Unusual extracardiac findings detected on myocardial perfusion single photon emission computed tomography studies with Tc-99m sestamibi

Parathyroid Scintigraphy with an Incidental Indirect Finding of Pancreatic Cancer

Modifications of the biodistribution of ^99mTc-sestamibi seen during myocardial perfusion and parathyroid imaging may be secondary to benign or malignant processes in visualized anatomic structures not related to the target organs of these imaging procedures. This article presents a case of pancreatic adenocarcinoma indirectly depicted on parathyroid scintigraphy.

Recurrent 99mTc Sestamibi Emboli in the Lungs Revealed on Consecutive Rest and Stress Single-Photon Emission Computed Tomography/Computed Tomography Myocardial Perfusion Images

Many causes of incidental focal uptake on raw data images using myocardial perfusion imaging, including malignant diseases, metastatic processes, benign pathologies, and physiological conditions, have been reported in the literature. However, iatrogenic ^99mTc sestamibi emboli have not yet been reported. Herein, we demonstrated iatrogenic ^99mTc sestamibi embolization on consecutive rest and stressed myocardial perfusion images at different locations.

Incidental Non-cardiac Findings in Cardiovascular Imaging

Improvements in imaging techniques have led to an expansion in the number of cross-sectional cardiac studies being performed. This means that incidental non-cardiac findings (INCF) identified on cardiac imaging have become an important clinical concern. The majority of INCF are not clinically significant. However, some INCF will require follow-up or changes in management. Differentiating clinically significant from non-significant INCF can be challenging, particularly given the breadth of potential findings and the range of organ systems involved. Following up INCF also has economic implications. Recent changes to the lung nodule follow-up guidelines will reduce the cost of following up incidental lung nodules. In this manuscript, we discuss the common and important INCF which may be identified in cardiovascular imaging and explore potential implications of these findings.

False-Positive Results in 18F-Fluorocholine PET/CT for a Thymoma in Workup of a Hereditary Primary Hyperparathyroidism

We present the case of a severe familial primary hyperparathyroidism related to a germline deletion in the HRPT2 (CDC73) gene. Morphological explorations revealed 2 potential hyperfunctioning parathyroid glands: a left cervical lesion on the neck ultrasound, and an ectopic mediastinal lesion on the parathyroid scintigraphy using Tc-methoxyisobutylisonitrile and on F-fluorocholine PET/CT. Surgery removal and histopathological examination determined that the mediastinal mass corresponded to a thymoma and the cervical lesion to a parathyroid adenoma. Those interesting images illustrate that a thymoma can produce false-positive results both on Tc-methoxyisobutylisonitrile scintigraphy and F-fluorocholine PET/CT.

Hepatic Hemangioma on SPECT Myocardial Perfusion Imaging

Extracardiac uptake on SPECT MPI, seen with physiologic radiotracer distribution, benign or malignant neoplasm, infection, inflammation, or granulomatous disease, may confound the accuracy of MPI or lead to unsuspected pathology. A 38-year-old woman with end-stage renal disease on hemodialysis had SPECT MPI for renal transplant preoperative risk stratification, showing left anterior descending artery ischemia and an intense extracardiac soft tissue focus adjacent to the diaphragmatic right ventricle concerning for focal infection related to prior coronary or gastric surgeries or tumor. CT revealed focal herniation of liver containing a flash-fill hemangioma into the left hemithorax accounting for this focal uptake.

Safety of coronary CT angiography and functional testing for stable chest pain in the PROMISE trial: A randomized comparison of test complications, incidental findings, and radiation dose

BACKGROUND

Coronary computed tomography angiography (CTA) and functional testing strategies for stable chest pain yield similar outcomes; one aspect that may guide test choice is safety.

METHODS

We compared test safety (test complications, incidental findings, and effective radiation dose) between CTA and functional testing as-tested in PROMISE (PROspective Multicenter Imaging Study for Evaluation of Chest Pain). In the subgroup whose physicians intended nuclear stress over other functional tests if randomized to the functional arm, we compared radiation dose of CTA versus nuclear stress and identified characteristics associated with dose.

RESULTS

Of 9470 patients, none had major and <1% had minor complications (CTA: 0.8% [37/4633] vs. functional: 0.6% [27/4837]). CTA identified more incidental findings (11.6% [539/4633] vs. 0.7% [34/4837], p < 0.001), most commonly pulmonary nodules (9.4%, 437/4633). CTA had similar 90-day cumulative radiation dose to functional testing. However, in the subgroup whose physicians intended nuclear stress (CTA 3147; nuclear 3203), CTA had lower median index test (8.8 vs. 12.6 mSv, p < 0.001) and 90-day cumulative (11.6 vs. 13.1 mSv, p < 0.001) dose, independent of patient characteristics. The lowest nuclear doses employed 1-day Tc-99m protocols (12.2 mSv). The lowest CTA doses were at sites performing ≥500 CTAs/year (6.9 mSv) and with advanced (latest available) CT scanners (5.5 mSv).

CONCLUSION

Complications were negligibly rare for both CTA and functional testing. CTA detects more incidental findings. Compared to nuclear stress testing, CTA's lower radiation dose, independent of patient characteristics, makes it an attractive test choice. Radiation dose varies with imaging protocol, indicating opportunities to further reduce dose. (ClinicalTrials.gov number, NCT01174550).

Incidental detection of bronchial carcinoid on Tc-99m sestamibi SPECT/CT myocardial perfusion scintigraphy

Technetium-99m sestamibi MPS is a commonly employed imaging study for myocardial perfusion; however, incidental extracardiac sestamibi uptake requires further evaluation, and the tracer uptake in the thorax/mediastinum may be pathological. The authors present a case of significant extra-cardiac uptake seen on stress MPS images helping in the incidental detection of bronchial carcinoid.

99mTc MIBI THYMIC SCINTIGRAPHY IN DIAGNOSIS AND THERAPEUTIC DECISION MAKING: WHAT IS BEHIND THE IMAGE?

CONTEXT

Despite CT being generally used in thymic pathology, in the case of regions with the same tissue density, only functional radioisotopic imaging can hint towards malignity.

OBJECTIVES

To assess the usefulness of 99mTc MIBI scintigraphy for diagnosis and treatment planning in thymoma, in relation with the radiotracer uptake mechanism.

PATIENTS AND METHODS

99mTc MIBI thymic scans for 19 patients diagnosed with thymic disorders were assessed using tumor uptake ratio (UR). Specimens of thymectomies were examined and cytological assessments were correlated with the UR.

RESULTS

The UR of all surgical patients was higher than 1.2, with a 1.5 cutoff between lymphoid hyperplasia and thymoma. The UR values were correlated with the histopathologic diagnosis (Pearson correlation 0.91, significant at p<0.01). The highest UR was 3.24, found in the case of an AB thymoma where the rate lymphocytes/epithelial cells (L/E) was 1.6. In B1 thymoma UR was 1.14 and L/E was 2.46.

CONCLUSION

Phenotype differences between thymoma types correlate with 99mTc MIBI cellular uptake: lower rate L/E corresponds to higher UR, higher malignity potential and invasiveness. A thymic 99mTc MIBI UR higher than 1.5, corresponding to a CT tumoral image, is suggestive for a thymoma, requiring surgical treatment first.

Looking outside the "cardiac" box: incidental detection of a metastatic lung tumor on cardiac position emission tomography/computed tomography

Incidental extracardiac findings are not uncommon in patients undergoing cardiac positron emission tomography/computed tomography (PET/CT) and some of these findings can have significant clinical impact. We report a case of a 74-year-old man who presented with dyspnea and left sided chest pain. 82-rubidium PET/CT imaging showed normal myocardial perfusion. Review of the low dose CT scan performed for attenuation correction purposes (CTAC) incidentally revealed a 4 cm mass in the left lung, which was histologically shown to be a squamous cell carcinoma. A subsequent staging CT showed chest wall metastases and rib destruction in the upper left thorax, which were outside the image reconstruction field of view of the CTAC. This report illustrates the importance of vigilant review of all acquired images by the PET/CT reader to look for extracardiac abnormalities that may explain symptoms in the absence of coronary artery disease. It also raises the question as to whether a larger field of CT image acquisition should be routinely performed to scan the entire chest during cardiac PET/CT imaging. However, the latter needs to be weighed against the increase in patient dose, which we estimated to be an additional 15%.

Cervical lymph node sarcoidosis mimicking a parathyroid adenoma: a clinical case

We report a case of cervical lymph node sarcoidosis misdiagnosed as parathyroid adenoma. This is the second case described in the literature in which lymph node sarcoidosis was misdiagnosed as parathyroid adenoma on Tc-99m sestamibi (MIBI) scan, the first case localized in the neck. A 64-year-old woman presented with a hypercalcemia. Neck ultrasonography revealed a paratracheal hypoechoic mass of 15 mm with peripheral vascularization. MIBI scan and SPECT/CT identified a MIBI-positive area corresponding to the nodule detected by ultrasonography suggestive for a lower right parathyroid adenoma. A mass interpreted as the lower parathyroid was excised associated to a total thyroidectomy. Pathologic examination revealed a granulomatous lymph node consistent with active sarcoidosis. Sarcoidosis should be suspected as a cause of unexplained hypercalcemia and the differential diagnosis of hypercalcemia, even in presence of MIBI uptake, must include sarcoidosis localized in an isolated cervical lymph node.

Evaluation by SPECT-CT of an incidental finding of a thymoma and breast cancer in a myocardial perfusion SPECT with 99mTc-MIBI

We present a case of a 78-year-old female with effort angina. A myocardial perfusion SPECT (MPS) showed increased tracer uptake in two synchronic tumor lesions, a thymoma and a breast cancer. This case highlights the contribution of SPECT-CT in the characterization of these findings and its essential role in rapid decision-making. The patient underwent surgery of both lesions that had gone undetected prior to the conduction of the MPS.

Accurate localization of incidental findings on the computed tomography attenuation correction image: the influence of tube current variation

This observer performance study assessed lesion detection in the computed tomography attenuation correction image, as would be produced for myocardial perfusion imaging over a tube current (mA) range. A static anthropomorphic chest phantom containing simulated pulmonary lesions was scanned using the four available mA values (1, 1.5, 2 and 2.5) on a GE Infinia Hawkeye 4. All other computed tomography acquisition parameters remained constant throughout. Twenty-seven cases showing zero to four lesions were produced for a free-response receiver-operating characteristic method. Image observations were completed using our novel web-based ROCView software under controlled conditions. The Jackknife alternative free-response receiver-operating characteristic (JAFROC) figure of merit was used for significance testing, wherein a difference in lesion detection performance was considered significant at P values less than 0.05. Twenty readers with varying computed tomography experience (0-24 years) evaluated 108 images using an ordinal scale to score confidence. The JAFROC analysis showed that there was no statistically significant difference in performance between mA values (P=0.439) for this sample of observers. In conclusion, no significant difference in lesion detection performance was seen between the mA values. This suggests that there is no value in using anything other than the lowest mA value for the investigation of incidental extracardiac findings.

The Role of Routine Whole Volume SPECT Reconstruction in Comparison to Cine Raw Data in the Detection of Extracardiac Uptake on Myocardial Perfusion Scans

The objective of this study was to determine the role of routine whole volume reconstructed single-photon emission tomography (rSPECT) compared to cine raw data to detect extracardiac uptake of Sestamibi (MIBI). In a retrospective study, the myocardial perfusion studies of 426 patients were inspected separately for extracardiac uptake on cine raw data and rSPECT. The acquisition parameters for all the images were done according to departmental protocol. The whole volume SPECT data was selected and processed by HOSEM iterative reconstruction using the HERMES computer software system. The images were assessed by two observers, a student in training and a senior consultant nuclear medicine physician. The overall mean age and standard deviation of the 426 patients at the time of the study was 60 ± 12 years. Statistical analysis was performed using the Kappa and McNemars tests. The clinical significance of the extracardiac uptake was evaluated using hospital folders and /or laboratory results after viewing images. rSPECT detected 25 patients (5.9%) and cine raw data identified 18 patients (4.2%) with extracardiac uptake. All the areas of extracardiac uptake noted on cine raw data were seen on the rSPECT images. Only 21 of the 25 patients had complete 5-year clinical follow-up. The value of the clinical significance of the extracardiac uptake was limited due to the study being retrospective. The proportion of positives identified by rSPECT was significantly larger than those identified by cine raw data (P = 0.0082). Although our study demonstrates that rSPECT is more sensitive than cine raw data in detecting extracardiac uptake, it also shows that there is no benefit in routine whole volume rSPECT in daily clinical practice.

Tc-99m methoxyisobutylisonitrile parathyroid scintigraphy: the value of adding a whole-body scan

PURPOSE

The aim of this study was to estimate the frequency of incidental findings on Tc-99m-methoxyisobutylisonitrile (MIBI) scan performed for suspected parathyroid adenoma and to evaluate the benefit of additional whole-body scan.

MATERIALS AND METHODS

A total of 109 patients (37 men and 72 women; age range, 16-96 years; mean, 58.42 years) with clinically suspected parathyroid adenoma underwent Tc-99m MIBI whole-body scans and single-photon emission computed tomography of the base of the skull, the neck, and the thorax. Each case with suspected abnormal tracer accumulation was analyzed and correlated with clinical information.

RESULTS

MIBI single-photon emission computed tomography of the base of the skull, the neck, and the thorax and whole-body scans of 109 patients were assessed. A total of five incidental findings were detected. The anatomical distribution of the incidental findings was as follows: two (40%) were located in the head and neck areas and three (60%) were in the abdomen and pelvis. Two (40%) were detected in standard acquisition view, which includes the base of the skull, the neck, and the thorax. Three (60%) incidentalomas were detected in whole-body scan. In addition, we found 23 cases of abnormal tracer distribution that were correlated with known clinical history of patients. Three (13%) were located in the head and neck areas, 10 (43.6%) in the thoracic region, six (26%) in the abdomen and pelvis, and four (17.4%) in the extremities.

CONCLUSION

Whole-body imaging in patients with suspected parathyroid adenoma who underwent MIBI scans does not alter patient management in most cases.