Dosimetric Effect on Selectable Optimization Parameters of Volumatric Modulated Arc Therapy / 의학물리

The aim of this study is to evaluate plan quality and dose accuracy for Volumetric Modulated Arc Therapy (VMAT) on the TG-119 and is to investigate the effects on variation of the selectable optimization parameters of VMAT. VMAT treatment planning was implemented on a Varian iX linear accelerator with ARIA record and verify system (Varian Mecical System Palo Alto, CA) and Oncentra MasterPlan treatment planning system (Nucletron BV, Veenendaal, Netherlands). Plan quality and dosimetric accuracy were evaluated by effect of varying a number of arc, gantry spacing and delivery time for the test geometries provided in TG-119. Plan quality for the target and OAR was evaluated by the mean value and the standard deviation of the Dose Volume Histograms (DVHs). The ionization chamber and Delta4PT bi-planar diode array were used for the dose evaluation. For treatment planning evaluation, all structure sets closed to the goals in the case of single arc, except for the C-shape (hard), and all structure sets achieved the goals in the case of dual arc, except for C-shape (hard). For the variation of a number of arc, the simple structure such as a prostate did not have the difference between single arc and dual arc, whereas the complex structure such as a head and neck showed a superior result in the case of dual arc. The dose distribution with gantry spacing of 4degrees was shown better plan quality than the gantry spacing of 6degrees, but was similar results compared with gantry spacing of 2degrees. For the verification of dose accuracy with single arc and dual arc, the mean value of a relative error between measured and calculated value were within 3% and 4% for point dose and confidence limit values, respectively. For the verification on dose accuracy with the gantry intervals of 2degrees, 4degrees and 6degrees, the mean values of relative error were within 3% and 5% for point dose and confidence limit values, respectively. In the verification of dose distribution with Delta4PT bi-planar diode array, gamma passing rate was 98.72+/-1.52% and 98.3+/-1.5% for single arc and dual arc, respectively. The confidence limit values were within 4%. The smaller the gantry spacing, the more accuracy results were shown. In this study, we performed the VMAT QA based on TG-119 procedure, and demonstrated that all structure sets were satisfied with acceptance criteria. And also, the results for the selective optimization variables informed the importance of selection for the suitable variables according to the clinical cases.

Rotational Alignment of Femoral Component for Minimal Medial Collateral Ligament Release in Total Knee Arthroplasty

PURPOSE: We attempted to determine the degree of rotation of the femoral component to achieve an ideal rectangular flexion gap with minimal medial collateral ligament (MCL) release using a modified measured technique. MATERIALS AND METHODS: Group I consisted of 60 osteoarthritis patients (72 cases) who underwent total knee arthroplasty (TKA) with minimal MCL release and Group II consisted of 48 patients without osteoarthritis (61 cases). We performed computed tomography (CT) scanning of the knee with 90 degree flexion in all of the patients and analyzed the angles between the distal femur landmarks and the tibial mechanical axis using a Picture Archiving Communication system. External rotation of the femoral component from the Whiteside line and posterior condylar line was measured in group I who underwent TKA with minimum MCL release. The variance in the mediolateral flexion gap according to the degree of rotation was also measured using an Auto-Computer Aided Design program. RESULTS: The CT scans showed that the Whiteside line, posterior condylar line, and transepicondylar line was more internally rotated on average from the longitudinal axis of tibia by 4.12degrees, 5.54degrees, and 4.64degrees, respectively, in group I compared to group II. In group I, the femoral component was inserted with an average external rotation of 5.6degrees from the posterior condylar line and with an average external rotation of 2.0degrees from the Whiteside line with minimal MCL release. From the measurements of the femoral component size and the variance in the degree of rotation using an Auto-CAD program, it was found that the change in the mediolateral flexion gap was greater when the rotation angle was greater and it was greater when the size of femoral component was larger at the same rotation angle. CONCLUSIONS: The average rotation angle of the femoral component to achieve an ideal rectangular flexion gap with minimal MCL release in TKA was an external rotation of 5.6degrees from the posterior condylar line and an external rotation of 2.0degrees from the Whiteside line. We concluded that when a femoral component is small in size, greater than average external rotation needs to be applied and when a femoral component is large in size, less than average external rotation needs to be applied.

Incomplete Reduction that Influence Reduction of Sesamoid as a Cause for Recurrence of Hallux Valgus / 대한족부족관절학회지

PURPOSE: The incomplete reduction of the sesamoid has lately been issued as cause for recurrence. In this study, we analysed factors that may influence reduction of sesamoid. MATERIALS AND METHODS: The study consists of 50 cases operated by single surgeon. Eighteen cases were done by proximal chevron osteotomy, and 32 cases were done by scarf osteotomy. Hallux valgus (HV) angle and intermetatarsal (IM) angle were measured before and three months after the surgery. Sesamoid position (SP) was classified according to Hardy and Clapham grade system. RESULTS: After the proximal chevron osteotomy, the correction of the mean HV angle was 19.5degrees, and IM angle was 6.2degrees. SP was changed from 5.6 to 3.4 grade. After the Scarf osteotomy, the correction of the mean HV angle was 25 degree, and IM angle was 9degrees. SP was changed from 5.5 to 2.8 grade. There was difference of sesamoid's correction between two different method of surgery (p=0.127). However, better correction of sesamoid was witnessed with bigger correction angle regardless of method of surgery (p=0.002, 0.001). CONCLUSION: We believe surgical method do not effect sesamoid's correction but more correction angle can result in better correction of sesamoid position.

Incomplete Reduction that Influence Reduction of Sesamoid as a Cause for Recurrence of Hallux Valgus / 대한족부족관절학회지

PURPOSE: The incomplete reduction of the sesamoid has lately been issued as cause for recurrence. In this study, we analysed factors that may influence reduction of sesamoid. MATERIALS AND METHODS: The study consists of 50 cases operated by single surgeon. Eighteen cases were done by proximal chevron osteotomy, and 32 cases were done by scarf osteotomy. Hallux valgus (HV) angle and intermetatarsal (IM) angle were measured before and three months after the surgery. Sesamoid position (SP) was classified according to Hardy and Clapham grade system. RESULTS: After the proximal chevron osteotomy, the correction of the mean HV angle was 19.5degrees, and IM angle was 6.2degrees. SP was changed from 5.6 to 3.4 grade. After the Scarf osteotomy, the correction of the mean HV angle was 25 degree, and IM angle was 9degrees. SP was changed from 5.5 to 2.8 grade. There was difference of sesamoid's correction between two different method of surgery (p=0.127). However, better correction of sesamoid was witnessed with bigger correction angle regardless of method of surgery (p=0.002, 0.001). CONCLUSION: We believe surgical method do not effect sesamoid's correction but more correction angle can result in better correction of sesamoid position.

A Study on Dose Response of MAGAT (Methacrylic Acid, Gelatin Gel and THPC) Polymer Gel Dosimeter Using X-ray CT Scanner / 의학물리

In this study, we evaluated the dose response of MAGAT (Methacrylic Acid Gelatin gel and THPC) normoxic polymer gel dosimeters based on the X-ray CT scanner. To perform this study, we determined the proper ratio of the gel composition and acquired X-ray scan parameters. MAGAT gel dosimeters were manufactured using MAA (MethacrylicAcid) and gelatin of various concentration, irradiated up to 20 Gy. We obtained the 20 CT images from the irradiated gel dosimeters by using on a Phillips Brilliance Big Bore CT scanner with the various scan parameters. This CT images were used to determine the N(CT)-dose response, dose sensitivity and dose resolution As an amount of MAA and gelatin were increase, the slope and intercept were increase in each MAGAT gel dosimeter with various concentration of the N(CT)-dose response curve. The dose sensitivity was 0.38+/-0.08 to 0.859+/-0.1 and increased were amount of the MAA was increased or the gelatin was decreased. However, the change of gelatin concentration was very small compare to MAA. The Dose resolution (D(delta)(95%)) varies considerably from 2.6 to 6 Gy, dependent on dose resolution and CT image noise. The slope and dose sensitivity was almost ident verywith the variation of the tube voltage, tube current and slice thickness in the dose response curve, but the noise (standard deviation of averamalg CT number) was decreased when the tube voltage, tube current and slice thickness are increase. The optimal MAGAT polymer gel dosimeter based on the CT were evaluated to determine the CT imaging scan parameters of the maximum tube voltage, tube current and slice thickness (commonly used in clinical) using the composition ratio of a 9% MAA, 8% gelatin and 83% water. This study could get proper composition ratio and scan parameter evaluating dose response of MAGAT normoxic polymer gel dosimeter using CT scanner.

Monte Carlo Study Using GEANT4 of Cyberknife Stereotactic Radiosurgery System / 의학물리

Cyberknife with small field size is more difficult and complex for dosimetry compared with conventional radiotherapy due to electronic disequilibrium, steep dose gradients and spectrum change of photons and electrons. The purpose of this study demonstrate the usefulness of Geant4 as verification tool of measurement dose for delivering accurate dose by comparing measurement data using the diode detector with results by Geant4 simulation. The development of Monte Carlo Model for Cyberknife was done through the two-step process. In the first step, the treatment head was simulated and Bremsstrahlung spectrum was calculated. Secondly, percent depth dose (PDD) was calculated for six cones with different size, i.e., 5 mm, 10 mm, 20 mm, 30 mm, 50 mm and 60 mm in the model of water phantom. The relative output factor was calculated about 12 fields from 5 mm to 60 mm and then it compared with measurement data by the diode detector. The beam profiles and depth profiles were calculated about different six cones and about each depth of 1.5 cm, 10 cm and 20 cm, respectively. The results about PDD were shown the error the less than 2% which means acceptable in clinical setting. For comparison of relative output factors, the difference was less than 3% in the cones lager than 7.5 mm. However, there was the difference of 6.91% in the 5 mm cone. Although beam profiles were shown the difference less than 2% in the cones larger than 20 mm, there was the error less than 3.5% in the cones smaller than 20 mm. From results, we could demonstrate the usefulness of Geant4 as dose verification tool.

Comparative Analysis of Clinical Parameters in Acute Pyelonephritis / 대한비뇨기과학회지

PURPOSE: To compare the variable inflammatory parameters of acute pyelonephritis patients treated with inpatient therapy at 13 hospitals, according to the age and gender distributions. MATERIALS AND MATHODS: A total of 3,544 medical records of patients with confirmed acute pyelonephritis, and admitted to hospital between January 2000 and December 2005, were retrospectively analyzed. RESULTS: The mean age of the patients was 43.2+/-16.2 years old, with a male:female ratio of 1 : 5.1. The average duration of hospital admission was 7.9+/-5.3 days. Underlying diseases were found in 23.0% (749/3,252 patient), largely due to diabetes (35.1%). Radiological abnormal findings were found in 13.7%. The leukocyte count, ratio of segmented form, erythrocyte sedimentation rate (ESR), c-reactive protein, pyuria, positive blood culture, positive urine culture were 11,014+/-5,778/mm(3), 74.8+/-14.5%, 44.0+/-32.0 mm/hr, 12.4+/-9.3mg/dl, 83.9%, 10.5% and 46.7%, respectively. E. coli grow in 79% of the urine culture positive patients. In a comparison of 3 age groups (61 years), the elderly patients had a greater number of underlying diseases and more pathogens in cultured blood. When divided into males and females, the elderly male patients had more pathogen in cultured urine, but contrary to the male patients, the elderly female patients had elevated leukocyte count and erythrocyte sedimentation rate. Also, the old patient group had more resistance to ampicillin when they had E. coli as the uropathogen (p=0.021). Patients with higher ESR required longer hospital admission periods. CONCLUSIONS: It was found that variable clinical parameters of acute pyelonephritis patients treated with inpatient therapy differed according to both gender and age group in Korea. Therefore, these factors should be taken into account in the treatment plan.