Hyperostosis frontalis interna on fluorine-18 sodium fluoride PET/computed tomography of obese cancer patients: a potential mimicker of metastasis.

OBJECTIVE: The objective of this retrospective study was to identify the uptake patterns and suggest a quantitative method to detect hyperostosis frontalis interna (HFI) on fluorine-18 sodium fluoride ([18F]NaF) PET/computed tomography (CT). METHODS: Between January 2019 and December 2021, patients who underwent [18F]NaF PET/CT with a BMI of 30 and above, were included. Three nuclear medicine consultants reviewed the studies to determine the presence and identify the uptake patterns of HFI. Quantitative evaluation was performed on PET images using the total number of counts over the frontal bone and the ratio of counts between the frontal bone and iliac crest. RESULTS: A total of 105 out of 249 cases were included in this study. Among these scans, there were 67 positive HFI in [18F]NaF PET scans representing 64% of the studied population. As for the [18F]NaF PET uptake pattern, there were 53 with uniformly diffused and 14 with heterogeneous uptake pattern. There were 17 out of 67 with positive HFI in [18F]NaF PET scans but negative CT scans. CONCLUSION: HFI is a common finding on [18F]NaF PET in obese patients and is probably underdiagnosed. HFI may present with a heterogeneous and diffuse pattern of uptake on [18F]NaF PET. The proposed quantitative analysis using the count ratios is in agreement with the visual evaluation of [18F]NaF PET images regardless of the CT findings. Awareness of this condition and its scintigraphic patterns is warranted since it can have clinical significance and may mimic other pathologies including metastasis in cancer patients.

Potential Pitfalls of Steatopygia on Bone Scintigraphy and the Added Value of SPECT and SPECT/CT.

OBJECTIVES: A retrospective study of bone scintigraphy to assess the prevalence of steatopygia on bone scintigraphy of obese patients and evaluate its effect on the appearance of the lumbar spine, and the added benefit of SPECT and SPECT/CT in overcoming possible artifacts. METHODS: Between 2016 and 2019, patients who underwent bone scintigraphy, BMI ≥ 30, were included. Three nuclear medicine consultants reviewed the studies to determine whether significant steatopygia is present, if it resulted in attenuation of underlying lumber spine and crease edge artifact. SPECT or SPECT/CT images were reviewed to evaluate their impact in diagnosis. RESULTS: 56 patients out of the 100 were noted with steatopygia on planar images. Among the group of 80 obese patients, 50% patients showed steatopygia, while in the group of 20 morbidly obese patients, 80% patients showed steatopygia. 32 patients of the 56 with steatopygia, had significant attenuation at the lower lumber vertebrae. Nine of these patients showed crease edge artifact. SPECT and SPECT/CT clarified the scintigraphic abnormalities noted in all patients including patients with edge artifact alleviating diagnostic difficulty. Among the nine patients with edge artifact, six patients showed normal appearance on SPECT/CT images while three showed true abnormalities. CONCLUSIONS: Steatopygia is common on bone scintigraphy of obese patients, higher in females and morbidly obese patients. Obesity related artifacts in bone scintigraphy, including attenuation effect and edge artifact, are common in this patient group. SPECT or SPECT/CT improves the diagnostic accuracy by overcoming the steatopygia effects seen on planar images.

Reducing Radiation Exposure from PET Patients.

This study measured the typical emitted radiation rate from the urinary bladder of PET patients after their scan and investigated simple methods for reducing the emitted radiation before discharge. Methods: The study included 83 patients (63 18F-FDG and 20 18F-NaF patients). Emitted radiation from the patients' urinary bladder was measured with an ionization survey meter at a 1-m distance, presuming the urinary bladder to be the primary source of radiation. The measurements were taken at different time points after PET image acquisition: immediate (prevoid 1), voided (postvoid 1), after waiting 30 min in the uptake room while drinking 500 mL of water (prevoid 2), and voided again (postvoid 2). Results: For 18F-FDG patients, the reduction of emitted radiation due to drinking water and voiding alone from prevoid 1 to decay-corrected postvoid 2 was an average of 22.49% ± 7.48% (13.65 ± 3.42 µSv/h to 10.48 ± 2.37 µSv/h, P < 0.001). For 18F-NaF patients, the reduction was an average of 25.80% ± 10.03% (9.83 ± 2.01 µSv/h to 7.23 ± 1.49 µSv/h, P < 0.001). Conclusion: In addition to the physical decay of the radiotracers, using the biologic clearance properties resulted in a significant decrease of the emitted radiation in this study. Implementing additional water consumption to facilitate voiding with 30 min of wait time before discharging certain 18F-FDG and 18F-NaF patients who need to be in close contact with others, such as elderly, caregivers, and inpatients, might facilitate lowering their emitted radiation by an average of 22%-25% due to voiding, not counting in the physical decay that should add an additional 17% reduction.

Assessing oral glucose and intravenous insulin loading protocol in 18F-fluorodeoxyglucose positron emission tomography cardiac viability studies.

Oral glucose and intravenous insulin (G/I) loading protocols are commonly used in 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) cardiac viability studies. Although the amount of insulin to be given per blood glucose range has been well described in guidelines, the amount of glucose to be given is not detailed well. In this retrospective study, we aimed to assess if certain parameters, particularly the amount of glucose and insulin given, may affect 18F-FDG uptake in the hibernating myocardium and also determine the problems with this protocol. 18F-FDG PET cardiac viability study with G/I loading protocols was performed in 49 patients. Fasting blood glucose (FBG), amount of glucose given, blood glucose level after glucose load, amount of insulin given, and blood glucose level at the time of 18F-FDG injection were recorded. Statistical analysis was performed to determine if there is any difference in the above values in PET viable and PET nonviable groups and also in subgroups assessing 18F-FDG uptake also in normal myocardium. For G/I loading, we used our local protocol in 43 patients, and other protocols in six. 18F-FDG PET showed viability in 31 patients, and it was negative for viability in 18. In 22 patients, mainly in PET viable group, there was varying degree of reduced 18F-FDG uptake in normal myocardium. There was no significant difference in FBG, amount of glucose given, blood glucose level after glucose load, amount of insulin given, and blood glucose level at the time of 18F-FDG injection in PET viable and PET nonviable groups and also in subgroups. The problems with G/I loading protocol included deciding on the amounts of glucose and insulin given, maximum amount of insulin to be given, handling diabetics, optimal time to measure blood glucose after insulin administration, and interpretation of findings in cases with diffusely reduced 18F-FDG uptake. Further improvements in current guidelines are necessary to obtain images in optimal conditions for accurate results.

Effect of brown adipose tissue activation on myocardial fluorine-18-fluorodeoxyglucose uptake.

The aim of this study is to investigate the relationship between brown adipose tissue (BAT) activation and myocardial fluorine-18-fluorodeoxyglucose ([18F] FDG) uptake in terms of intensity and patterns. The patients were divided into two groups as follows: BAT and control groups. The BAT group consists of 34 cases that showed BAT uptake. The control group, with no BAT uptake, included 68 patients who were matched for body mass index, gender, and season. The scans were retrospectively reviewed by two nuclear medicine physicians who visually evaluated the intensity of myocardial [18F] FDG uptake. The myocardial [18F] FDG uptake was visually classified into the following three patterns: diffuse, heterogeneous, and focal. The regions of activated BAT distribution were noted. The mean myocardial [18F] FDG uptake was 2.50 ± 0.75 for the BAT group and 2.13 ± 0.88 for the control group with a statistically significant difference (P = 0.031). The myocardial [18F] FDG uptake pattern was similar in the BAT and control groups with the diffuse pattern being the most common, followed by the heterogeneous and less commonly focal. In the BAT group, the anatomical distribution of BAT was mainly in supraclavicular, paravertebral, and axillary and to a lesser extent in cervical regions. BAT group had a significantly higher intensity of [18F] FDG myocardial uptake compared to that of the control group. The presence of activated BAT did not affect the pattern of myocardial uptake. Knowledge of these findings may help in understanding the variability of myocardial [18F] FDG uptake and consequently in avoiding misinterpretation of cardiac findings in positron-emission tomography/computed tomography studies.

The added value of SPECT-CT in the detection of heterotopic ossification on bone scintigraphy.

PURPOSE: Heterotopic ossification (HO) is the abnormal osteogenesis in non-skeletal tissue. It can be difficult to detect, as it can mimic other conditions clinically and on imaging studies. The purpose of this study was to find the added value of SPECT-CT in accurate detection of HO. MATERIALS AND METHODS: A total of 1780 reports on the PACS system of patients underwent bone scintigraphy at the Department of Nuclear Medicine and were filtered for the term "HO" or "heterotopic bone formation" and "SPECT-CT". Thirty-four patients fulfilled this criterion. All patients had bone scintigraphy and SPECT/CT in the same occasion. Images were reviewed by two nuclear medicine physicians blindly. The certainty of the presence of extra-skeletal soft tissue ossification on the planar with SPECT was graded as "definitely present", "maybe present", or "not present", and the same was determined on planar with SPECT-CT images. RESULTS: Based on SPECT/CT, 23 (67.6%) patients were found to have HO, and 11 (32.4%) did not have confirming findings. Of the 23 positive patients on SPECT/CT, eight (34.8%) showed "definitely present" and 12 (52.2%) patients were under "maybe present" on SPECT only. Three (13%) patients were negative on the SPECT and showed evidence of HO on CT. Of the 11 patients that did not demonstrate definite evidence of HO on SPECT/CT, seven (63.6%) were negative on SPECT alone and, four (36.4%) were under "maybe present" on SPECT. The definite detection of HO was statistically significant higher when CT is added to SPECT. CONCLUSIONS: Our findings suggest that adding the CT component to SPECT is valuable in the detection of HO.

Effect of Causative Micro-organisms on Patterns of Labeled White Blood Cells in Osteomyelitis.

OBJECTIVE: The aim of this study is to investigate the effect of microbiological characteristics of causative organisms on the scintigraphic patterns of labeled-white blood cells (WBC) scan in cases of proven osteomyelitis. MATERIALS AND METHODS: Retrospective analysis of 25 patients referred with suspected osteomyelitis and had both bone and labeled-WBC scans performed and complete records of the microbiological culture of the causative organism. The bone and labeled-WBC scans were retrieved and reviewed by two nuclear medicine physicians. Any definite focal accumulation of labeled WBCs within the bone was considered positive for osteomyelitis. Diagnosis of osteomyelitis in the discharge summary was considered the reference standard and was based on a combination of the clinical scenario, imaging, and laboratory findings including microbiology. Correlation of the pattern of labeled WBC and the type of microorganisms was done. RESULTS: A total of 16 patients were included in this study, seven females and nine males. Of these, seven patients had Gram-positive whereas nine patients had Gram-negative organisms. The majority (85.7%) of Gram-positive organisms showed increased accumulation of labeled WBCs, whereas only one-third (33.3%) of patients with Gram-negative organisms had such finding. CONCLUSION: The pattern observed in this study shows that the false-negative results of labeled-WBC scans were mainly noted in patients with Gram-negative as opposed to Gram-positive infections. This confirms the experimental animal study findings that the secretion of anti-chemotactic factors by Gram-negative organisms, seems to be inhibiting the migration of labeled WBCs to the site of infection. The inhabitation is decreasing the accumulation of labeled WBCs and consequently resulting in a false-negative finding. The study adds to evidence that microbiological characteristics of the causative organisms are another explanation for the false-negative WBC in proven osteomyelitis.

Effect of Verapamil on Kidney Function Using Radionuclide Imaging.

BACKGROUND AND OBJECTIVE: Calcium channel blockers (CCBs) are among the most widely used prescribed drugs for the treatment of cardiovascular diseases. The present study investigates the effect of verapamil, which is most commonly used as a CCB, on kidney function using radionuclide imaging. METHODS: Ten New Zealand white rabbits were used in vitro (4) and in vivo (6) studies. Isometric tensions were recorded for isolated renal artery ring segments, while renographic studies were performed using Technetium-99m mercaptoacetyltriglycine and Gamma camera. Time to peak activity (Tmax) and time from peak to 50% activity (T1/2), were calculated from the renograms for control and treated rabbits with verapamil. RESULTS: In vitro, verapamil shifted the curve of phenylephrine concentration-dependent contraction on renal artery to the right, and decrease the highest contraction by 30 ± 3%. In vivo, the average values of Tmax for control and treated rabbits were 2.8 ± 0.1 and 2.2 ± 0.2 min respectively. The T1/2 for control and treated rabbits were 4.7 ± 0.05 and 4.2 ± 0.08 min respectively. The differences were statistically significant: p < 0.05. There is 30 ± 4% decrease in the 2 values. This indicates that there is a rapid renal uptake of the tracer and clearance of the radioactivity after verapamil. CONCLUSION: Verapamil dilates the renal artery and accelerates both the Tmax and T1/2 in the renogram. It increases renal blood perfusion and protects kidney function and therefore improves its work. However, verapamil should not be used while performing renograms to avoid misleading results.

Prostate-specific antigen cutoff value for ordering sodium fluoride positron emission tomography/computed tomography bone scan in patients with prostate cancer.

The use of F-18 sodium fluoride (NaF) positron emission tomography/computed tomography (PET/CT) bone scan is increasing because of its higher sensitivity and specificity over standard bone scintigraphy (BS). Studies previously reported a prostate-specific antigen (PSA) cutoff value for ordering standard BS. However, this has not been determined for NaF PET yet. In this study, our goal was to determine a PSA cutoff level for ordering NaF PET/CT bone scan. Newly diagnosed and previously treated prostate cancer patients who had NaF PET/CT scan and PSA measurements within 2 mos of PET study were selected for analysis. When available, other parameters, such as Gleason score (GS), clinical stage, alkaline phosphatase levels, skeletal symptoms, and correlative image findings, were recorded. Receiver operating characteristic (ROC) analysis was performed to determine PSA cutoff values. Sixty-two patients (32 newly diagnosed and 30 previously treated) met the inclusion criteria. Near half of previously treated patients were on hormone therapy. NaF PET/CT was positive in 9 newly diagnosed (PSA mean: 91.6 ng/ml, range: 6.2-226 ng/ml) and in 6 previously treated patients (PSA mean: 146.4 ng/ml, range: 6.6-675 ng/ml). ROC analysis indicated that PSA cutoff value for NaF PET/CT positivity was >20 ng/ml in newly diagnosed and >6 ng/ml in previously treated patients. PSA cutoff value for ordering NaF PET/CT in newly diagnosed patients does not seem significantly different than the previous results for BS (>20 ng/ml). However, we found a lower PSA cutoff value of >6 ng/ml in previously treated patients.

Current Status of 18F-FDG PET Brain Imaging in Patients with Dementia.

18F-FDG PET brain imaging is commonly used in the early detection and differential diagnosis of various subtypes of dementias. 18F-FDG PET images are mainly evaluated visually, and semiquantitative analysis programs are also commonly used in many centers. However, visual and semiquantitative analysis carry certain limitations. Visual assessment is subjective and dependent on expertise. Commercially available semiquantitative analysis programs have certain limitations such as suboptimal selection of brain areas or erroneous uptake normalization procedures that may provide inaccurate results, and physicians reporting semiquantitative results should be aware of these. In this pictorial review article, we will discuss the current status of 18F-FDG PET brain imaging in patients with dementia and present figures and semiquantitative analysis results of various subtypes of dementias as well as certain artifacts seen on 18F-FDG PET brain imaging studies.

Gallbladder activity on sodium fluoride positron emission tomography/computed tomography bone scan.

We incidentally identified gallbladder activity on 18F sodium fluoride (NaF) positron emission tomography/computed tomography (PET/CT) bone images in five patients. Variable degree of bowel activity is usually seen on NaF PET/CT images, and its mechanism is unknown. Gallbladder activity in our cases may indicate that hepatobiliary excretion of the 18F NaF is the reason for bowel activity on NaF PET/CT images. However, excretion of radiotracer through bowel may also contribute to the bowel activity.

Fluorodeoxyglucose, sodium fluoride, and prostate-specific membrane antigen positron emission tomography studies for treatment response assessment in prostate cancer.

Various positron emission tomography (PET) studies are available for prostate cancer which show various successes at demonstrating primary, recurrent, or metastatic tumor and assessing response to treatment. In this case report, we will present and compare pre- and post-therapy fluorodeoxyglucose, sodium fluoride, and gallium-68 prostate-specific membrane antigen PET images of a patient with prostate cancer.

Can Gallium-68 Prostate-specific Membrane Antigen Ligand be a Potential Radiotracer for Renal Cortical Positron Emission Tomography Imaging?

Gallium-68 prostate-specific membrane antigen (Ga-68 PSMA) ligand (HBED-CC) is a new promising positron emission tomography (PET) tracer for prostate cancer. Intense renal parenchymal uptake is a physiologic finding on Ga-68 PSMA ligand PET images. Evaluation of kidneys in low intensity demonstrates excellent distribution of this radiotracer in renal parenchyma with excellent image quality and resolution. In this article, we present the Ga-68 PSMA ligand PET renal images of four patients with prostate cancer. In two patients, there is normal distribution of radiotracer, and in other two, there are renal cysts causing parenchymal defects.

Can 68Ga-DOTA Peptides Be Potential Radiotracers for PET Imaging of the Spleen?

On radionuclide somatostatin receptor imaging studies, the spleen shows high physiologic uptake. Reducing the intensity of the image settings helps to better assess the distribution of radiotracer in the spleen. In our routine studies, we incidentally recognized that 68Ga-DOTANOC PET provides higher-resolution splenic images than 111In-octreotide SPECT. Autoradiography and immunohistochemistry studies have shown that somatostatin receptors are located mainly in the red pulp of the spleen. The distribution of 68Ga-DOTANOC in the spleen appears to correlate with the distribution of red pulp. In this article, we present 68Ga-DOTANOC PET/CT spleen images of our patients.

Myocardial perfusion abnormalities in asymptomatic type 2 diabetic patients.

OBJECTIVE: The prevalence of coronary artery disease (CAD) is high in patients with diabetes. Because ischemia and infarction are often silent in diabetic patients, diagnosis of CAD occurs inevitably late. It is essential to identify the presence of CAD in diabetic patients to start early treatment. Therefore, the aim of this study was to determine the prevalence of abnormal myocardial perfusion in asymptomatic type 2 diabetic patients using myocardial perfusion imaging. METHODS: Fifty-nine patients with type 2 diabetes, who did not have any history of CAD, but did have risk factors underwent myocardial perfusion single-photon emission computed tomography (SPECT) imaging using 99mTc-tetrofosmin and a 2-day stress-rest protocol. Two nuclear medicine specialists independently interpreted the images. Statistical analysis was performed to determine if there is a correlation between the presence of perfusion abnormalities and the history of diabetes (duration of disease, type of treatment, level of control, and presence and type of complications). The influence of other factors such as age, sex, smoking history, and family history of CAD, with abnormal scans were also studied. RESULTS: Of the 59 patients, abnormal scans were detected in 22 (37%) including 16 with reversible defects due to stress-induced ischemia. Hence the prevalence was 37%. Duration of diabetes, use of insulin, nephropathy, and neuropathy were significantly associated with abnormal scans (p = 0.048, p = 0.045, p = 0.006, and p = 0.03, respectively). Additionally, positive family history of CAD was highly associated with perfusion abnormalities (p < 0.001). No significant association was found between other risk factors, such as hyperlipidemia and the presence of perfusion defects. CONCLUSIONS: We found a high prevalence of myocardial perfusion abnormalities in asymptomatic type 2 diabetic patients. Perfusion abnormalities on myocardial perfusion SPECT images were associated with disease duration, insulin use, nephropathy, and neuropathy. Asymptomatic diabetic patients might be candidates with CAD abnormalities that can be studied using myocardial perfusion SPECT.

The efficacy of the available peptide receptor radionuclide therapy for neuroendocrine tumors: a meta-analysis.

AIM: This study was carried out to compare the efficacy of Y, Lu, and combination of both radiotracers (tandem) peptide receptor radionuclide therapy (PRRT) in patients with inoperable and metastatic neuroendocrine tumors. MATERIALS AND METHODS: Systematic searches of PubMed and SciVerse Scopus databases were performed till December of 2016. The data were categorized into three groups: Y-PRRT, Lu-PRRT, and tandem-PRRT. Each group was subdivided on the basis of the response criteria used: Response Evaluation Criteria in Solid Tumors (RECIST) or Southwest Oncology Group (SWOG) criteria. Disease response and disease control rates of each group were analyzed. RESULTS: For the RECIST group, Y-PRRT disease response rates ranged from 22.81 to 56.1%, with a pooled random effect of 42.92%, and the disease control rate was 100%. Lu-PRRT disease response rates ranged from 27.63 to 57.35%, with a pooled random effect of 33.41%, and disease control rates ranged between 71.88 and 100%, with a pooled fixed effect of 79.32%. As for tandem-PRRT, disease response rates ranged between 42.11 and 66.67%, with a pooled fixed effect of 50.52%, and the disease control rate ranged between 93.33 and 100%, with a pooled fixed effect of 98.97%.For the SWOG group, Y-PRRT disease response rates ranged from 5.13 to 26.56%, with a pooled random effect of 13.4%, and disease control rates ranged between 76.56 and 85.9%, with a pooled fixed effect of 80.93%. Lu-PRRT disease response rates ranged from 6.06 to 60.29%, with a pooled random effect of 26.4%, and the disease control rates between 48.48 and 85.29%, with a pooled random effect of 74.53%. CONCLUSION: Y-PRRT had the highest disease control rates under both RECIST and SWOG criteria. Tandem-PRRT had the highest disease response rate in the RECIST criteria, indicating that PRRT should be customized to each patient individually for maximum benefit.

Scintigraphic Patterns of Indium-111 Oxine-Labeled White Blood Cell Imaging of Gram-Negative versus Gram-Positive Vertebral Osteomyelitis.

OBJECTIVE: The goal of the study was to investigate whether or not gram-negative organisms that secrete antichemotactic factors cause the nonaccumulation pattern of 111In-oxine-labeled white blood cell (111In-WBC) scans. MATERIALS AND METHODS: Staphylococcus aureus (gram-positive) (group 1) was injected into 25 rabbits and Escherichia coli (gram-negative) (group 2) into another 25 to induce infection in the lumbar vertebrae or left thigh bone (femur). Sixteen successfully infected and surviving rabbits from each group were used for imaging and analysis. Of the 16 rabbits, each group included 8 with vertebral infection and 8 with femur infection. For imaging, each rabbit was injected intravenously with 11.1 MBq (300 µCi) 111In-WBC, and images were acquired 24 h later. Microscopic histopathology was performed after decalcification to confirm osteomyelitis. RESULTS: The 111In-WBC accumulation was observed in 7 (87.5%) of the 8 rabbits infected with S. aureus in the vertebrae and thigh bone. Of the rabbits infected with the gram-negative vertebrae, 1 (12.5%) showed little accumulation of 111In-WBC. Of the 8 rabbits with gram-negative-infected femurs, 1 had high accumulation and another had low accumulation of 111In-WBC, while the rest did not show any uptake. Osteomyelitis was confirmed by histopathology in all the successfully infected rabbits used for imaging. CONCLUSION: In the majority of the gram-positive-infected rabbit vertebrae there was high accumulation of 111In-WBC. However, no accumulation of 111In-WBC was observed in most of the vertebrae infected with gram-negative organisms, which release antichemotactic factors that prevent adequate accumulation of WBC at the infected area.

Normal bone and soft tissue distribution of fluorine-18-sodium fluoride and artifacts on 18F-NaF PET/CT bone scan: a pictorial review.

Fluorine-18-sodium fluoride (F-NaF) PET/CT is a relatively new and high-resolution bone imaging modality. Since the use of F-NaF PET/CT has been increasing, it is important to accurately assess the images and be aware of normal distribution and major artifacts. In this pictorial review article, we will describe the normal uptake patterns of F-NaF in the bone tissues, particularly in complex structures, as well as its physiologic soft tissue distribution and certain artifacts seen on F-NaF PET/CT images.

Ultrastructure of Hyperfunctioning Parathyroid Glands: Does it Explain Various Patterns of 99mTc-sestamibi Uptake.

The aim of this study was to correlate the uptake of 99mTc-methoxy-isobutyl-isonitrile (MIBI) with ultra-structural features of parathyroid adenomas. Twenty patients with proven primary hyperparathyroidism were evaluated prospectively. Preoperative double-phase 99mTc-MIBI scintigraphy was performed in all patients and the degree of tracer uptake by the parathyroid lesions was assessed visually and semi-quantitatively. The excised glands were examined histologically and ultrastructurally, and their features were correlated with the degree of the radiotracer uptake. At surgery, 21 parathyroid adenomas were removed (double adenoma in one patient and a solitary adenoma in each of the remaining 19 patients). 99mTc-MIBI scan detected 18 of the 21 adenomas. There was positive correlation between the degree of 99mTc-MIBI uptake and the mitochondrial contents of the parathyroid adenoma cells. Four adenomas with intense uptake had high content of mitochondria in the cells. The three false-negative scans had low-to-moderate mitochondrial content. 99mTc-MIBI uptake is related to the mitochondrial content of the parathyroid adenoma cells.