The impact of infection and inflammation in oncologic 18F-FDG PET/CT imaging.

Sites of infection and inflammation can be misleading in oncology PET/CT imaging because these areas commonly show 18F-FDG activity. Caution in the interpretation must be taken to avoid the misdiagnosis of malignancy. Utilization of both CT findings as well as patient history can help differentiate benign infectious and inflammatory processes from malignancy, although occasionally additional work-up may be required. This article discusses the mechanism of 18F-FDG uptake in infection and inflammation with illustrative examples.

Effects of plasma glucose levels on regional cerebral 18F-fluorodeoxyglucose uptake: Implications for dementia evaluation with brain PET imaging.

PURPOSE: Hyperglycemia affects FDG uptake in the brain, potentially emulating Alzheimer's disease in normal individuals. This study investigates global and regional cerebral FDG uptake as a function of plasma glucose in a cohort of patients. METHODS: 120 consecutive male patients with FDG PET/CT for initial oncologic staging (July-Dec 2015) were reviewed. Patients with dementia, cerebrovascular accident, structural brain lesion, prior oncology treatment or high metabolic tumor burden (recently shown affecting brain FDG uptake) were excluded. 53 (24 nondiabetic) eligible patients (age 65.7 ± 2.8 mean ± SE) were analyzed with parametric computer software, MIMneuro™. Regional Z-scores were evaluated as a function of plasma glucose and age using multi variable linear mixed effects models with false discovery analysis adjusting for multiple comparisons. If the regression slope was significantly (p < 0.05) different than zero, hyperglycemia effect was present. RESULTS: There was a negative inverse relationship (p < 0.001) between global brain FDG uptake and hyperglycemia. No regional hyperglycemia effect on uptake were present when subjects were normalized using pons or cerebellum. However, regional hyperglycemia effects were seen (p < 0.047-0.001) when normalizing by the whole brain. No obvious pattern was seen in the regions affected. Age had a significant effect using whole brain normalization (p < 0.04-0.01). CONCLUSIONS: Cortical variation in FDG uptake were identified when subjects were hyperglycemic. However, these variations didn't fit a particular pattern of dementia and the severity of the affect is not likely to alter clinical interpretation.

Nuclear Medicine Therapy With 223Radium-dichloride for Osseous Metastases in Prostate Carcinoma.

Painful osseous metastasis resulting from castration-resistant prostate carcinoma is a common clinical problem. Historically, nuclear medicine offered several palliative beta-emitting radiopharmaceuticals targeting the skeleton with the goal of decreasing pain. However, these have largely been replaced by the alpha-emitting agent 223radium (Ra). 223Ra received Food and Drug Administration approval in 2013 for the treatment of metastatic castration-resistant prostate cancer with symptomatic bone metastases without visceral metastases. 223Ra offers an improved therapeutic profile due to its alpha-particle emissions resulting in a relatively higher linear energy transfer and lower particle range compared with beta-emitters. 223Ra also has demonstrated to increase overall survival in patients and to delay adverse skeletal events. Running a successful clinical nuclear therapy program with Ra requires a multidisciplinary team approach and this article suggests an implementation strategy from the authors' institution. Potential new nuclear radiopharmaceuticals still under investigation offering the future possibility of radioligand therapy are also discussed briefly.

Synchronous Metastatic Breast Carcinoma and Parathyroid Adenoma on 18F-FDG PET/CT and 99mTc-Sestamibi Imaging.

In addition to nuclear cardiac and breast imaging, Tc-sestamibi scintigraphy is often used to localize parathyroid adenomas. F- fluorodeoxyglucose (FDG) PET is heavily utilized in oncology, although its use in identifying parathyroid adenomas is limited. We describe a case of a 57-year-old woman who underwent parathyroid scintigraphy and F-FDG PET/CT in the same week due to hyperparathyroidism and an enlarging breast mass, respectively. A right paratracheal mediastinal mass that otherwise would be suspicious for nodal metastases by CT alone was correctly identified to be an ectopic parathyroid adenoma using a combination of the nuclear medicine studies performed.

Efficacy of radioactive iodine treatment of graves' hyperthyroidism using a single calculated 131I dose.

OBJECTIVE: To evaluate the success rate of therapeutic administration of a single calculated 131I activity for eliminating hyperthyroidism due to Graves' disease. METHODS AND MATERIALS: Patients with Graves' hyperthyroidism underwent pinhole thyroid imaging, 24-h radioactive iodine uptake (RAIU) measurements and clinical examination and received a calculated 131I activity of 0.2 mCi per estimated gram of thyroid tissue, adjusted for the 24-h RAIU. The goal of RAI treatment was to achieve hypothyroidism within 3-6 months of 131I administration. Response to RAI therapy was assessed at 7 weeks and 3 months by clinical and biochemical follow-up. RESULTS: The study included 316 hyperthyroid patients with Graves' disease (F238:M78, mean age 42.1 ± 16 y, 4-94). 179 patients (56.6%) had no prior therapeutic intervention (treatment-naive patients), whereas 6 patients had prior thyroid surgery, and 131 (41.5%) had been treated with anti-thyroid medications.The mean estimated thyroid gland size was 50.2 g ± 18, range 15-100. Mean RAIU was 0.57 ± 0.17 (normal 0.07-0.30). RAI doses ranged from 5 to 70 mCi (mean dose = 18.1 mCi). Successful treatment of hyperthyroidism at our institution was obtained after a single therapeutic 131-I activity administration in 295 of 316 (93.3%) patients. Multivariate logistic regression analysis demonstrated that failure of 131I therapy was associated with previous PTU therapy (p <  0.001).The mean response time after successful RAI therapy was 110.2 days, with cumulative response of 25% at 61 days, 50% by 84 days and 75% by 118 days after radioiodine administration. The mean time to respond for those on prior PTU medications was 297 days compared to 116 days for those on MMI and 109 days for those not previously treated with antithyroid medications. In patients with persistent hyperthyroidism, failure of RAI therapy was documented in 16 patients (76.2%) within (less than) one year after 131I administration and in 5 patients (23.8%) more than one year after initial therapy, considered late failure. CONCLUSION: Successful 131I therapy for Graves' hyperthyroidism with a single calculated dose can be achieved in the majority (> 90%) of patients, adjusting for the thyroid size and 24 h uptake measurement.

Effects of Tumor Burden on Reference Tissue Standardized Uptake for PET Imaging: Modification of PERCIST Criteria.

Purpose To examine the effect metabolic burden (tumor and/or cardiac myocyte uptake) has on fluorine 18 fluorodeoxyglucose (FDG) distribution in organs and tissues of interest. Materials and Methods Positron emission tomographic (PET)/computed tomographic (CT) scans at the Ann Arbor Veterans Affairs hospital from January to July 2015 were reviewed. A total of 107 scans (50 patients; mean age, 64.3 years ± 13.2 [standard deviation]) had metabolic tissue burden assessed by using total lesion glycolysis (TLG) obtained from autosegmentation of the tumor and/or cardiac tissue. Standardized uptake value (SUV) and subsequent normalized SUV uptake in target organs and tissues were compared with 436 FDG PET/CT scans previously reported in 229 patients as a function of TLG to describe the effect(s) that metabolic burden has on reference tissue (blood pool, liver, and brain) FDG uptake. Subsequent regression by using linear mixed-effects models was used. If the slope of the regression was significantly (P < .05) different than zero, then an effect from TLG was present. Results There was a negative inverse relationship (P < .0001) between FDG uptake within reference tissues (blood pool, liver, and brain) and TLG in comparison to the study population at similar blood glucose levels. This TLG effect was no longer statistically significant (P > .05) when FDG uptake was normalized to a reference tissue (eg, blood pool or liver). Conclusion Metabolic tissue burden can have a significant effect on SUV measurements for PET imaging. This effect can be mitigated by normalizing FDG uptake to a reference tissue. © RSNA, 2018.

Effect of hyperglycemia on brain and liver 18F-FDG standardized uptake value (FDG SUV) measured by quantitative positron emission tomography (PET) imaging.

PURPOSE: Blood glucose is routinely measured prior to 18F-fluorodeoxyglucose (FDG) administration in positron emission tomography (PET) imaging to identify hyperglycemia that may affect image quality. In this study we explore the effects of blood glucose levels upon semi-quantitative standardized uptake value (SUV) measurements of target organs and tissues of interest and in particular address the relationship of blood glucose to FDG accumulation in the brain and liver. METHODS: 436 FDG PET/CT consecutive studies performed for oncology staging in 229 patients (226 male) at the Ann Arbor Veterans Administration Healthcare System were reviewed. All patients had blood glucose measured (112.4±34.1mg/dL) prior to injection of 466.2±51.8MBq (12.6±1.4mCi) of FDG. SUV measurements of brain, aortic arch blood-pool, liver, and spleen were obtained at 64.5±10.2min' post-injection. RESULTS: We found a negative inverse relationship of brain SUV with increasing plasma glucose, levels for both absolute and normalized (either to blood-pool or liver) values. Higher blood glucose levels had a mild effect upon liver and blood-pool SUV. By contrast, spleen SUV was independent of blood glucose, but demonstrated the greatest variability (deviation on linear regression). In contrast to other tissues, liver and spleen SUV normalized to blood-pool SUV were not dependent upon blood glucose levels. CONCLUSION: The effects of hyperglycemia upon FDG uptake in brain and liver, over a range of blood glucose values generally considered acceptable for clinical PET imaging, may have measurable effects on semi-quantitative image analysis.

Contemporary imaging of incidentally discovered adrenal masses.

Adrenal lesions are routinely encountered incidentally in clinical practice. Although most of these lesions are benign, malignancy needs to be excluded. Therefore, the initial clinical workup is to exclude aggressive characteristics suggesting malignancy and to identify characteristics predictive of the most common benign lesion, an adrenal adenoma. Predicting a benign adenoma using a variety of imaging modalities has been widely studied using unenhanced computed tomography (CT), contrast enhanced CT, and magnetic resonance (MR) imaging. This review article describes the currently used imaging protocols and clinical interpretation criteria of common adrenal lesions. An adenoma can be predicted if a homogenous soft tissue adrenal mass demonstrates low attenuation (upper threshold value of 10 Hounsfield Units) on unenhanced CT, demonstrates an absolute enhancement washout of ≥ 60% and/or relative enhancement washout of ≥ 40% on adrenal washout contrast enhanced CT, or demonstrates signal loss in opposed-phased MR imaging. If an adrenal adenoma cannot be predicted based upon these criteria, the lesion should be evaluated for other imaging characteristics that suggest a specific pathology, such as an adrenal cyst or myelolipoma. Although nonspecific and with limitations, 18F-fluorodeoxyglucose (FDG) PET/CT has a potential role for differentiating benign from malignant lesions based upon the amount of radiopharmaceutical uptake with malignant lesions generally having greater uptake. If clinical and/or hormonal screening suggests a pheochromocytoma, consideration can be given to 18F-dihydroxyphenylalanine (DOPA) or 123I-metaiodobenzylguanidine (MIBG) in addition to CT and MR. Finally, this review proposes a diagnostic work-up strategy for routine use in clinical practice.

Frostbite: Spectrum of Imaging Findings and Guidelines for Management.

Frostbite is a localized cold thermal injury that results from tissue freezing. Frostbite injuries can have a substantial effect on long-term limb function and mobility if not promptly evaluated and treated. Imaging plays a critical role in initial evaluation of frostbite injuries and in monitoring response to treatment. A multimodality approach involving radiography, digital subtraction angiography (DSA), and/or multiphase bone scintigraphy with hybrid single photon emission computed tomography (SPECT)/computed tomography (CT) is often necessary for optimal guidance of frostbite care. Radiographs serve as an initial survey of the affected limb and may demonstrate characteristic findings, depending on the time course and severity of injury. DSA is used to evaluate perfusion of affected soft tissues and identify potential targets for therapeutic intervention. Angiography-directed thrombolysis plays an essential role in tissue preservation and salvage in deep frostbite injuries. Multiphase bone scintigraphy with technetium 99m-labeled diphosphonate provides valuable information regarding the status of tissue viability after initial treatment. The addition of SPECT/CT to multiphase bone scintigraphy enables precise anatomic localization of the level and depth of tissue necrosis before its appearance at physical examination and can help uncover subtle findings that may remain occult at scintigraphy alone. Multiphase bone scintigraphy with SPECT/CT is the modality of choice for prognostication and planning of definitive surgical care of affected limbs. Appropriate use of imaging to direct frostbite care can help limit the effects that these injuries have on limb function and mobility. ©RSNA, 2016.

Endocrine radionuclide scintigraphy with fusion single photon emission computed tomography/computed tomography.

AIM: To review the benefits of single photon emission computed tomography (SPECT)/computed tomography (CT) hybrid imaging for diagnosis of various endocrine disorders. METHODS: We performed MEDLINE and PubMed searches using the terms: "SPECT/CT"; "functional anatomic mapping"; "transmission emission tomography"; "parathyroid adenoma"; "thyroid cancer"; "neuroendocrine tumor"; "adrenal"; "pheochromocytoma"; "paraganglioma"; in order to identify relevant articles published in English during the years 2003 to 2015. Reference lists from the articles were reviewed to identify additional pertinent articles. Retrieved manuscripts (case reports, reviews, meta-analyses and abstracts) concerning the application of SPECT/CT to endocrine imaging were analyzed to provide a descriptive synthesis of the utility of this technology. RESULTS: The emergence of hybrid SPECT/CT camera technology now allows simultaneous acquisition of combined multi-modality imaging, with seamless fusion of three-dimensional volume datasets. The usefulness of combining functional information to depict the bio-distribution of radiotracers that map cellular processes of the endocrine system and tumors of endocrine origin, with anatomy derived from CT, has improved the diagnostic capability of scintigraphy for a range of disorders of endocrine gland function. The literature describes benefits of SPECT/CT for (99m)Tc-sestamibi parathyroid scintigraphy and (99m)Tc-pertechnetate thyroid scintigraphy, (123)I- or (131)I-radioiodine for staging of differentiated thyroid carcinoma, (111)In- and (99m)Tc- labeled somatostatin receptor analogues for detection of neuroendocrine tumors, (131)I-norcholesterol (NP-59) scans for assessment of adrenal cortical hyperfunction, and (123)I- or (131)I-metaiodobenzylguanidine imaging for evaluation of pheochromocytoma and paraganglioma. CONCLUSION: SPECT/CT exploits the synergism between the functional information from radiopharmaceutical imaging and anatomy from CT, translating to improved diagnostic accuracy and meaningful impact on patient care.

Lingual Thyroid Ectopia: Diagnostic SPECT/CT Imaging and Radioactive Iodine Treatment.

BACKGROUND: Lingual thyroid is a rare abnormality of thyroid development that is usually treated conservatively with levothyroxine replacement. Rarely, it becomes large enough to cause obstructive symptoms in the oral cavity, requiring definitive treatment. PATIENT FINDINGS: This study reports on three patients with lingual thyroid treated with radioactive iodine-131 ((131)I) with successful radioablation of their ectopic thyroid tissues. Measurement of 24-hour radioactive iodine uptake within thyroidal tissues and hybrid single-photon emission computed tomography/computed tomography imaging using either iodine-123 or technetium-99m pertechnetate scans were performed in all patients demonstrating the location and size of lingual thyroid and absence of an orthotopic thyroid gland. SUMMARY: The aim of this study was to describe nonsurgical management of obstructive lingual thyroid tissue with (131)I therapy for lingual thyroid radioablation. Patients were prepared with a low-iodine diet and levothyroxine withdrawal prior to radioablation for optimizing (131)I uptake in ectopic thyroid tissues. Hybrid single-photon emission computed tomography/computed tomography measurement of anatomic size of lingual thyroid tissue and radioactive iodine uptake guided the selection of therapeutic doses, resulting in administration of 10.7, 17.5, and 15.4 mCi of (131)I, respectively. There were no post-therapy complications, and clinical follow-up demonstrated resolution of obstructive oropharyngeal symptoms. CONCLUSIONS: Ectopic lingual thyroid tissue is rarely associated with obstructive oropharyngeal symptoms due to progressive enlargement. Radioiodine therapy with (131)I is an effective treatment modality for ablation of ectopic thyroid tissue as an alternative to surgery.

Molecular Imaging in the Management of Adrenocortical Cancer: A Systematic Review.

Adrenocortical cancer (ACC) is an uncommon primary neoplasm of the adrenal cortex with dismal prognosis. It often presents with symptoms and signs of adrenal cortical hormone hypersecretion and abdominal mass effect or is incidentally detected as an adrenal mass on imaging performed for other indications. Endocrine evaluation, comprehensive staging, and meticulous resection are crucial to ensure the best possible outcome. Despite extensive initial surgical resection, local and distant metastases are not uncommon with disappointing 5-year survival, although progress is being made at high-volume centers. Accurate restaging of recurrent disease is important to guide further management. Mitotane, external beam radiation and chemotherapy, and newer anticancer systemic treatments are used as adjunctives for inoperable disease and distant metastases. Contrast-enhanced CT and MRI are first-line imaging modalities for evaluation of ACC to characterize adrenal masses and to determine tumor resectability. Emerging literature supports F-FDG PET/CT use to determine the malignant potential of adrenal masses. In patients with a diagnosis of ACC, FDG PET/CT is sensitive for detecting metastatic disease, and its tumor accumulation has been correlated to pathology, Weiss scores, and prognosis. Metomidate, labeled with C for PET or with I for SPECT/CT, allows characterization of an adrenal mass as being of adrenocortical origin with high specificity. Taking advantage of its adrenocortical avidity, metomidate has been labeled with I for radionuclide therapy in a subset of ACC. In this review, we describe how nuclear medicine imaging, and specifically PET, can assist surgical management of ACC.

Use of radiopharmaceuticals in diagnostic nuclear medicine in the United States: 1960-2010.

To reconstruct reliable nuclear medicine-related occupational radiation doses or doses received as patients from radiopharmaceuticals over the last five decades, the authors assessed which radiopharmaceuticals were used in different time periods, their relative frequency of use, and typical values of the administered activity. This paper presents data on the changing patterns of clinical use of radiopharmaceuticals and documents the range of activity administered to adult patients undergoing diagnostic nuclear medicine procedures in the U.S. between 1960 and 2010. Data are presented for 15 diagnostic imaging procedures that include thyroid scan and thyroid uptake; brain scan; brain blood flow; lung perfusion and ventilation; bone, liver, hepatobiliary, bone marrow, pancreas, and kidney scans; cardiac imaging procedures; tumor localization studies; localization of gastrointestinal bleeding; and non-imaging studies of blood volume and iron metabolism. Data on the relative use of radiopharmaceuticals were collected using key informant interviews and comprehensive literature reviews of typical administered activities of these diagnostic nuclear medicine studies. Responses of key informants on relative use of radiopharmaceuticals are in agreement with published literature. Results of this study will be used for retrospective reconstruction of occupational and personal medical radiation doses from diagnostic radiopharmaceuticals to members of the U.S. radiologic technologists' cohort and in reconstructing radiation doses from occupational or patient radiation exposures to other U.S. workers or patient populations.

Parathyroid adenoma localization with 99mTc-sestamibi SPECT/CT: a meta-analysis.

PURPOSE: The aim of the study was to determine the diagnostic utility of parathyroid scintigraphy with technetium-99m (99mTc)-sestamibi single-photon emission computed tomography/computed tomography (SPECT/CT) for localization of parathyroid adenoma. MATERIALS AND METHODS: We performed a systematic search of medical databases PubMed and Medline/OVID for literature on 99mTc-sestamibi SPECT/CT parathyroid scintigraphy, using the search terms hyperparathyroidism, parathyroid adenoma/hyperplasia, SPECT/CT, and SPECT-CT. Citations for 981 articles and 128 abstracts of full articles were reviewed by two coauthors for relevance. Twenty-four peer-reviewed studies on SPECT/CT parathyroid scintigraphy qualified for inclusion. The Quality Assessment of Diagnostic Accuracy Studies-2 tool was used to assess study quality. Meta-analytical techniques were used to obtain pooled estimates of the parathyroid adenoma localization rate using a random-effects model. RESULTS: A total of 24 studies published between January 2003 and March 2014 with 1276 patients (334 men, 762 women, and 180 of unspecified sex) met the inclusion criteria. Data on the test performance of dual-phase 99mTc-sestamibi SPECT/CT showed an estimated pooled sensitivity (per-patient analysis) of 0.86 [confidence interval (CI) 0.81-0.90]. Sensitivity of SPECT/CT was superior to that of SPECT (0.74; CI 0.66-0.82) and planar (0.70; CI 0.61-0.80) techniques. Heterogeneity was present in the reported literature (I2=80.3%). The rate of ectopic parathyroid adenomas ranged between 4 and 20% and SPECT/CT was superior to SPECT and planar imaging for localization of ectopic sites. CONCLUSION: Utilization of SPECT/CT fusion imaging for 99mTc-sestamibi parathyroid scintigraphy improves the test performance compared with planar and SPECT imaging; it assists preoperative planning for a minimally invasive surgical approach for the neck and is of value in subgroups with ectopic glands or coexisting nodular thyroid disease.

Metabolic and anatomic characteristics of benign and malignant adrenal masses on positron emission tomography/computed tomography: a review of literature.

PET/CT with (18)F-fluorodeoxyglucose (FDG) or using different radiocompounds has proven accuracy for detection of adrenal metastases in patients undergoing cancer staging. It can assist the diagnostic work-up in oncology patients by identifying distant metastases to the adrenal(s) and defining oligometastatic disease that may benefit from targeted intervention. In patients with incidentally discovered adrenal nodules, so-called adrenal "incidentaloma" FDG PET/CT is emerging as a useful test to distinguish benign from malignant etiology. Current published evidence suggests a role for FDG PET/CT in assessing the malignant potential of an adrenal lesion that has been 'indeterminately' categorized with unenhanced CT, adrenal protocol contrast-enhanced CT, or chemical-shift MRI. FDG PET/CT could be used to stratify patients with higher risk of malignancy for surgical intervention, while recommending surveillance for adrenal masses with low malignant potential. There are caveats for interpretation of the metabolic activity of an adrenal nodule on PET/CT that may lead to false-positive and false-negative interpretation. Adrenal lesions represent a wide spectrum of etiologies, and the typical appearances on PET/CT are still being described, therefore our goal was to summarize the current diagnostic strategies for evaluation of adrenal lesions and present metabolic and anatomic appearances of common and uncommon adrenal lesions. In spite of the emerging role of PET/CT to differentiate benign from malignant adrenal mass, especially in difficult cases, it should be emphasized that PET/CT is not needed for most patients and that many diagnostic problems can be resolved by CT and/or MR imaging.

Nuclear medicine practices in the 1950s through the mid-1970s and occupational radiation doses to technologists from diagnostic radioisotope procedures.

Data on occupational radiation exposure from nuclear medicine procedures for the time period of the 1950s through the 1970s is important for retrospective health risk studies of medical personnel who conducted those activities. However, limited information is available on occupational exposure received by physicians and technologists who performed nuclear medicine procedures during those years. To better understand and characterize historical radiation exposures to technologists, the authors collected information on nuclear medicine practices in the 1950s, 1960s, and 1970s. To collect historical data needed to reconstruct doses to technologists, a focus group interview was held with experts who began using radioisotopes in medicine in the 1950s and the 1960s. Typical protocols and descriptions of clinical practices of diagnostic radioisotope procedures were defined by the focus group and were used to estimate occupational doses received by personnel, per nuclear medicine procedure, conducted in the 1950s to 1960s using radiopharmaceuticals available at that time. The radionuclide activities in the organs of the reference patient were calculated using the biokinetic models described in ICRP Publication 53. Air kerma rates as a function of distance from a reference patient were calculated by Monte Carlo radiation transport calculations using a hybrid computational phantom. Estimates of occupational doses to nuclear medicine technologists per procedure were found to vary from less than 0.01 µSv (thyroid scan with 1.85 MBq of administered I-iodide) to 0.4 µSv (brain scan with 26 MBq of Hg-chlormerodin). Occupational doses for the same diagnostic procedures starting in the mid-1960s but using Tc were also estimated. The doses estimated in this study show that the introduction of Tc resulted in an increase in occupational doses per procedure.

Endocrine scintigraphy with hybrid SPECT/CT.

Nuclear medicine imaging of endocrine disorders takes advantage of unique cellular properties of endocrine organs and tissues that can be depicted by targeted radiopharmaceuticals. Detailed functional maps of biodistributions of radiopharmaceutical uptake can be displayed in three-dimensional tomographic formats, using single photon emission computed tomography (CT) that can now be directly combined with simultaneously acquired cross-sectional anatomic maps derived from CT. The integration of function depicted by scintigraphy and anatomy with CT has synergistically improved the efficacy of nuclear medicine imaging across a broad spectrum of clinical applications, which include some of the oldest imaging studies of endocrine dysfunction.

Nuclear medicine imaging of endocrine neoplasms.

Endocrine tumors are hormonally active benign or malignant neoplasms arising within endocrine organs or from specialized cells of the amine precursor uptake and decarboxylation system. The detection rate of these tumors is increasing as a result of sensitive biochemical tests and high-resolution diagnostic imaging. Medical imaging has become a key component in the diagnosis and staging of endocrine malignancies; however, despite the impressive advances in computed tomography (CT) and MRI, detection of small primary tumors and metastases continues to be a challenge. Functional imaging techniques use radiopharmaceuticals targeted at unique tumor cellular processes in order to provide sensitive and highly specific whole-body imaging. Functional imaging allows prediction of the efficacy of radionuclide or receptor-based therapies and surveillance after therapy. Advances in imaging have not been limited to radiopharmaceuticals. Hybrid scanner technology in the form of PET/CT and single photon emission computed tomography (SPECT)/CT, designed to combine functional images with anatomic maps, has further improved the diagnostic accuracy. High-resolution hybrid imaging when deployed with novel PET and SPECT radiopharmaceuticals has the potential to dramatically change, individualize, and optimize imaging plans based on the histological grade, degree of differentiation, and genetic profile of each patient's endocrine neoplasm.

SPECT/CT evaluation of unusual physiologic radioiodine biodistributions: pearls and pitfalls in image interpretation.

Radioiodine imaging has a well-established role in depicting metastatic disease after thyroidectomy in patients with well-differentiated thyroid cancer. Uptake of radioiodine in thyroid metastases depends on expression of sodium-iodide symporter (NIS) by tumor tissues. However, because radioiodine may also accumulate in normal structures and tissues, it is important to distinguish physiologic radioiodine activity from metastatic disease. Furthermore, secretions that contain radioiodine may also simulate pathologic uptake. A spectrum of physiologic distributions, normal variants, and benign mimics of disease have been described in the literature; yet, even when armed with a comprehensive knowledge of these patterns, interpreting radiologists and nuclear physicians may still encounter diagnostic uncertainty. Single-photon emission computed tomography (SPECT) with integrated computed tomography (CT) is a novel technology that, when applied to diagnostic iodine 123 or iodine 131 ((131)I) radioiodine scintigraphy, may accurately localize and help distinguish benign mimics of disease, with the potential to alter the management plan. SPECT/CT is increasingly being used with radioiodine scintigraphy to evaluate patients with thyroid cancer and shows promise for improving imaging specificity and reducing false-positive results.

Preablation 131-I scans with SPECT/CT in postoperative thyroid cancer patients: what is the impact on staging?

CONTEXT: The utility of preablation radioiodine scans for the management of differentiated thyroid cancer remains controversial. OBJECTIVE: To determine the contribution of preablation Iodine 131 (131-I) planar with single-photon emission computed tomography/computed tomography (SPECT/CT; diagnostic [Dx] scans) to differentiated thyroid cancer staging. DESIGN: Prospective sequential series at university clinic. METHODS: Using American Joint Committee on Cancer (AJCC) tumor, node, metastasis (TNM) staging, seventh edition 320 patients post-total thyroidectomy were initially staged based on clinical and pathology data (pTN) and then restaged after imaging (TNM). The impact of Dx scans with SPECT/CT on N and M scores, and TNM stage, was assessed in younger, age <45 years, n = 138 (43%), and older, age ≥ 45 years, n = 182 (57%) patients, with subgroup analysis for T1a and T1b tumors. RESULTS: In younger patients Dx scans detected distant metastases in 5 of 138 patients (4%), and nodal metastases in 61 of 138 patients (44%), including unsuspected nodal metastases in 24 of 63 (38%) patients initially assigned pathologic (p) N0 or pNx. In older patients distant metastases were detected in 18 of 182 patients (10%), and nodal metastases in 51 of 182 patients (28%), including unsuspected nodal metastases in 26 of 108 (24%) patients initially assigned pN0 or pNx. Dx scans detected distant metastases in 2 of 49 (4%) T1a, and 3 of 67 (4.5%) T1b patients. CONCLUSIONS: Dx scans detected regional metastases in 35% of patients, and distant metastases in 8% of patients. Information acquired with Dx scans changed staging in 4% of younger, and 25% of older patients. Preablation scans with SPECT/CT contribute to staging of thyroid cancer. Identification of regional and distant metastases prior to radioiodine therapy has significant potential to alter patient management.