• Radiation Oncology Journal
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• v.19 no.1
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• pp.74-80
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• 2001

Purpose : Irradiation cones by using backscatter electrons are made for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. Methods and Materials : Backscatter electrons are produced from the primary electron beams from the linear accelerators. The design consists of a cylindrical cone that has a thick circular plate of high atomic number medium (Pb or Cu) attached to the distal end, and the plate can be adjusted the reflected angle. Primary electrons strike the metal plate perpendicularly and produce backscatter electrons that reflect through the lateral hole for treatment. Using film and a parallel plate ion chamber, backscatter electron dose characteristics are measured. Results : The depth dose characteristic of the backscatter electron is very similar to that of the hard x-ray beam that is commonly used for the intracavitary and superficial lesions. The basckscatter electron energy is nearly constant and effectively about 1.5 MeV from the clinical megavoltage beams. The backscatter electron dose rate of $35\~85\;cGy/min$ could be achieved from modern accelerators without any modification. and the depth in water of $50\%$ depth dose from backscatter electron located at 6mm for $45^{\circ}$ angled lead scatter. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. Conclusions : The measured data for backscatter electron energy, depth dose flatness dose rate and absolute dose indicates that the backscatter electrons are suitable for clinical use.

• The Journal of Korean Society for Radiation Therapy
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• v.30 no.1_2
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• pp.129-138
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• 2018

Purpose : An aim of this study was to compare the effect of multi leaf collimator(MLC) types for high dimension radiotherapy in treatment sites used clinically. Material and Method : 70 patients with lung cancer, spine cancer, prostate cancer, whole pelvis, head and neck, breast cancer were included in this study. High definition(HD) MLC of TrueBeam STx (Varian Medical system, Palo Alto, CA) and millenium(M) MLC of VitalBeam (Varian Medical system, Palo Alto, CA) were used. Radiotherapy plans were performed for each patient under same treatment goals with Eclipse (Version 13.7, Varian Palo Alto USA, CA). To compare the indicators of the radiotherapy plans, planning target volume(PTV) coverage, conformity index(CI), homogeneity index(HI), and clinical indicators for each treatment sites in normal tissues were evaluated. To evaluate low dose distribution, $V_{30%}$ values were compared according to MLC types. Additionally, length and volume of targets for each treatment sites were investigated. Result : In stereotatictic body radiotherapy(SBRT) plan for lung, the average value of PTV coverage was reduced by 0.52 % with HD MLC. With SBRT plan using HD MLC for spine, the average value of PTV coverage decreased by 0.63 % and maximum dose decreased by 1.13 %. In the test of CI and HI, the values in SBRT plan with HD MLC for spine were 1.144, 1.079 and the values using M MLC were 1.160, 1.092 in SBRT plan for lung, The dose evaluation of critical organ was reduced by 1.48 % in the ipsilateral lung mean dose with HD MLC. In prostate cancer volumetric modulated arc therapy(VMAT) with HD MLC, the mean dose and the $V_{30}$ of bladder and the mean dose and the $V_{25}$ of rectum were reduced by 0.53 %, 1.42 %, 0.97 %, and 0.69 %, respectively (p<0.05). The average value of heart mean dose was reduced by 0.83 % in breast cancer VMAT with M MLC. Other assessment indices for treatment sites showed no significant difference between treatment plans with two types of MLC. Conclusion : Using HD MLC had a positive impact on the PTV coverage and normal tissue sparing in usually short or small targets such as lung and spine SBRT and prostate VMAT. But, there was no significant difference in targets with long and large such as lung, head and neck, and whole pelvis for VMAT.

• Radiation Oncology Journal
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• v.8 no.2
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• pp.241-253
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• 1990

331 patients of stage IIb uterine cervix cancer trated by radiation alone at Kosin Medical Center between June 1980 and Dec. 1985 were analysed to determine parameters of radiotherapy associated to disease states. Survival rate was highest among the reported ($82.8{\%}$ for crude and $82.4{\%}$ for disease free survival). Pelvic control rate in 6 weeks after the end of radiotherapy was $93.6{\%}$ in the patients treated with ICR following total pelvic radiation and $71.6{\%}$ with small field additional external irradiation. 5 year survival rate in those who achieved pelvic control was $98.9{\%}$ and $12.9{\%}$ in those who had pelvic failure and/or metastasis after radiation. The survival rate figured maximal $88.5{\%}$ with dosage of $7500{\~}8500$ cGy to point A with acceptable incidence of complications ($4.9{\%}$) but without increasing survival above it and minimal $74.1{\%}$ with dosage of less than 6500 cGy. The treatment failure was counted $18.7{\%}$ (62 of 331 patients): Local failure $72.6{\%}$ (45 of 62 patients), locoregional failure $3.2{\%}$ (2 of 62 patients) and distant failure $24{\%}$ (15 of 62 patients). Late complications were found in 50 patients ($15.1{\%}$) and $42{\%}$ of them was rectal bleeding and stenosis. The dose of 8500 cGy to point A was found to be critical for complication and $70{\%}$ of complications occurred above it and was more serious one such as fistula. Rectal complications were developed above rectal dose 6500 cGy and bladder complication above bladder dose 7500 cGy. Major cause of death was cachexia due to locoregional failure ($73.7{\%}$ of death), next was due to metastasis to lung, liver and bone, and only 3 patients died of complication of intestinal perforations and obstruction. In conclusion higher external radiation dose for a bulky uterine cervix and barrel shaped uterus was essential for local control.

• Radiation Oncology Journal
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• v.14 no.3
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• pp.191-199
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• 1996

Purpose : To evaluate 5-year survival rate, patterns of failure and complications of cervical cancer treatment, fifty nine patients treated by curative radiotherapy for the uterine cervical cancer were analyzed retrospectively. Materials and Methods : From March 1986 to May 1990, fifty nine patients with histologically proven uterine cervical cancer were analyzed. According to FIGO stage, there were 2 patients ($3.4\%$) in stage Ib, 2 patients ($3.4\%$) in stage IIa, 31 patients ($52.5\%$) in stage IIb, 15 patients ($25.4\%$) in stage IIIb, 9 patients ($15.3\%$) in stage IV. External RT was per formed by 6 MVLINAC with daily 1.8 Gy, 5 times per week and followed by ICR. A point dose of ICR was calculated to 30-43.66 Gy (median: 34.6 Gy). These techniques delivered total A Point dose of 80.4 to 109.8 Gy (median: 85 Gy). Patients had been followed up from 2 to 110 months (median: 61 months) Results : The overall 5-year survival rate & disease free survival rate were $55.9\%$ and $55.0\%$ respectively. According to FIGO stage, the 5-year survival rate for less than IIa, IIb, IIIb, IV were $75.0\%$, $74.8\%$, $26.7\%$, $33.3\%$, respectively. In univariate analysis, the 5-year survival rate for stage IIb and below versus stage IIIa and above revealed $74.8\%$, $29.2\%$ respectively (P<0.005). According to the hemoglobin level during RT, the 5-rear survival rate of was $73.3\%$ for patients with Hg 10 gm/dL or higher, in contrast to $0\%$ for those with lower than 10 gm/dL (p<0.005). In 18 patients with nonbulky tumor (<5cm), the 5-year survival rates were $71.8\%$. The 5-rear survival rates for 18 patients with 5 cm or greater in tumor diameter were $22.2\%$ (p<0.005). The 5-year survival rate for Patient age of above 50 years and below were $65.3\%$ $34.2\%$ respectively (p<0.05). ECOG performance status. pathologic finding, total dose, total treatment time were not statistically significant factors. The significant prognostic factors affecting overall 5-year survival rate by multivariate analysis showed the hemoglobin level during RT (P=0.0001), tumor size (p=0.0390), FIGO stage (p=0.0468). Total recurrence rate was $23.7\%$ local failure $15.2\%$ (9/59), distant metastasis $6.8\%$ (4/59), local and distant metastasis $1.7\%$ (1/59). According to the RTOG/EORTC Soma Scales, the late complication rate was $23.8\%$ (14/59) The late complication rate of colorectum and genitourinary tract were $15.3\%$ (9/59), $8.5\%$ (5/59), respectively: 10 patients ($17.0\%$) were grade 2, 3 Patients ($5.1\%$) were grade 3 and one patient ($1.7\%$) was grade 4. The late complications were radiation proctitis, rectal bleeding, radiation colitis, diarrhea and radiation cystitis in decreasing order. Conclusion : For improvement of therapeutic results, prospective randomized trials are recomended to discover new prognostic factors and more aggressive radiation therapeutic methods are needed for poor prognostic patients. The adjuvant chemotherapy or radiation-sensitizing agents must be considered to inhibit regional and distant metastasis.

• The Journal of Korean Society for Radiation Therapy
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• v.32
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• pp.17-29
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• 2020

Purpose: The purpose of this work was to investigate the dosimetric impact of mixed energy partial arc technique on prostate cancer VMAT. Materials and Methods: This study involved prostate only patients planned with 70Gy in 30 fractions to the planning target volume (PTV). Femoral heads, Bladder and Rectum were considered as oragan at risk (OARs). For this study, mixed energy partial arcs (MEPA) were generated with gantry angle set to 180°~230°, 310°~50° for 6MV arc and 130°~50°, 310°~230° for 15MV arc. Each arc set the avoidance sector which is gantry angle 230°~310°, 50°~130° at first arc and 50°~310° at second arc. After that, two plans were summed and were analyzed the dosimetry parameter of each structure such as Maximum dose, Mean dose, D2%, Homogeneity index (HI) and Conformity Index (CI) for PTV and Maximum dose, Mean dose, V70Gy, V50Gy, V30Gy, and V20Gy for OARs and Monitor Unit (MU) with 6MV 1 ARC, 6MV, 10MV, 15MV 2 ARC plan. Results: In MEPA, the maximum dose, mean dose and D2% were lower than 6MV 1 ARC plan(p<0.0005). However, the average difference of maximum dose was 0.24%, 0.39%, 0.60% (p<0.450, 0.321, 0.139) higher than 6MV, 10MV, 15MV 2 ARC plan, respectively and D2% was 0.42%, 0.49%, 0.59% (p<0.073, 0.087, 0.033) higher than compared plans. The average difference of mean dose was 0.09% lower than 10MV 2 ARC plan, but it is 0.27%, 0.12% (p<0.184, 0.521) higher than 6MV 2 ARC, 15MV 2 ARC plan, respectively. HI was 0.064±0.006 which is the lowest value (p<0.005, 0.357, 0.273, 0.801) among the all plans. For CI, there was no significant differences which were 1.12±0.038 in MEPA, 1.12±0.036, 1.11±0.024, 1.11±0.030, 1.12±0.027 in 6MV 1 ARC, 6MV, 10MV, 15MV 2 ARC, respectively. MEPA produced significantly lower rectum dose. Especially, V70Gy, V50Gy, V30Gy, V20Gy were 3.40, 16.79, 37.86, 48.09 that were lower than other plans. For bladder dose, V30Gy, V20Gy were lower than other plans. However, the mean dose of both femoral head were 9.69±2.93, 9.88±2.5 which were 2.8Gy~3.28Gy higher than other plans. The mean MU of MEPA were 19.53% lower than 6MV 1 ARC, 5.7% lower than 10MV 2 ARC respectively. Conclusion: This study for prostate radiotherapy demonstrated that a choice of MEPA VMAT has the potential to minimize doses to OARs and improve homogeneity to PTV at the expense of a moderate increase in maximum and mean dose to the femoral heads.

• Radiation Oncology Journal
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• v.14 no.1
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• pp.25-31
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• 1996

Purpose : To evaluate the potential advantage for 'sandwich' technique radiotherapy compared to Postoperative radiotherapy in resectable rectal cancer. Materials and Methods : Between January 1989 and Mar 1994, 60 patients with resectable rectal cancer were treated at Inje University Seoul and Sanggye Paik Hospital. Fifty one patients were available for analysis: 20 patients were treated with sandwich technique radiotherapy and 31 patients were treated with Postoperative radiotherapy. In sandwich technique radiotherapy(RT), Patients were treated with preoperative RT 1500 cGy/5fx, followed by immediate curative resection. Patients staged as Astler-Coiler B2, C were considered for postoperative RT with 2500-4500 cGy. in postoperative RT total radiation dose of 4500-6120 cGy, 180 cGy daily at 4-Sweets was delivered. Patients were followed for median period of 25 months. Results : The overall 5-year survival rates for sandwich RT group and postoperative RT group were $60\%$ and $71\%$, respectively(p>0.05). The 5-rear disease free survival rates for each group were $63\%$. There was no difference in local failure rate between two groups($11\%$ versus $7\%$) Incidence of distant metastasis was $11\%$(2/20) in the sandwich technique RT group and $20\%$(6/31) in the postoperative RT group(p>0.05). The frequencies of acute and chronic complications were comparable in both groups. Conclusion : The sandwich technique radiotherapy group shows local recurrence and survival similar to those of Postoperative RT alone group but reduced distant metastasis compared to Postoperative RT group. But long term follow-up and large number of patients is needed to make an any firm conclusion regarding the value of this sandwich technique RT.

• Radiation Oncology Journal
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• v.18 no.1
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• pp.17-25
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• 2000

Purpose : To evaluate the side effects, pattern of failure, and survival rate according to the sequence of postoperative adjuvant radiotherapy and chemotherapy, patients with stages II and III rectal cancer who had undergone curative resection were randomized to 'early radiotherapy group (arm I)' or' late radiotherapy group (arm II)', then we intend to determine the most effective sequence of the radiotherapy and chemotherapy. Materials and Methods . From January 1996 to March 1999, 313 patients with curatively resected stages II and III rectal cancer have been randomized to' early' or' late' radiation therapy group and received combined chemotherapy (5-FU 375 mg/m$^{2}$/day, ieucovorin 20 mg/m$^{2}$, IV bolus daily Dl-5, 8 cycles) and radiation therapy (whole pelvis with 45 Gy/25 fractions/s weeks). Arm I received radiation therapy from day 1 with first cycle of chemotherapy and arm II received radiation therapy from day 57 with third cycle of chemotherapy after completion of first two cycles. Preliminary analysis was peformed with 228 patients registered up to Jun 1998. Two out of the 228 patients were excluded because of double primary cancer. Median follow-up period was 23 months. Results :Local recurrence occurred in 11 patients (9.7$\%$) for arm I and 9 patients (8$\%$) for arm 11. There was no significant difference between both groups ( p=0.64). However, distant metastasis was found in 22 patients (19.5$\%$) for arm I and 35 patients (31.0$\%$) for arm II and which showed statistically significant difference between the two groups ( p=0.046). And neither 3-year disease-free survival (70.2$\%$ vs 59.2$\%$, p=0.2) nor overall survival (89.4$\%$ vs 88.0$\%$, p=0.47) showed significant differences. The incidence of leukopenia during radiation therapy and chemotherapy was 78.3$\%$ and 79.9$\%$ respectively but leukopenia more than RTOG grade 3 was only 2.1$\%$ and 6.0$\%$ respectively. The incidence of diarrhea more than 10 times per day was significantly higher in the patients for arm I than for arm II (71.2$\%$ vs 41.6$\%$, p=0.02) but this complication was controlled with supportive cares. Conclusion : Regardless of the sequence of postoperative adjuvant radiation therapy and chemotherapy after curative resection for rectal cancer, local recurrence rate was low with combined chemoradlotherapy. But distant metastasis rate was lower in early radiation therapy group than in late radiation therapy group and the reason is unclear. Most patients completed these treatments without severe complication, so these were thought to be safe treatments but the treatment compliance should be improved.

• Clinical and Experimental Pediatrics
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• v.46 no.3
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• pp.236-241
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• 2003

Purpose : This study was performed to know the clinical profile and effectiveness of colonoscopic polypectomy in patients with solitary juvenile polyp. Methods : This study included 19 children, aged 1.8 to 11.4 years, who underwent colonoscopic polypectomy and histologically proven solitary juvenile polyps between March 1998 and August 2002. We analyzed their detailed history, clinical manifestations, colonoscopic examination, method of anesthesia and results of colonoscopic polypectomy. Results : The mean age of the 19 cases was $4.7{\pm}2.8year$. The male to female ratio was 1 : 1.1. Hematochezia, the main indication of colonoscopy, was present in all cases. Combined symptoms were mucoid stool or diarrhea(42%), abdominal pain(26%), constipation(11%) and anal fissure(11%). Anemia(Hb <10 g/dL) in four cases recovered spontaneously after polypectomy. Complications associated with premedication, sedation and colonoscopy itself did not occur. Bleeding developed in two cases(11%) after polypectomy. One of them was controlled with hemoclipping. The main site of polyps was the rectosigmoid colon in 15 cases(79%). The size of the polyps ranged from 0.5 to 3.5 cm. The interval between the onset of symptoms and polypectomy was from 0.1 to 42 months. Conclusion : Juvenile polyps are a common cause of benign, chronic and recurrent rectal bleeding. Colonoscopic polypectomy is a simple, safe and effective therapeutic method. So earlier colonoscopy might avoid uneffective treatment and prevent untoward problems such as fear of parents and anemia.

• Nuclear Medicine and Molecular Imaging
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• v.40 no.5
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• pp.249-256
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• 2006

Purpose: Although computed tomography (CT) is widely used for diagnosing liver metastasis from colorectal cancer, diagnostic accuracy of CT is not satisfactory. Magnetic resonance (MR) imaging and F-18 FDG PET has been reported to be superior to CT. However, studies on direct comparison of PET and MR are scarce. We compared the diagnostic accuracy of FDG PET and MR in detecting liver metastasis from colorectal cancer. Materials and Methods: Among 363 colorectal cancer patients who underwent F-18 FDG PET (ECAT, Siemens-CTI, Knoxville; Gemini, Philips, Milpitas, U.S.), 26 patients (M:F=17:9, age=$62{\pm}11$) underwent MR to evaluate suspicious metastatic liver lesions. Finally, 35 liver lesions detected by CT from 26 patients were enrolled for analysis. PET and MR results were compared with pathologic reports, clinical findings or follow-up results. Results: Of the 35 lesions, 18 lesions (51.4%) were diagnosed as liver metastases, while remaining 17 (48.6%) as benign. The sensitivity and the specificity of PET were 94.4% and 94.1%, respectively, compared to 100% and 82.4% for MR. MR and PET was concordant in 30 lesions (85.7%: 17 metastatic (94.4%) and 13 benign (76.5%) lesions. ROC curve analysis revealed maximal SUV of 3.1 as the optimum standard in differentiating metastatic from benign liver lesions (AUC=0.897, p<0.001, sensitivity 83.3%, specificity 94.1%). For small lesions less than 1 cm ln diameter (n=20), diagnostic accuracy of PET was comparable to that of MR. Conclusion: F-18 FDG PET showed good diagnostic performance in detecting liver metastasis from colorectal cancer, which was comparable to MR.

• Radiation Oncology Journal
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• v.28 no.3
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• pp.166-176
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• 2010

Purpose: To determine the appropriate prostate planning target volume (PTV) margins for 3-dimensitional (3D) conformal radiotherapy (CRT) and intensity-modulated radiation therapy (IMRT) patients treated with an endorectal balloon (ERB) under our institutional treatment condition. Materials and Methods: Patients were treated in the supine position. An ERB was inserted into the rectum with 70 cc air prior to planning a CT scan and then each treatment fraction. Electronic portal images (EPIs) and digital reconstructed radiographs (DRR) of planning CT images were used to evaluate inter-fractional patient's setup and ERB errors. To register both image sets, we developed an in-house program written in visual $C^{++}$. A new method to determine prostate PTV margins with an ERB was developed by using the common method. Results: The mean value of patient setup errors was within 1 mm in all directions. The ERB inter-fractional errors in the superior-inferior (SI) and anterior-posterior (AP) directions were larger than in the left-right (LR) direction. The calculated 1D symmetric PTV margins were 3.0 mm, 8.2 mm, and 8.5 mm for 3D CRT and 4.1 mm, 7.9 mm, and 10.3 mm for IMRT in LR, SI, and AP, respectively according to the new method including ERB random errors. Conclusion: The ERB random error contributes to the deformation of the prostate, which affects the original treatment planning. Thus, a new PTV margin method includes dose blurring effects of ERB. The correction of ERB systematic error is a prerequisite since the new method only accounts for ERB random error.