Ka Kit Wong

Incremental Value of Diagnostic 131I SPECT/CT Fusion Imaging in the Evaluation of Differentiated Thyroid Carcinoma

OBJECTIVE The purpose of this study was to determine the incremental value of (131)I SPECT/CT over traditional planar imaging of patients with differentiated thyroid carcinoma. MATERIALS AND METHODS Fifty-six planar and SPECT/CT scans were obtained for 53 patients. Forty-eight scans were diagnostic (131)I studies before first radioiodine therapy, four were diagnostic (131)I studies with recombinant human thyroid-stimulating hormone stimulation, and four scans were posttherapy (131)I studies. Two nuclear physicians interpreted central neck and distant activity on planar scans and reviewed SPECT/CT images to assess the incremental diagnostic value with respect to localization and characterization of focal activity and to evaluate reader confidence. One of the readers was unblinded and had access to clinical, imaging, histologic, and biochemical information. RESULTS Planar scans depicted 130 neck foci and 17 distant foci. At SPECT/CT these foci were further characterized as thyroglossal duct and thyroid bed remnant (n = 98), cervical nodal metastasis or local residual disease (n = 26), physiologic activity (n = 11), and distant metastasis (n = 12). Interobserver disagreement occurred on eight of 147 foci (5%). Because of superior lesion localization and additional anatomic information derived from the low-dose CT component, incremental diagnostic value with SPECT/CT over planar imaging was found for 70 of 147 foci (47.6%), including 53 of 130 neck foci (40.8%) and all 17 (100%) distant foci. Reader confidence increased regarding 104 of 147 foci (70.7%). CONCLUSION Iodine-131 SPECT/CT is useful for accurate evaluation of regional and distant activity in characterization of foci as residual thyroid tissue or nodal, pulmonary, or osseous metastasis. Suspected physiologic mimics of disease can be confirmed with increased reader confidence.

Dynamic Bone Imaging with 99mTc-Labeled Diphosphonates and 18F-NaF: Mechanisms and Applications

Dynamic bone scanning with 99mTc-labeled diphosphonates and 18F-labeled sodium fluoride provides functional information sensitive for subtle changes in bone turnover and perfusion, which assists the clinical management of numerous osseous pathologies. This article reviews the mechanisms of uptake of 99mTc-labeled diphosphonates and 18F-sodium fluoride and discusses and compares the performance of these bone-seeking radiotracers for clinical and research applications, using dynamic and multiple-time-point imaging protocols and quantitative techniques.

Brain PET in Suspected Dementia: Patterns of Altered FDG Metabolism

The diagnosis of dementia syndromes can be challenging for clinicians, particularly in the early stages of disease. Patients with higher education levels may experience a marked decline in cognitive function before their dementia is detectable with routine testing methods. In addition, comorbid conditions (eg, depression) and the use of certain medications can confound the clinical assessment. Clinicians require a high degree of certainty before making a diagnosis of Alzheimer disease or some other neurodegenerative disorder, since the impact on patients and their families can be devastating. Moreover, accurate diagnosis is important because emerging therapeutic regimens vary depending on the cause of the dementia. Clinically based testing is useful; however, the results usually do not enable the clinician to make a definitive diagnosis. For this reason, imaging biomarkers are playing an increasingly important role in the workup of patients with suspected dementia. Positron emission tomography with 2-[fluorine-18]fluoro-2-deoxy-D-glucose allows detection of neurodegenerative disorders earlier than is otherwise possible. Accurate interpretation of these studies requires recognition of typical metabolic patterns caused by dementias and of artifacts introduced by image processing. Although visual interpretation is a vital component of image analysis, computer-assisted diagnostic software has been shown to increase diagnostic accuracy.

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.

Hybrid SPECT–CT and PET–CT imaging of differentiated thyroid carcinoma

Hybrid imaging modalities such as radioiodine single photon emission CT with integrated CT ((131)I SPECT-CT) and 2-(fluorine-18)-fluoro-2-deoxy-D-glucose positron emission tomography with integrated CT (FDG PET-CT) allow the rapid and efficient fusion of functional and anatomic images, and provide diagnostic information that may influence management decisions in patients with differentiated thyroid carcinoma (DTC). Diagnostic localisation and therapy of these tumours are dependent upon their capacity to concentrate radioiodine ((131)I) via uptake through the sodium-iodide symporter and retention within the tumour. The prognosis for most patients with DTC is favourable, although controversy exists regarding the role of post-operative (131)I therapy in patients at low-risk for disease. Accurate identification of functional thyroid tissue (benign or malignant) using diagnostic (131)I planar scintigraphy complemented by SPECT-CT imaging enables the completion of post-operative staging and patient risk stratification prior to (131)I therapy administration. In patients with non-iodine-avid tumours (negative (131)I scan but elevated thyroglobulin indicative of persistent or recurrent disease), FDG PET-CT is used to identify tumours with enhanced glucose metabolism and to localise the source of thyroglobulin production. The CT component of this hybrid technology provides anatomic localisation of activity and allows CT-based attenuation correction of PET images. Images from 15 patients illustrate the applications of (131)I SPECT-CT and FDG PET-CT.

Incremental Value of 111-In Pentetreotide SPECT/CT Fusion Imaging of Neuroendocrine Tumors

RATIONALE AND OBJECTIVES Hybrid single photon-emission computed tomographic (SPECT) and computed tomographic (CT) imaging for the investigation of neuroendocrine tumors allows the fusion of functional and anatomic information in a rapid and efficient method. The aim of this study was to assess the incremental diagnostic value of (111)In pentetreotide SPECT/CT imaging compared with traditional planar and SPECT imaging with respect to lesion localization and characterization and reader confidence. MATERIALS AND METHODS Forty-nine patients (23 male, 26 female; mean age, 56.9 years; range, 14-88 years) who underwent (111)In pentetreotide planar, SPECT, and SPECT/CT imaging were eligible for this retrospective study, including patients with suspected or confirmed carcinoid tumors (n = 24), endocrine pancreatic tumors (n = 18), medullary thyroid cancer (n = 3), paragangliomas (n = 2), and multiple endocrine neoplasia type I (n = 2). Planar and SPECT images were reviewed by two blinded readers, followed by interpretation using additional SPECT/CT images in a subsequent session. A third reader provided consensus in cases with disagreements. RESULTS In 55 of 89 lesions (61.8%), (111)In pentetreotide SPECT/CT imaging improved lesion localization compared to planar and SPECT imaging; in 25 of 89 lesions (28.1%), SPECT/CT imaging changed lesion classification. In 20 of 49 patients (40.8%) for reader 1 and 14 of 49 patients (28.6%) for reader 2, (111)In pentetreotide SPECT/CT imaging provided incremental diagnostic value, which was considered likely to affect patient management in twelve of 20 and seven of 14 patients, respectively. Increased reader confidence was found in 32 of 49 patients (65.3%) for both readers with uniformly high confidence after SPECT/CT interpretation. CONCLUSIONS Hybrid (111)In pentetreotide SPECT/CT imaging provides incremental diagnostic value and greater reader confidence over planar and SPECT imaging. This is achieved though superior lesion localization, the identification of physiologic activity, and additional anatomic information derived from the nondiagnostic CT portion of the study.

Olfactory loss and nigrostriatal dopaminergic denervation in the elderly.

Olfactory dysfunction may precede common neurodegenerative disorders in the elderly, such as Alzheimer (AD) or Parkinson disease (PD). However, pathobiological mechanisms of olfactory loss in the elderly are poorly understood. Although nigrostriatal dopaminergic denervation is a key patholobiological feature of PD, age-associated nigrostriatal denervation (AASDD) occurs also with normal aging and can be more prominent in some elderly. We investigated the relationship between AASDD and olfactory performance in community-dwelling subjects. Community-dwelling subjects (n=73, 44 F/29 M, mean age 64.0±16.4, range 20-85) underwent brain dopamine transporter (DAT) [(11)C]2-β-carbomethoxy-3β-(4-fluorophenyl) tropane (β-CFT) positron emission tomography (PET) imaging and olfactory assessment using the 40-odor University of Pennsylvania Smell Identification Test (UPSIT). Subjects with clinical or DAT PET evidence of Parkinson disease (PD) were not eligible for the study. AASDD was defined based on normative data in young and middle-aged subjects. Compared to a mild and general linear decline in odor identification observed in most subjects (R(2)=0.18, P=0.0002), there were 13 subjects who deviated below the 5% confidence interval level in age-predicted UPSIT scores. Analysis limited to elderly subjects 60 years and over demonstrated a significant association between poor smell (n=10 out of 49, 20.4%) and AASDD (χ(2)=4.4, P<0.05). There is a significant association between olfactory dysfunction and more prominent nigrostriatal denervation in the elderly. Olfactory assessment may have potential as a screening tool to detect age-accelerated neurodegeneration in the elderly.

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.

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.

Evaluation of incidentally discovered adrenal masses with PET and PET/CT.

BACKGROUND AND PURPOSE Incidentally discovered adrenal masses are commonly seen with high resolution diagnostic imaging performed for indications other than adrenal disease. Although the majority of these masses are benign and non-secretory, their unexpected discovery prompts further biochemical and often repeated imaging evaluations, sufficient to identify hormonally active adrenal masses and/or primary or metastatic neoplasms to the adrenal(s). In the present paper we investigate the role of PET and PET/CT for the detection of adrenal incidentalomas in comparison with CT and MRI. MATERIALS AND METHODS a systematic revision of the papers published in PubMed/Medline until September 2010 was done. RESULTS The diagnostic imaging approach to incidentally discovered adrenal masses includes computed tomography (CT), magnetic resonance imaging (MRI) and more recently positron emission tomography (PET) with radiopharmaceuticals designed to exploit mechanisms of cellular metabolism, adrenal substrate precursor uptake, or receptor binding. CONCLUSION The functional maps created by PET imaging agents and the anatomic information provided by near-simultaneously acquired, co-registered CT facilitates localization and diagnosis of adrenal dysfunction, distinguishes unilateral from bilateral disease, and aids in characterizing malignant primary and metastatic adrenal disease.