Hatice Savas

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.

Frequent Monitoring of A1C During Pregnancy as a Treatment Tool to Guide Therapy

OBJECTIVE No guidelines for A1C measurement exist for women with gestational diabetes mellitus (GDM). The aim of this study was to document the rate of A1C decline in women with GDM. RESEARCH DESIGN AND METHODS Women with GDM in the Santa Barbara County Endocrine Clinic are managed with a carbohydrate-restricted diet and self-monitored blood glucose before and 1-h postprandial. Insulin is started if the preprandial glucose concentration is ≥90 mg/dl and/or a 1-h postprandial glucose concentration is ≥120 mg/dl. Capillary A1C was tested weekly using the DCA2000+ analyzer. RESULTS Twenty-four women with GDM (aged 29.0 ± 7.3 years) with initial A1C ≥7.0% were recruited. Baseline A1C was 8.8 ± 1.8%. Mean A1C decline was 0.47% per week (range 0.10–1.15%); the maximum was 4.3% in 4 weeks. CONCLUSIONS This study documents rapid decline in A1C during pregnancy and the utility of weekly A1C to guide therapy.

Tumor-Absorbed Dose Predicts Progression-Free Survival Following 131I-Tositumomab Radioimmunotherapy

The study aimed at identifying patient-specific dosimetric and nondosimetric factors predicting outcome of non-Hodgkin lymphoma patients after 131I-tositumomab radioimmunotherapy for potential use in treatment planning. Methods: Tumor-absorbed dose measures were estimated for 130 tumors in 39 relapsed or refractory non-Hodgkin lymphoma patients by coupling SPECT/CT imaging with the Dose Planning Method (DPM) Monte Carlo code. Equivalent biologic effect was calculated to assess the biologic effects of nonuniform absorbed dose including the effects of the unlabeled antibody. Evaluated nondosimetric covariates included histology, presence of bulky disease, and prior treatment history. Tumor level outcome was based on volume shrinkage assessed on follow-up CT. Patient level outcome measures were overall response (OR), complete response (CR), and progression-free survival (PFS), determined from clinical assessments that included PET/CT. Results: The estimated mean tumor-absorbed dose had a median value of 275 cGy (range, 94–711 cGy). A high correlation was observed between tracer-predicted and therapy-delivered mean tumor-absorbed doses (P < 0.001; r = 0.85). In univariate tumor-level analysis, tumor shrinkage correlated significantly with almost all of the evaluated dosimetric factors, including equivalent biologic effect. Regression analysis showed that OR, CR, and PFS were associated with the dosimetric factors and equivalent biologic effect. Both mean tumor-absorbed dose (P = 0.025) and equivalent biologic effect (P = 0.035) were significant predictors of PFS whereas none of the nondosimetric covariates were found to be statistically significant factors affecting PFS. The most important finding of the study was that in Kaplan–Meier curves stratified by mean dose, longer PFS was observed in patients receiving mean tumor-absorbed doses greater than 200 cGy than in those receiving 200 cGy or less (median PFS, 13.6 vs. 1.9 mo for the 2 dose groups; log-rank P < 0.0001). Conclusion: A higher mean tumor-absorbed dose was significantly predictive of improved PFS after 131I-tositumomab radioimmunotherapy. Hence tumor-absorbed dose, which can be estimated before therapy, can potentially be used to design radioimmunotherapy protocols to improve efficacy.

SPECT/CT Characterization of Oral Activity on Radioiodine Scintigraphy

CONTEXT Oral activity on radioiodine scintigraphy is commonly seen and may cause diagnostic dilemma. Determining the precise mechanism of oral uptake on radioiodine scintigraphy will increase the accuracy and confidence of interpretation and avoid possible misinterpretation. OBJECTIVE To determine the etiology of focal persistent radioiodine oral uptake seen on radioiodine scans. DESIGN Retrospective sequential series at a university clinic and a phantom study experiment. METHODS Preablation iodine-131 planar and single photon emission computed tomography/computed tomography (SPECT/CT) scans of 216 patients after total thyroidectomy were reviewed. Planar images were inspected for the presence of oral activity above the salivary gland background and SPECT/CT was reviewed to determine the location and nature of oral activity. A post-hoc phantom study was designed using typodont stone models fitted with various dental materials, immersed in a diluted iodine-131 solution, and imaged with SPECT/CT to characterize radioiodine uptake by high-attenuation dental materials. RESULTS Oral activity was seen on planar images in 123 of 216 (57%) patients; 12 patients were excluded from analysis because the SPECT/CT field of view did not cover the entire oral cavity. In the remainding 111 patients SPECT/CT images demonstrated focal uptake localizing to high-attenuation dental material on the CT in 95 of 111 (86%) patients. All cases of oral activity on planar imaging were interpreted as benign etiology on SPECT/CT. The phantom study confirmed focal in vitro uptake within high-attenuation dental materials representing a range of commonly used metal alloys. CONCLUSION Focal oral activity on diagnostic radioiodine scans frequently localizes to high-attenuation dental material on SPECT/CT. We postulate that an affinity between negatively charged iodide ions (I(-)) in saliva and positively charged metal ions (eg, Ag(+), Hg(+), Au(2+), Pd(2+)) within the dental materials is at the basis of persistent focal radioiodine uptake in the oral cavity. This represents a new mechanism underlying benign radioiodine activity not previously described in the medical literature.

Extraosseous findings on bone scintigraphy using fusion SPECT/CT and correlative imaging

OBJECTIVE Extraosseous radioactivity outside of the expected biodistribution is often encountered on (99m)Tc-methylene diphosphate (MDP) bone scintigraphy, and proper interpretation requires an understanding of the mechanisms underlying this uptake and knowledge of the possible causes, depending on the site or structure involved. CONCLUSION We present examples of extraosseous radiotracer uptake seen on (99m)Tc-MDP bone scans in which either SPECT with integrated CT or correlative imaging improved the studys interpretation.

Utility of minimally invasive thoracoscopy for assessment of residual mediastinal lymphoma

Background: Patients with primary mediastinal lymphomas frequently present with a residual mass after completion of first‐line therapy. Although a positron emission tomography scan is usually recommended, it fails to distinguish between persistent lymphoma and inflammation. Although percutaneous biopsy may have a high diagnostic yield for the initial diagnosis of mediastinal lymphomas, this biopsy has poor accuracy for detecting persistent disease in a residual mass given the heterogeneity of these residual masses. Because persistent disease has important therapeutic implications, we evaluated the role of operative biopsy in detecting lymphoma in the residual mass. Methods: Between 2009 and 2015, consecutive patients (n=77) undergoing tissue biopsy for initial diagnosis as well as for a positron emission tomography‐positive residual mass were included. Tissue biopsy for a residual mass was repeated until frozen section was diagnostic or at least the mass on the ipsilateral hemi‐mediastinum was resected. Results: Of the initial 77 patients, 34 underwent operative restaging for a residual mass after chemotherapy, while 43 had a complete response. In these 34 patients, operative biopsy revealed the presence of lymphoma in 53%, predominantly Hodgkins disease and diffuse large B‐cell lymphoma. There was no significant difference in tumor volume (51% versus 39%) and a decrease in the positron emission tomography‐standardized uptake valuemax (68% vs 60%) in patients with or those without persistent lymphoma. There were no surgical complications and the duration of stay for all patients undergoing thoracoscopy was <24 hours. Residual lymphoma was treated with second‐line therapy guided by the pathologic analysis. Conclusion: A large proportion of patients with residual positron emission tomography‐avidity after first‐line chemotherapy of mediastinal lymphomas have residual disease that can be detected safely using minimally invasive thoracoscopy.

Watch Out" for Unexpected Radioiodine Uptake on Post-therapy Thyroid Cancer Imaging

Unexpected radioiodine distributions may be encountered on post-therapy I-131 thyroid cancer scans due to a range of benign physiological processes, causing diagnostic dilemma and potentially mimicking metastatic disease. We present two cases of intense focal uptake related to concentration of radioiodine activity on wrist-watches by differing mechanisms, which should be confirmed by clinical history and not be mistaken for metastatic disease.