Establishment of a ¹⁸F-FDG-PET/MRI Imaging Protocol for Gastric Cancer PDX as a Preclinical Research Tool

PURPOSE: The utility of 18-fluordesoxyglucose positron emission tomography ([¹⁸F]-FDG-PET) combined with computer tomography or magnetic resonance imaging (MRI) in gastric cancer remains controversial and a rationale for patient selection is desired. This study aims to establish a preclinical patient-derived xenograft (PDX) based [¹⁸F]-FDG-PET/MRI protocol for gastric cancer and compare different PDX models regarding tumor growth and FDG uptake.MATERIALS AND METHODS: Female BALB/c nu/nu mice were implanted orthotopically and subcutaneously with gastric cancer PDX. [¹⁸F]-FDG-PET/MRI scanning protocol evaluation included different tumor sizes, FDG doses, scanning intervals, and organ-specific uptake. FDG avidity of similar PDX cases were compared between ortho- and heterotopic tumor implantation methods. Microscopic and immunohistochemical investigations were performed to confirm tumor growth and correlate the glycolysis markers glucose transporter 1 (GLUT1) and hexokinase 2 (HK2) with FDG uptake.RESULTS: Organ-specific uptake analysis showed specific FDG avidity of the tumor tissue. Standard scanning protocol was determined to include 150 μCi FDG injection dose and scanning after one hour. Comparison of heterotopic and orthotopic implanted mice revealed a long growth interval for orthotopic models with a high uptake in similar PDX tissues. The H-score of GLUT1 and HK2 expression in tumor cells correlated with the measured maximal standardized uptake value values (GLUT1: Pearson r=0.743, P=0.009; HK2: Pearson r=0.605, P=0.049).CONCLUSIONS: This preclinical gastric cancer PDX based [¹⁸F]-FDG-PET/MRI protocol reveals tumor specific FDG uptake and shows correlation to glucose metabolic proteins. Our findings provide a PET/MRI PDX model that can be applicable for translational gastric cancer research.

Sodium Iodide Symporter (NIS) in the Management of Patients with Thyroid Carcinoma / 대한핵의학회잡지

Although radioiodine has been applied in thyroid diseases including carcinoma for over 70 years, it was only in 1996 that the basic molecular mechanism of iodine uptake was identified. Iodide is actively transported into the thyroid via a membrane glycoprotein known as sodium iodide symporter (NIS). NIS mediates radioiodine uptake into thyroid normal and cancer cells. The knowledge on NIS expression has provided scientific background to the empirical management of thyroid carcinoma. Based on recent studies of the NIS gene, this paper provides current clinical applications and future studies.

Recurrence of Melanoma After Initial Treatment: Diagnostic Performance of FDG PET in Posttreatment Surveillance / 대한핵의학회잡지

PURPOSE: In malignant melanoma, recurrence is often observed in distant areas from the primary site. While FDG PET is a sensitive imaging for detecting malignant lesions, the role of FDG PET in posttreatment surveillance period has not been investigated sufficiently. The aim of this study was to evaluate the value of PET during posttreatment surveillance in melanoma.METHODS: A total of 76 melanoma patients who underwent FDG PET during surveillance period after completion of the first treatment were retrospectively enrolled. PET scans were grouped according to the purpose and clinical situations, routine surveillance, or evaluating clinical suspicion. Final diagnosis of recurrence was determined by complete clinical evaluation or long-term follow-up. In each situation, the diagnostic role of FDG PET was assessed.RESULTS: A total of 143 scans of 76 patients were analyzed: 51 for clinical suspicion and 92 for routine surveillance. In the clinical suspicion group, PET correctly diagnosed non-recurrence in 10 cases (20%). In routine surveillance group, 16 cases (17%) presented recurrence, all of which was correctly diagnosed on PET. NPVand PPV were 100% and 76%, respectively. In subgroup analysis, sensitivity and NPV were higher in the low-risk group (stages I–II(A)) than in the high-risk group (stages II(B)–IV), while specificity and PPV were higher in the high-risk group.CONCLUSION: In conclusion, FDG PET is an effective diagnostic tool in posttreatment surveillance of melanoma. Even in cases without clinical suspicion, melanoma recurs in a considerable proportion of patients, which can be sensitively diagnosed on PET.

Application of Quantitative Indexes of FDG PET to Treatment Response Evaluation in Indolent Lymphoma / 대한핵의학회잡지

PURPOSE: Although ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a standard imaging modality for response evaluation in FDG-avid lymphoma, there is a controversy using FDG PET in indolent lymphoma. The purpose of this study was to investigate the effectiveness of quantitative indexes on FDG PET in response evaluation of the indolent lymphoma.METHODS: Fifty-seven indolent lymphoma patients who completed chemotherapy were retrospectively enrolled. FDG PET/computed tomography (CT) scans were performed at baseline, interim, and end of treatment (EOT). Response was determined by Lugano classification, and progression-free survival (PFS) by follow-up data. Maximumstandardized uptake value (SUV(max)), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured in the single hottest lesion (target A) or five hottest lesions (target B). Their efficacies regarding response evaluation and PFS prediction were evaluated.RESULTS: On EOT PET, SUV(max), and MTVof both targets were well associated with visual analysis. Changes between initial and EOT PET were not significantly different between CR and non-CR groups. On interim PET, SUV(max), and %ΔSUV(max) in both targets were significantly different between CR and non-CR groups. For prediction of PFS, most tested indexes were significant on EOT and interim PET, with SUVmax being the most significant prognostic factor.CONCLUSION: Quantitative indexes of FDG PET are well associated with Lugano classification in indolent lymphoma. SUV(max) measured in the single hottest lesion can be effective in response evaluation and prognosis prediction on interim and EOT PET.

Measurement of ⁶⁸Ga-DOTATOC Uptake in the Thoracic Aorta and Its Correlation with Cardiovascular Risk / 대한핵의학회잡지

PURPOSE: ⁶⁸Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid-D-Phe1-Tyr3-octreotide (⁶⁸Ga-DOTATOC) is taken up by activated macrophages, which accumulate in active inflammatory lesions. The purpose of this study was to investigate the feasibility of ⁶⁸Ga-DOTATOC PET/CT for assessment of vulnerable plaque, by evaluating correlation between aortic uptake of ⁶⁸Ga-DOTATOC and cardiovascular risk factors.METHODS: Fifty patients with neuroendocrine tumors who underwent ⁶⁸Ga-DOTATOC PET/CT were retrospectively enrolled. The uptakes in the thoracic aorta were measured by two methods: multi-sample region-of-interest (ROI) method and single volume-of-interest (VOI) method. TBRmax-avg, TBRmean-avg, TBRmax-VOI, and TBRmean-VOI were defined by maximum and mean target-to-background ratio (TBR) from the multi-sample ROI method and the single VOI method, respectively.RESULTS: Framinghamrisk score (FRS) exhibited significant correlations with TBRmax-avg and TBRmean-avg, aswell as TBRmax-VOI (r = 0.3389–0.4593, P < 0.05 for all). TBRmax-avg and TBRmax-VOI were significantly higher in high FRS group than in low FRS group (1.48 ± 0.21 vs. 1.70 ± 0.17, P < 0.001 for TBRmax-avg and 1.90 ± 0.33 vs. 2.25 ± 0.36, P = 0.002 for TBRmax-VOI). TBR exhibited high correlations between the two measuring methods (r = 0.9684, P < 0.001 for TBRmean-avg and TBRmean-VOI and r = 0.8681, P < 0.001 for TBRmax-avg and TBRmax-VOI).CONCLUSIONS: ⁶⁸Ga-DOTATOC uptake in the thoracic aorta exhibited a significant correlation with cardiovascular risk factors, which suggests the feasibility of ⁶⁸Ga-DOTATOC PET for vulnerable plaque imaging, with a simple measurement of the single VOI method that is comparable to the multi-sample ROI-based approach.

Correlation of FDG PET/CT Findings with Long-Term Growth and Clinical Course of Abdominal Aortic Aneurysm / 대한핵의학회잡지

PURPOSE: Herein, we report characteristics of ¹⁸F–fluorodeoxyglucose (FDG) uptake in abdominal aortic aneurysms (AAAs) during a long-term follow-up. In addition, we investigated the association between FDG uptake and the physician decision to perform an intervention.METHODS: We performed a retrospective review of 42 patients with AAAs who underwent FDG positron emission tomography (PET)/computed tomography (CT). The size of the AAA was measured in serial CT or PET/CT images. The long-term growth rate of AAAs was calculated by linear regression of the size change. Maximal SUV of the AAA (SUV(AAA)) and mean SUV of the blood pool (SUV(Blood)) were measured in PET/CT fusion images. To assess the FDG uptake of AAAs, the target-to-background ratio (TBR) was defined as the ratio of SUV(AAA) to SUV(Blood). We compared FDG uptake of AAAs with the long-term growth rate of AAAs and clinical data.RESULTS: TBR was not significantly different between patients with and without significant growth (1.55 ± 0.20 vs. 1.57 ± 0.14; P = 0.5599).However, in patients with significant growth, TBR exhibited a significant positive correlation with the growth rate (r² = 0.2601, P = 0.0306). TBR also exhibited a significant difference between patients with and without intervention (P = 0.0228).CONCLUSION: FDG uptake of AAA is associated with long-term growth of AAAs in a specified group that exhibits growth. FDG PET/CT may only be effective in predicting the long-term growth of AAAs in specific subgroups of patients. It is also suggested that FDG PET is potentially related to the clinical conditions of AAA patients who need surgical or interventional treatment.

Effects of Maternal Iodine Status during Pregnancy and Lactation on Maternal Thyroid Function and Offspring Growth and Development: A Prospective Study Protocol for the Ideal Breast Milk Cohort

BACKGROUND: Iodine is an intrinsic element of thyroid hormone, which is essential for childhood growth and development. The Ideal Breast Milk (IBM) cohort study aims to evaluate the effects of maternal iodine status during pregnancy and lactation on maternal thyroid function, offspring growth and development, and offspring thyroid function. METHODS: The IBM cohort study recruited pregnant women from Seoul National University Hospital between June 2016 and August 2017, followed by enrollment of their offspring after delivery. For the maternal participants, iodine status is evaluated by urinary iodine concentration (UIC) and dietary records in the third trimester and at 3 to 4 weeks and 12 to 15 months postpartum. For the child participants, cord blood sampling and UIC measurements are performed at birth. At 3 to 4 weeks of age, UIC and breastmilk iodine concentrations are measured. At 12 to 15 months of age, growth and development are assessed and measurements of UIC, a thyroid function test, and ultrasonography are performed. RESULTS: A total of 198 pregnant women in their third trimester were recruited. Their mean age was 35.1±3.5 years, and 78 (39.4%) of them were pregnant with twins. Thirty-three (16.7%) of them had a previous history of thyroid disease. CONCLUSION: Korea is an iodine-replete area. In particular, lactating women in Korea are commonly exposed to excess iodine due to the traditional practice of consuming brown seaweed soup postpartum. The study of the IBM cohort is expected to contribute to developing guidelines for optimal iodine nutrition in pregnant or lactating women.

Sodium Iodide Symporter (NIS) in the Management of Patients with Thyroid Carcinoma / 대한핵의학회잡지

Although radioiodine has been applied in thyroid diseases including carcinoma for over 70 years, it was only in 1996 that the basic molecular mechanism of iodine uptake was identified. Iodide is actively transported into the thyroid via a membrane glycoprotein known as sodium iodide symporter (NIS). NIS mediates radioiodine uptake into thyroid normal and cancer cells. The knowledge on NIS expression has provided scientific background to the empirical management of thyroid carcinoma. Based on recent studies of the NIS gene, this paper provides current clinical applications and future studies.

Recurrence of Melanoma After Initial Treatment: Diagnostic Performance of FDG PET in Posttreatment Surveillance / 대한핵의학회잡지

PURPOSE@#In malignant melanoma, recurrence is often observed in distant areas from the primary site. While FDG PET is a sensitive imaging for detecting malignant lesions, the role of FDG PET in posttreatment surveillance period has not been investigated sufficiently. The aim of this study was to evaluate the value of PET during posttreatment surveillance in melanoma.@*METHODS@#A total of 76 melanoma patients who underwent FDG PET during surveillance period after completion of the first treatment were retrospectively enrolled. PET scans were grouped according to the purpose and clinical situations, routine surveillance, or evaluating clinical suspicion. Final diagnosis of recurrence was determined by complete clinical evaluation or long-term follow-up. In each situation, the diagnostic role of FDG PET was assessed.@*RESULTS@#A total of 143 scans of 76 patients were analyzed: 51 for clinical suspicion and 92 for routine surveillance. In the clinical suspicion group, PET correctly diagnosed non-recurrence in 10 cases (20%). In routine surveillance group, 16 cases (17%) presented recurrence, all of which was correctly diagnosed on PET. NPVand PPV were 100% and 76%, respectively. In subgroup analysis, sensitivity and NPV were higher in the low-risk group (stages I–II(A)) than in the high-risk group (stages II(B)–IV), while specificity and PPV were higher in the high-risk group.@*CONCLUSION@#In conclusion, FDG PET is an effective diagnostic tool in posttreatment surveillance of melanoma. Even in cases without clinical suspicion, melanoma recurs in a considerable proportion of patients, which can be sensitively diagnosed on PET.

Application of Quantitative Indexes of FDG PET to Treatment Response Evaluation in Indolent Lymphoma / 대한핵의학회잡지

PURPOSE@#Although ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a standard imaging modality for response evaluation in FDG-avid lymphoma, there is a controversy using FDG PET in indolent lymphoma. The purpose of this study was to investigate the effectiveness of quantitative indexes on FDG PET in response evaluation of the indolent lymphoma.@*METHODS@#Fifty-seven indolent lymphoma patients who completed chemotherapy were retrospectively enrolled. FDG PET/computed tomography (CT) scans were performed at baseline, interim, and end of treatment (EOT). Response was determined by Lugano classification, and progression-free survival (PFS) by follow-up data. Maximumstandardized uptake value (SUV(max)), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured in the single hottest lesion (target A) or five hottest lesions (target B). Their efficacies regarding response evaluation and PFS prediction were evaluated.@*RESULTS@#On EOT PET, SUV(max), and MTVof both targets were well associated with visual analysis. Changes between initial and EOT PET were not significantly different between CR and non-CR groups. On interim PET, SUV(max), and %ΔSUV(max) in both targets were significantly different between CR and non-CR groups. For prediction of PFS, most tested indexes were significant on EOT and interim PET, with SUVmax being the most significant prognostic factor.@*CONCLUSION@#Quantitative indexes of FDG PET are well associated with Lugano classification in indolent lymphoma. SUV(max) measured in the single hottest lesion can be effective in response evaluation and prognosis prediction on interim and EOT PET.

Correlation of FDG PET/CT Findings with Long-Term Growth and Clinical Course of Abdominal Aortic Aneurysm / 대한핵의학회잡지

PURPOSE@#Herein, we report characteristics of ¹⁸F–fluorodeoxyglucose (FDG) uptake in abdominal aortic aneurysms (AAAs) during a long-term follow-up. In addition, we investigated the association between FDG uptake and the physician decision to perform an intervention.@*METHODS@#We performed a retrospective review of 42 patients with AAAs who underwent FDG positron emission tomography (PET)/computed tomography (CT). The size of the AAA was measured in serial CT or PET/CT images. The long-term growth rate of AAAs was calculated by linear regression of the size change. Maximal SUV of the AAA (SUV(AAA)) and mean SUV of the blood pool (SUV(Blood)) were measured in PET/CT fusion images. To assess the FDG uptake of AAAs, the target-to-background ratio (TBR) was defined as the ratio of SUV(AAA) to SUV(Blood). We compared FDG uptake of AAAs with the long-term growth rate of AAAs and clinical data.@*RESULTS@#TBR was not significantly different between patients with and without significant growth (1.55 ± 0.20 vs. 1.57 ± 0.14; P = 0.5599).However, in patients with significant growth, TBR exhibited a significant positive correlation with the growth rate (r² = 0.2601, P = 0.0306). TBR also exhibited a significant difference between patients with and without intervention (P = 0.0228).@*CONCLUSION@#FDG uptake of AAA is associated with long-term growth of AAAs in a specified group that exhibits growth. FDG PET/CT may only be effective in predicting the long-term growth of AAAs in specific subgroups of patients. It is also suggested that FDG PET is potentially related to the clinical conditions of AAA patients who need surgical or interventional treatment.

Measurement of ⁶⁸Ga-DOTATOC Uptake in the Thoracic Aorta and Its Correlation with Cardiovascular Risk / 대한핵의학회잡지

PURPOSE@#⁶⁸Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid-D-Phe1-Tyr3-octreotide (⁶⁸Ga-DOTATOC) is taken up by activated macrophages, which accumulate in active inflammatory lesions. The purpose of this study was to investigate the feasibility of ⁶⁸Ga-DOTATOC PET/CT for assessment of vulnerable plaque, by evaluating correlation between aortic uptake of ⁶⁸Ga-DOTATOC and cardiovascular risk factors.@*METHODS@#Fifty patients with neuroendocrine tumors who underwent ⁶⁸Ga-DOTATOC PET/CT were retrospectively enrolled. The uptakes in the thoracic aorta were measured by two methods: multi-sample region-of-interest (ROI) method and single volume-of-interest (VOI) method. TBRmax-avg, TBRmean-avg, TBRmax-VOI, and TBRmean-VOI were defined by maximum and mean target-to-background ratio (TBR) from the multi-sample ROI method and the single VOI method, respectively.@*RESULTS@#Framinghamrisk score (FRS) exhibited significant correlations with TBRmax-avg and TBRmean-avg, aswell as TBRmax-VOI (r = 0.3389–0.4593, P < 0.05 for all). TBRmax-avg and TBRmax-VOI were significantly higher in high FRS group than in low FRS group (1.48 ± 0.21 vs. 1.70 ± 0.17, P < 0.001 for TBRmax-avg and 1.90 ± 0.33 vs. 2.25 ± 0.36, P = 0.002 for TBRmax-VOI). TBR exhibited high correlations between the two measuring methods (r = 0.9684, P < 0.001 for TBRmean-avg and TBRmean-VOI and r = 0.8681, P < 0.001 for TBRmax-avg and TBRmax-VOI).@*CONCLUSIONS@#⁶⁸Ga-DOTATOC uptake in the thoracic aorta exhibited a significant correlation with cardiovascular risk factors, which suggests the feasibility of ⁶⁸Ga-DOTATOC PET for vulnerable plaque imaging, with a simple measurement of the single VOI method that is comparable to the multi-sample ROI-based approach.

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.

Comparison of Quantitative Methods on FDG PET/CT for Treatment Response Evaluation of Metastatic Colorectal Cancer / 대한핵의학회잡지

PURPOSE: FDG PET is effective in treatment response evaluation of cancer. However, there is no standard method for quantitative evaluation of FDG PET, particularly regarding cytostatic drugs. We compared various FDG PET quantitative methods in terms of response determination.METHODS: A total of 39 refractory metastatic colorectal cancer patients who received a multikinase inhibitor treatment were included. Baseline and posttreatment FDG PET/CT scans were performed before and two cycles after treatment. Standardized uptake value (SUV) and total lesion glycolysis (TLG) values using various margin thresholds (30–70 % of maximum SUV with increment 10 %, twice mean SUV of blood pool, SUV 3.0, and SUV 4.0) were measured, with measurement target of the hottest lesion or a maximum of five hottest lesions. Treatment response by the PERCIST criteria was also determined. Predictive values of the PET indexes were evaluated in terms of the treatment response determined by the RECIST 1.1 criteria.RESULTS: The agreement rate was 38 % between response determined by the PERCIST and the RECIST criteria (κ = 0.381). When patients were classified into disease control group (PR, SD) and non-control group (PD) by the RECIST criteria, percent changes of TLG with various margin thresholds (particularly, 30–50%of maximum SUV) exhibited significant differences between the two groups, and high diagnostic power for the response by the RECIST criteria. TLG-based criteria, which used a margin threshold of 50 % of maximum SUV, exhibited a high agreement with the RECIST criteria compared with the PERCIST criteria (κ = 0.606).CONCLUSION: In metastatic colorectal cancer, FDG PET/CT could be effective for treatment response evaluation by using TLG measured by margin thresholds of 30–50%of maximum SUV. Further studies are warranted regarding the optimal cutoff values for this method.

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.

Feasibility of sentinel lymph node dissection using Tc-99m phytate in papillary thyroid carcinoma

PURPOSE: Various methods of sentinel lymph node (SLN) biopsy in thyroid cancer have been introduced. Tc-99m phytate as a radiotracer has been successfully utilized for SLN biopsy in breast, cervix, and endometrial cancer. We assessed the feasibility of SLN dissection using Tc-99m phytate in papillary thyroid carcinoma (PTC). METHODS: Seventeen patients with PTC were prospectively enrolled. Ultrasound-guided peritumoral injection of 55.5 MBq Tc-99m phytate in 0.25-mL normal saline was performed. Preoperative single-photon emission-computed tomography (SPECT) and intraoperative gamma-probe were used for SLN detection during operation. RESULTS: Identification rate of SLNs was 70.6% (12 of 17) with SPECT, and 88.2% (15 of 17) with gamma-probe. Combined SPECT and gamma-probe had identification rates of 88.2% (15 of 17). Identification rates of SLNs in central LN compartments were 82.4% (14 of 17) and 41.2% (7 of 17) in lateral LN compartments. Overall sensitivity, specificity, positive predictive value, and negative predictive value of the results of SLN biopsy were 91.6%, 100%, 88.4%, and 100%, respectively. Eight patients (47.1%) had metastasis in SLNs; all patients had SLN metastasis in the central compartment and 2 patients had SLN metastasis in both the central and lateral compartments. CONCLUSION: Combined SPECT and gamma-probe could detect SLNs with an 88.2% identification rate in PTC. SLN biopsy using Tc-99m phytate is technically feasible. Further investigation is warranted for clinical application of Tc-99m phytate in PTC.

Radiation Dose from Whole-Body F-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography: Nationwide Survey in Korea

The purpose of this study was to estimate average radiation exposure from 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) examinations and to analyze possible factors affecting the radiation dose. A nation-wide questionnaire survey was conducted involving all institutions that operate PET/CT scanners in Korea. From the response, radiation doses from injected FDG and CT examination were calculated. A total of 105 PET/CT scanners in 73 institutions were included in the analysis (response rate of 62.4%). The average FDG injected activity was 310 +/- 77 MBq and 5.11 +/- 1.19 MBq/kg. The average effective dose from FDG was estimated to be 5.89 +/- 1.46 mSv. The average CT dose index and dose-length product were 4.60 +/- 2.47 mGy and 429.2 +/- 227.6 mGycm, which corresponded to 6.26 +/- 3.06 mSv. The radiation doses from FDG and CT were significantly lower in case of newer scanners than older ones (P < 0.001). Advanced PET technologies such as time-of-flight acquisition and point-spread function recovery were also related to low radiation dose (P < 0.001). In conclusion, the average radiation dose from FDG PET/CT is estimated to be 12.2 mSv. The radiation dose from FDG PET/CT is reduced with more recent scanners equipped with image-enhancing algorithms.

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.

Graves' Patient with Thymic Expression of Thyrotropin Receptors and Dynamic Changes in Thymic Hyperplasia Proportional to Graves' Disease Activity

Thymic hyperplasia is frequently observed in Graves' disease. However, detectable massive enlargement of the thymus is rare, and the mechanism of its formation has remained elusive. This case showed dynamic changes in thymic hyperplasia on serial computed tomography images consistent with changes in serum thyrotropin receptor (TSH-R) antibodies and thyroid hormone levels. Furthermore, the patient's thymic tissues underwent immunohistochemical staining for TSH-R, which demonstrated the presence of thymic TSH-R. The correlation between serum TSH-R antibody levels and thymic hyperplasia sizes and the presence of TSH-R in her thymus suggest that TSH-R antibodies could have a pathogenic role in thymic hyperplasia.