A comparison of the image quality of full-time myocardial perfusion SPECT vs wide beam reconstruction half-time and half-dose SPECT.

OBJECTIVES: Wide Beam Reconstruction (WBR) (UltraSPECT, Ltd) uses resolution recovery and noise modeling to cope with decreased SPECT count statistics. Because WBR processing reconstructs half the usual SPECT count statistics, we postulate that image quality equivalent to a full-time acquisition can be achieved in either half the time or with half the radiopharmaceutical activity. METHODS: In 156 consecutive patients (pts) rest and 8-frame gated post-stress myocardial perfusion SPECT was performed following 333-444 and 1184-1480 MBq (9-12 and 32-40 mCi) Tc-99m sestamibi injections, respectively, with full-time (rest = 14 min; stress = 12.3 min) acquisitions processed with OSEM and also separate "half-time" acquisitions processed with WBR. A subsequent group of 160 consecutive pts matched in gender, weight, and chest circumference received "half-dose" rest and stress injections 214.6 ± 22.2 and 647.5 ± 92.5 MBq (5.8 ± 0.6 and 17.5 ± 2.5 mCi) with full-time SPECT acquisitions. Image quality (1 = poor to 5 = excellent) was judged by myocardial count density and uniformity, endocardial edge definition, perfusion defect delineation, right ventricular visualization, and background noise. RESULTS: Mean image quality for rest, stress, and post-stress gated images were 3.6 ± 0.7, 3.8 ± 0.7, and 3.9 ± 1.0, respectively, for "full-time OSEM; 3.7 ± 0.8, 4.0 ± 0.7, and 4.8 ± 0.4 for "half-time" WBR; and 4.3 ± 0.8, 4.6 ± 0.6, and 4.7 ± 0.6 for "half-dose" WBR. "Half-time" and "half-dose" WBR image quality were both superior to standard full-time OSEM (P's < .001). There was no significant difference between the summed stress and rest scores for "full-time" OSEM vs "half-time" WBR in 82 patients with perfusion defects. CONCLUSIONS: Both "half-time" and "half-dose" WBR provide myocardial perfusion SPECT quality superior to full-time OSEM, with an associated decrease in scan acquisition time and patient radiation exposure, respectively.

Wide beam reconstruction "quarter-time" gated myocardial perfusion SPECT functional imaging: a comparison to "full-time" ordered subset expectation maximum.

BACKGROUND: Previously we reported that compared to iterative reconstruction with ordered subset expectation maximum (OSEM), wide beam reconstruction (WBR), which incorporates resolution recovery and controls noise during reconstruction without applying a post-processing filter, allows half-time SPECT acquisition with preserved diagnostic quality. We now postulate that with further Poisson noise treatment, quarter-time acquisition is possible. METHODS: The half-time WBR algorithm was optimized for quarter-time acquisition based upon anthropomorphic cardiac phantom data and a pilot group of 48 patients (pts). Then using the modified algorithm, 209 pts (91 men, 118 women, mean chest circumference = 40 in) were imaged at rest (R) and stress (S) (9/32 mCi (99m)Tc-sestamibi) full-time with OSEM, and again quarter-time with the modified WBR algorithm. The 180 degrees , 64-stop, full-time single-day rest (R) (25 second-per-stop, sps) and 8-frame per cardiac cycle post-stress (S) (20 sps) gated SPECT, and then quarter-time R (6 sps) and post-S (4 sps) gated SPECT were acquired. Blinded observers graded scan quality (1 = poor to 5 = excellent) based on myocardial uniformity, endocardial/epicardial edge definition, and background noise. Perfusion defects were scored using a 17-segment model. Using three commercially available software methods, end-diastolic volume (EDV), end-systolic volume (ESV), and left ventricular ejection fraction (LVEF) were calculated. RESULTS: For the 209 prospective pts, mean image quality for R full-time OSEM and quarter-time WBR were similar (3.5 +/- 0.9 vs 3.6 +/- 0.7, p NS). For S, quarter-time WBR quality was superior to full-time OSEM (4.3 +/- 0.7 vs 3.9 +/- 0.7) (P = 1.78 x 10(-17)). In 35 pts with chest circumferences >44 inches a longer, 10 sps WBR acquisition improved resting image quality. Of 48 pts with abnormal scans (SSSs > 2 by OSEM) mean summed stress scores, summed rest scores, and summed difference scores were not significantly different with quarter-time WBR vs full-time OSEM (11.2 vs 10.9), (9.1 vs 9.0), (2.0 vs 1.9) (P NS). For the three software methods, there was a good correlation of LVEF, EDV, and ESV determined by WBR vs OSEM (all r > 0.92). ESVs were generally higher with WBR, primarily due to better delineation of the valve plane at end-systole, whereas EDVs were similar. Thus, EFs were significantly lower with WBR. CONCLUSIONS: For perfusion SPECT quarter-time WBR affords image quality, defect characterization, and functional assessment equivalent to full-time OSEM.

Follicular variant of papillary thyroid carcinoma presenting as a toxic nodule by I-123 scintigraphy.

The risk of malignancy in a "hot" thyroid nodule detected by radioiodine scintigraphy is rare. We report a case of a 63-year-old man with a hyperfunctioning nodule demonstrated by radioiodine scintigraphy and cytology suspicious for follicular variant of papillary thyroid carcinoma (FVPTC). There were no locoregional or distant metastases at initial diagnosis. Histopathologic examination following thyroidectomy confirmed the presence of an encapsulated FVPTC. A year into follow-up, his I-131 whole body scan performed following the withdrawal from exogenous thyroid hormone was negative, whereas his serum thyroglobulin (Tg) levels were intermediate. A subsequent PET/CT scan revealed a small, but stable, metabolically active pretracheal lymph node, which on biopsy was confirmed to be stage III FVPTC. In conclusion, the presence of hyperfunctioning thyroid nodule(s) does not preclude malignancy and, therefore, proper cytohistologic evaluation in such patients may help to exclude a coexistent thyroid carcinoma. Patients treated for localized PTC may benefit from serial PET/CT follow-up in the early detection and management of recurrence or distant metastases.

Spontaneous transition of an autonomously functioning thyroid adenoma to Graves' disease.

We report a case of a 57-year-old postmenopausal woman with an autonomously functioning thyroid adenoma spontaneously developing Graves' disease (GD) as documented by I-123 scintigraphy. To date, anecdotal case reports citing the progression of an autonomous nodule to GD have documented either a major thyroidal insult, spontaneous or therapeutic, or the activation of thyroid tissue by circulating thyroid stimulating IgG, with variable progression characteristics. In contradiction to the proposed inciting factors, our patient underwent a minimally invasive fine needle aspiration biopsy followed by suppressive pharmacotherapy. Her antithyroid antibody assay detected low titers of thyroperoxidase antibody (<10 U/mL). We conclude that this is a rare case of autonomously functioning adenoma where neither significant thyroid tissue damage nor the presence of thyroid stimulating IgG can be implicated as an inciting trigger in its progression to GD.

Effect of proton pump inhibitors and H2 antagonists on the stomach wall in 99mTc-sestamibi cardiac imaging.

UNLABELLED: On the basis of previously unpublished observations, we hypothesized that prolonged use of proton pump inhibitors (PPIs) causes an increase in (99m)Tc-sestamibi uptake in the stomach wall, manifested as curvilinear activity surrounding the photopenic fundus of the stomach cavity. We prospectively evaluated the frequency of stomach wall uptake in patients undergoing myocardial perfusion SPECT who were taking PPIs or H(2) antagonists. METHODS: Patients (n = 138) who were scheduled for single-day rest/stress (99m)Tc-sestamibi SPECT were randomly selected. Poststress SPECT was performed 30 min after treadmill exercise or 45 min after dipyridamole infusion. The rest scan was obtained 45 min after tracer injection. All patients drank 473 mL of water 5-10 min after both the rest and the stress radiotracer injections. Patients were questioned regarding their use of PPIs and H(2) antagonists. The significant use of either was defined as more than 2 wk of continuous therapy before cardiac SPECT. Masked observers assessed poststress planar projection images in endless-loop cinematic format for the following 3 patterns: stomach cavity uptake, attributable to duodenogastric reflux of tracer; stomach wall uptake; and no stomach uptake. A 2-tailed chi(2) test with Yates correction was used to calculate statistically significant associations among variables. RESULTS: Only patients with observed patterns of stomach wall uptake (n = 30) and no stomach wall uptake (n = 91) were included. Patients with stomach cavity uptake (n = 17) were excluded because the assessment of the adjacent stomach wall uptake was not possible. Of the patients included (n = 121), 30 were men and 91 were women. Sixty-seven patients were older than 60 y; 26 patients were taking PPIs. Of the 95 patients not taking PPIs, 14 were taking H(2) antagonists. No patients were taking both medications. Stomach wall uptake was strongly associated with prolonged use of PPIs (chi(2) = 51.9, P < 0.0001). No statistically significant association was noted among age, sex, or use of H(2) antagonists (P = NS). CONCLUSION: Prolonged PPI therapy, but not H(2) antagonist therapy, contributes to a significant increase in stomach wall activity, potentially resulting in Compton scatter or ramp filter artifacts affecting the inferior wall of the left ventricle. Stomach wall activity, unlike the stomach cavity activity, cannot be prevented by the ingestion of water before imaging. Therefore, it is important to elicit a history of prolonged PPI use to better anticipate the possibility of increased stomach wall activity, which can confound the image quality and interpretation.

FDG PET Appearance of "Cannonball" Pulmonary Metastases.

We present the case of a 67-year-old woman with a recent tissue diagnosis of endometrial cancer whose FDG PET scan exhibited multiple hypermetabolic foci through out both the lungs. Contemporaneously acquired conventional radiolographs showed parenchymal nodules that demonstrated the classic "cannon ball" appearance of pulmonary metastases. Pulmonary metastasis from an endometrial primary is a rare event, as are the presence of pulmonary findings at the time of initial staging. Thus, this case demonstrates rare, and yet, distinctive aspects of the disease presentation and image correlation across the various imaging modalities.

HIV-associated lymphocytic interstitial pneumonitis causes diffuse sestamibi lung uptake in myocardial perfusion imaging.

Technetium-99m ((99m)Tc) sestamibi myocardial perfusion scintigraphy (MPI) is widely used for the diagnosis and assessment of prognosis in patients with suspected coronary artery disease. During these investigations, inspection of raw projected data for the purpose of quality control may occasionally yield incidental noncardiac findings that suggest the presence of another primary noncardiac disease. We present a 66-year-old HIV patient with a tissue diagnosis of lymphoid interstitial pneumonitis (LIP), who demonstrated a diffuse increase of (99m)Tc sestamibi in bilateral lung fields both in rest and stress MPI.