Zohar Keidar

SPECT/CT hybrid imaging with 111In-pentetreotide in assessment of neuroendocrine tumours.

objective  Somatostatin receptor scintigraphy (SRS) of neuroendocrine (NE) tumours is often challenging because of minute lesion size and poor anatomic delineation. This study evaluates the impact of sequentially performed single‐photon emission computed tomography (SPECT)/CT fusion on SRS study interpretation and clinical management of these tumours.

Fever of Unknown Origin: The Role of 18F-FDG PET/CT

Fever of unknown origin (FUO) is a challenging diagnostic problem. Timely identification and precise localization of the causing process are critical for appropriate patient management. The present prospective study evaluates the role of PET/CT using 18F-FDG in the investigation of FUO. Methods: A total of 48 consecutive patients (25 men, 23 women; age range, 24–82 y) with FUO underwent 18F-FDG PET/CT scans. FUO was defined as a fever of more than 38.3°C that lasted for more than 3 wk and failure to reach diagnosis after more than 1 wk of inpatient investigation. The performance of PET/CT for identifying the etiology of FUO was assessed. Final diagnosis was based on histopathology, microbiologic assays, or clinical and imaging follow-up. Results: PET/CT detected suggestive foci of increased 18F-FDG uptake in 27 patients. In 22 of these 27 positive studies (81%), PET/CT identified the underlying disease and diagnosed infection in 9 patients, an inflammatory process in 10 patients, and malignancy in 3 patients. 18F-FDG PET/CT was negative in 21 patients. All these patients were diagnosed as having systemic nonfocal infection or drug-induced fever or showed spontaneous resolution of the febrile state with no further evidence of a localized inflammatory, infectious, or malignant process for a clinical follow-up period of 12–36 mo. Conclusion: 18F-FDG PET/CT identified the underlying cause of the fever in 46% of the present study population and contributed to the diagnosis or exclusion of a focal pathologic etiology of the febrile state in 90% of patients. 18F-FDG PET/CT has a high negative predictive value (100%) for assessment of FUO. If confirmed by further studies, 18F-FDG PET/CT may be used in the future as an initial noninvasive diagnostic modality for assessment of this group of patients.

Prosthetic Vascular Graft Infection: The Role of 18F-FDG PET/CT

Graft infection after prosthetic vascular reconstruction is an uncommon but severe complication. The clinical presentation is often subtle and nonspecific and may occur long after surgery. Although defining a prosthetic vascular graft infection can be difficult, early diagnosis and treatment are important because of the relatively high rates of amputation and death. The present study assessed the role of PET/CT using 18F-FDG for the diagnosis of vascular graft infections. Methods: Thirty-nine patients (35 men and 4 women; age range, 44–82 y) with suspected vascular graft infection underwent 18F-FDG PET/CT. The performance of PET/CT for the diagnosis of an infectious process and its localization to the graft or soft tissues was assessed. The final diagnosis was based on histopathologic findings and microbiologic assays obtained at surgery or on clinical and imaging follow-up. Results: PET/CT detected foci of increased 18F-FDG uptake suspected as infection in 27 patients and localized these findings to the graft in 16 patients. Vascular graft infection was confirmed in 14 of these patients (88%). PET/CT excluded graft involvement in 11 patients, and in 10 (91%) of these 11, long-term follow-up further confirmed that the infectious process was limited to surrounding soft tissues only. No abnormal 18F-FDG uptake was found in any of the 12 patients with no further evidence of infection. PET/CT had a sensitivity of 93%, specificity of 91%, positive predictive value of 88%, and negative predictive value of 96% for the diagnosis of vascular graft infection. Conclusion: 18F-FDG PET/CT is a reliable noninvasive imaging modality for the diagnosis of vascular graft–related infection. The precise anatomic localization of increased 18F-FDG uptake provided by PET/CT enables accurate differentiation between graft and soft-tissue infection.

Technetium-99m-MIBI SPECT/CT in Primary Hyperparathyroidism

The novel trend toward focused parathyroidectomy requires precise preoperative localization of the parathyroid adenoma in patients with primary hyperparathyroidism (PHPT). The present study evaluated the impact of hybrid single photon emission computed tomography/computed tomography (SPECT/CT), using 99mTc-sestamibi (MIBI), on the surgical management of these patients. In a retrospective study of 36 patients with PHPT, SPECT/CT was undertaken when planar 99mTc-MIBI scintigraphy was negative or when an ill-defined focus in the neck or an ectopic site on planar views was visualized. Imaging data were compared with intraoperative findings, and the incremental value of SPECT/CT to lesion localization and surgical procedure was assessed. Three patients with both negative planar and SPECT/CT studies subsequently underwent bilateral neck exploration, with multiglandular hyperplasia diagnosed in two patients and a parathyroid adenoma in one. Of 33 patients with a positive MIBI study, parathyroid adenoma was confined to the neck in 23 patients and to the lower neck-mediastinum in 10. SPECT/CT facilitated the surgical exploration of all 10 ectopic parathyroid adenomas and 4 of 23 cervical parathyroid adenomas, the latter four either at reexploration or in patients with nonvisualization of the thyroid after thyroidectomy. SPECT/CT contributed to the localization of parathyroid adenomas in patients with PHPT and to planning the surgical exploration in 14 of 36 (39%) patients, predominantly those with ectopic parathyroid adenomas or who had distorted neck anatomy.

The additional value of PET/CT over PET in FDG imaging of oesophageal cancer

PurposeThe aim of this study was to assess the value of combined PET/CT compared with PET reviewed side-by-side with CT, in patients with oesophageal cancer, before and after surgery.MethodsForty-one FDG PET/CT studies were performed in 32 patients with oesophageal cancer, before surgery (n=18) or during follow-up after resection of the primary tumour (n=23). One hundred and fifteen sites suspicious for malignancy were evaluated. PET/CT was prospectively compared with PET reviewed side-by-side with CT, for detection, accurate localisation and characterisation of malignant sites. PET/CT performance in different anatomical regions was compared before and after surgery. The impact of fused data on patient management was retrospectively assessed.Results PET/CT had an incremental value over PET for interpretation of 25 of 115 sites (22%), changing the initial characterisation of ten sites to either malignant (n=1) or benign (n=9), and defining the precise anatomical location of 15 sites. PET/CT provided better specificity and accuracy than PET for detecting sites of oesophageal cancer (81% and 90% vs 59% and 83% respectively, p<0.01). Fusion was of special value for interpretation of cervical and abdomino-pelvic sites, for disease assessment in loco-regional lymph nodes before surgery and in regions of postoperative anatomical distortion. PET/CT had an impact on the further management of four patients (10%), by detecting nodal metastases that warranted disease upstaging (n=2) and by excluding disease in sites of benign uptake after surgery (n=2).ConclusionPET/CT improves the accuracy of FDG imaging in oesophageal cancer and provides data of diagnostic and therapeutic significance for further patient management.

Correction of Heart Motion Due to Respiration in Clinical Myocardial Perfusion SPECT Scans Using Respiratory Gating

Several studies have described nonuniform blurring of myocardial perfusion imaging (MPI) due to respiration. This article describes a technique for correcting the respiration effect and assesses its effectiveness in clinical studies. Methods: Simulated phantoms, physical phantoms, and patient scans were used in this study. A heart phantom, which oscillated back and forth, was used to simulate respiration. The motion was measured on a γ-camera supporting list-mode functionality synchronized with an external respiratory strap or resistor sensor. Eight clinical scans were performed using a 1-d 99mTc-sestamibi protocol while recording the respiratory signal. The list-mode capability along with the strap or sensor signals was used to generate respiratory bin projection sets. A segmentation process was used to detect the shift between the respiratory bins. This shift was further projected to the acquired projection images for correction of the respiratory motion. The process was applied to the phantom and patient studies, and the rate of success of the correction was assessed using the conventional bulls eye maps. Results: The algorithm provided a good correction for the phantom studies. The shift after the correction, measured by a fitted ellipsoid, was <1 mm in the axial direction. The average motion due to respiration in the clinical studies was 9.1 mm in the axial direction. The average shift between the respiratory phases was reduced to 0.5 mm after correction. The maximal change in the bulls eye map for the clinical scans after the correction was 6%, with a mean of 3.75%. The postcorrection clinical summed perfusion images were more uniform, consistent, and, for some patients, clinically significant when compared with the images before correction for respiration. Conclusion: Myocardial motion generated by respiration during MPI SPECT affects perfusion image quality and accuracy. Motion introduced by respiration can be corrected using the proposed method. The degree of correction depends on the patient respiratory pattern and can be of clinical significance in certain cases.

Do Hyperglycemia and Diabetes Affect the Incidence of False-Negative 18F-FDG PET/CT Studies in Patients Evaluated for Infection or Inflammation and Cancer? A Comparative Analysis

Diabetes mellitus (DM) is a common metabolic disorder. Hyperglycemia occurs in a significant proportion of patients with uncontrolled DM but can also be found in patients without diabetes. Although the relationship between 18F-FDG uptake in malignant tumors and blood glucose levels has been previously addressed, it has not been investigated in cases of infection and inflammation, despite the high incidence of these entities in diabetic patients. The current study assessed whether hyperglycemia and DM affect the detectability rate of disease in 18F-FDG PET/CT studies performed for patients with suspected infectious and inflammatory processes, as compared with a group of patients with malignant tumors. Methods: 18F-FDG PET/CT studies of 123 consecutive patients investigated for suspected infection or inflammation and 320 patients evaluated for malignancy were retrospectively analyzed. The presence of DM and the level of glucose at the time of the study were recorded. Differences between the 2 study populations in false-negative (FN) rates in patients with and without hyperglycemia and DM were compared and analyzed for statistical significance. Results: In the infection or inflammation group, 19 of 123 patients (15%) had serum glucose levels greater than 180 mg/dL and 43 of 123 (35%) had DM. There were no FN studies in patients with hyperglycemia and 4 FN studies in patients with normal glucose levels. There were 2 FN studies each in patients with and without DM. Neither glucose levels nor DM affects the detection rate of infection or inflammation with 18F-FDG PET/CT. In the oncology group, 84 of 320 patients (26%) had serum glucose levels greater than 180 mg/dL and 183 of 320 (57%) had DM. There were 6 FN studies in cancer patients with hyperglycemia and 7 in patients with normal glucose levels. There were 8 FN studies in cancer patients with DM and 5 FN studies in patients without DM. Higher glucose levels but not DM affected the detection rate of malignancy with 18F-FDG PET/CT. Conclusion: High glucose levels at the time of the study but not DM may reduce the sensitivity of 18F-FDG PET/CT in the assessment of malignancy. No significant impact on the FN rate was found in patients with infection and inflammatory processes with either DM or hyperglycemia.

Fluorodeoxyglucose-positron emission tomography/computed tomography imaging in patients with carcinoma of the larynx: diagnostic accuracy and impact on clinical management.

Objectives: The objectives of this study were to assess the value of 18F‐fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in patients with carcinoma of the larynx as compared with PET and CT alone and to assess the impact of PET/CT on further clinical management.

Hybrid Imaging (SPECT/CT and PET/CT)—Improving the Diagnostic Accuracy of Functional/Metabolic and Anatomic Imaging

In-line combined systems, single-photon emission computed tomography (SPECT)/computed tomography (CT) and positron emission tomography (PET)/CT, allow an instant generation of fused images of scintigraphy and CT data. The accumulated clinical data on the use of these systems in various clinical scenarios indicate that this hybrid technology improves the diagnostic accuracy as compared to scintigraphy and CT alone and even to side-by-side interpretation of scintigraphy and CT, which were acquired separately. The improved diagnostic accuracy is reflected by improving image quality of SPECT and PET, detection of more clinically relevant lesions, better localization of disease and differentiation between physiologic and pathologic uptake, characterization of disease by its functional and morphologic appearance before and after therapy and accurate delineation of disease, optimizing biopsy and therapy planning.

The role of FDG-PET/CT imaging in head and neck malignant conditions: impact on diagnostic accuracy and patient care.

BACKGROUND: To assess the value of positron emission tomography/computed tomography (PET/CT) with 18 F-Fluorodeoxyglucose (FDG) in patients with head and neck carcinoma as compared with PET and conventional imaging alone, and to assess the impact of PET/CT on further clinical management. STUDY DESIGN: Prospective nonrandomized study. SETTING: Ninety patients with head and neck tumors had 107 PET/CT examinations. RESULTS: The study analysis showed that PET/CT had a sensitivity of 89%, specificity 95%, PPV 94%, NPV 90%, and accuracy of 92%. PET/CT altered management in 51 patients (56%). PET/CT eliminated the need for previously planned diagnostic procedures in 24 patients, induced a change in the planned therapeutic approach in 21 patients and guided biopsy in 6 patients. CONCLUSIONS: PET/CT is an imaging modality with high diagnostic performance in the assessment of head and neck cancer, and induced a change in further clinical management in more than half of the study population.