FDG SPECT in patients with lung masses.

STUDY OBJECTIVES: To determine whether 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) single-photon emission CT (SPECT) is useful in characterizing pulmonary masses. DESIGN: Scans were prospectively acquired and interpreted. Interpretations were performed with CT or chest radiograph but interpreters were blinded to eventual diagnosis. SETTING: University hospital practice and affiliated Veterans Administration medical center. PATIENTS OR PARTICIPANTS: Forty patients participated as part of an institutional review board-approved research protocol, and informed consent was obtained in all. Eight additional patient scans were acquired as part of their clinical evaluation for pulmonary mass. MEASUREMENTS AND RESULTS: There were 26 malignant lesions (12 were 1 to 2 cm in size, the rest were larger) and 17 benign lesions (3 were < 1 cm in size, 9 were 1 to 2 cm in size, and 5 were larger). Averaged sensitivity, specificity, positive predictive value, and negative predictive value were, respectively, 50% (12 of 24), 94% (17 of 18), 92% (12 of 13), and 59% (17 of 29) for lesions 1 to 2 cm in size, 100% (28 of 28), 90% (9 of 10), 97% (28 of 29), and 100% (9 of 9) for lesions > 2 cm in size. There was good correlation between readers (p < 0.0001). CONCLUSION: FDG SPECT is useful in characterizing pulmonary masses > 2 cm in size and appears to be equivalent to positron emission tomography for these lesions. Although currently clinically suboptimal for characterizing lesions < or = 2 cm in size, FDG SPECT appears to be better than current anatomic imaging methods. In addition, the positive predictive value of FDG SPECT for small lesions is also high (92%), and this technique appears potentially useful in the subset of patients in whom a positive result would alter clinical diagnostic pathways or care.

Prediction of myocardial viability: Tl-201 versus sestamibi versus teboroxime compared with FDG uptake.

Several radionuclide imaging agents have been used for assessing the presence of myocardial viability. These include Tl-201 chloride, Tc-99m sestamibi, and Tc-99m teboroxime. Currently, the most reliable indicator is F-18 FDG, which accumulates in severely hypoperfused myocardium, indicating preserved metabolic activity. The presence of chronically ischemic myocardium that has preserved metabolic activity is referred to as "hibernating" myocardium. In this series, the ability of Tl-201, sestamibi, and teboroxime to establish the existence of viable myocardium was compared with that of F-18 FDG. Seventy-seven patients with ischemic cardiomyopathy were referred for determination of myocardial viability. FDG images were compared with representative resting blood-flow images obtained from either: 1) 24 hour Tl-201 reinjection-redistribution images, 2) resting sestamibi blood-flow images, or 3) early images from resting teboroxime washout analysis. Tl-201 was found to underestimate myocardial viability in 41% of patients, Tc-99m sestamibi underestimated viability in 38% of patients, and Tc-99m teboroxime underestimated viability in 26% of patients. There was no significant difference in the prediction of viable myocardium among the three radiopharmaceuticals, as all three underestimated myocardial viability.

Comparative value of thallium and glucose SPECT imaging in childhood brain tumors.

Thallium-201 chloride (201Tl) single-photon emission computed tomography (SPECT) detects a high percentage of histologically and anatomically diverse pediatric brain tumors. Thallium-201 chloride SPECT and F-18 fluoro-deoxy-glucose (18F-FDG) positron emission tomography (PET) are the most commonly used radionuclide techniques in neuro-oncology. Having developed a methodology to image 18F-FDG with SPECT, the authors performed SPECT scans coupled with magnetic resonance imaging to assess the comparative sensitivity of 201Tl and 18F-FDG in 19 children with brain tumors. Tumors were detected using 201Tl SPECT in 14 of 19 patients. Five of five postoperative residual tumors were detected by 201Tl SPECT, and six of seven after irradiation recurrences were detected. F-18 fluoro-deoxy-glucose SPECT detected tumors in only three of 19 patients, all of whom had abnormal 201Tl studies (all three after therapy recurrences). Thallium-201 chloride SPECT could be interpreted in 18 of 19 patients without magnetic resonance imaging confirmation, but none of the 19 18F-FDG SPECT studies could be interpreted without magnetic resonance imaging. Thallium-201 chloride SPECT is more sensitive than 18F-FDG SPECT in the detection of primary or recurrent childhood brain tumors. The failure of 18F-FDG SPECT in follow-up after therapy is primarily a problem of limited fluoro-deoxy-glucose uptake, not spatial resolution. Thallium-201 chloride SPECT is a promising imaging modality in neuro-oncology.

Combined Tc-99m MIBI and Tc-99m RBC for anatomic localization of ectopic mediastinal parathyroid adenomas.

Preoperative localization of abnormal parathyroid tissue in patients with persistent or recurrent hyperparathyroidism is recommended as a standard of care. A high percentage of these patients have ectopic tissue in the mediastinum. Tc-99m MIBI imaging alone for detection of ectopic parathyroid tissue in the mediastinum does not provide a sufficient number of anatomic landmarks, which makes communication regarding the exact location of any area of abnormal uptake difficult. We report the use of concomitant Tc-99m RBC and Tc-99m MIBI imaging for precise anatomic localization of ectopic mediastinal parathyroid tissue in 4 patients. It is thought that this combination of studies allows improved communication with referring physicians, surgeons, and radiologists for planning both surgical approach and correlative imaging studies. It is hoped that in the future this combination of studies may obviate the need for other imaging studies.

Prospective localization of epileptogenic foci: comparison of PET and SPECT with site of surgery and clinical outcome.

PURPOSE: To correlate prospective imaging findings in patients with intractable partial epilepsy with site of surgery and clinical outcome. MATERIALS AND METHODS: Thirty-five patients (25 male, 10 female) underwent positron emission tomography (PET; n=25), interictal single photon emission computed tomography (SPECT; n=33), or postictal SPECT (n=23) for localization of epileptogenic foci. The standard of reference was site of surgery. RESULTS: Sensitivity was 60%, 61%, and 52%; positive predictive value was 83%, 71%, and 55%; and localization was incorrect in 12% (three of 25 cases), 24% (eight of 33 cases), and 43% (10 of 23 cases) in PET, interictal SPECT, and postictal SPECT, respectively. There was no statistically significant difference in localization capabilities in a comparison of interictal SPECT and PET (correct localization, P=.999; incorrect localization, P=.625). There was a trend toward higher incorrect localization with interictal SPECT. CONCLUSION: Postictal SPECT has low sensitivity and a high incorrect localization rate and should not be performed in these patients. Interictal SPECT with 6-8-mm full-width at half-maximum is an alternative to PET. However, the trend toward higher false-localization rates must be taken into consideration.

Tc-99m DMSA SPECT imaging in patients with acute symptoms or history of UTI. Comparison with ultrasonography.

Although planar cortical scintigraphy has been demonstrated to be a sensitive test for the detection of renal infection and scarring, one criticism has been radiation dose to the renal cortex. Recent studies of cortical SPECT suggest a sensitivity for detection of lesions equal to, or greater than, that of planar scans. The authors prospectively performed SPECT scans on 36 patients referred for recurrent urinary tract infection (UTI) (11 of 36), or recent onset of symptoms of UTI (25/36) after 30-40% of the standard 130 MBq (3.5 mCi) adult dose of Tc-99m DMSA was administered. Comparison was made with ultrasonography (US) performed at, or near, the same time. Of 67 kidneys evaluated, 34 (51%) demonstrated focal cortical loss on Tc-99m DMSA scintigraphy, 1 kidney was small in size, and 32 kidneys were normal. Abnormalities were noticed in only 13 (19%) of kidneys on US. Previously, US has been the primary imaging modality in the evaluation of the young patient with UTI. Triple-headed Tc-99m DMSA SPECT scintigraphy is a more sensitive, low-dose (12 mGy, 1.2 r) method of detecting renal cortical abnormalities. As such, it is a more appropriate test for identifying sites of cortical infection and scarring and for following patients on prophylactic therapy for evidence of asymptomatic break-through infections.

Technology for FDG SPECT with a relatively inexpensive gamma camera. Work in progress.

PURPOSE: At the time of the co-development of a commercial dual-headed gamma camera for whole-body single photon emission computed tomography (SPECT), modifications were made to permit imaging of 511-keV photons (from positron emitters) while maintaining versatility and cost-effectiveness in nuclear medicine for routine nonpositron studies. MATERIALS AND METHODS: Special collimators were made, and gantry stability was increased. Detector shielding and crystal thickness were not changed. In phantoms, healthy volunteers (two men, aged 34 and 38 years), and 109 patients (71 male and 38 female patients, aged 2-74 years [mean, 56 years]), SPECT was performed with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG). In patients, 36 myocardial viability, 47 oncologic, and 26 brain examinations were performed. RESULTS: All FDG SPECT scans were subjectively judged to be of acceptable quality. Preliminary results in regard to diagnostic findings are reviewed; this analysis is intended to be a feasibility study not a conclusive review of imaging accuracy. CONCLUSION: FDG SPECT provides images that are interpretable for cardiac or oncologic diagnosis, without the need for or expense of a positron emission tomography (PET) center or a dedicated PET scanner.

Dynamic simultaneous anterior and posterior imaging of transplant and native renal function using dual-headed gamma camera.

The authors describe the nonvisualization of a renal transplant on DTPA scan with late visualization of activity within the bladder in a 27-year-old patient with diabetes. Origin of bladder activity was later clarified by dynamic anterior and posterior imaging using MAG 3 and an extra large field-of-view, dual-headed gamma camera.

Normal variations of pelvic fat distribution implications on CT staging of pelvic tumors.

In order to determine the normal variations of pelvic fat distribution, 25 men and 25 women normal pelvic computer tomography (CT) scans were reviewed. No distinct fat planes were demonstrated between the prostate and pelvic side walls, bladder and seminal vesicles, and prostate and rectum in 69%, 81%, and 86% of the men patients, respectively. Similarly, there were no distinct fat planes between the uterus and pelvic side walls, and uterus and rectum in 86% and 96% of the women patients, respectively. We conclude that there are no distinct fat planes around pelvic organs in the majority of normal people and this may be a major source of error in the CT staging of pelvic tumors.