Hybrid imaging of neuroendocrine tumors in the heart: Union is strength.

Cardiac neuroendocrine tumors (NETs) are particularly rare tumors that can lead to a very poor clinical outcome, partly because of metastases but mainly because of manifestations of the hormonal activity they exhibit. Prompt diagnosis is important in order to start the most effective treatment for their removal or management, with the fewest complications. They are often difficult to diagnose, especially in their early stages. One of the reasons for this is that the heart is an organ with a high rate of metabolism and is located in close proximity to other high-metabolism organs. In addition, the anatomic location and their small size render their diagnosis extremely challenging. In recent years, hybrid imaging methods have revolutionized the diagnostic approach to oncology patients and have established a place in the diagnosis of cardiac NETs, because they provide both anatomical and functional information at the same time. Positron emission tomography/computed tomography (PET/CT), PET/magnetic resonance imaging (PET/MRI) and single-photon emission computed tomography/CT (SPECT/CT) are widely used in clinical practice because of the very important metabolic information, the high sensitivity and specificity. However, prospective studies are needed to confirm the true clinical and prognostic value of various hybrid imaging diagnostic techniques in cardiac NETs.

SPECT/CT SUV-based metrics: A promising diagnostic tool in classifying patients with suspected transthyretin cardiac amyloidosis among the different Perugini grades?

OBJECTIVE: The purpose of this study was to evaluate the contribution of single photon emission computed tomography/computed tomography (SPECT/CT) standardized uptake value (SUV) metrics in classifying patients with suspected transthyretin cardiac amyloidosis (ATTR-CA) among the different Perugini grades. SUBJECTS AND METHODS: One hundred four patients suspected of ATTR-CA underwent planar scintigraphy with bone seeking tracer (99mTc pyrophosphate-PYP). Patients were classified according to the Perugini scale, the H/CL, H/Bone and H/Bkg ratios. A subset of 48 patients received additional SPECT/CT. Single photon emission computed tomography/CT SUV quantitative parameters, of the heart, myocardium, lungs, liver, soft tissues, bone, and SUV ratios (SUVmaxmyo, SUVmaxlungs, SUVmaxliver, SUVmaxbone and SUVmaxsoft tissue ratios), were evaluated in order to investigate potential metrics that could more clearly differentiate Perugini grades. RESULTS: A total of 33.7% of patients were considered grade 0, 34.6% grade 1 and 31.7% grade 2/3. A combination of H/CL >1.33 and H/Bone >0.85 showed the highest sensitivity 100%. Standardized uptake value-based metrics clearly differentiated grade 0 or 1 vs grades 2 or 3, whereas no significant difference was found between grades 0 and 1, or between grades 1 and 2. The combined cut-off values H/CL 1.33 and SUVmaxmyo 2.88 yielded 100% sensitivity and 84.6% specificity in differentiating ATTR-CA positives vs negatives. The metric SUVmaxmyo/SUVmaxliver was the best metric to classify patients with grade 1 as negative (grade 0) or positive (grade 2 or 3). CONCLUSION: Single photon emission computed tomography/CT SUV metrics could be complementary to planar scintigraphy in classifying patients among the different Perugini grades. The ratio SUVmaxmyo/SUVmaxliver was the only parameter with high affinity to differentiate patients with grade 1, as grade 0 or grade 2/3 for ATTR-CA.

The clinical utility of SPECT/CT hybrid imaging on bleeding Meckel's diverticulum in adults.

Technetium-99m pertechnetate planar scintigraphy is the procedure of choice to localize ectopic gastric mucosa. However, single photon emission computed tomography/computed tomography (SPECT/CT) provides precise landmarks and scintigraphic findings. We report a case of an adult patient with Meckel's diverticulum involving an atypical location, within the pelvic region, next to the right margin of the urinary bladder. Imaging characteristics supported the diagnosis of either Meckel's or bladder diverticulum. Single photon emission computed tomography /CT was the key method to obtain definite diagnosis, since the low-dose CT revealed the presence of air within the lesion of radiotracer uptake. This finding was suggestive of an outpouching of the bowel wall.

Alterations of global gastrointestinal motility after sleeve gastrectomy: a prospective study.

OBJECTIVES: To evaluate the role of sleeve gastrectomy (SG) in gastrointestinal motility. BACKGROUND: SG is a widely used bariatric operation leading to weight loss and early improvement of patient's metabolic profile. Current data indicate faster postoperative gastric emptying, but detailed studies on alterations in small bowel motility are missing. DESIGN: We evaluated 21 morbidly obese patients who underwent laparoscopic SG before and 4 months after the procedure. After consumption of a semisolid radiolabeled meal, their gastric and intestinal transit times were studied with a gamma camera. Particularly the times of 10% gastric emptying, 50% gastric emptying, maximal intestinal filling, 10% terminal ileum filling, duodenal to terminal ileum transit, cecal filling initiation, and ileocecal valve transit (T ICVt) were studied pre- and postoperatively. RESULTS: Ten percent gastric emptying and 50% gastric emptying were decreased postoperatively as well as maximal intestinal filling, indicating faster gastric emptying and intestinal filling. Duodenal to terminal ileum transit and 10% terminal ileum filling also decreased as small bowel transit time accelerated and the meal reached the terminal ileum more rapidly. Contrary opening of the ileocecal valve and food transit through it were delayed, with postoperative increase in cecal filling initiation and T ICVt, respectively. CONCLUSIONS: SG accelerates gastric emptying and small bowel transit of semisolids. In addition, it delays the initiation of cecal filling and T ICVt. This early and prolonged contact of food with the distal small bowel mucosa may explain the metabolic effects of SG occurring before substantial weight loss.

The impact of sentinel lymph node mapping with hybrid single photon emission computed tomography/computed tomography in patients with melanoma. Comparison to planar radioisotopic lymphoscintigraphy.

We studied the diagnostic value of 16 slices of single photon emission computed tomography (SPECT)/computed tomography (CT) in the anatomical localization, image interpretation and extra-sentinel lymph nodes (SLNs) detection compared to dynamic and static planar radioisotopic lymphoscintigraphy (PLS) in patients with melanoma. Eighty-two patients with melanoma underwent dynamic PLS, static PLS and SPECT/CT. Data were obtained using a dual head SPECT/CT 16 slices γ-camera. We evaluated the number and localization of SLNs detected with each imaging method. SPECT/CT demonstrated 48 additional SLNs in comparison with PLS in 29 patients. In five truncal and seven head-neck lesions, dynamic and static PLS failed to detect the SLNs found on SPECT/CT (false negative). In one case of truncal and one case of lower limb melanoma, the foci of increased activity interpreted on PLS as possible SLNs were confirmed to be non-nodal sites of uptake on SPECT/CT (false positive). PLS underestimated the number of SLNs detected, whereas SPECT/CT revealed higher agreement compared to the respective number from histological reports. SPECT/CT showed a better prediction of the number of SLNs and higher diagnostic parameters in comparison to planar imaging. SPECT/CT is an important complementary diagnostic modality to PLS, that improves detection, preoperative evaluation, anatomical landmarks of SLNs and surgical management of patients with melanoma.

Cardiac autonomic disturbances in patients with vasovagal syndrome: comparison between iodine-123-metaiodobenzylguanidine myocardial scintigraphy and heart rate variability.

AIMS: The aim of this study was to examine autonomic disorders in patients with different types of vasovagal syndrome by performing both a cardiac sympathetic innervation evaluation and a head-up tilt-test with heart rate variability (HRV) analysis. METHODS AND RESULTS: We enrolled 60 patients with vasovagal syncope (32 women, mean age 40 ± 16 years), and 20 age-matched controls. We assessed the integrity and function of the myocardial pre-synaptic nerve endings and in the sympathovagal activity, using (123)I-metaiodobenzylguanidine (MIBG) scintigraphy and time-domain indexes of HRV. A significantly lower heart/mediastinum ratio was found in the syncopal patients compared with the control group, both at 10 min (1.9 ± 0.25 vs. 3.6 ± 1.7, P = 0.02) and at 4 h (1.79 ± 0.12 vs. 2.07 ± 0.19, P = 0.04), whereas washout rate was significantly greater in syncopal patients (5.5 ± 3.7 vs. 2 ± 0.19, P = 0.04). There were no significant differences in any of the above parameters between patients with different types of syncope. In addition, the majority of the patients showed multiple adrenergic innervation defects in the left ventricular myocardium. No significant difference was found in any of the HRV time-domain indexes. However, a correlation was found between root-mean-square of the difference between successive RRs and washout rate in syncopal patients (r = -0.256, P = 0.48). CONCLUSION: Patients with vasovagal syncope induced by tilt testing reveal a high degree of disturbance of myocardial adrenergic innervation and multiple adrenergic innervation defects. This suggests a possible predominance of cardiac adrenergic activity in those with abnormal cardiac MIBG scintigraphy.

Pelvic hypoplastic kidney in a patient with Williams-Beuren syndrome.

Renal and renovascular abnormalities constitute features of the Williams-Beuren syndrome (WBS), one multisystem genetic disorder in childhood, caused by a microdeletion of chromosome 7. We report a 12 years old boy who was diagnosed with WBS and had an ectopic pelvic hypoplastic left kidney, detected by ultrasonography and renal scintigraphy. Dystopic hypoplastic kidney is an infrequent finding in patients with WBS and our report showed the importance of a complete clinical and laboratory study of renal function in WBS.

Clinical impact of targeted single-photon emission computed tomography/computed tomography (SPECT/CT) bone scintigraphy on the assessment of bone metastasis in cancer patients.

OBJECTIVES: We investigated the clinical impact of single-photon emission computed tomography/computed tomography (SPECT/CT) bone scintigraphy combined with 16-slice CT on metastatic workup and treatment planning in a large cancer patient series. METHODS: Between January 2019 and January 2020, a total of 600 cancer patients were prospectively evaluated with whole-body planar bone scan (wbPBS) for staging or restaging purposes. 272/600 had equivocal lesions on wbPBS and 265/272 underwent additionally a targeted SPECT/CT bone scintigraphy on designated regions. Findings were classified as benign (score 1), metastatic (score 2) and inconclusive (score 3). Findings from SPECT/CT bone scintigraphy were compared with the results of wbPBS. RESULTS: A total of 668 lesions were considered as unclear οn wbPBS and were re-evaluated through targeted SPECT/CT bone scintigraphy. Definite diagnostic findings on SPECT/CT bone scintigraphy were obtained in 227/265 (85.7%) patients and in 592/668 (88.6%) lesions vs. 15.4% of wbPBS alone. On per-patient analyses, 38.9% of patients were considered definitely nonmetastatic and 46.8% as definitely metastatic. On per lesion analyses using SPECT/CT bone scintigraphy, corresponding diagnostic rates were 47.5 and 41.2%. Although the addition of SPECT/CT bone scintigraphy significantly reduced the rate of equivocal wbPBS results (83.1%), it failed to provide a conclusive diagnosis in a relatively small proportion of lesions 76/668 (11.4%) in 38 patients. CONCLUSIONS: SPECT/CT bone scintigraphy afforded a significant reduction of the number of patients with equivocal findings who needed further evaluation with other imaging modalities, preventing unnecessary delays in diagnosis and potential changes in disease staging and treatment planning. Moreover, SPECT/CT bone scintigraphy slightly increased diagnostic sensitivity.

The role of scintigraphy in the evaluation of brain malignancies.

The gold standard for diagnosis of primary brain tumors is histopathological evaluation of the obtained tissue samples. Nevertheless, anatomical and functional imaging modalities have a determinative role in the precise localization and characterization of these lesions. In this review we focus on the clinical applications and future potentials of nuclear medicine procedures. Several single photon emission tomography (SPET) tracers such as thallium-201 chloride ((201)TlCl(2)), technetium-99m ((99m)Tc) methoxyisobutylisonitrile (MIBI), (99m)Tc-tetrofosmin (TF) and 3-[iodine-123] iodo-α- methyl-L-tyrosine ((123)I-IMT) have been utilized in the diagnosis of brain tumors. Positron emission tomography (PET) alone or fused with computed tomography (CT), are widely acceptable methods in oncology, at present and for the future.

Is There Any Clinical Value of Adding 123I-Metaiodobenzylguanidine Myocardial Scintigraphy to 123I-Ioflupane (DaTscan) in the Differential Diagnosis of Parkinsonism?

PURPOSE: The aim of the study is to evaluate the impact of myocardial I-metaiodobenzylguanidine (MIBG) in the diagnosis, clinical management, and differential diagnosis of Parkinson disease (PD) and non-PD parkinsonism. METHODS: The study enrolled 41 patients with parkinsonism. An initial diagnosis was reached after thorough clinical and imaging evaluation. After 2 to 5 years of follow-up, a final diagnosis was established. All patients underwent, soon after their initial visit, presynaptic striatal DaT scintigraphy with I-FP-CIT (DaTscan) and I-MIBG myocardial scintigraphy. DaTscan is not specific to distinguish among different types of neurodegenerative parkinsonism. I-MIBG myocardial scintigraphy displays the functional status of cardiac sympathetic nerves, which is reduced in PD/dementia with Lewy bodies (DLB) and normal in atypical parkinsonian syndromes and secondary or nondegenerative parkinsonism. RESULTS: No patients showed adverse effects during or after both scintigraphies. A positive DaTscan was found in all patients in the PD/DLB group (17/17) and in 15 of 24 patients in the non-PD group. Myocardial I-MIBG scintigraphy was associated with lower sensitivity (82% vs 100%) but higher specificity than DaTscan (79% vs 38%) in diagnosis PD/DLB from non-PD parkinsonism. A positive scan result on both techniques, to confirm diagnosis of PD/DLB, significantly improved the specificity of DaTscan, from 38% to 75%, with no reduction in sensitivity. CONCLUSIONS: Myocardial I-MIBG imaging provides complementary value to I-FP-CIT in the proper diagnosis, treatment plan, and differential diagnosis between PD and other forms of parkinsonism.

Is there any benefit from sentinel lymph node biopsy using the combined radioisotope/dye technique in breast cancer patients with clinically negative axilla?

OBJECTIVE: We evaluated the eventual benefits from sentinel lymph node biopsy (SLNB) in comparison with axillary lymph node dissection (ALND) using a combined radioisotope/dye technique versus dye alone in breast cancer patients. METHODS: SLNB was performed in 501 breast cancer patients (250 patients with dye alone and 251 with combined technique). Patients were divided in three groups: (A) clinical stage T1,2N0 (SLNB followed by ALND only in cases with positive histology), (B) clinical stage T1,2N0 (SLNB followed by ALND), and (C): advanced clinical stage (SLNB immediately followed by ALND). The incidence of recurrences and surgery morbidity was comparatively evaluated. RESULTS: The overall successful identification rate in patients of groups A and B was 97.7% (95.3% with dye and 99.3% with dye and isotope, P = 0.04) and in patients of group C 96.1% (93.3% with dye and 1000% with the combined technique, P = 0.02). The false-negative rate did not reach statistical significance between groups. Although locoregional recurrence rate was similar in groups A and B (less than 1.88%) the distant metastasis rate was significantly lower in group A (0.9 vs. 6.6%, P = 0.04). Arm edema was significantly more frequent in group B (0 vs. 5.3%, P = 0.02). CONCLUSION: The combined technique, improves the ID rate of SLNs in patients with breast cancer. The recurrence rate in the axilla was negligible and the metastasis-free rate was better in patients treated with SLNB alone, which further supports the concept that ALND has no clinical relevance and adds nothing more than morbidity to breast cancer patients with clinically node-negative disease.

Sleeve gastrectomy-a "food limiting" operation.

BACKGROUND: Sleeve gastrectomy (SG), which, thus far, is showing good resolution of comorbidities and good weight loss, shows increasing popularity among bariatric surgeons. The aim of this study was to evaluate clinical outcome and the gastric emptying of solid foods, 24 months after SG. METHODS: Fourteen morbidly obese patients, four males and ten females, median age 41 years (range 29-65), median body mass index (BMI) 49.46 kg/m(2) (range 41.14-55.63), who underwent SG for weight loss, were studied prospectively. Nine patients underwent gastric emptying studies, using radioisotopic technique before, 6 months and 24 months after the operation. The remaining five patients underwent gastric emptying studies, 6 months and 24 months after the operation. RESULTS: A significant reduction in patients' weight and BMI was evident at 6, 12 and 24 months postoperatively. In the nine patients who underwent gastric emptying studies pre-, 6 and 24 months postoperatively, the T-lag phase duration significantly decreased, following the SG, from 17.30 (range 15.50-20.90) min, to 12.50 (range 9.20-18.00) min at 6 months and 12.16 (range 10.90-20.00) min at 24 months postoperatively (P < 0.05). The gastric emptying half time (T1/2) accelerated significantly postoperatively from 86.50 (range 77.50-104.60) min, to 62.50 (range 46.30-80.00) min at 6 months and 60.80 (range 54.80-100.00) min at 24 months after SG (P < 0.05). The percentage of gastric emptying (%GE) increased significantly postoperatively, from 52 (range 43-58) % to 72 (range 57-97) % at 6 months and 74 (range 45-82) % at 24 months, following SG (P < 0.05). No differences in gastric emptying were observed, when values at 24 months were compared to those at 6 months postoperatively. When the whole group of 14 patients was studied, there were also no significant changes in T-lag, T1/2 and %GE between 6 and 24 months postoperatively. CONCLUSIONS: Our study indicates the constant effect of SG in the acceleration of gastric emptying of solids, which occurs faster, not only in short but also in long-term postoperatively. Such effects on gastric motility, in combination with the reported alterations in gut hormones, may explain how this 'food limiting' operation results in weight loss.

Active inflammatory bowel disease: head-to-head comparison between 99mTc-hexamethylpropylene amine oxime white blood cells and 99mTc(V)-dimercaptosuccinic acid scintigraphy.

PURPOSE: Evaluation and comparison between pentavalent 99mTc dimercaptosuccinic acid (99mTc(V)-DMSA) and 99mTc-hexamethylpropylene amine oxime white blood cell (99mTc-HMPAO WBC) scintigraphy in the detection and assessment of disease activity in patients with active inflammatory bowel disease (IBD). MATERIALS AND METHODS: 99mTc(V)-DMSA scintigraphy was performed in 23 patients with active IBD and true positive 99mTc-HMPAO WBC scintigraphy. Images were considered positive when an area of increased uptake was observed. To assess severity of IBD, semi-quantitative analysis was included with reference to the uptake in the iliac crest. Comparison with endoscopic, radiological and clinical data was performed. RESULTS: The diagnostic accuracy of 99mTc-HMPAO WBC and 99mTc(V)-DMSA was 91% and 84%, respectively. A significant correlation between the findings of both radioisotopic methods and scintigraphy score was demonstrated. Endoscopic findings were significantly correlated with scintigraphic results. Kappa statistics showed a moderate to good agreement between the two scintigraphic methods. Two patients (8.8%) had negative findings with 99mTc(V)-DMSA scintigraphy (false negative results). CONCLUSION: 99mTc(V)-DMSA compared to 99mTc-HMPAO WBC could provide a simple, non-invasive alternative method for the assessment of disease activity, although it is slightly inferior to 99mTc-HMPAO WBC scintigraphy especially in the evaluation of disease localization in IBD patients.

Does lung perfusion scintigraphy continue to have a role in the clinical management of patients suspected of pulmonary embolism in the CT pulmonary angiography era?

OBJECTIVE: Acute pulmonary embolism (PE) is a life-threatening disorder with high mortality. A prompt diagnosis and treatment is essential for reducing the mortality rate. The purpose of the study is to evaluate if lung perfusion scintigraphy (LPS) continues to have a role in the clinical management of patients suspected of pulmonary embolism in the CT pulmonary angiography (CTPA) era. METHODS: For this study, 1183 patients who had been subjected to LPS were retrospectively evaluated and classified into the following groups: A (positive LPS), B (negative LPS) and C (indeterminate LPS). Patients were further classified into A1 ('PE likely' and LPS-negative), B1 (PE unlikely and LPS-positive) and C1 (PE likely and indeterminate LPS) by combining the LPS findings and the clinical pretest probability (cpp). Subgroups A1, B1 and C1 underwent additional CTPA. RESULTS: Groups A, B, and C included 1086/1183, 69/1183 and 28/1183 patients, respectively. The proportion of patients with inconsistent cpp LPS findings who underwent additional CTPA was 106/1183 patients: subgroup A1 (n = 73), B1 (n = 21), and C1 (n = 12). In subgroup A1, CTPA was negative in 61/73, non-diagnostic in 12/73 and positive in 0/73 patients. In subgroup B1, CTPA excluded PE in 2/21, non-diagnostic in 3/21 and positive in 16/21 patients. In group C1, CTPA was negative in 8/12, positive in 2/12 and non-diagnostic in 2/12 patients. CONCLUSION: In the CTPA era, LPS continues to have a role in the clinical management of patients suspected of PE.

Renal artery stenting for atherosclerotic renal artery stenosis identified in patients with coronary artery disease: Does captopril renal scintigraphy predict outcomes?

The authors evaluated the effectiveness of percutaneous renal revascularization (PRR) with stenting for the treatment of atherosclerotic renal artery stenosis (ARAS) in patients with coronary artery disease and the usefulness of captopril renal scintigraphy for predicting clinical outcomes after PRR. Sixty-four consecutive patients, referred for evaluation of suspected ARAS, after coronary angiography, underwent baseline captopril renal scintigraphy followed by renal angiography. Forty-four patients (68.7%) were diagnosed with a significant ARAS≥ 60% and were treated with PRR plus medical therapy. Twenty-four months after PRR, 86.4% and 73.3% of patients showed a hypertension and renal benefit, respectively. Captopril renal scintigraphy positivity had moderate sensitivity and high specificity in predicting a hypertension and renal benefit. In patients with ARAS≥ 70%, the sensitivity and specificity were 100% for both a hypertension and renal benefit.PRR for ARAS conferred a substantial benefit in patients with a high coronary artery disease burden. Captopril renal scintigraphy was highly accurate in predicting clinical outcomes.

Diagnostic efficacy of technetium-99m pentavalent-dimercapto succinic acid versus gallium-67 citrate, imaging in patients with highly suspected acute bone and joint infections.

The purpose of this study was to evaluate and compare the diagnostic efficacy of (99m)Tc(V) dimercaptosuccinic acid ((99m)Tc(V)DMSA) with the (67)Ga-citrare ((67)Ga-C) scintigraphy in patients with suspected bone and joint infection. Thirty one patients, 19 men and 12 women, aged 18-78 y with median age 56 y, with suspected acute bone infection, were enrolled in this study. Besides (67)Ga-C and (99m)Tc(V)DMSA scintigraphy, all patients underwent X-ray radiography and technetium-99m methylene disphosphonate ((99m)Tc-MDP) bone scan for supporting the initial diagnosis. The (99m)Tc-MDP bone scan was considered positive for acute bone and joint infection when all its four scintigraphic phases were positive. Final diagnosis was based on needle aspiration and/or biopsy findings. Sensitivity, specificity, accuracy, positive and negative predictive values (PPV and NPV) were calculated. Our results have shown the following: Seventeen patients (17/31) had histologically confirmed acute bone and joint infections, while the remaining patients had no infection. (99m)Tc(V)DMSA diagnosed bone and joint infections in all positive (17/31) patients while (67)Ga-C in 16/31 patients. Discordant scintigraphic results were observed by (67)Ga-C in 2/31 cases: in one positive case of femur postoperative infection (false negative for (67)Ga-C) and in one case of clinicaly suspected infection in the femur while the patient had a preexisting fracture (false positive with (67)Ga-C). No false negative results were observed with (99m)Tc(V)DMSA. Sensitivity, specificity, PPV, NPV and accuracy were maximum for (99m)Tc(V)DMSA, while for (67)Ga-C were: 94.1%, 93%, 94.1%, 93%, and 93.5% respectively. It is concluded that considering the high sensitivity and specificity of (99m)Tc(V)DMSA in the detection of acute bone and joint infections, the lower radiation dose, the cost and the shorter time spent for the imaging procedure, as compared to (67)Ga-C, (99m)Tc(V)DMSA should be preferred to (67)Ga-C as a bone scan agent for the detection of acute bone and joint infections.

The Benefits of Prone SPECT Myocardial Perfusion Imaging in Reducing Both Artifact Defects and Patient Radiation Exposure.

BACKGROUND: Prone imaging has been demonstrated to minimize diaphragmatic and breast tissue attenuation. OBJECTIVES: To determine the role of prone imaging on the reduction of unnecessary rest perfusion studies and coronary angiographies performed, thus decreasing investigation time and radiation exposure. METHODS: We examined 139 patients, 120 with an inferior wall and 19 with an anterior wall perfusion defect that might represented attenuation artifact. Post-stress images were acquired in both the supine and prone position. Coronary angiography was used as the "gold standard" for evaluating coronary artery patency. The study was terminated and rest imaging was obviated in the presence of complete improvement of the defect in the prone position. Quantitative interpretation was performed. Results were compared with clinical data and coronary angiographic findings. RESULTS: Prone acquisition correctly revealed defect improvement in 89 patients (89/120) with inferior wall and 12 patients (12/19) with anterior wall attenuation artifact. Quantitative analysis demonstrated statistically significant difference in the mean summed stress scores (SSS) of supine and mean SSS of prone studies in patients with disappearing inferior wall defect in the prone position and patent right coronary artery (true negative results). The mean difference between SSS in supine and in prone position was higher with disappearing than with remaining defects. CONCLUSION: Technetium-99m (Tc-99m) tetrofosmin myocardial perfusion imaging with the patient in the prone position overcomes soft tissue attenuation; moreover it provides an inexpensive, accurate approach to limit the number of unnecessary rest perfusion studies and coronary angiographies performed.