Isolated Splenic Metastasis of Sigmoid Colon Cancer Detected by 18F-FDG PET/CT / 핵의학분자영상

Splenic metastasis from colon carcinoma are rare and usually occur in the presence of disseminated visceral metastasis. The liver is the most common site of metastatic spread from colon cancer. Several hypotheses have attempted to explain the low incidence of splenic metastasis. It should be difficult for colorectal cancer cells to reach the spleen through the portal venous system, in which the blood flow is usually from the spleen to the liver. Reticuloendothelial system or rhythmic contraction of the spleen may squeeze out the tumor in the spleen. The absence of afferent lymphatic to the spleen, phagocytic activity and humoral anticancer substances are considered to be other reason for low incidence of splenic metastasis. We report the case of 18F-FDG PET/CT finding in a 70-year-old woman who develop isolated splenic metastasis of sigmoid colon cancer.

18F-FDG PET/CT in POEMS Syndrome / 핵의학분자영상

POEMS syndrome is a rare disorder, also known as Crow-Fukase, PEP or Takatsuki syndrome. The acronym, POEMS, represents polyneuropathy, organomegaly, endocrinopathy, M protein and skin change. However, there are associated features not included in the acronym such as sclerotic bone lesions, Castleman disease, papilledema, thromobocytosis, peripheral edema, ascites, effusion, polycythemia, fatigue and clubbing. In most cases, osseous lesions in POEMS syndrome present as an isolated sclerotic deposit and that reveal as osteosclerotic myeloma. Several cases of 18F-FDG PET in multiple myeloma involvements were reported, but there was no previous literature that reported FDG PET findings in POEMS syndrome. We describe here a 66-year-old patient with POEMS syndrome who underwent 18F-FDG PET/CT image.

Correlation of Hepatic 18F-Fluorodeoxyglucose Uptake with Fatty Liver / 핵의학분자영상

PURPOSE: Liver demonstrates heterogeneous FDG uptake and sometimes it shows abnormally increased uptake even though there is no malignant tissue. However, there was no previous study to correlate these various pattern of hepatic FDG uptake with benign liver disease. Therefore, we evaluated the significance of hepatic FDG uptake associated with various clinical factors including fatty liver, liver function tests and lipid profiles. MATERIALS AND METHODS: We reviewed a total of 188 patients (male/female: 120/68, mean age: 50+/-9) who underwent PET/CT for screening of malignancy. Patients with DM, impaired glucose tolerance, previous severe hepatic disease or long-term medication history were excluded. The FDG uptake in liver was analyzed semi-quantitatively using ROI on transaxial images (segment 8) and we compared mean standardized uptake value (SUV) between fatty liver and non-fatty liver group. We also evaluated the correlation between hepatic FDG uptake and various clinical factors including serum liver function test (ALT, AST), gamma-GT, total cholesterol and triglyceride concentration. The effect of alcoholic history and body mass index on hepatic FDG uptake was analyzed within the fatty liver patients. RESULTS: The hepatic FDG uptake of fatty liver group was significantly higher than that of non-fatty liver group. Serum total cholesterol and triglyceride concentration showed significant correlation with hepatic FDG uptake. However, there was no significant correlation between other factors (ALT, AST, and gamma-GT) and FDG uptake. Also there was no difference of mean SUV between normal and abnormal groups on the basis of alcoholic history and body mass index within fatty liver patients. Fatty liver and high serum triglyceride concentration were the independent factors affecting hepatic FDG uptake according to multivariate analysis. CONCLUSION: In conclusion, hepatic FDG uptake was strongly correlated with fatty liver and serum triglyceride concentration.

Usefulness of Low Dose Oral Contrast Media in 18F-FDG PET/CT / 핵의학분자영상

PURPOSE: The standard protocol using large volume of oral contrast media may cause gastrointestinal discomfort and contrast-related artifacts in PET/CT. The aim of this study was to evaluate the usefulness of low dose oral contrast in 18F-FDG PET/CT. MATERIALS AND METHODS: We retrospectively reviewed the whole-body PET/CT images in a total of 435 patients. About 200 ml of oral contrast agent (barium sulfate) was administered immediately before injection of 18F-FDG. The FDG uptake of intestines was analyzed by visual and semi-quantitative method on transaxial, coronal and saggital planes. RESULTS: Seventy (16%, 113 sites) of 435 images showed high FDG uptake (peak SUV > 4); 50 (74%, 84 sites) with diffuse and 20 (26%, 29 sites) with focal uptake. The most commonly delivered site of oral contrast media was small bowel (n=27, 39%). On PET/CT images, FDG uptake coexisted with oral contrast media in 26 patients (54%, 38 sites) with diffuse pattern and 9 (45%, 9 sites) with focal pattern, and by sites, those were 38 (45%) and 9 (31%), respectively. In small bowel regions, the proportion of coexistence reached as high as 61% (29/47 sites). A visual analysis of available non-attenuation corrected PET images of 27 matched regions revealed no contrast-related artifact. CONCLUSION: We concluded that the application of low dose contrast media could be helpful in the evaluation of abdominal uptake in the FDG PET/CT image.

Determination of Tumor Volume in PET for the Radiation Treatment Planning : Computer Simulation / 의학물리

The utilization of PET has been increased so fast since the usefulness of the PET has been proved in various clinical and research fields. Among the many applications, the PET is especially useful in oncology and most of the clinical PET scans are performed for the oncologic examination including the different diagnosis of malignant and benign tumors and assessment of the treatment effects and recurrent tumors. As the PET-CT scanners are widely available, there is increasing interest in the application of the PET images to the radiation treatment planning. Although the CT images are conventionally used for the target volume determination in the radiation treatment planning, there are fundamental limitation in use of only the anatomical information. Therefore, the volume determination of the functionally active tumor region using the PET would be important for the treatment planning. However, the accurate determination of the tumor boundary is not simple in PET due to the relatively low spatial resolution of the currently available PET scanners. In this study, computer simulations were performed to study the relationship between the lesion size, PET resolution, lesion to background ratio and the threshold of image intensity to determine the true tumor volume.

F-18-FDG Whole Body Scan using Gamma Camera equipped with Ultra High Energy Collimator in Cancer Patients: Comparison with FDG Coincidence PET / 대한핵의학회잡지

PURPOSE: The aim of this study is to demonstrate the feasibility of 2-[fluorine-18] fluoro-2-deoxy-D-glucose (F-18-FDG) whole body scan (FDG W/B Scan) using dual-head gamma camera equipped with ultra high energy collimator in patients with various cancers, and compare the RESULTS with those of coincidence imaging. MATERIALS AND METHODS: Phantom studies of planar imaging with ultra high energy and coincidence tomography (FDG CoDe PET) were performed. Fourteen patients with known or suspected maligancy were examined. F-18-FDG whole body scan was performed using dual-head gamma camera with high energy (511 keV) collimators and regional FDG CoDe PET immediately followed it. Radiological, clinical follow up and histologic RESULTS were correlated with F-18-FDG finding. RESULTS: Planar phantom study showed 13.1 mm spatial resolution at 10 cm with a sensitivity of 2638 cpm/MBq/ml. In coincidence PET, spatial resolution was 7.49 mm and sensitivity was 5351 cpm/MBq/ml. Eight out of 14 patients showed hypermetabolic sites in primary or metastatic tumors in FDG CoDe PET. The lesions showing no hypermetabolic uptake of FDG in both methods were all less than 1 cm except one lesion of 2 cm sized metastatic lymph node. The metastatic lymph nodes of positive FDG uptake were more than 1.5 cm in size or conglomerated lesions of lymph nodes less than 1 cm in size. FDG W/B scan showed similar RESULTS but had additional false positive and false negative cases. FDG W/B scan not visualize liver metastasis in one case that showed multiple metastatic sites in FDG CoDe PET. CONCLUSION:S: FDG W/B scan with specially designed collimators depicted some cancers and their metastatic sites, although it had a limitation in image quality compared to that of FDG CoDe PET. This study suggests that F-18-FDG positron imaging using dual-head gamma camera is feasible in oncology and helpful if it should be more available by regional distribution of FDG.

Verification of Dose Distribution for Stereotactic Radiosurgery with a Linear Accelerator / 대한치료방사선과학회지

The calculation of dose distribution in multiple arc stereotactic radiotherapy is a three-dimensional problem and, therefore, the three-dimensional dose calculation algorithm is important and the algorithm's accuracy and reliability should be confirmed experimentally. The aim of this study is to verify the dose distribution of stereotactic radiosurgery experimentally and to investigate the effect of the beam quality, the number of arcs of radiation, and the tertiary collimation on the resulting dose distribution. Film dosimetry with phantom measurements was done to get the three-dimensional orthogonal isodose distribution. All experiments were carried out with a 6 MV X-ray, except for the study of the effects of beam energy on dose distribution, which was done for X-ray energies of 6 and 15 MV. The irradiation technique was from 4 to 11 arcs at intervals of from 15 to 45 degrees between each arc with various field sizes with additional circular collimator. The dose distributions of square field with linear accelerator collimator compared with the dose distributions obtained using circular field with tertiary collimator. The parameters used for comparing the results were the shape of the isodose curve, dose fall-offs from 90% to 50 % and from 90% to 20% isodose line for the steepest and shallowest profile, and A= (90% idsose area) /( 50% isodose area - 90% isodose area (modified from Chierego)). This ratio may be considered as being proportional to the sparing of normal tissue around the target volume. The effect of beam energy in 6 and 15 MV X-ray indicated that the shapes of isodose cuties were the same. The value of ratio A and the steepest and shallowest dose fall-offs for 6 MV X-ray was minimally better than that for 15 MV X-ray. These data illustrated that an increase in the dimensions of the field from 10 to 28 mm in diameter did not significantly change the isodose distribution. There was no significant difference in dose gradient and the shape of isodose cutie regardless of the number of arcs for field sizes of 10, 21, and 32 mm in diameter The shape of isodose cuties was more circular in circular field and square in square field. And the dose gradient for the circular field was slightly better than that for the square field.