Kathryn A. Morton

Positron emission mammography: initial clinical results.

Background: Evaluation of high-risk mammograms represents an enormous clinical challenge. Functional breast imaging coupled with mammography (positron emission mammography [PEM]) could improve imaging of such lesions. A prospective study was performed using PEM in women scheduled for stereotactic breast biopsy.Methods: Patients were recruited from the surgical clinic. Patients were injected with 10 mCi of 2-[18F] fluorodeoxyglucose. One hour later, patients were positioned on the stereotactic biopsy table, imaged with a PEM scanner, and a stereotactic biopsy was performed. Imaging was reviewed and compared with pathologic results.Results: There were 18 lesions in 16 patients. PEM images were analyzed by drawing a region of interest at the biopsy site and comparing the count density in the region of interest with the background. A lesion-to-background ratio >2.5 appeared to be a robust indicator of malignancy and yielded a sensitivity of 86%, specificity of 91%, and overall diagnostic accuracy of 89%. No adverse events were associated with the PEM imaging.Conclusions: The data show that PEM is safe, feasible, and has an encouraging accuracy rate in this initial experience. Lesion-to-background ratios >2.5 were found to be a useful threshold value for identifying positive (malignant) results. This study supports the further development of PEM.

Evaluation of the quantitative capability of a high-resolution positron emission tomography scanner for small animal imaging.

Objective: The quantitative capability of a positron emission tomog-raphy scanner for small animal imaging was evaluated in this study. Methods: The microPET P4 (Concorde Microsystems, Knoxville, TN) scanners capability for dynamic imaging and corrections for radioactive decay, dead time, and attenuation were evaluated. Rat brain and heart studies with and without attenuation correction were compared. A calibration approach to convert the data to nanocuries per milliliter was implemented. Calibration factors were determined using calibration phantoms of 2 sizes with and without attenuation correction. Quantitation was validated using the MiniPhantom (Data Spectrum, Chapel Hill, NC) with hot features (5:1 ratio) of different sizes (4, 6.4, 8, 13, and 16 mm). Results: The microPET P4 scanners ability to acquire dynamic studies and to correct for decay, dead time, and attenuation was demonstrated. The microPET P4 scanner provided accurate quantitation to within 6% for features larger than 10 mm. Sixty percent of object contrast was retained for features as small as 4 mm. Conclusions: The microPET P4 scanner can provide accurate quantitation.

Providing optimal preoperative localization for recurrent parathyroid carcinoma: A combined parathyroid scintigraphy and computed tomography approach

Purpose: The incidence of parathyroid carcinoma is approximately 0.5% to 5% in patients with primary hyperparathyroidism. Recurrent parathyroid carcinoma is treated with surgical resection of all sites of disease to ameliorate systemic manifestations of hyperparathyroidism, primarily hypercalcemia. This study investigates the role of parathyroid scintigraphy and computed tomography (CT) imaging in recurrent parathyroid carcinoma. Materials and Methods: A retrospective chart review was performed on 8 patients diagnosed with recurrent parathyroid carcinoma at our tertiary care institution between 1975 and 2001. Surgical reports, histopathology, parathyroid scintigraphy, and CT findings were recorded. Surgical reports and radiologic studies were compared for concordance of recurrence sites. Results: There were 32 imaging studies before reoperation: 15 parathyroid scintigraphy and 17 CTs. Of 15 sites of recurrence potentially seen on scintigraphy, 10 were true-positive (67%). Of 17 sites of recurrence potentially seen on CT, 9 were true-positive (53%). Of the 8 false-negatives on CT, 7 of these recurrences were in the surgical bed (88%). There were 9 instances in which CT and scintigraphy were performed preoperatively for comparison and correlation. CT and scintigraphic findings were incongruent in 7 of 9 of these cases (78%). Conclusion: Successful surgical intervention for recurrent parathyroid carcinoma requires accurate preoperative localization studies and complete excision of metastases. Our data supports combined analysis of parathyroid scintigraphy and CT for patients with recurrent disease before reoperation. Additionally, our review suggests that sensitivity may be optimized with SPECT parathyroid scintigraphy and close correlation with CT.

Enhanced Scintigraphic Protocol Required for Optimal Preoperative Localization Before Targeted Minimally Invasive Parathyroidectomy

At our tertiary care institution, a targeted minimally invasive parathyroidectomy (MIP) is the preferred surgical procedure for primary hyperparathyroidism. Similar to unilateral neck exploration (UNE), preoperative scintigraphic localization of the adenoma in relation to the midline is required. However, in contrast to the abbreviated standard incision for UNE, 2 distinct incision sites, 1 medial and 1 lateral, are available on each side with MIP. The incision site is ultimately chosen based on scintigraphic determination of the adenomas vascular origin to facilitate ligation and removal. Unfortunately, the scintigraphic location of a parathyroid adenoma does not necessarily reflect the site of its vascular origin. We reviewed our database to identify factors that accurately predict the site of vascular origin of parathyroid adenomas. A retrospective chart review was performed on 125 patients who underwent Tc-99m sestamibi scintigraphy and parathyroidectomy. Scintigraphic localization, surgical findings, and histopathology were recorded. Preoperative image interpretations that were discordant with operative findings were independently reviewed. Scintigraphy identified the presence of an adenoma in 105 of 118 patients (89%) with primary hyperparathyroidism. In 17 of the 105 cases (16%), the scintigraphic interpretation did not accurately reflect the site of superior or inferior vascular origin seen at surgery. In many discordant cases, anterior images were insufficient for determining the vascular origin. The posterior displacement of an adenoma in relation to the thyroid on early lateral images was often critical in determining the superior or inferior vascular origin. Scintigraphic determination of the superior or inferior vascular origin of a parathyroid adenoma directs incision placement for MIP. Imaging protocols should include early lateral images when localizing parathyroid adenomas before minimally invasive parathyroidectomy.

Applications of a PET device with 1.5 mm FWHM intrinsic spatial resolution to breast cancer imaging

Operation of a high resolution compact clinical PET Scanner (PEM Flex/spl trade/) device as a breast scanner is described. The device features high spatial resolution (1.5 mm FWHM intrinsic resolution) as a result of small crystals and compact position-sensitive photomultipliers. The compactness of the system allows it to reside within a stereotactic X-ray mammography unit, or as a separate standalone system capable of breast compression. The gamma rays are detected for a volumetric reconstruction by two heads, each of which contains 2,028 2 mm by 2 mm by 10 mm lutetium-containing crystals. The heads travel within X-ray transparent compression paddles. A window is provided in one of the paddles for direct correlation with ultrasound transducers and for interventional access. To enable real-time interventions, images are reconstructed and displayed while the detectors are still acquiring data. The maximum-likelihood reconstruction provides quantitative images with threefold improved contrast as compared to simple back-projections.