18F-FDG PET/CT Evaluation of Thymomas: a Pictorial Review / 대한핵의학회잡지

The World Health Organization classification divides thymomas according to morphology, epithelial component, and cell atypia. They are grouped into 3 large subgroups: low-risk thymomas (types A, AB, and B1), high-risk thymomas (types B2 and B3), and thymic carcinomas. Tumor subtype represents an independent prognostic factor, which determines therapeutic decision. All thymomas show some degree of 18 F-FDG uptake, which tends to increase with the grade of malignancy; this is related to glucose transporter 1 (GLUT1) expression. This review collects all types of thymomas with illustrative images and provides a guide to get familiar with histological characteristics of the lesions and have them in mind because, even imaging findings can overlap among subtypes, certain characteristics can be combined to make an accurate diagnosis based on 18 F-FDG PET-CT findings.

Bilateral Renal Metastasis of Hürthle Cell Thyroid Cancer with Discordant Uptake Between I-131 Sodium Iodide and F-18 FDG / 대한핵의학회잡지

Renal metastasis of thyroid cancer is extremely rare. We report the case of a 62-year-old woman with Hürthle cell thyroid cancer (HCTC) with lungs, bones, and bilateral kidneys metastases. The renal metastatic lesions were clearly demonstrated by ¹³¹I whole body scan (WBS) with SPECT/CT. However, they exhibited false-negative results in ¹⁸F-FDG PET/CT, kidney ultrasonography, and contrast-enhanced CT scan. The findings imply that tumors have low glucose metabolism and are able to accumulate radioiodine, which is not commonly found in the relatively aggressive nature of HCTC. The patient received two sessions of 200 mCi ¹³¹I therapy within 6 months duration. There was complete treatment response as evaluated by the second post-therapeutic ¹³¹I SPECT/CT and serum thyroglobulin. To our knowledge, renal metastasis from HCTC with positive ¹³¹I but negative ¹⁸F-FDGuptake has not been reported in the literature. This case suggests that ¹³¹I SPECT/CTis useful for lesion localization and prediction of ¹³¹I therapy response.

Clinical Significance of Pretreatment FDG PET/CT in MIBG-Avid Pediatric Neuroblastoma / 대한핵의학회잡지

PURPOSE: ¹⁸F-fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging is well known to have clinical significance in the initial staging and response evaluation of the many kinds of neoplasms. However, its role in the pediatric neuroblastoma is not clearly defined. In the present study, the clinical significance of FDG-PET/computed tomography (CT) in ¹²³I- or ¹³¹I-metaiodobenzylguanidine (MIBG)-avid pediatric neuroblastoma was investigated.METHODS: Twenty patients with neuroblastoma who undertook pretreatment FDG PET/CT at our institute between 2008 and 2015 and showed MIBG avidity were retrospectively enrolled in the present study. Clinical information—including histopathology, and serum markers—and several PET parameters—including SUVmax of the primary lesion (Psuv), target-to-background ratio (TBR), metabolic tumor volume (MTV), and coefficient of variation (CV)—were analyzed. The prognostic effect of PET parameters was evaluated in terms of progression-free survival (PFS).RESULTS: Total 20 patients (4.5 ± 3.5 years) were divided as two groups by disease progression. Six patients (30.0 %) experienced disease progression and one patient (5.0 %) died during follow-up period. There were not statistically significant in age, stage, MYCN status, primary tumor size, serum lactate dehydrogenase (LDH), neuron-specific enolase (NSE), and ferritin level between two groups with progression or no progression. However, Psuv (p = 0.017), TBR (p = 0.09), MTV (p = 0.02), and CV (p = 0.036) showed significant differences between two groups. In univariate analysis, PFS was significantly associated with Psuv (p = 0.021) and TBR (p = 0.023).CONCLUSIONS: FDG-PET parameters were significantly related with progression of neuroblastoma. FDG-PET/CT may have the potential as a valuable modality for evaluating prognosis in the patients with MIBG-avid pediatric neuroblastoma.

Comparison of Two Different Segmentation Methods on Planar Lung Perfusion Scan with Reference to Quantitative Value on SPECT/CT / 대한핵의학회잡지

PURPOSE: Until now, there was no single standardized regional segmentation method of planar lung perfusion scan.We compared planar scan based two segmentation methods, which are frequently used in the Society of Nuclear Medicine, with reference to the lung perfusion single photon emission computed tomography (SPECT)/computed tomography (CT) derived values in lung cancer patients.METHODS: Fifty-five lung cancer patients (male:female, 37:18; age, 67.8 ± 10.7 years) were evaluated. The patients underwent planar scan and SPECT/CT after injection of technetium-99 m macroaggregated albumin (Tc-99 m-MAA). The % uptake and predicted postoperative percentage forced expiratory volume in 1 s (ppoFEV1%) derived from both posterior oblique (PO) and anterior posterior (AP) methods were compared with SPECT/CT derived parameters. Concordance analysis, paired comparison, reproducibility analysis and spearman correlation analysis were conducted.RESULTS: The % uptake derived from PO method showed higher concordance with SPECT/CT derived % uptake in every lobe compared to AP method. Both methods showed significantly different lobar distribution of%uptake compared to SPECT/CT. For the target region, ppoFEV1% measured from PO method showed higher concordance with SPECT/CT, but lower reproducibility compared to AP method. Preliminary data revealed that every method significantly correlated with actual postoperative FEV1%, with SPECT/CT showing the best correlation.CONCLUSIONS: The PO method derived values showed better concordance with SPECT/CT compared to the AP method. Both PO and AP methods showed significantly different lobar distribution compared to SPECT/CT. In clinical practice such difference according to different methods and lobes should be considered for more accurate postoperative lung function prediction.

High Serum Levels of Thyroid-Stimulating Hormone and Sustained Weight Gain in Patients with Thyroid Cancer Undergoing Radioiodine Therapy

BACKGROUND AND OBJECTIVES: The extent of weight gain and its association with clinical factors in patients undergoing radioiodine therapy for differentiated thyroid cancer remain unclear. We analyzed clinical factors related to sustained weight gain after serum thyroid-stimulating hormone (TSH) stimulation for radioiodine (I-131) therapy. MATERIALS AND METHODS: The study population included 301 adult patients who underwent total thyroidectomy followed by radioiodine therapy and visited the thyroid clinic regularly. Group 1 received a single radioiodine therapy treatment, while group 2 received multiple radioiodine treatment. Data on transient weight gain, defined as weight gain that resolved (±5%) within 1 year after radioiodine therapy, were collected from medical records. Sustained weight gain was defined as body mass index after treatment (BMI(post)) - BMI before treatment (BMI(pre)) ≥2 kg/m2 more than 1 year following radioiodine therapy. Subjective symptoms were scored by questionnaire. Logistic regression analysis was performed using various clinical and laboratory factors to identify risk factors associated with sustained weight gain. RESULTS: Two hundred and fifty-nine (86%) patients showed transient weight gain and 23 (8%) patients showed sustained weight gain. TSH at therapy and T4-on TSH differed significantly in all patients and in the patients in group 1 with sustained weight gain. The proportion of patients with basal BMI≥25 kg/m2 in group 1 with sustained weight gain also differed significantly. Univariate analysis revealed that high serum levels of TSH at therapy (≥100 µIU/mL) and hypercholesterolemia were associated with sustained weight gain in group 1. Multivariate analysis showed that TSH at therapy levels ≥100 µIU/mL was associated with sustained weight gain in group 1. Of 283 patients remaining after excluding those with insufficient TSH suppression during follow-up, T4-on TSH levels were lower in the sustained weight gain group compared to those without sustained weight gain. TSH at therapy levels ≥100 µIU/mL were significantly associated with sustained weight gain in multivariate analysis. CONCLUSION: Most patients (86%) had transient weight gain after TSH at therapy, while 8% of patients showed sustained weight gain. Univariate and multivariate analysis revealed relatively high TSH levels (≥100 µIU/mL) to be a risk factor for patients that received a single dose of radioiodine therapy. Insufficient T4 dose was not associated with sustained weight gain.

The Effectiveness of Recombinant Human Thyroid-Stimulating Hormone versus Thyroid Hormone Withdrawal Prior to Radioiodine Remnant Ablation in Thyroid Cancer: A Meta-Analysis of Randomized Controlled Trials

We evaluated the efficacy of recombinant human thyroid-stimulating hormone (rhTSH) versus thyroid hormone withdrawal (THW) prior to radioiodine remnant ablation (RRA) in thyroid cancer. A systematic search of MEDLINE, EMBASE, the Cochrane Library, and SCOPUS was performed. Randomized controlled trials that compared ablation success between rhTSH and THW at 6 to 12 months following RRA were included in this study. Six trials with a total of 1,660 patients were included. When ablation success was defined as a thyroglobulin (Tg) cutoff of 1 ng/mL (risk ratio, 0.99; 95% confidence interval, 0.96-1.03) or a Tg cutoff of 1 ng/mL plus imaging modality (RR 0.97; 0.90-1.05), the results of rhTSH and THW were similar. There were no significant differences when ablation success was defined as a Tg cutoff of 2 ng/mL (RR 1.03; 0.95-1.11) or a Tg cutoff of 2 ng/mL plus imaging modality (RR 1.02; 0.95-1.09). When a negative 131I-whole body scan was used solely as the definition of ablation success, the effects of rhTSH and THW were not significantly different (RR 0.97; 0.93-1.02). Therefore, ablation success rates are comparable when RRA is prepared by either rhTSH or THW.

MRI Evaluation for the Histologic Components of Soft-tissue Tumors: Comparison of MEDIC and Fast SE T2-weighted Imaging

PURPOSE: To compare Multi Echo Data Image Combination (MEDIC) and fast SE T2- weighted images with fat saturation (T2FS) to suggest more accurate evaluation of the histologic components of soft-tissue tumors. MATERIALS AND METHODS: The experimental group included 25 histologic tissues (5 vascular, 4 neural, 4 fibrous, 4 hypercellular, 2 hemorrhagic necroses, 2 cystic, 2 lipoid, 1 myxoid stroma, and 1 thrombus) in 10 patients who had pathologically confirmed schwannoma (n = 3), hemangioma (n = 2), lipoma (n = 1), angiokeratoma (n = 1), synovial sarcoma (n = 1), liposarcoma (n = 1), and malignant fibrous histiocytoma (n = 1). The inhomogeneity values were measured using the standard deviation value (SD) divided by the mean value as SD presents an error amount similar to that of imaging heterogeneity. RESULTS: The inhomogeneity values of 25 histologic components were lower on MEDIC than those on T2FS (p < .001). CONCLUSION: We conclude that MEDIC is more accurate than T2FS for evaluating the tissue components of soft-tissue tumors using digitalized data because MEDIC images have far lower inhomogeneity.

Advances in Nuclear Oncology / Journal of the Korean Cancer Association, 대한암학회지

No abstract available.

Targeted Molecular Imaging

Molecular imaging aims to visualize the cellular and molecular processes occurring in living tissues, and for the imaging of specific molecules in vivo, the development of reporter probes and dedicated imaging equipment is most important. Reporter genes can be used to monitor the delivery and magnitude of therapeutic gene transfer, and the time variation involved. Imaging technologies such as micro-PET, SPECT, MRI and CT, as well as optical imaging systems, are able to non-invasively detect, measure, and report the simultaneous expression of multiple meaningful genes. It is believed that recent advances in reporter probes, imaging technologies and gene transfer strategies will enhance the effectiveness of gene therapy trials.

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.

Biodistribution and Scintigraphy of Iodine-131-Iododeoxyadenosine in Rats Bearing Breast Cancer / 대한핵의학회잡지

PURPOSE: I-131 labeled (2'-deoxy-2-iodo-p-D-arabinofuranosyl) adenine (IAD) may be involved in DNA synthesis during active proliferation of tumor cells. We conducted this study to find out the biodistribution of IAD and its feasibility for scintigraphic tumor imaging. MATERIALS AND METHODS: Tosyl acetyl-adenosine was dissolved in acetonitrile, and I-131-NaI was added and heated to synthesize IAD. Female Fisher 344 rats innoculated with breast tumor cells were injected witb 0.27 MBq of IAD. Rats were sacrificed at 0.5, 1, 2, 4, 24h and the % of injected dose per gram of tissue (%ID/g) was determined. For scintigraphy, rats bearing breast cancer were administered with 1.11 MBq of IAD and imaging was perforrned after 2 and 24h. Then, rat body was fixed and rnicrotomized slice was placed on radiographic film for autoradiography, RESULTS: %ID/g of tumor wa.' 0.74 (0.5h), 0.73 (1h), 0.55 (2h), 0.38 (4h), and 0.05 (24h), respectively. At 1h after injection, %ID/g of tumor was higher than that of heart (0.34), liver (0.42), spleen (0.47), kidney (0,69), muscle (0.14), bone (0.33) and intestine (0.51). However, %1D/g of tumor was lower than blood (1.06), lung (0.77), and thyroid (177.71). At 4h, %ID/g of tumor in comparison with other tissue did not change. Tumor contrast expressed by tumor to blood ratio was 0.69 and tumor to muscle ratio was 5.11 at 1h. However, these ratios did not improve through 24h. On autoradiogram and scintigraphy at 2 and 24 hour, the tumor was well visualized. CONCLUSION: This results suggest that Ial) may have a potential for tumor scintigraphy. However, further work is needed to improve localization in tumor tissue.

Efficacy of IVIRI for Therapeutic Evaluation of Bone Lymphoma

PURPOSE:A retrospective study was performed to assess the efficacy of MRI in evaluation of therapeutic response of bone lymphoma. MATERIALS AND METHODS:We reviewed 17 cases of bone lymphoma on MRI that were follow-up studies during or after therapy. Among them, the cases with contrast study during therapy were 5, and those after therapy were 6. The four findings of follow-up MRI considered representative of improvement of bone lymphoma were the decreased size of tumor mass, the decreased signal intensity on T2-weighted images, the increased signal intensity of the tumor on T1 -weighted images, and the decreased or absent enhancement of post-contrast T1 -weighted images. RESULTS: The findings of improvement on T1 and T2-weighted images were shown in 50%(7/14) during therapy and 85.7%(12/14) after therapy. Those On post-contrast T1 -weighted images were shown in 20%(1/5) during therapy and 50%(3/6) after therapy. CONCLUSION:On MRI, both findings of the decreased signal intensity on T2-weighted images and the increased signal intensity of on T1 -weighted images of the tumor were significant in evaluating therapeutic response of bone lymphoma.

Measurment of Functioning Hepatocyte Mass using Cardiac Blood Pool Clearance Rates of 99mTc-DISIDA

PURPOSE: The authors investigated the ability of cardiac blood pool clearance rates(CBCR) of 99mTc-DiSiDA in the measure merit of functioning hepatocyte mass. MATERIALS AND METHODS: We measured the volume of Iobectomized liver after completion of postoperative scanning with CBCR of 99rnTc-DISIDA in 5 rabbits who the functional hepatic Iobectomy performed by ligation of hepatic artery, portal vein and biliary tracts. Regarding the measurement of CBCR of 99mTc-DISIDA, we set the time which was decreased to the half of the clearance amount of the cardiac radioactivity by hepatic extraction of 99mTc-DISIDA at the point of 50 sec after the renal peak of the radioactivity to prevent confusing with the blood dilution of the radioactivity, that have called DI-K50. RESULTS: The results were followed that the volumes of the functional hepatic Iobectomy in 5 rabbits were 25%, 25%, 41%, 52%, 75% and the residual functioning hepatocyte masses measured by CBCR of 99rnTc-DISIDA were preserved to 75. 1%, 70. 8%, 63. 0%, 52. 2%, 30. 8% respectively. CONCLUSION: we made decision that CBCR of 99rnTc-DISlDA was useful to evaluate the functioning hepatocyte mass.