Carcinoma papilar de tiroides no captante de radioyodo (I131): a propósito de un caso / Papillary thyroid carcinoma not collecting radioiodine (I131): presentation of a case

RESUMEN El carcinoma papilar de tiroides (CPT) corresponde a una neoplasia frecuente en el mundo y en nuestro país. Generalmente se asocia a buen pronóstico y altas tasas de sobrevida, gracias a características propias del tumor, precisas herramientas diagnósticas y terapias eficaces. Formas infrecuentes de CPT suelen tener comportamientos más agresivos y respuestas parciales a tratamientos habituales, tales como el CPT no captante de radioyodo (5% de los casos). Poca literatura existe respecto a este último y a su manejo. Diversas opciones de tratamiento han sido propuestas, según si hay evidencia de tejido tumoral, como el uso empírico de I131, cirugía, radioterapia, embolización e inhibidores de tirosina kinasa, sin embargo, sigue habiendo una respuesta incierta.

ABSTRACT Papillary thyroid carcinoma (PTC) is a common cancer in the world and in our country. It is usually associated with good prognosis and high survival rates, due to the tumor's characteristics, precise diagnostic tools and effective therapies. Unusual varieties of PTC have more aggressive behaviors and partial responses to usual treatments, such as negative uptake to radioiodine PTC (5% of cases). There is few literature about this variety and its treatment. Diverse treatment options have been proposed, according to whether there is evidence of tumor tissue, such as the empirical use of I131, surgery, radiotherapy, embolization and inhibitors of thyrosine kinase, however an uncertain response remains.

Features of post-radioiodine whole body scan in non-invasive Follicular Thyroid Neoplasm with papillary-like nuclear features (NIFTP)

carcinoma has been reclassified as non-invasive follicularthyroid neoplasm with papillary-like nuclear features (NIFTP)to emphasize the benign nature of this entity. In ourinstitution, we have assessed 455 patients treated withradioiodine ablation for differentiated thyroid carcinoma and20 of them were retrospectively found to fulfill the newNIFTP criteria. There was no evidence of metastasis on postradioiodine whole body scans for NIFTP cases and thesepatients were in remission subsequently. The benignfeatures of these patients’ whole body scans and goodclinical outcome following treatment further support NIFTPas a low risk thyroid neoplasm.

Clinical utility of 18F-FDG PET/CT in the follow-up of a large cohort of patients with high-risk differentiated thyroid carcinoma

ABSTRACT Objective To evaluate the clinical utility of 18F-FDG PET/CT in patients with high-risk DTC. Subjects and methods Single-center retrospective study with 74 patients with high-risk differentiated thyroid cancer (DTC), classified in 4 groups. Group 1: patients with positive sTg or TgAb, subdivided in Group 1A: negative RxWBS and no foci of metastases identified at conventional image (n = 9); Group 1B: RxWBS not compatible with suspicious foci at conventional image or not proportional to sTg level (n = 13); Group 2: patients with histological findings of aggressive DTC variants (n = 21) and Group 3: patients with positive RxWBS (n = 31). Results 18F-FDG PET/CT identified undifferentiated lesions and helped restage the disease in groups 1B and 2. The scan helped guide clinical judgment in 9/13 (69%) patients of group 1B, 10/21 (48%) patients of group 2 and 2/31 (6%) patients of group 3. There was no clinical benefit associated with group 1A. 18F-FDG PET/CT was associated with progressive disease. Conclusion 18F-FDG PET/CT is a useful tool in the follow-up of patients with high-risk DTC, mainly in the group of RxWBS not compatible with suspicious foci at conventional image or not proportional to sTg level and in those with aggressive DTC variants. Additionally, this study showed that 18F-FDG PET/CT was associated with progression and helped display undifferentiated lesions guiding clinical assessments regarding surgeries or expectant treatments.

Optimal Threshold of Stimulated Serum Thyroglobulin Level for 18F-FDG PET/CT imaging in Patients with Thyroid Cancer / 华中科技大学学报（医学）（英德文版）

This study was to explore the optimal threshold of thyroid-stimulating hormone (TSH)-stimulated serum thyroglobulin (s-Tg) for patients who were to receive 18F-fluorodeoxyglucose (18F-FDG) PET/CT scan owing to clinical suspicion of differentiated thyroid cancer (DTC) recurrence but negative post-therapeutic 131I whole-body scan (131I-WBS).A total of 60 qualified patients underwent PET/CT scanning from October 2010 to July 2014.The receiver operating characteristic (ROC) curve analyses showed that s-Tg levels over 49 μg/L led to the highest diagnostic accuracy of PET/CT to detect recurrence,with a sensitivity of 89.5％ and a specificity of 90.9％.Besides,bivariate correlation analysis showed positive correlation between s-Tg levels and the maximum standardized uptake values (SUVmax) of 18F-FDG in patients with positive PET/CT scanning,suggesting a significant influence of TSH both on Tg release and uptake of 18F-FDG.So,positive PET/CT imaging is expected when patients have negative 131I-WBS but s-Tg levels over 49 μg/L.

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.

The use of SPECT-CT improves accuracy of post radioiodine therapy imaging and changes the management strategy in a case of advanced follicular thyroid carcinoma

This is a case of follicular thyroid carcinoma with extensive lung, bone and brain metastases. Multi-modality treatments including total thyroidectomy, modified radical neck dissection, cranial radiotherapy and Iodine-131 (RAI) therapy were instituted. Post RAI therapy planar whole body scan showed RAI avid metastases in the skull, cervical spine, bilateral lungs and abdomen. With the use of SPECTCT imaging, rare adrenal metastasis and additional rib metastasis were identified. Besides, management strategy was altered due to detection of non-RAI avid brain and lung metastatic lesions.

Value of PET/CT for diagnosis of recurrence and metastasis of differentiated thyroid carcinoma / 中华内分泌外科杂志

Objective To analyze the value of PET/CT for diagnosis of recurrence and metastasis of dif-ferentiated thyroid carcinoma ( DTC) .Methods 65 patients with DTC in Thyroid Surgery Department of the First Affiliated Hospital of Zhengzhou University from Dec .2005 to Jan.2015 were collected.Based on the values of serum thyroglobulin(Tg),the patients were divided into 2 groups.29 cases with positive Tg were the observation group and 36 cases with negative Tg were the control group .All patients underwent PET/CT examination one year after surgery.Patients with positive findings from image studies underwent surgical excision and postoperative pathological diagnosis .Clinical data of the 2 groups were then summarized and discussed .Results There was no significant difference on the general conditions between the 2 groups(P>0.05).Tg values were statistically dif-ferent 6 months and 1 year after surgery between the 2 groups(P0.05).9 cases in the observation group and 1 case in the control group had positive findings on image study .All the cases with cervical lymph nodes presented as high uptake of 18 F-FDG.All patients who had positive findings on PET/CT underwent surgical removal of the abnormal lymph nodes which confirmed by pathology as lymph node metastasis .Conclusion PET/CT is very important for diagno-sis of recurrence and metastasis on Tg(Tg>2μg/L)positive,131I Dx-WBS imaging and US negative patients.

Clinical Determinants of Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Differentiated Thyroid Cancer Patients with Elevated Thyroglobulin and Negative 131Iodine Whole Body Scans after 131Iodine Therapy

Background: A cross-sectional prospective study has been conducted on differentiated thyroid cancer (DTC) patients using negative 131Iodine (131I) whole body scans and elevated thyroglobulin (Tg) levels. The main objective of this research was to determine the prevalence of the conversion of differentiated to dedifferentiated thyroid cancer patients during follow up at the Hospital Kuala Lumpur. It has been demonstrated that fluorodeoxyglucose (FDG) uptake is inversely proportional to the iodine concentration and to differentiation of the cells. Methodology: Thirty-five patients with histologically proven DTC that have undergone total or near total thyroidectomy, and post 131I radioactive iodine ablation therapy, were selected and prospectively analysed. The patients also had to show at least one negative whole body scan and Tg levels of 10 μg/L and above. The results of the FDG-Positron Emission Tomography/Computed Tomography (PET/CT) were then studied to determine the association and the predictors influencing the outcome by using univariable and multivariable analyses. Results: Out of the thirty-five patients, 60% of them (twenty-one) showed positive results and 40% (fourteen) showed negative. Age, gender, and type of histopathology (HPE) showed significant associations with the positive results of the FDG-PET/CT. The results also showed no correlations observed between the Tg levels and standardised uptake value (SUV)max in the DTC patients with positive disease findings in the FDG-PET/CT. The predictor for this study was age. Conclusion: The prevalence of the conversion of differentiated to dedifferentiated thyroid cancer among patients with negative 131I and elevated Tg was 60%, with age as the predictor. DTC patients aged 45 year-old and older were seven times more likely to have positive results of FDG-PET/CT imaging.

Influencing factor of whole-body scan imaging on radioactive io-dine treatment for lung metastases of differentiated thyroid carci-noma / 中国肿瘤临床

Objective: Lung metastases are common in patients with differentiated thyroid carcinoma (DTC). Post-therapeutic 131I-whole-body scan (WBS) was conventionally administered after the radioactive iodine treatment (RAI) of DTC lung metastases. This study aimed to investigate the influencing factors of WBS imaging on the RAI of DTC lung metastases. Methods:DTC patients (n=60) with lung metastases treated with 131I were retrospectively included. Before treatment, the thyroid function was assessed. Neck and chest computed tomography (CT) was performed, and WBS was inspected. Patients with lung metastases were classified into negative and positive subgroups according to the imaging of 131I WBS, and the relative influencing factors were analyzed. Results:Univariate analy-sis showed that age and chest CT imaging, which revealed pulmonary fibrosis, calcification, and patchy shadows, were related to WBS imaging. Binary variable logistic regression analysis revealed that pulmonary fibrosis (OR=0.175, P<0.001) and calcification (OR=0.088, P<0.05) went against the development of WBS. Conclusion:WBS imaging on RAI of lung metastases was not obvious in the el-derly. The fibrosis, calcification, and patchy shadows of the lung were not conducive for WBS imaging. The fibrosis and calcification of the lung were the main factors that affect WBS imaging.

Effectiveness of 124I-PET/CT and 18F-FDG-PET/CT for Localizing Recurrence in Patients with Differentiated Thyroid Carcinoma

Although the prognosis of patients with differentiated thyroid carcinoma (DTC) is generally encouraging, a diagnostic dilemma is posed when an increasing level of serum thyroglobulin (Tg) is noted, without detection of a recurrent tumor using conventional imaging tools such as the iodine-131 whole-body scanning (the [131I] scan) or neck ultrasonography (US). The objective of the present study was to evaluate the diagnostic value of [124I]-PET/CT and [18F]-FDG-PET/CT in terms of accurate detection of both iodine- and non-iodine-avid recurrence, compared with that of conventional imaging such as the [131I] scan or neck ultrasonography (US). Between July 2009 and June 2010, we prospectively studied 19 DTC patients with elevated thyroglobulin levels but who do not show pathological lesions when conventional imaging modalities are used. All involved patients had undergone total thyroidectomy and radioiodine (RI) treatment, and who had been followed-up for a mean of 13 months (range, 6-21 months) after the last RI session. Combined [18F]-FDG-PET/CT and [124I]-PET/CT data were evaluated for detecting recurrent DTC lesions in study patients and compared with those of other radiological and/or cytological investigations. Nine of 19 patients (47.4%) showed pathological [18F]-FDG (5/19, 26.3%) or [124I]-PET (4/19, 21.1%) uptake, and were classed as true-positives. Among such patients, disease management was modified in six (66.7%) and disease was restaged in seven (77.8%). In particular, the use of the described imaging combination optimized planning of surgical resection to deal with locoregional recurrence in 21.1% (4/19) of patients, who were shown to be disease-free during follow-up after surgery. Our results indicate that combination of [18F]-FDG-PET/CT and [124I]-PET/CT affords a valuable diagnostic method that can be used to make therapeutic decisions in patients with DTC who are tumor-free on conventional imaging studies but who have high Tg levels.

Clinical Significance of Observation without Repeated Radioiodine Therapy in Differentiated Thyroid Carcinoma Patients with Positive Surveillance Whole-Body Scans and Negative Thyroglobulin

BACKGROUND/AIMS: Currently, there is no consensus on the necessity of repeated radioiodine therapy (RAI) in patients who show iodine uptake in the thyroid bed on a diagnostic whole-body scan (DxWBS) despite undetectable thyroglobulin (Tg) levels after remnant ablation. The present study investigated the clinical outcomes of scan-positive, Tg-negative patients (WBS+Tg-) who did or did not receive additional RAI. METHODS: We retrospectively reviewed 389 differentiated thyroid carcinoma patients who underwent a total thyroidectomy and received high-dose RAI from January 2003 through December 2005. The patients were classified according to surveillance DxWBS findings and TSH-stimulated Tg levels 6 to 12 months after the initial RAI. RESULTS: Forty-four of the 389 patients (11.3%) showed thyroid bed uptake on a DxWBS despite negative Tg levels (WBS+Tg-). There was no difference in clinical and pathological parameters between WBS+Tg- and WBS-Tg- patients, except for an increased frequency of thyroiditis in the WBS+Tg- group. Among the 44 WBS+Tg- patients, 27 subjects were treated with additional RAI; 25 subjects showed no uptake in subsequent DxWBS. Two patients were evaluated only by ultrasonography (US) and displayed no persistent/recurrent disease. The other 17 patients received no further RAI; Eight patients and two patients showed no uptake and persistent uptake, respectively, on subsequent DxWBS. Six patients presented negative subsequent US findings, and one was lost to follow-up. Over the course of 53.2 +/- 10.1 months, recurrence/persistence was suspicious in two patients in the treatment group. CONCLUSIONS: There were no remarkable differences in clinical outcomes between observation and treatment groups of WBS+Tg- patients. Observation without repeated RAI may be an alternative management option for WBS+Tg- patients.

Cisto hepático benigno simulando metástase de carcinoma diferenciado de tireoide / Benign hepatic cyst mimicking thyroid carcinoma metastasis

INTRODUÇÃO: Pesquisa de corpo inteiro após dose terapêutica de (131I) NaI (PCI) associada à tireoglobulina (Tg) sérica, anticorpo antitireoglobulina (anti-Tg) e ultrassom (US) cervical representam os métodos de referência para detecção de carcinoma diferenciado de tireoide (CDT) residual ou metastático. Algumas causas de PCI falsos-positivas, como processos inflamatórios, alguns tumores não tireoidianos e até mesmo cistos renais e sebáceos, são bem conhecidas. MÉTODOS: Neste trabalho, descreveu-se um caso de cisto hepático benigno simulando metástase de carcinoma de tireoide em PCI após dose terapêutica de (131I) NaI. RESULTADOS: Ressalta-se a importância do reconhecimento dos cistos hepáticos benignos como fator complicador do seguimento dos pacientes com câncer de tireoide. CONCLUSÕES: Para minimizar erros de diagnóstico e, consequentemente, na condução dos casos de CDT, é necessário conhecer as possíveis causas de PCI falsos-negativas e positivas.

INTRODUCTION: The follow-up of differentiated thyroid carcinoma (DTC) for detecting persistent or recurrent disease is based on iodine whole body scan (WBS), the evaluation of the tumor marker thyroglobulin (Tg), the anti-thyroglobulin antibody (anti-Tg) and neck ultrasonography (US). Well known false-positive causes of WBS include inflammatory processes, some non-thyroid tumors, kidney or even sebaceous cysts . METHODS: We reported a case of false-positive WBS, after therapeutic dose of (131I) NaI. RESULTS: We enphasize the importance of recognizing benign liver cysts mimicking DTC metastasis. CONCLUSIONS: False-positive and negative results may occur with WBS and must be recognized to avoid mismanagement.

Molecular technology and the recombinant TSH have changed diagnostics of thyroid carcinoma with positive I-131 whole body scan but low serum thyroglobulin

The early detection of recurrent differentiated thyroid carcinoma (DTC) cells in the post surgery DTC patients relies on the sensitivity of measuring both the level of thyroglobulin (Tg) and 131-Iodine distribution by Whole Body Scan (WBS). Undetectable level of Tg associated with negative WBS or elevated levels of Tg associated with positive WBS ("concordant") is ordinarily indicative of either absence or presence of disease. At times, elevated level of Tg with negative WBS or low levels of Tg with positive WBS ("discordant") could also occur. In the present study, we retrospectively reviewed series of 573 patients with DTC followed in the Diagnostic Imaging and Radiotherapy of the University "Federico II" of Naples between 1993 and 1997. We focused on 9 out of 573 patients (1.56%) who had a discordant pattern with low level of Tg/positive WBS in the post-surgical follow-up. Four patients were metastatic at presentation while 5 patients with metastasis during follow-up still remained in persistently low levels of Tg (<5 ng/mL). This result does point to some flaw in the evaluation of "discordant" cases. Reviewing data previously described series by resetting cut-off values of Tg <1 ng/ml as undetectable changed the apparent "discordant" subgroup of patients into "concordant". Recent introduction of recombinant human TSH (rhTSH) to enhance the expression level of Tg brought significant increase in the sensitivity of diagnostic evaluation of thyroid cancer patients. The role of burdensome WBS in the follow up evaluation of DTC patients is significantly reduced over time especially in low-risk patients while the relevance of Tg assay is steadily increased. Sensitive Tg assays, significantly improved our ability to assess disease status in follow-up of DTC. Given the possibility of late disease relapses, the need for long-term follow-up, and reduced delay in treatment of persistent disease, there is still need for greater sensitive diagnostic tools for DTC.

99mTc-tetrofosmin, 131I Whole Body Scan and Thyroglobulin in Detecting Differentiated Thyroid Carcinoma Metastases

PURPOSE: The purpose of this study was to assess the detectability of differentiated thyroid carcinoma metastases by 99mTc-tetrofosmin and to compare these results with a 131I whole body scan (131I WBS). The results of two scans were also compared with the T4 off-thyroglobulin (Tg) concentration. METHODS: A prospective study was performed on 43 patients (40 females, 3 males) with differentiated thyroid carcinomas (41 papillary, 2 follicular) having undergone a total thyroidectomy, and received 100~200 mCi (3,700~7,400 MBq) of radioiodine for ablation of residual thyroid tissue, or treatment of metastasis. All patients (n=43) had a 99mTc- tetrofosmin scan, and a 131I WBS following the discontinuation of thyroid hormone replacement. The T4 off-Tg level was checked immediately prior to the radioiodine therapy, with T4 off-Tg levels above 20 ng/ml defined as positive for metastasis or a remnant disease. RESULTS: Cervical metastases were considered in 6 patients and distant metastases in 7, based on the clinical, radiological, and histopathological findings. The 131I WBS (70.2%) was much more sensitive than the 99mTc-tetrofosmin scan (29.8%) in demonstrating the residual thyroid tissue following surgery. The 131I WBS revealed cervical metastases in 3 of the 6 patients, but only 2 of the 6 were revealed by the 99mTc-tetrofosmin scan. Of the 3 patients with negative 131I WBS, two were detected by the 99mTc-tetrofosmin scan. The sensitivities of the 131I WBS and 99mTc-tetrofosmin scan in diagnosing distant metastases were comparable (71%, and 57% respectively), but in 2 patients with negative 131I WBS, the 99mTc-tetrofosmin revealed distant metastases. The specificities of the 131I WBS and 99mTc-tetrofosmin scan were not comparable (100%, 97%, respectively) in the diagnosis distant metastases. The mean T4 off-Tg level of the patients with cervical or distant metastases was 317 ng/ml, with a sensitivity and specificity of 100%, and 83% respectively. In the patients with a T4 off-Tg level above 50 ng/ml, the two scans and clinical studies could not reveal any metastases in 3 of the patients. CONCLUSION: Although the specificity of the 99mTc-tetrofosmin scan was slightly lower than that of the 131I WBS, it is a useful tool for detecting cervical or distant metastases in differentiated thyroid carcinomas and does not require prior withdrawal from thyroid hormones. Therefore the concomitant use of a 99mTc-tetrofosmin scan, a 131I WBS and Tg, is more effective in detecting metastases in differentiated thyroid carcinomas.

The Value of FDG-PET in Reoperation of the Recurrent Papillary Thyroid Carcinoma with Elevated Thyroglobulin Levels and Negative I131 WBS

PURPOSE: We evaluated the diagnostic accuracy and useful ness of FDG-PET to determine the proper extent of surgery in recurrent papillary thyroid cancer patients with elevated thyroglobulin levels and negative I131 WBS. METHODS: FDG-PET was performed in 16 recurrent papillary thyroid cancer patients with elevated thyroglobulin levels and negative I131 WBS. In 9 patients, FDG-PET was performed to localize the recurrent lesions. In 7 patients, the recurrent lesions were initially diagnosed by physical examination or other image studies and the FDG-PET was subsequently performed to detect additional recurrent lesions. All suspected lesions detected by FDG-PET and other studies were explored. RESULTS: Among the 9 patients in whom FDG-PET was performed to localize the recurrent lesions, the recurrent lesions were detected only by FDG-PET in 4 patients. Among the 7 patients in whom FDG-PET was performed additionally to detect additional recurrent lesions, another recurrent cervical regions were detected by FDG-PET in 2 patients. However, the same lesions were able to be identified by ultrasonography. A total of 26 cervical regions were explored in 16 patients. There were 4 FDG-PET false positive regions and 2 FDG-PET false negative regions. Unnecessary surgery was performed in 4 cervical regions in 4 patients. CONCLUSION: FDG-PET was very useful in detecting small early recurrent lesions but was unable to contribute to the detection of additional recurrent cervical regions in the pa-tients in which the recurrent lesion had already been by physical examination or other studies. Other image studies are necessary to supplement the FDG-PET in false positive or false negative cases.

Comparison of Diagnostic and Post-therapy Radioiodine Scan in Well-Differentiated Thyroid Cancer and the Clinical Outcome / 대한핵의학회잡지

PURPOSE: We compared the first postoperative diagnostic and post-therapy scans of patients who received therapeutic doses of I-131, to investigate the difference in clinical outcomes between patients with concordant findings of diagnostic and post-therapy scans and patients with discrepant (more lesions in post-therapy scan) findings. MATERIALS AND METHODS: The first postoperative diagnostic and post-therapy radioiodine scans of one hundred forty three patients with well differentiated thyroid carcinoma were reviewed. Diagnostic scans were obtained following ingestion of 185 MBq of I-131 and post-therapy scans were obtained after therapeutic dose of 3.7~9.3 GBq of I-131. Successful ablation was defined as no radioiodine uptake on diagnostic radioiodine scan and normal range of serum thyroglobulin level (<10 ng/ml) during serum TSH elevation. RESULTS: Discrepant scan findings were noted in 25 (17.5%) patients. Twenty-two patients (15.4%) showed more lesions in post-therapy scan and 3 patients (2.1%) showed stunning effect. Nine (64.3%) of 14 patients with distant metastasis revealed metastatic lesion(s) only on post-therapy scan. Stunning effect was considered as sublethal damage in 1 patient and treatment by a diagnostic dose in 2 patients. Ablation was achieved in 52.4% (75/143) of all patients. Ablation rate and mean cumulative radioiodine dose were not different statistically between concordant and discrepant groups. CONCLUSION: There were 17.5% difference between diagnostic and post-therapy scan findings when using 185 MBq of I-131 as a diagnostic dose. However, 64.3% of distant metastases were revealed only on post-therapy scan. Ablation rate and mean cumulative radioiodine dose were not different statistically between concordant and discrepant groups. The stunning effect was considered as not only sublethal damage but also treatment by a small diagnostic dose of radioiodine.

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.