Transiently Altered Distribution of F-18 FDG in a Patient with Subacute Thyroiditis / 대한핵의학회잡지

F-18 fluorodeoxyglucose (FDG) is a highly influential radiotracer that provides valuable information in many cancer types. However, the normal biodistribution of F-18 FDG is often variable and can be altered by intrinsic or iatrogenic factors. We report a case of diffuse symmetrically increased skeletal muscle uptake and relatively decreased hepatic uptake on F-18 FDG PET/CT in a 57-year-old female with pulmonary adenocarcinoma. Detailed clinical evaluation and retrospective radiologic evaluation revealed that she had been diagnosed with subacute thyroiditis 2 weeks ago. After 6 weeks, F-18 FDG distribution was normalized at the follow-up PET/CT study.

Transiently Altered Distribution of F-18 FDG in a Patient with Subacute Thyroiditis / 대한핵의학회잡지

F-18 fluorodeoxyglucose (FDG) is a highly influential radiotracer that provides valuable information in many cancer types. However, the normal biodistribution of F-18 FDG is often variable and can be altered by intrinsic or iatrogenic factors. We report a case of diffuse symmetrically increased skeletal muscle uptake and relatively decreased hepatic uptake on F-18 FDG PET/CT in a 57-year-old female with pulmonary adenocarcinoma. Detailed clinical evaluation and retrospective radiologic evaluation revealed that she had been diagnosed with subacute thyroiditis 2 weeks ago. After 6 weeks, F-18 FDG distribution was normalized at the follow-up PET/CT study.

Usefulness of Tc-99m Pertechnetate SPECT/CT in the Diagnosis of Testicular Infarction After Inguinal Herniorrhaphy / 대한핵의학회잡지

A 77-year-old male underwent open repair for a right indirect inguinal hernia and complained of right scrotal pain on the third postoperative day. Color Doppler imaging revealed decreased blood flow with heterogeneous hypoechogenicity in the right testis. A Tc-99m pertechnetate testicular scan showed diffuse hyperemia and increased uptake in the right scrotum. Additional SPECT/CT revealed a photon defect in the right testicle with increased uptake in the peri-testicular area. A subsequent operation revealed a large hematoma in the right spermatic cord and consequent right testicular infarction, and right orchiectomy was performed.

Detecting the Recurrence of Gastric Cancer after Curative Resection: Comparison of FDG PET/CT and Contrast-Enhanced Abdominal CT

The purpose of this study was to evaluate the value of fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) for detecting the recurrence of gastric cancer. We performed a retrospective review of 139 consecutive patients who underwent PET/CT and contrast-enhanced abdominal CT (CECT) for surveillance of gastric cancer after curative resection. Recurrence of gastric cancer was validated by histopathologic examination for local recurrence or serial imaging study follow-up with at least 1 yr interval for recurrence of distant metastasis form. Twenty-eight patients (20.1%) were confirmed as recurrence. On the patient based analysis, there was no statistically significant difference in the sensitivity, specificity and accuracy of PET/CT (53.6%, 84.7%, and 78.4%, respectively) and those of CECT (64.3%, 86.5%, and 82.0%, respectively) for detecting tumor recurrence except in detection of peritoneal carcinomatosis. Among 36 recurrent lesions, 8 lesions (22.2%) were detected only on PET/CT, and 10 lesions (27.8%) only on CECT. PET/CT had detected secondary malignancy in 8 patients. PET/CT is as accurate as CECT in detection of gastric cancer recurrence after curative resection, excepting detection of peritoneal carcinomatosis. Moreover, additional PET/CT on CECT could improve detection rate of tumor recurrence and provide other critical information such as unexpected secondary malignancy.

Metabolic Super Scan in 18F-FDG PET/CT Imaging

A 50-yr-old man presented with intermittent hemoptysis and was diagnosed small cell lung cancer. 18F-FDG PET/CT for staging demonstrated extensive hypermetabolic lesions throughout the skeleton and liver. Interestingly, skeletal muscles of limbs, mediastinum, bowel, and especially brain showed very low FDG uptake. Because of some characteristics in common with super scan on skeletal scintigraphy, this case could be considered as 'metabolic super scan'.

Are Medical Personnel Safe from Radiation Exposure from Patient Receiving Radioiodine Ablation Therapy? / 핵의학분자영상

Radioiodine ablation therapy has been considered to be a standard treatment for patient with differentiated thyroid cancer after total thyroidectomy. Patients may need to be hospitalized to reduce radiation exposure of other people and relatives from radioactive patients receiving radioiodine therapy. Medical staffs, nursing staffs and technologists sometimes hesitate to contact patients in radioiodine therapy ward. The purpose of this paper is to introduce radiation dosimetry, estimate radiation dose from patients and emphasize the safety of radiation exposure from patients treated with high dose radioiodine in therapy ward. The major component of radiation dose from patient is external exposure. However external radiation dose from these patients treated with typical therapeutic dose of 4 to 8 GBq have a very low risk of cancer induction compared with other various risks occurring in daily life. The typical annual radiation dose without shielding received by patient is estimated to be 5 to 10 mSv, which is comparable with 100 to 200 times effective dose received by chest PA examination. Therefore, when we should keep in mind the general principle of radiation protection, the risks of radiation exposure from patients are low and the medical personnel are considered to be safe from radiation exposure.

Assessment of Tumor Response to Therapy in Lymphoma Using (18)F-FDG PET: Diagnostic Performance of (18)F-FDG PET and Interval Likelihood Ratio / 핵의학분자영상

In this paper, the authors intended to summarize briefly the features of lymphoma with regard to (18)F-FDG PET for assessment of tumor response to therapy, to describe why assessment of treatment response should be performed, to review what method so far has been used in monitoring treatment response, to discuss what limitations of morphologic imaging criteria for assessing tumor response are, in compared with (18)F-FDG PET, and to introduce recently proposed criteria for assessing tumor response in malignant lymphoma. And also the authors emphasize the need to understand the characteristics of diagnostic performance of (18)F-FDG PET in several clinical settings in order to interpret (18)F-FDG PET results appropriately, and to encourage the use of interval likelihood ratio to enhance clinical implications of test results which, in turns, allows referring physicians to understand the meaning of interpretation with easy. Until recently, treatment response has been assessed according to the morphologic criteria. Metabolic imaging with (18)F-FDG PET was adopted to have important role for treatment assessment in IWC+PET criteria proposed recently by IHP. To accomplish this role, we should perform and interpret (18)F-FDG PET according to IWC+PET criteria. It is important for referring physicians to understand the various limitations of (18)F-FDG PET and pitfalls in PET interpretation, and to understand that clinical information are needed by nuclear medicine physicians to optimize the interpretation of (18)F-FDG PET.

Clinical Significance of Reverse Redistribution Phenomenon on Delayed Tc-99m Tetrofosmin Myocardial Perfusion Imaging in Patients with Acute Myocardial Infarction / 핵의학분자영상

PURPOSE: This study was performed to investigate the clinical significance of reverse redistribution (RR) phenomenon detected on delayed Tc-99m tetrofosmin myocardial single photon emission computed tomography (SPECT) in patients with acute myocardial infarction after revascularization. MATERIALS AND METHODS: A Tc-99m tetrofrosmin myocardial SPECT was performed in 67 consecutive patients after revascularization for acute myocardial infarction. Myocardial SPECT imaging was performed for early imaging at 40 min and for delayed imaging at 180 min after reinjection at myocardial stress. Regional myocardial uptakes were scored by 4-point scoring in the left ventricular wall divided into 17 segments. Reverse redistribution was defined as an increase of more than 2 point in the activity score on the delayed image. Follow-up myocardial SPECT and coronary angiography (CAG) were performed 9 months later. RESULTS: On myocardial SPECT performed following revascularization, RR was observed in 100 of all 319 segments (31%) and in 43 patients (64%). The abnormalities of perfusion and regional wall motion were more severe in the patients with RR compared to those without RR (p<0.05). On follow-up myocardial SPECT, the myocardial perfusion, regional wall motion, and myocardial thickness were significantly improved in the patients with RR (p<0.05) however, these changes were not significant in those without RR. There was no significant difference between the patients with RR and those without RR in the occurrence of restenosis on CAG. CONCLUSIONS: In patients with acute myocardial infarction, the regions showing the RR phenomenon on delayed Tc-99m tetrofosmin SPECT may reflect viable myocardium and indicate recovery of salvaged myocardium.

Gastric Accumulation of Bone Seeking Agent in a Patient with Advanced Gastric Cancer

Soft tissue uptake of Tc-99m labeled bone seeking agents, such as Tc-99m 3,3-diphosphono-1,2-propanedicarboxylic acid (DPD), is commonly seen in clinical practice, even though bone scintigraphy is mainly used to detect bone disease. However, gastric uptake of bone agents in patients with gastric cancer is very rare. And it has been reported that calcified gastric adenocarcinoma appears in only about 5% of all gastric cancer. We report a rare case of bone scintigraphy, single photon emission computed tomography and computed tomography fusion images that demonstrated diffuse gastric uptake of Tc-99m DPD in a patient with advanced gastric cancer.

Pretreatment with Ursodeoxycholic Acid (UDCA) as a Novel Pharmacological Intervention in Hepatobiliary Scintigraphy

The purpose of this volunteer study was to investigate whether pretreatment with UDCA before the administration of 99mTc DISIDA affects the biliary excretion of the DISIDA, and whether it can shorten the total imaging time. Ten young, healthy volunteers (eight males, two females, mean age: 26.3 +/- 2.1 years) participated in the study. Hepatobiliary scintigraphies were performed twice per volunteer within three days, for the control and the UDCA-pretreated studies. In the control study, the gallbladder (GB) was observed first in four cases and the intestine was observed first in another four cases; in contrast, in the UDCA challenge study, the GB was observed first in eight cases. The quantitative results for the factors related to the GB differed significantly between the control and challenge studies. When the subjects were pretreated with UDCA, the time duration until visualization of the GB was shortened, and the maximum activity of the GB became more intense. In conclusion, UDCA pretreatment before hepatobiliary scintigraphy can shorten the total imaging time for evaluating functional obstructions of the cystic duct and increase the specificity of the process.

A Study on the Labeling Efficiency and Cytotoxicity of Hepatocyte-targeting Galactosylated Chitosan Compounds / 대한핵의학회잡지

PURPOSE: In prior study, we synthesized 99mTc-galactosylated chitosan (GC) and performed in vivo biodistribution study, showed specific targeting to hepatocyte. The aim of this study is to evaluate the labeling efficiency and cytotoxicity of modified galactosylated chitosan compounds, galactosyl methylated chitosan (GMC) and HYNIC-galactosylated chitosan (GCH). MATERIALS AND METHODS: GC, GMC and GCH were synthesized and radiolabeled with 99mTc. Then, they were incubated for 6 hours at room temperature and human serum at 37 degrees C. Labeling efficiencies were determined at 15, 30 m, 1, 2, 3 and 6 h after radiolabeling. To evaluate cytotoxicity, MTT assay was performed in HeLa and HepG2 cells. RESULTS: In comparison with them of 99mTc-GC, labeling efficiencies of 99mTc-GMC were significantly improved (100, 97 and 89% in acetone and 96.3, 95.8 and 75.6% in saline at 15 m, 1 and 6 h, respectively). Moreover, 99mTc-GCH showed more improved labeling efficiencies (> 95% in acetone and human serum and > 90% in saline at 6 h). In MTT assay, cytotoxicity was very low and not different from that of controls. CONCLUSION: These results represent that these compounds are radiochemically compatible radiopharmaceuticals, can be used in hepatocyte specific imaging study and in vivo gene or drug delivery monitoring.

ReVersible Changes of Clinical Chemical Tests in Severe Hypothyroid Patients with Differentiated Thyroid Cancer Who Were Admitted for Radioiodine Therapy

PURPOSE: Severe hypothyroidism can cause abnormalities in numerous clinical chemical test results. We observed various reVersible changes of clinical chemical test results in patients with severe hypothyroidism who were admitted for radioiodine ablation therapy after total thyroidectomy. The purpose of this study was to describe and discuss the findings. METHODS: The study comprised 168 patients (24 males, 144 females, mean age 49+/-14 years) who underwent total thyroidectomy due to differentiated thyroid cancer and who were admitted for I-131 ablation therapy. Patients who had hepatic or renal dysfunction were excluded. RESULTS: Serum mean levels of aspartate transaminase, alanine transaminase, cholesterol, high density lipoprotein, lactic dehydrogenase, total bilirubin, indirect bilirubin, and creatinine were significantly increased to the upper normal range during severe hypothyroid state (serum thyroid stimulating hormone >30 uIU/ml). While serum levels of alkaline phosphatase (ALP), triglyceride (TG) and blood urea nitrogen (BUN) remained unchanged. Six patients who showed abnormal serum creatinine level during hypothyroid condition returned to normal after recovery of thyroid function. CONCLUSION: Results of clinical chemical tests for hepatic, lipid and renal function are often increased reversibly in severely hypothyroid patients. Reversible, abnormal serum creatinine levels may develop in some cases. Follow-up study is necessary in induced severely hypothyroid patients for radioiodine therapy to differentiate the reversibility of chemical tests.

Nuclear Imaging Evaluation of Galactosylation of Chitosan / 대한핵의학회잡지

PURPOSE: Chitosan has been studied as a non-viral gene delivery vector, drug delivery carrier, metal chelater, food additive, and radiopharmaceutical, among other things. Recently, galactose-graft chitosan was studied as a non-viral gene and drug delivery vector to target hepatocytes. The aim of this study was to investigate the usefulness of nuclear imaging for in vivo evaluation of targeting the hepatocyte by galactose grafting. METHODS AND MATERIALS: Galactosyl methylated chitosan (GMC) was produced by methylation to lactobionic acid coupled chitosan. Cytotoxicity of 99mTc-GMC was determined by MTT assay. Rabbits were injected via their auricular vein with 99mTc-GMC and 99mTc-methylated chitosan (MC), the latter of which does not contain a galactose group, and images were acquired with a gamma camera equipped with a parallel hole collimator. The composition of the galactose group in galactosylated chitosan (GC), as well as the tri-, di-, or mono-methylation of GMC, was confirmed by NMR spectroscopy. RESULTS: The results of MTT assay indicated that 99mTc-GMC was non-toxic. 99mTc-GMC specifically accumulated in the liver within 10 minutes of injection and maintained high hepatic uptake. In contrast, 99mTc-MC showed faint liver uptake. 99mTc-GMC scintigraphy of rabbits showed that the galactose ligand principally targeted the liver while the chitosan functionalities led to excretion through the urinary system. CONCLUSION: Bioconjugation with a specific ligand endows some degree of targetability to an administered molecule or drug, as in the case of galactose for hepatocyte in vivo, and evaluating said targetabililty is a clear example of the great benefit proffered by nuclear imaging.

Intratumoral Injection of (188)Re labeled Cationic Polyethylenimine Conjugates: A Preliminary Report

(188)Re(Rhenium) is easily obtained from an in-house (188)W/(188)Re generator that is similar to the current (99)Mo/(99m)Tc generator, making it very convenient for clinical use. This characteristic makes this radionuclide a promising candidate as a therapeutic agent. Polyethylenimine (PEI) is a cationic polymer and has been used as a gene delivery vector. Positively charged materials interact with cellular blood components, vascular endothelium, and plasma proteins. In this study, the authors investigated whether intratumoral injection of (188)Re labeled transferrin (Tf)-PEI conjugates exert the effect of radionuclide therapy against the tumor cells. When the diameters of the Ramos lymphoma (human Burkitt's lymphoma) xenografted tumors reached approximately 1 cm, 3 kinds of (188)Re bound compounds (HYNIC-PEI-Tf, HYNIC-PEI, (188)Re perrhenate) were injected directly into the tumors. There were increases in the retention of (188)Re inside the tumor when PEI was incorporated with (188)Re compared to the use of free 188Re. The (188)Re HYNIC-Tf-PEI showed the most retention inside the tumor (retention rate=approximately 97%). H&E stain of isolated tumor tissues showed that (188)Re labeled HYNIC-PEI-Tf caused extensive tumor necrosis. These results support (188)Re HYNIC-PEI-Tf as being a useful radiopharmaceutical agent to treat tumors when delievered by intratumoral injection.

Differential Effects of Green Tea Polyphenol in the gamma-irradiation Induced Human Leukemic and Lymphoblastic Cell Damage / 대한핵의학회잡지

PURPOSE: The green tea polyphenol (GTPP) has been known to exert antioxidant activity as a radical scavenger as well as cancer preventive and cancer growth inhibition effect. The aim of this study was to identify whether GTPP not only potentiate the growth inhibition effect in gamma-irradiated human cancer cell but also exert protection action for irradiated human normal cell. MATERIALS AND METHODS: GTPP (80% catechin including > 45% EGCG) added in the HL60, human leukemia, and NC37, human lymphoblast, before irradiation. After establishing the amount of GTPP and the dose of radiation, the cells were treated with the GTPP for 6 hours and irradiated with the determined doses. RESULTS: Viability when 10 mug/ml GTPP added before gamma-irradiation with 1 Gy to NC37 cells was not different in comparison with control but it when was irradiated with 3 Gy significantly different (1 Gy; P=0.126, 3 Gy; P=0.010). 20 mug/ml GTPP did not show significant difference in both NC37 cells irradiated with 1 Gy and 3 Gy (1 Gy; P=0.946, 3 Gy; P=0.096). Viabilities were significantly decreased with concentration of additional GTPP in HL60 with 1 or 3 Gy (1 Gy; 69.0+/-1.7% vs 42.4+/-1.3%, 3 Gy; 66.9+/-3.9% vs 44.2+/-1.6 %). CONCLUSION: In vitro study, we certified that when the cells were irradiated with dose below 3 Gy, GTPP provide not only anticancerous effect against cancer cells but also radioprotective effect in normal cells simultaneously. Theses results suggest the possibility that consumption of green tea could give the radioprotective effect and maximize the effect on internal radiation such as radioiodine therapy concomitantly.

A Modified Protocol for Myocardial Perfusion SPECT Using Natural Plant Extracts for Enbancement of Biliorg Excretion / 대한핵의학회잡지

PURPOSE: For good quality of myocardial perfusion images, an approximately 30 min to 1 hour of waiting time after radiopharmaceutical injection and ingestion of fatty meal are asked of the patients. The aim of this study was to investigate the shortening of waiting time after radiopharmaceutical injection and improvement of image quality using natural plant extracts that promote bile excretion. MATERIALS AND METHODS: Ten volunteers participated in protocol 1 (7 men, 3 women; mean age, 24.1+/-2.4 years) and protocol 2 (8 men, 2 women; mean age, 26.1+/-2.9 years), respectively. For the modified method of both protocols, subjects took natural plant extracts 15 minutes before the first injection of 99mTc MIBI without taking fatty meals. Control (Conventional) methods were performed with intake of a fatty meal 20 to 30 minutes after 99mTc MIBI injection. RESULTS: As the results of protocol 1 and 2, the ratio of myocardial to lung ratio were not different between modified and conventional method. Liver to lung ratio of modified method showed significantly lower value than that of conventional method. In modified method, myocardial to liver ratio was higher persistently. In protocol 2, natural plant extracts took before the first injection of 99mTc MIBI exerted accelerating effect of excretion of bile juice into intestine until the end of examination. CONCLUSION: These results represent that natural plant extracts for facilitation of bile excretion before injection of 99mTc MIBI may provide better quality of myocardial perfusion images without the need for preparations such as ingestion of fatty meal within the 2 hours compared with conventional method.

Comparison between Echocardiography and Gated SPECT in the Assessment of Left Ventricular Wall Motion in Patients with Acute Myocardial Infarction

BACKGROUND AND OBJECTIVES: Assessment of the regional left ventricular function provides valuable diagnostic and prognostic information of patients with coronary artery disease. The aim of the study was to analyze the agreement between wall motion scores, derived by gated single photon emission computed tomography (SPECT) and echocardiography (Echo) in myocardial infarction patients with a perfusion defect. SUBJECTS AND METHODS: We studied the regional wall motion in 81 patients with an acute myocardial infarction, who underwent adenosine stress gated SPECT and Echo. Echo was performed in all the patients immediately prior to, or following, gated SPECT. The regional wall motion was evaluated by both modalities, and scored using a 16-segment model with a 4-point scoring system: 1=normal, 2=mild and moderate hypokinesia, 3=severe hypokinesia, 4=akinesia or dyskinesia. RESULTS: There was a high agreement in the left ventricular regional wall motion scores between the gated SPECT and the Echo of 84.2% of segments (1091/1296 segments, k=0.76, p<0.0001). The agreement in the regional wall motion scores between the two modalities decreased significantly along the longitudinal axis of the left ventricle from 92.9% (301/324, k=0.89, p<0.0001) at the apex, 84.6% (411/486, k=0.77, p<0.0001) at the mid point, to 77.9% (379/486, k=0.65, p<0.0001) at the basal segments (p<0.0001). Also, the agreement based on the degree of myocardial perfusion was 86.6% for segments with normal, or mild hypoperfusion, and 82.6% with moderate to severe hypoperfusion (p=0.072). CONCLUSION: The gated SPECT had a good agreement with the Echo for the assessment of the left ventricular regional wall motion in patients with an acute myocardial infarction. These results support the clinical use of gated SPECT.

Usefulness of High-Resolution Sonography for Assessement of Hepatocellular Carcinoma in the Transgenic Mice Expressing Hepatitis B Virus X-protein: A Preliminary Study

PURPOSE: To determine the value of high resolution ultrasonography (US) for the detection of hepatocellular carcinoma in the HBx transgenic mice. MATERIALS AND METHODS: Forty-two HBx transgenic mice aged 8-20 (mean, 14) months underwent high-resolution ultrasound using a 10 -12 MHz linear transducer. US findings indicating the presence or absence, number, size and echogenicity of each hepatic tumor were analyzed, and inaddition, color or power Doppler US was used to analyse tumoral vascularity. In each animal, sacrificed less than five hours after US examination, sonographic and pathologic findings were correlated. RESULT: On gross pathologic examination, 20 hepatocellular carcinomas measuring 1.5 -15 (mean, 4.7) mm in diameter were found in 16 mice; US revealed that 17 of the tumors were homogeneous hypoechoic nodules. With regard to tumor detection, sensitivity was 85%, specificity 96%, positive predictive value 0.944, negative predictive value 0.897, and overall accuracy 90%. Doppler US revealed that in three nodules, intratumoral vessels were present. Inthe other 26 mice, gross examination showed that no mass was present; microscopically, however, four nodules measuring 0.3 -1.2 mm were found in four of these animals. Tumoral vascularity detected by color Doppler US corresponded to the intratumoral vessel within the nodules. One peritoneal nodule, confirmed as a metastatic tumor, was found at the greater omentum. CONCLUSION: In HBx transgenic mice, high-resolution US is valuable for the detection of hepatocellular carcinoma.

Solitary Necrotic Nodules of the Liver Mimicking Hepatic Metastasis: Report of Two Cases

We present two cases of solitary necrotic nodules of the liver which on radiologic images mimicked hepatic metastasis. Solitary necrotic nodule of the liver is a rare but benign entity which histopathologically consists of an outer fibrotic cap-sule with inflammatory cells and a central core of amorphous necrotic material. The lesion was seen on contrast-enhanced CT as an ovoid-shaped hypoattenu-ating nodule; on CT during hepatic arteriography as enhancing nodule; on intra-operative US as a target-appearing hypoechoic nodule; on T2WI as a hyperinten-sity nodule, and on dynamic MR as a subtle peripheral enhancing nodule. Although the radiologic features are not specific, solitary necrotic nodule of the liver should be included in the differential diagnosis of hepatic metastasis.

Biodistribution of Iodine-131-Iodomisonidazole and Imaging of Tumor Hypoxia in Mice bearing CT-26 Adenocarcinoma / 대한핵의학회잡지

urpose: Misonidazole is a radiosensitizer that binds in hypoxic cells. The purpose of this study was to find out the feasibility of I-131-Iodomisonidazole (IMISO) for imaging of tumor hypoxia. MATERIALS AND METHODS: Tosyl precursor was dissolved in acetonitrile and I-131-NaI was added to synthesize IMISO. Balb/c mice inoculated with CT-26 adenocarcinoma were injected with IMISO. Mice were sacrificed at 1,2,4,24 hr and % of injected dose per gram of tissue (%ID/g) was determined. For scintigraphy and MRI, mouse bearing CT-26 adenocarcinoma was administered with IMISO and imaging was performed 4 hr after. Then, mouse body was fixed and microtomized slice was placed on radiographic film for autoradiography. RESULTS: %ID/g of tumor was 1.64 (1h), 0.98 (2h), 0.85 (4h) and 0.20 (24h), respectively. At 24h, %ID/g of tumor was higher than that of all other tissues except thyroid. Tumor to muscle ratio increased with time and tumor to blood ratio also increased with time and reached 1.53 at 24 hr. On autoradiogram, tumor was well visualized as an increased activity in central hypoxic area of the tumor which corresponds to the area of high signal intensity on T2-weighted MR image. On scintigraphy, tumor uptake was visualized. CONCLUSION:: This RESULTS suggest that IMISO may have a potential for tumor hypoxia imaging in mouse model. However, further study is needed to improve it's localization in tumor tissue and to achieve acceptable images of tumor hypoxia.