Time-of-Flight PET/CT Imaging of Ga-68-Dotatate: Normal Pattern, SUV Quantification, and Differences from Non-Time-of-Flight Imaging.

Purpose The biodistribution of gallium-68-dotatate (Ga-68-dotatate) and standardized uptake values (SUVs) using non-time-of-flight (TOF) positron emission tomography/computed tomography (PET/CT) cameras is well established. However, with the eventual retirement of older PET cameras and their replacement with newer, highly sensitive TOF PET/CT cameras, where SUV max measurements are reportedly higher, updated knowledge of normal SUV max range is needed and, to our knowledge, not previously reported. Our objectives are as follows: To establish normal Ga-68-dotatate TOF SUV max database for common structures and to aid the visual detection of abnormalities objectively. To compare SUV max values using the TOF and non-TOF algorithms. Methods Fifty consecutive patients referred routinely to our nuclear medicine service (20 men, 30 women; median age 55 years) with presumed neuroendocrine tumors underwent Ga-68-dotatate scans on a PET-CT camera having capability of reconstructing both TOF/non-TOF images. Region of interests (ROIs) were drawn around 24 normal structures as well as the primary lesion with abnormal radiotracer uptake and SUV max was measured. The same ROI was analyzed using both algorithms simultaneously and both TOF and non-TOF SUV max values were compared. Results Twelve hundred ROIs were evaluated. Non-TOF Ga-68-dotatate uptake in normal structures was in alignment with previously published studies. As compared to non-TOF, TOF images had better target to background ratios visually. TOF SUV max was higher for all structures except for lung and brain. TOF SUV max was more than double in adrenals/uncinate process of the pancreas; approximately 1.8 times in abnormal lesions, lymph nodes, pineal gland; and greater than 1.5 times in thyroid, breast, and pancreatic head. Conclusion Normal database of Ga-68-dotatate TOF SUV max is provided for common structures to aid visual detection of abnormalities objectively. Overall, TOF SUV max measures higher in identical ROIs, with abnormal lesions measuring approximately 1.8 times higher versus non-TOF technology. These findings need to be taken in consideration when comparing patient scans imaged on different PET/CT technologies.

Simulated Fewer-Angle SPECT/CT Imaging Protocol for Parathyroid Adenoma.

A new SPECT/CT protocol for parathyroid imaging detailing fewer image-angle acquisitions (fewer-angle SPECT/CT [FASpecT/CT]) was evaluated for identification of parathyroid adenoma. The motivation for validating this protocol was to be able to use it in the future to decrease patient imaging time in our clinic. Methods: This was a retrospective review of existing data performed as a simulated case control study evaluating 50 parathyroid SPECT/CT scans acquired using the standard 60-stop protocol and the tested 15-stop FASpecT protocol acquired using angular sampling software. Agreement on the final interpretations between imaging methods was evaluated using the McNemar test and the Cohen κ. Interrater reliability among the 3 readers was described for each method using the Fleiss κ interpreted as in the strength-of-agreement guidelines by Landis and Koch. Results: Of the 50 evaluated images, 45 (90%) had concordant final image interpretations between imaging methods. The sensitivity of FASpecT/CT relative to SPECT/CT was 17 of 19 (89.5%; 95% CI, 66.9%-98.7%), and the specificity was 28 of 31 (90.3%; 95% CI, 74.2%-98.0%). Additionally, there was statistically significant substantial agreement between protocols and among readers for each protocol. Conclusion: Adequate diagnostic-quality SPECT/CT images can be acquired using significantly fewer imaging stops given advances in camera quality and processing algorithms such as iterative reconstruction.

2022 Update on Clinical Management of Graves Disease and Thyroid Eye Disease.

The management of hyperthyroidism and extrathyroidal manifestations of Graves disease remains complex. Considerations that include patient preference, age, comorbidity, pregnancy, tobacco smoking, and social determinants of health must all be weaved into a cohesive management plan. A multidisciplinary team is required to manage all aspects of Graves disease, particularly thyroid eye disease, for which new therapeutic options are now available.

The effect of body mass index on high versus low administered activity protocol myocardial perfusion imaging scan time and effective dose using a cadmium zinc telluride camera in clinical practice.

Cadmium Zinc Telluride (CZT) crystal-based myocardial perfusion imaging (MPI) cameras have increased count sensitivity compared to Anger cameras and can be used to lower either the injected activity or the image acquisition time. Institutions adopting CZT cameras need to decide whether to lower the injected activity or imaging time or attempt to lower both with a compromise. The aim of our study was to compare the scan time required to obtain similar count images using high activity protocol (HAP) versus low activity protocol (LAP) stratified by body mass index (BMI) and assess the impact on effective dose and our clinic workflow. Using a CZT camera, a cohort of 100 consecutive clinical patients imaged with LAP rest-stress MPI with approximately 185 MBq and 555 MBq activity was retrospectively compared to a similar cohort of 100 consecutive clinical patients imaged with HAP rest-stress MPI using approximately 370 MBq and 1110 MBq. Administered activity and BMI both had a statistically significant effect on scan time and radiation effective dose. LAP scans took an average of 9 min longer than HAP scans overall, P < 0.0001 and larger BMIs took longer than smaller BMIs, P < 0.0001. In addition, scan times were longer in men than women, P = 0.007. Effective dose was inversely proportional to BMI with an overall decrease of approximately 50% comparing LAP to HAP. For the same CZT camera, the LAP increased scan time while lowering the radiation effective dose when compared to HAP. The increase in scan time increased proportionally to BMI. The effective dose was inversely proportional to BMI. This increase in time did not have a significant impact on our local workflow, but its implications should be considered in the setting of LAP implementation, especially in obese or high patient volume practices.

The added benefit of a dedicated neck F-18 FDG PET-CT imaging protocol in patients with suspected recurrent differentiated thyroid carcinoma.

PURPOSE: To retrospectively analyze whether adding a delayed high-resolution dedicated neck F-18 FDG positron emission tomography-computerized tomographic (PET-CT) imaging protocol in patients with recurrent differentiated thyroid cancer increases the number of abnormal foci within the neck. MATERIALS AND METHODS: Seventeen PET-CT studies from a total of 10 patients with suspected recurrent differentiated thyroid cancer between March 2003 and June 2004 were retrospectively reviewed. Each study included a whole body acquisition (WBA), followed by higher resolution dedicated neck acquisition (DNA). Two board-certified nuclear medicine physicians reviewed either the DNA or WBA for each study and recorded the number of abnormal foci, along with presence or absence of a soft tissue abnormality, and maximum standardized uptake value for each foci. Consensus review was used for all discrepancies. Statistical analysis was performed to determine whether there was a statistically significant increase in the number of studies demonstrating new abnormal foci with the addition of a DNA. RESULTS: Five of 17 studies demonstrated an increase in the number of abnormal foci with the addition of the DNA (P < 0.04). A total of 8 abnormal foci were noted on the WBA, 4 of which were within the neck. Eleven additional abnormal foci were seen on the DNA. All abnormal foci within the neck had corresponding soft tissue abnormalities except for one. CONCLUSION: Adding a higher resolution delayed DNA to the WBA for patients undergoing PET-CT imaging to detect recurrent thyroid cancer increases the number of abnormal sites of FDG accumulation.

Low-iodine diet revisited: importance in nuclear medicine imaging and management.

PURPOSE: The need for a low-iodine diet (LID) to maximize the results of radioactive iodine uptake (RAIU), nuclear medicine thyroid scintigraphy, and ultimately treatment of thyroid cancer patients is widely accepted. Failure to follow the prescribed diet can alter RAIU results, thyroid scan findings, and poststudy management. OBJECTIVE: Provided is a case presentation that illustrates the need for adequate patient understanding and compliance with the LID. METHODS: We present the clinical history, laboratory values, and pertinent imaging of a 21-year-old woman with papillary thyroid cancer. The patient's post-thyroidectomy I-123 and 2 subsequent thyroid (I-123 and post-RAI ablation I-131) scintigraphy examinations are reviewed as well as the patient's urine iodine levels. RESULTS: In this case of a woman with papillary thyroid cancer, the nuclear medicine whole body and neck pinhole images revealed that compliance to an LID positively impacts the overall management. After an LID was followed, the patient's urine iodine level appropriately declined from the previously elevated level. Initial negative results on thyroid scintigraphy caused by noncompliance with the LID became positive when the patient adhered to the prescribed dietary regimen. CONCLUSION: An LID is an integral element in the management of differentiated thyroid cancer. Proper guidance and emphasis on the implementation of the diet needs to be provided to patients. Noncompliance may lead to false negative imaging results, misleading the medical professionals and patient. Potentially inadequate management of the patient's thyroid cancer may follow.

Acute Wernicke's encephalopathy following bariatric surgery: clinical course and MRI correlation.

Postoperative complications and nutritional deficits resulting from bariatric surgery can lead to severe vitamin-deficiency states, such as Wernicke's encephalopathy (WE). Patients with acute WE generally present with the classic clinical triad of inattentiveness, ataxia, and ophthalmoplegia. We describe a patient who presented with acute WE at 2 months after laparoscopic bariatric surgery. Initial MRI of the brain demonstrated the characteristic injuries of WE, and repeat imaging showed resolution after 4 months of thiamine supplementation, at which time the patient had normal gait but persistent memory deficits. Even with early recognition and aggressive therapy, acute WE commonly results in permanent disability due to the irreversible cytotoxic effects on specific regions of the brain. Since the clinical onset of acute WE follows a predictable time-course in post-bariatric surgery patients with malnutrition, we recommend prevention by administration of parenteral thiamine beginning at 6 weeks postoperatively in malnourished patients.

Management of the bariatric surgery patient.

Morbid obesity has reached epidemic proportions in the United States. Unfortunately, medical interventions have been largely ineffective in this growing population. Currently bariatric surgery is the most effective intervention in managing morbid obesity and its comorbidities. As more patients become eligible for and pursue weight reduction surgery, it becomes important for the clinician to possess a thorough understanding of the different procedures available and the management of patients before, during, and after these surgeries. Significant weight loss and improvement in weight-related comorbidities are possible, with the best results available to the well-informed patient whose care is provided by a dedicated multidisciplinary team.

Bilateral external laryngoceles following radioiodine ablation for Graves disease.

A 28-year-old trumpet player underwent multiple treatments with radioactive iodine for Graves disease associated with an unusually large goiter. Following his second treatment, the patient developed acute neck pain and swelling. Radiographic studies and a laryngoscopy demonstrated bilateral symptomatic external laryngoceles, a very rare entity, not previously known to be associated with radioiodine treatment or Graves disease. The patient's profession placed him at risk for the development of a laryngocele, but the temporal relationship to goiter regression following radioiodine therapy suggests that this occurred as a result of this treatment. The patient's disease was managed nonsurgically, and he has subsequently done well. This represents the first known association of symptomatic laryngocele with radioiodine treatment for Graves disease.

Thyroid cancer yield in patients with Graves' disease selected for surgery on the basis of cold scintiscan defects.

Previous studies have suggested that thyroid nodules found in patients with Graves' disease (GD) have a higher likelihood of being malignant, and that thyroid cancer behaves more aggressively when associated with GD, although both of these assertions remain controversial. The purpose of this study was to assess the frequency of cold scintiscan (SC) defects in patients with GD, and to determine the prevalence of thyroid cancer in such patients. Our secondary objective was to determine if there are any risk factors for developing cold defects by comparing clinical characteristics of both GD patients with cold SC defects and age and gender-matched GD patients without cold defects. We included in this analysis patients with a confirmed diagnosis of GD for whom SC results and adequate follow-up information were available. Clinic records were available in 772 patients with GD. Of these, 325 patients met eligibility criteria. Cold defects were found in 39 of 325 (12.0%) patients. Among these, 22 (56.4%) were referred for surgery, of whom 6 (1.85% of all GD patients, 15.2% of GD patients with cold nodules, 25% of GD patients with palpable nodules, and 27.3% of those undergoing surgery) had papillary thyroid cancer (PTC) in the location corresponding to the SC defect. In 2 PTC patients, no palpable abnormality corresponded to the cold defect found to contain cancer at surgery. One PTC patient was found to have metastatic disease to bone, and 2 additional PTC patients required multiple therapies with radioiodine. Compared to age and gender-matched control patients with GD and without cold SC defects, there were no differences in radioactive iodine uptake (RAIU), goiter size, duration of disease, degree of elevation in microsomal antibody (MA) titers, or thyroid-stimulating immunoglobulin (TSI). We conclude that thyroid scintigraphy is an important preliminary test in the evaluation of patients with GD, and that the prevalence of thyroid cancer in the location corresponding to a focal cold SC defect provides justification for further diagnostic evaluation or surgical management.

Do specialists differ on do-not-resuscitate decisions?

STUDY OBJECTIVE: Opinions regarding do-not-resuscitate (DNR) decisions differ between individual physicians. We attempted to determine whether the strength of DNR recommendations varies with medical specialty and experience. DESIGN: Written survey. PARTICIPANTS: Physicians from the pulmonary/critical-care medicine (PCCM), cardiology, internal medicine, gastroenterology, hematology/oncology, and infectious disease services as well as the Department of Medicine house staff at our tertiary-care referral center participated in the study. INTERVENTIONS: Physicians were asked confidentially to quantify the strength of their opinions on discussing and recommending DNR orders for each of 20 vignettes made from the summaries of actual cases. Reasons for their opinions and demographic data also were recorded. MEASUREMENTS AND RESULTS: One hundred fifteen of 155 physicians (74%) responded. PCCM physicians (mean [+/- SD] DNR score, 157 +/- 22) more strongly recommended DNR orders than cardiologists (mean DNR score, 122 +/- 32; p = 0.006), house staff (mean DNR score, 132 +/- 24; p = 0.014), and general internists (mean DNR score, 129 +/- 30; p = 0.043). PCCM physicians also trended toward recommending DNR orders for more of the 20 patients described in the vignettes compared to cardiologists (mean DNR number, 16.5 +/- 3.0 vs 11.9 +/- 5.8, respectively; p = 0.066). There were no differences between PCCM physicians and hematology/oncology, infectious disease, and gastroenterology specialists. Among the house staff, the likelihood of recommending a DNR order correlated significantly with increasing years of experience (r = 0.45; p = 0.002). The opposite trend was present in the specialty staff groups. No significant differences in opinion by gender, religion, or personal experiences were found. CONCLUSIONS: The strength of DNR order recommendations varies with medicine specialty and years of training and experience. An awareness of these differences and the determination of the reasons behind them may help to target educational interventions and to ensure effective collaboration with colleagues and communication with patients.