm to 5 mm at each couch motion direction. Calculated positions of all center positions of the BBs at three different images were agreed with the actual points within a millimeter and each other. Calculated center positions of the BBs from the reference and obtained EPIs after 2D-2D matching agreed within a millimeter. We could tentatively conclude that the OBI system was mechanically quite reliable for image guided radiation therapy (IGRT) purpose.

A Monte Carlo Simulation for the Newly Developed Head-and-Neck IMRT Phantom: a Pilot Study / 의학물리

A head-and-neck phantom was designed in order to evaluate remotely the quality of the delivery dose of intensity modulated radiation therapy (IMRT) in each institution. The phantom is homogeneous or inhomogeneous by interchanging the phantom material with the substructure like an air or bone plug. Monte Carlo simulations were executed for one beam and three beams to the phantom and compared with ion chamber and thermoluminescent dosimeter (TLD) measurements of which readings were from two independent institutions. For single beam, the ion chamber results and the MC simulations agreed to within about 2%. TLDs agreed with the MC results to within 2% or 7% according to which institution read the TLDs. For three beams, the ion chamber results showed -5% maximum discrepancy and those of TLDs were +2~+3%. The accuracy of the TLD readings should be increased for the remote dose monitoring. MC simulations are a valuable tool to acquire the reliability of the measurements in developing a new phantom.

The Comparison of Beam Data between Measured Beam Data and Calculated Beam Data Using Treatment Planning System / 의학물리

The first step in the commissioning procedure of a treatment planning system is always verification of the basic beam data. In this work, we have measured PDD curves and beam profiles between 1x1 cm2 and 40x40 cm2. In an attempt, Pinnacle 7.4f detect discrepancies between predicted dose distribution and delivered dose distribution. The discrepancies between measurement data and caculation data was found. The delivered dose was underestimated in field but overestimated out of field. The Dmax depth of 1x1 cm2 was reduced about 2 mm. For the larger field size (> or = 4x4 cm2), the beam profile and PDD curve showed good agreement between measurement data and calculation data.

Monte Carlo Photon and Electron Dose Calculation Time Reduction Using Local Least Square Denoising Filters / 의학물리

The Monte Carlo method cannot have been used for routine treatment planning because of heavy time consumption for the acceptable accuracy. Since calculation time is proportional to particle histories, we can save time by decreasing the number of histories. However, a small number of histories can cause serious uncertainties. In this study, we proposed Monte Carlo dose computation time and uncertainty reduction method using specially designed filters and adaptive denoising process. Proposed algorithm was applied to 6 MV photon and 21 MeV electron dose calculations in homogeneous and heterogeneous phantoms. Filtering time was negligible comparing to Monte Carlo simulation time. The accuracy was improved dramatically in all situations and the simulation of 1% to 10% number of histories of benchmark in photon and electron dose calculation showed the most beneficial result. The empirical reduction of necessary histories was about a factor of ten to fifty from the result.

Analysis of Respiratory Motion Artifacts in PET Imaging Using Respiratory Gated PET Combined with 4D-CT / 대한핵의학회잡지

PURPOSE: Reduction of respiratory motion artifacts in PET images was studied using respiratory-gated PET (RGPET) with moving phantom. Especially a method of generating simulated helical CT images from 4D-CT datasets was developed and applied to a respiratory specific RGPET images for more accurate attenuation correction. MATERIALS AND METHODS: Using a motion phantom with periodicity of 6 seconds and linear motion amplitude of 26 mm, PET/CT (Discovery ST; GEMS) scans with and without respiratory gating were obtained for one syringe and two vials with each volume of 3, 10, and 30 ml respectively. RPM (Real-Time Position Management, Varian) was used for tracking motion during PET/CT scanning. Ten datasets of RGPET and 4D-CT corresponding to every 10% phase intervals were acquired. From the positions, sizes, and uptake values of each subject on the resultant phase specific PET and CT datasets, the correlations between motion artifacts in PET and CT images and the size of motion relative to the size of subject were analyzed. RESULTS: The center positions of three vials in RGPET and 4D-CT agree well with the actual position within the estimated error. However, volumes of subjects in non-gated PET images increase proportional to relative motion size and were overestimated as much as 250% when the motion amplitude was increased two times larger than the size of the subject. On the contrary, the corresponding maximal uptake value was reduced to about 50%. CONCLUSION: RGPET is demonstrated to remove respiratory motion artifacts in PET imaging, and moreover, more precise image fusion and more accurate attenuation correction is possible by combining with 4D-CT.

The Effect of the CT Number for Each CT on Dose Calculation / 의학물리

The CT number corresponds to electron density and its influence on dose calculation was studied. Five kinds of CT scanners were used to obtain images of electron density calibration phantom (Gammex RMI 467). Then the differences between CT numbers for each scanners were +/-2% in homogeneous medium and 9.5% in high density medium. In order to investigate the influence of CT number to dose calculation, patients' thoracic CT images were analyzed. The maximum dose difference was 0.48% for each organ. It acquired the phantom images inserted high density material in the water phantom. Comparing the doses calculated with CT images from each CT scanner, the maximum dose difference was 2.1% in 20 cm in depth. The exact density to CT number conversion according to CT scanner is required to minimize the uncertainty of dose depends on CT number. Especially the each hospital with various CT scanners has to discriminate CT numbers for each CT scanner. Moreover a periodic quality assurance is required for reproducibility of CT number.

Characteristics of Detectors for Measurements of Photon Depth Doses in Build-Up Region / 의학물리

To determine the appropriate method out of various available methods to measure build-up doses, the measurements and comparisons of depth doses of build-up region including the surface dose were executed using the Attix parallel-plate ionization chamber, the Markus chamber, a cylindrical ionization chamber, and a diode detector. Based on the measurements using the Attix chamber, discrepancies of the Markus chamber were within 2% for the open field and increased up to 3.9% in the case of photon beam containing the contaminant electrons. The measurements of an cylindrical ionization chamber and a diode detector accord with those of the Attix chamber within 1.5% and 1.0% after those detectors were completely immersed in the water phantom. The results suggest that the parallel-plate chamber is the best choice to measure depth doses in the build-up region containing the surface, however, using cylindrical ionization chamber or diode detector would be a reasonable choice if no special care is necessary for the exact surface dose.

GafChromic Film Dosimetry for Stereotactic Radiosurgery with a Linear Accelerator / 대한방사선종양학회지

PURPOSE: The purpose of this study was to evaluate whether a GafChromic film applied to stereotactic radiosurgery with a linear accelerator could provide information on the value for acceptance testing and quality control on the absolute dose and relative dose measurements and/or calculation of treatment planning system. MATERIALS AND METHODS: A spherical acrylic phantom, simulating a patient's head, was constructed from three points. The absolute and relative dose distributions could be measured by inserting a GafChromic film into the phantom. We tested the use of a calibrated GafChromic film (MD-55-2, Nuclear Associate, USA) for measuring the optical density. These measurements were achieved by irradiating the films with a dose of 0-112 Gy employing 6 MV photon. To verify the accuracy of the prescribed dose delivery to a target isocenter using a five arc beams (irradiated in 3 Gy per one beam) setup, calculated by the Linapel planning system the absolute dose and relative dose distribution using a GafChromic film were measured. All the irradiated films were digitized with a Lumiscan 75 laser digitizer and processed with the RIT113 film dosimetry system. RESULTS: We verified the linearity of the Optical Density of a MD-55-2 GafChromic film, and measured the depth dose profile of the beam. The absolute dose delivered to the target was close to the prescribed dose of Linapel within an accuracy for the GafChromic film dosimetry (of +/- 3%), with a measurement uncertainty of +/- 1 mm for the 50~90% isodose lines. CONCLUSION: Our results have shown that the absolute dose and relative dose distribution curves obtained from a GafChromic film can provide information on the value for acceptance. To conclude the GafChromic film is a convenient and useful dosimetry tool for linac based radiosurgery.

Application of Intensity Modulated Radiation Therapy (IMRT) in Prostate Cancer / 대한방사선종양학회지

This study was done to implement intensity-modulated radiation therapy (IMRT) for the treatment of primary prostate cancer and to compare this technique with conventional treatment methods. A 72-year- old male patient with prostate cancer stage T2a was treated with IMRT delivered with dynamic multi-leaf collimation. Treatment was designed using an inverse planning algorithm, which accepts dose and dose- volume constraints for targets and normal structures. The IMRT plan was compared with a three-dimensional (3D) plan using the same 6 fields technique. Lower normal tissue doses and improved target coverage were achieved using IMRT at current dose levels, and facilitate dose escalation to further enhance locoregional control and organ movement during radiotherapy is an important issue of IMRT in prostate cancer.

Quality As surance for Intensity Modulated Radiation Therapy / 대한방사선종양학회지

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.

Beam Shaping by Independent Jaw Closure in Stereotactic Radiotherapy / 대한방사선종양학회지

INTRODUCTION: Stereotactic radiation therapy (SRT) can deliver highly focused radiation to a small and spherical target lesion with very high degree of mechanical accuracy. For non-spherical and large lesions, however, inclusion of the neighboring normal structures within the high dose radiation volume is inevitable in SRT. This is to report the beam shaping using the partial closure of the independent jaw in SRT and the verification of dose calculation and the dose display using a home-made soft ware. MATERIALS & METHODS: Authors adopted the idea to partially close one or more independent collimator jaw(s) in addition to the circular collimator cones to shield the neighboring normal structures while keeping the target lesion within the radiation beam field at all angles along the arc trajectory. The output factors (OF's) and the tissue-maximum ratios (TMR's) were measured using the micro ion chamber in the water phantom dosimetry system, and were compared with the theoretical calculations. A film dosimetry procedure was performed to obtain the depth dose profiles at 5 cm, and they were also compared with the theoretical calculations, where the radiation dose would depend on the actual area of irradiation. Authors incorporated this algorithm into the home-made SRT software for the isodose calculation and display, and was tried on an example case with single brain metastasis. The dose-volume histograms (DVH's) of the planning target volume (PTV) and the normal brain derived by the control plan were reciprocally compared with those derived by the plan using the same arc arrangement plus the independent collimator jaw closure. RESULTS: When using 5.0 cm diameter collimator, the measurements of the OF's and the TMR's with one independent jaw set at 30 mm (unblocked), 15.5 mm, 8.6 mm, and 0 mm from the central beam axis showed good correlation to the theoretical calculation within 0.5% and 0.3% error range. The dose profiles at 5 cm depth obtained by the film dosimetry also showed very good correlation to the theoretical calculations. The isodose profiles obtained on the home-made software demonstrated a slightly more conformal dose distribution around the target lesion by using the independent jaw closure, where the DVH's of the PTV were almost equivalent on the two plans, while the DVH's for the normal brain showed that less volume of the normal brain receiving high radiation dose by using this modification than the control plan employing the circular collimator cone only. CONCLUSION: With the beam shaping modification using the independent jaw closure, authors have realized wider clinical application of SRT with more conformal dose planning. Authors believe that SRT, with beam shaping ideas and efforts, should no longer be limited to the small spherical lesions, but be more widely applied to rather irregularly shaped tumors in the intracranial and the head and neck regions.

Setup Verification in Stereotactic Radiotherapy Using Digitally Reconstructed Radiograph (DRR) / 대한방사선종양학회지

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)

Experimental Intestinal Atresia in Chick Embryo

It is generally accepted that a vascular accident in utero during the fetal period plays an important role in the occurrence of intestinal atresia. An experimental study, making use of chick embryos was made to induce intestinal atresia by vascular occlusion or ligation of a loop of intestine. A study using the chick embryos made it relatively easy to obtain the experimental group. Its advantages are a short incubation period(21 days) and many operations can be performed with only a limited supply of surgical instruments. Physiologic umbilical hernia of the chick embryo is present from the 9th to the 18th day of development. We used chick embryos between 9th to 15th day of development to perform experiments. In group I, as a control group, round shaped opening was made in the eggshell, shell membrane and chorioallantoic membrane with diameter of 1 cm, and then closed with transparent tape. In group II, the mesenteric artery was ligated with prolene 7-0. In the group III, a loop of intestine was ligated with prolene 7-0. The survival rate of group I was 35.7%(50/140), group II, 5.1%(36/700) and group III was 7.6%(53/700)(p<0.001). The intestinal atresia in hatched embryos showed no case in group I, 14cases out of 36cases in Group II(type II 5cases, type III 9cases), and all cases in Group III(type I 3cases, type II 29cases, type III 21cases). There was no significant relation between experimental group and type of intestinal atresia(p=0.09). In this experiments, the survival rate and incidence of intestinal atresia of group III were higher than group II. We concluded that vascular accident of intestine during fetal period was a factor in development of intestinal atresia, but, mechanical obstruction of intestinal loop was more important.