• Title/Summary/Keyword: Cancer metastasis

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Radiation Therapy and Chemotherapy after Breast Conserving Surgery for Invasive Breast Cancer: An Intermediate Result (침윤성 유방암에서 유방보존수술 후 방사선치료 및 항암화학 병용치료의 성적 및 위험인자 분석)

  • Lee, Seok-Ho;Choi, Jin-Ho;Lee, Young-Don;Park, Heoung-Kyu;Kim, Hyun-Young;Park, Se-Hoon;Lee, Kyu-Chan
    • Radiation Oncology Journal
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    • v.25 no.1
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    • pp.16-25
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    • 2007
  • [ $\underline{Purpose}$ ]: Breast conserving surgery (BCS) followed by chemotherapy (CTx.) and radiation therapy (RT) is widely performed for the treatment of early breast cancer. This retrospective study was undertaken to evaluate our interim results in terms of failure patterns, survival and relative risk factors. $\underline{Materials\;and\;Methods}$: From January 1999 through December 2003, 129 patients diagnosed with invasive breast cancer and treated with BCS followed by RT were subject to retrospective review. The median age of the patients was 45 years (age distribution, $27{\sim}76$ years). The proportions of patients according to their tumor, nodes, and metastases (TNM) stage were 65 (50.4%) in stage I, 41 (31.7%) in stage IIa, 13 (10.1%) in stage IIb, 9 (7.0%) in stage III, and 1 patient (0.8%) in stage IIIc. For 32 patients (24.8%), axillary node metastasis was found after dissection. BCS consisted of quadrantectomy in 115 patients (89.1%) and lumpectomy in 14 patients (10.6%). Axillary node dissection at axillary level I and II was performed for 120 patients (93%). For 7 patients (5.4%), only sentinel node dissection was performed with BCS. For 2 patients (1.6%) axillary dissection of any type was not performed. Postoperative RT was given with 6 MV X-rays. A tumor dose of 50.4 Gy was delivered to the entire breast area using a tangential field with a wedge compensator. An aditional dose of $9{\sim}16\;Gy$ was given to the primary tumor bed areas with electron beams. In 30 patients (23.3%), RT was delivered to the supraclavicular node. Most patients had adjuvant CTx. with $4{\sim}6$ cycles of CMF (cyclophosphamide, methotrexate, 5-fluorouracil) regimens. The median follow-up period was 50 months (range: $17{\sim}93$ months). $\underline{Results}$: The actuarial 5 year survival rate (5Y-OSR) was 96.9%, and the 5 year disease free survival rate (5Y-DFSR) was 93.7%. Local recurrences were noted in 2 patients (true: 2, regional node: 1) as the first sign of recurrence at a mean time of 29.3 months after surgery. Five patients developed distant metastases as the first sign of recurrence at $6{\sim}33$ months (mean 21 months). Sites of distant metastatic sites were bone in 3 patients, liver in 1 patient and systemic lesions in 1 patient. Among the patients with distant metastatic sites, two patients died at 17 and 25 months during the follow-up period. According to stage, the 5Y-OSR was 95.5%, 100%, 84.6%, and 100% for stage I, IIa, IIb, and III respectively. The 5Y-DFSR was 96.8%, 92.7%, 76.9%, and 100% for stage I, IIa, IIb, and III respectively. Stage was the only risk factor for local recurrence based on univariate analysis. Ten stage III patients included in this analysis had a primary tumor size of less than 3 cm and had more than 4 axillary lymph node metastases. The 10 stage III patients received not only breast RT but also received posterior axillary boost RT to the supraclavicular node. During the median 53.3 months follow-up period, no any local or distant failure was found. Complications were asymptomatic radiation pneumonitis in 10 patients, symptomatic pneumonitis in 1 patient and lymphedema in 8 patients. $\underline{Conclusion}$: Although our follow up period is short, we had excellent local control and survival results and reaffirmed that BCS followed by RT and CTx. appears to be an adequate treatment method. These results also provide evidence that distant failure occurs earlier and more frequent as compared with local failure. Further studies and a longer follow-up period are needed to assess the effectiveness of BCS followed by RT for the patients with less than a 3 cm primary tumor and more than 4 axillary node metastases.

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 (비소세포성 폐암으로 수술 후 방사선치료가 시행된 N2병기 환자들에서 다발 부위 종격동 림프절 전이 여부에 따른 N2병기 구분의 임상적 의미)

  • Yoon, Hong-In;Kim, Yong-Bae;Lee, Chang-Geol;Lee, Ik-Jae;Kim, Song-Yih;Kim, Jun-Won;Kim, Joo-Hang;Cho, Byung-Chul;Lee, Jin-Gu;Chung, Kyung-Young
    • Radiation Oncology Journal
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    • v.27 no.3
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    • pp.126-132
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    • 2009
  • 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 ($\geq$T3) had significantly reduced OS and DFS (p<0.001, p=0.025). A large tumor size ($\geq$5 cm) and positive lymphovascular invasion reduced the OS (p=0.035, 0.034). Using multivariate analysis, we found that multiple-station N2 disease and an advanced T stage ($\geq$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.

Hyperfractionated Radiotherapy Following Induction Chemotherapy for Stage III Non-Small Cell Lung Cancer -Randomized for Adjuvant Chemotherapy vs. Observation- (절제 불가능한 제 3 기 비소세포 폐암의 MVP 복합 항암요법과 다분할 방사선 치료 -추가 항암요법에 대한 임의 선택 -)

  • Choi, Eun-Kyung;Chang, Hye-Sook;Ahn, Seung-Do;Yang, Kwang-Mo;Suh, Cheol-Won;Lee, Kyoo-Hyung;Lee, Jung, Shin;Kim, Sang-Hee;Ko, Youn-Suk;Kim, Woo-Sung;Kim, Won-Dong;Song, Koun-Sik;Sohn, Kwang-Hyun
    • Radiation Oncology Journal
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    • v.11 no.2
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    • pp.295-301
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    • 1993
  • Since Jan. 1991 a prospective randomized study for Stage III unresectable non small cell lung cancer (NSCLC) has been conducted to evaluate the response rate and tolerance of induction chemotherapy with MVP followed by hyperfractionated radiotherapy and evaluate the efficacy of maintenance chemotherapy in Asan Medical Center. All patients in this study were treated with hyperfractionated radiotherapy (120 cGy/fx BID, 6480 cGy/54 fx) following 3 cycles of induction chemotherapy, MVP (Mitomycin C 6 $mg/m^2,$ Vinblastin 6 $mg/m^2,$ Cisplatin 60 $mg/m^2$) and then the partial and complete responders from induction chemotherapy were randomized to 3 cycles of adjuvant MVP chemotherapy group and observation group. 48 patients were registered to this study until December 1992; among 48 patients 3 refused further treatment after induction chemotherapy and 6 received incomplete radiation therapy because of patient's refusal, 39 completed planned therapy. Twenty-three $(58\%)$ patients including 2 complete responders showed response from induction chemotherapy. Among the 21 patients who achieved a partial response after induction chemotherapy,1 patient rendered complete clearance of disease and 10 patients showed further regression of tumor following hyperfractionated radiotherapy. Remaining 10 patients showed stable disease or progression after radiotherapy. Of the sixteen patients judged to have stable disease or progression after induction chemotherapy, seven showed more than partial remission after radiotherapy but nine showed no response in spite of radiotherapy. Of the 39 patients who completed induction chemotherapy and radiotherapy, 25 patients $(64\%)$ including 3 complete responders showed more than partial remission. Nineteen patients were randomized after radio-therapy. Nine Patients were allocated to adjuvant chemotherapy group and 4/9 showed further regression of tumor after adjuvant chemotherapy. For the time being, there is no suggestion of a difference between the adjuvant chemotherapy group and observation group in distant metastasis rate and survival. Median survival time was 13 months. Actuarial survival rates at 6,12 and 18 months of 39 patients who completed this study were $84.6\%,\;53.7\%\;and\;40.3\%,$ respectively. The partial and complete responders from induction chemotherapy showed significantly better survival than non-responders (p=0.028). Incidence of radiation pneumonitis in this study group was less than that in historical control group inspite of induction chemotherapy. All patients tolerated hypertractionated radiotherapy without definite increase of acute complications compared with conventional radiotherapy group. The longer follow up is needed to evaluate the efficacies of induction and maintenance chemotherapy and survival advantage by hyperfractionated radiotherapy but authors are encouraged with an excellent tolerance, higher response rate and improvement of one year survival rate in patients of this study.

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Immunohistochemical Studies for TIMP-1 and TIMP-2 Expression after Irradiation in Lung, Liver and Kidney of C57BL/6 Mouse (C57BL/96 Mouse의 폐, 간, 신장에서 방사선조사 후 TIMP-1, TIMP-2의 발현에 대한 면역조직화학적 연구)

  • Noh, Young-Ju;Ahn, Seung-Do;Kim, Jong-Hoon;Choi, Eun-Kyung;Chang, Hye-Sook
    • Radiation Oncology Journal
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    • v.19 no.2
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    • pp.181-189
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    • 2001
  • Purpose : Changes in the balance between MMP and TIMP can have a profound effect on the composition in the extracellular matrix (ECM) and affect various cellular functions including adhesion, migration, differentiation of cells, and fibrosis and invasion and metastasis of cancer cells. Radiation therapy is a popular treatment modality for benign and malignant tumor, but the study for radiation effect on MMP and TIMP is scarce. In the current study, we have examined the expression of TIMP in fibrosis-prone (C57BL/6) mice after radiation. Methods and Materials : Adult female mice of $10\~12$ weeks were used. The whole body were irradiated using a Varian CL-4/100 with 2 and 10 Gy. Immunohistochemical staining was peformed according to Avidin Biotin complex method and evaluated by observing high power field. For TIMP-1, TIMP-2 antibodies, reactivity was assessed in the parenchymal cell and in the stromal cell. The scale of staining was assessed by combining the quantitative and qualiative intensity of staining. Results : TIMP-1 immunoreactivity did not change in lung. But, in liver, TIMP-1 immunoreactivity was localized in cytoplasm of hepatocyte and Kupffer cell. in kidney, TIMP-1 immunoreactivity was localized in cytoplasm of some tubular cell. Temporal variations were not seen. Dose-response relationship was not seen except kidney. TIMP-2 immunoreactivity in lung was a score (++) at 0 Gy and elevated to a score (+++) at 2 Gy. TIMP-2 immunoreactivity was a score (++) in liver at 0 Gy. TIMP-2 immunoreactivity was localized in cytoplasm of hepatocyte and Kupffer cell as same as patterns of TIMP-1 immunoreactivity. The TIMP-2 immunoreactivity in liver was elevated to (+++) at 2 Gy. Immunoreactivity to TIMP-2 in kidney was a score (+++) at 0 Gy and was not changed at 10 Gy. The score of TIMP-2 immunoreactivity was reduced to (++) at 2 Gy. TIMP-2 immunoreactivity was confined to tubules in kidney. Temporal variation of TIMP-2 immunoreactivity was irregular. Dose-response relationship of TIMP-2 immunoreactivity was not seen. Conclusions : Differences between intensity of expression of TIMP-1 and TIMP-2 in each organ was present. Expression of TIMP was localized to specific cell in each organ. Irradiation increased TIMP-1 immunoreactivity in the liver and the kidney. Irradiation increased TIMP-2 immunoreactivity in the lung. But, in the liver and the kidney, TIMP-2 expression to radiation was irregular. Temporal variation of TIMP-2 immunoreactivity was irregular. Dose-response relationship of TIHP-2 immunoreactivity was not seen. In the future, we expect that the study of immunohistochemical staining of longer period of postirradiation and quantitative analysis using western blotting and northern blotting could define the role of TIMP in the radiation induced tissue fibrosis.

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Large Cell Carcinoma of the Lung - An analysis of clinical features and survival (대세포 폐암의 임상적 양상과 생존률에 대한 분석)

  • Yang Jin Yeong;Lee Hyung Sik;Moon Sun Rock;Kim Gwi Eon;Suh Chang Ok;Loh Jojn J.K;Oh Won Yong;Whang In Soon
    • Radiation Oncology Journal
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    • v.8 no.2
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    • pp.219-223
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    • 1990
  • This is a retrospective review of 33 patients with large cell lung carcinoma treated at Yonsei University Cancer Center between Jan.1985 and Dec.1989. Of the thirty-three patients, twenty eight were men and five women. Median age was 59 years. Large cell undifferentiated carcinoma was the most common pathologic type, $78.8\%$. Twenty one of thirty three patients had far advanced diseases, stage IIIB-IV at the time of initial diagnosis. Pleural effusion was initially presented in 12 patients, and SVC syndrome appeared in 5 patients. As to location of the primary tumor,19($57.6\%$) appeared in the right lung and 14 ($42.4\%$) in the left. Patients with a centrally located primary tumor mass were nearly the same as those peripherally located (17 vs.16). Fifteen of thirty three patients developed metastasis involving not only bone, brain, the opposite lung, adrenal gland but also soft tissue, skin, pancreas and appendix. Treatment was individualized with 19 treated radically and 14 palliatively. After treatment, only two patients showed a complete response. Long term survival was observed in 4 patients: 1 (24 mo.),2 (41 mo.) and 1 (54 mo.). The overall 2 year survival rate was $14.3\%$ while the median survival time was 6.0 months. Through the analysis of the various factors affecting survival, we observed that pleural effusion-absent group and complete response group had a statistical significant better survival rate (p<0.01).

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Effect of Interleukin-12 on the Expression of E-selectin in Mouse Model of Lewis Lung Carcinoma (Lewis 폐암 마우스 모델에서 Interleukin-12가 E-selectin 발현에 미치는 영향)

  • Lee, Sang-Haak;Shin, Yoon;Yoon, Hyoung-Kyu;Lee, Sook-Young;Kim, Seok-Chan;Kwon, Soon-Seog;Kim, Young-Kyoon;Kim, Kwan-Hyoung;Moon, Hwa-Sik;Song, Jeong-Sup;Park, Sung-Hak
    • Tuberculosis and Respiratory Diseases
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    • v.47 no.2
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    • pp.161-171
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    • 1999
  • Background: Interleukin-12 (IL-12) can induce antitumor effects in vivo. This antitumor effect is associated with T cell infiltration but the effect of IL-12 on the steps of T cell migration into the tumor tissue has not been fully elucidated. This study focused on the effect of IL-12 on the tumor growth and the metastasis and on the expression of E-selectin, an adhesion molecule which is activated endothelial specific in its expression. In addition, we studied whether the expression of E-selectin is associated with the TNF-$\alpha$, a cytokine that its production is increased by IL-12 and has functions inducing a variety of adhesion molecules. Methods: Mice of C57BL/6 strain were injected with Lewis lung cancer cells followed by either IL-12, TNF-$\alpha$, or normal saline by intraperitoneal route. Twenty eight days after tumor cell inoculation, metastatic nodules of lung were enumerated and immunohistochemical staining of the subcutaneous tumors were performed with monoclonal antibodies to CD4, CD8, CD16, and E-selectin. In IL-12 treated mice, the subcutaneously implanted Lewis lung tumors were decreased in size and the metastases were also decreased in number compared to control mice. On tumor tissues, increased infiltration of CD4+, CD8+, and CD16+ cells were oberved in IL-12 treated mice compared to control mice. In control mice, E-selectin was absent on tumor vessels, but the expression of E-selectin was increased on tumor vessels of IL-12 treated mice. Administration of TNF-$\alpha$ increased not only the expression of E-selectin but also infiltrations of CD4+, CD8+, and CD16+ cells on tumor tissues. Conclusions: These results demonstrate that IL-12 inhibits tumor growth and metastases through infiltrations of inflammatory cells in mouse model of Lewis lung carcinoma and E-selectin may playa role in inflammatory cell recruitment on tumor tissue following IL-12 administration. Also, TNF-$\alpha$ may have a role as a mediator responsible for the IL-12 induced expression of E-selectin.

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Thioredoxin Peroxidase Manifestation in Radiation-Induced White Rat Lung Tissues (방사선 조사후 손상된 백서 폐조직에서의 Thioredoxin Peroxidase의 발현)

  • Chong, Seong-Cheoll;Park, Joon-Seong;Park, Jee-Won;Lee, Sun-Min;Park, Kwang-Joo;Hwang, Sung-Chul;Lee, Yi-Hyeong;Hahn, Myung-Ho;Oh, Young-Taek;Kim, Hyung-Joong
    • Tuberculosis and Respiratory Diseases
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    • v.47 no.5
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    • pp.650-659
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    • 1999
  • Background/Aims: It is well recognized that all aerobic cells have the protective mechanisms in order to minimize the tissue damage induced by various reactive oxygen species(ROS). Thioredoxin peroxidase(TPX) which has been recently identified and characterized functions to convert peroxide to water. The protein is also found in various subtypes(TPX-A & B, MER5, HS22 and HORF-06) and is known to be ubiquitous in most human cells. Especially, ischemic brain injuries, partial hepatectomy and radiation induced DNA damages. In treating lung cancer, radiation therapy has a major place in the local control and the relief of symptoms, but radiation induced free radical injury and resulting pulmonary fibrosis has been the major drawback of the therapy. However, little is known about the protective mechanisms and biologic modulations against radiation-induced tissue damages. Methods: Eighteen mice were divided into six groups, 3 in each group, and fifteen had received 900cGy of radiation. The mice were sacrificed according to the pre determined time schedule; immediate, 1, 2, 3 and 6 weeks after irradiation. Extracts were made from the lungs of each mice, Western blot analysis of various subtypes of TPX were done after SDS-P AGE. Examination of H & E stained slides from the same irradiated specimens and the control specimens were also performed. Results: No difference in the intensity of the immunoreactive bands in the irradiated lung samples of the mice compared to the unirradiated control was observed regardless of the time intervals, although H & E examination of the sample specimens demonstrated progressive fibrotic changes of the irradiated lung samples. Conclusion: In conclusion, according to our data, it is suggested that various thioredoxin peroxidase subtypes and catalase which are known to be increased in many repair processes may not be involved in the repair of the radiation injury to the lung and subsequent fibrosis.

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Evaluation between 3.0 T vs 1.5 T MRI in Detection of Brain Metastasis using Double Dose Gd-DTPA (뇌전이 종양의 발견에 있어서 Doble dose Gd-DTPA를 이용한 3 T MRI와 1.5 T MRI간의 비교연구)

  • Chung, Woo-Suk;Kim, Hyung-Jung;Ahn, Chul-Min;Lee, Jae-Hoon;Hur, Jin;Cho, Eung-Hyuck;Chung, Tae-Sub
    • Investigative Magnetic Resonance Imaging
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    • v.9 no.2
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    • pp.101-108
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    • 2005
  • Purpose : Early detection of small brain metastases is important. The purpose of this study was to compare the detectability of brain metastases according to the size between 1.5 T and 3.0 T MRI. Materials and Methods : We reviewed 162 patients with primary lung cancer who were examined for TNM staging. After administration of double dose of Gd-DTPA, MR imaging was performed with SPGR by 3.0 T MRI and then with T1 SE sequence by 1.5 T MRI. In each patient, three readers performed qualitative assessment. Sensitivity, positive predictive value, and diagnostic accuracy were calculated in 3.0 T and 1.5 T MRI according to size. Using the signal intensity (SI) measurements between the metastatic nodules and adjacent tissue, nodule-to-adjacent tissue SI ratio was calculated. Results : Thirty-one of 162 patients had apparent metastatic nodules in the brain at either 1.5 T or 3.0 T MR imaging. 143 nodules were detected in 3.0 T MRI, whereas 137 nodules were detected at 1.5 T MRI. Six nodules, only detected in 3.0 T MRI, were smaller than 3.0 mm in dimension. Sensitivity, positive predictive value, and diagnostic accuracy in 3.0 T MRI were 100 %, 100 %, and 100 % respectively, and in 1.5 T MRI were 95.8%, 88.3%, and 85.1% respectively. SI ratio was significantly higher in the 3.0 T MRI than 1.5 T MRI (p=0.025). Conclusion : True positive rate of 3.0 T MRI with Gd-DTPA was superior to 1.5 T MRI with Gd-DTPA in detection of metastatic nodules smaller than 3.0 mm.

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Evaluating the Impact of Attenuation Correction Difference According to the Lipiodol in PET/CT after TACE (간동맥 화학 색전술에 사용하는 Lipiodol에 의한 감쇠 오차가 PET/CT검사에서 영상에 미치는 영향 평가)

  • Cha, Eun Sun;Hong, Gun chul;Park, Hoon;Choi, Choon Ki;Seok, Jae Dong
    • The Korean Journal of Nuclear Medicine Technology
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    • v.17 no.1
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    • pp.67-70
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    • 2013
  • Purpose: Surge in patients with hepatocellular carcinoma, hepatic artery chemical embolization is one of the effective interventional procedures. The PET/CT examination plays an important role in determining the presence of residual cancer cells and metastasis, and prognosis after embolization. The other hand, the hepatic artery chemical embolization of embolic material used lipiodol produced artifacts in the PET/CT examination, and these artifacts results in quantitative evaluation influence. This study, the radioactivity density and the percentage error was evaluated by the extent of the impact of lipiodol in the image of PET/CT. Materials and Methods: 1994 NEMA Phantom was acquired for 2 minutes and 30 seconds per bed after the Teflon, water and lipiodol filled, and these three inserts into the enough to mix the rest behind radioactive injection with $20{\pm}10MBq$. Phantom reconfigure with the iterative reconstruction method the number of iterations for two times by law, a subset of 20 errors. We set up region of interest at each area of the Teflon, water, lipiodol, insert artifact occurs between regions, and background and it was calculated and compared by the radioactivity density(kBq/ml) and the% Difference. Results: Radioactivity density of the each region of interest area with the teflon, water, lipiodol, insert artifact occurs between regions, background activity was $0.09{\pm}0.04$, $0.40{\pm}0.17$, $1.55{\pm}0.75$, $2.5{\pm}1.09$, $2.65{\pm}1.16 kBq/ml$ (P <0.05) and it was statistically significant results. Percentage error of lipiodol in each area was 118%, compared to the water compared with the background activity 52%, compared with a teflon was 180% of the difference. Conclusion: We found that the error due to under the influence of the attenuation correction when PET/CT scans after lipiodol injection performed, and the radioactivity density is higher than compared to other implants, lower than background. Applying the nonattenuation correction images, and after hepatic artery chemical embolization who underwent PET/CT imaging so that the test should be take the consideration to the extent of the impact of lipiodol be.

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Beam Shaping by Independent Jaw Closure in Steveotactic Radiotherapy (정위방사선치료 시 독립턱 부분폐쇄를 이용하는 선량분포개선 방법)

  • Ahn Yong Chan;Cho Byung Chul;Choi Dong Rock;Kim Dae Yong;Huh Seung Jae;Oh Do Hoon;Bae Hoonsik;Yeo In Hwan;Ko Young Eun
    • Radiation Oncology Journal
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    • v.18 no.2
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    • pp.150-156
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    • 2000
  • Purpose : 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 and Methods : Authors adopted the idea to partially close one or more independent collimator jaw(5) 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 peformed 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 th 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. Conclusions : 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.

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