Molecular imaging of small animals with a triple-head SPECT system using pinhole collimation.

Pinhole collimation yields high sensitivity when the distance from the object to the aperture is small, as in the case of imaging small animals. Fine-resolution images may be obtained when the magnification is large since this mitigates the effect of detector resolution. Large magnifications in pinhole single-photon emission computed tomography (SPECT) may be obtained by using a collimator whose focal length is many times the radius of rotation. This may be achieved without truncation if the gamma camera is large. We describe a commercially available clinical scanner mated with pinhole collimation and an external linear stage. The pinhole collimation gives high magnification. The linear stage allows for helical pinhole SPECT. We have used the system to image radiolabeled molecules in phantoms and small animals.

Modulation of thyroidal radioiodine uptake by theophylline.

Diagnostic and therapeutic use of radioiodine in the management of thyroid disorders depends on the ability of thyroid cells to concentrate radioiodine, a process regulated by thyrotropin and dependent on the intracellular increase in cAMP. We tested the ability of theophylline, a drug known to increase intracellular cAMP via inhibition of phosphodiesterase, to modulate the thyroidal radioiodine uptake in FRTL-5 cells, in mice and in humans. In FRTL-5 cells, theophylline increased the uptake of radioactive iodine and intracellular cAMP only at low concentrations (1 microM). In mice, theophylline increased slightly the radioiodine uptake, although this increase varied from 1.5- to 6.6-fold. In humans, theophylline decreased slightly the radioiodine uptake, a decrease that became more pronounced with time after radioiodine administration. These studies suggest that theophylline modulates the radioiodine uptake in a dose-dependent fashion, although the modulation is mild and probably not applicable to the clinical setting.

111In oxine labelled mesenchymal stem cell SPECT after intravenous administration in myocardial infarction.

Mesenchymal stem cells (MSCs) have shown therapeutic potential if successfully delivered to the intended site of myocardial infarction. The purpose of this pilot study was to test the feasibility of 111In oxine labelling of MSCs and single photon emission computed tomography (SPECT) imaging after intravenous administration in a porcine model of myocardial infarction. Adult farm pigs (n=2) were subjected to closed chest experimental myocardial infarction. 111In oxine labelled MSCs (1 x 10(7) to 2 x 10(7) cells) were infused intravenously, and SPECT imaging was performed initially and on days 1, 2, 7 and 14. High quality SPECT images were obtained through 2 weeks of imaging. High initial MSC localization occurred in the lungs and slow progressive accumulation occurred in the liver, spleen and bone marrow. Renal activity was mild and persistent throughout imaging. No appreciable accumulation occurred in the myocardium. It is concluded that 111In oxine radiolabelling of MSCs is feasible, and in vivo imaging with SPECT provides a non-invasive method for sequentially monitoring cell trafficking with good spatial resolution. Because intravenous administration of MSCs results in significant lung activity that obscures the assessment of myocardial cell trafficking, alternative routes of administration should be investigated for this application.

18F-Fluoro-2-deoxyglucose positron emission tomography in the evaluation of gastrointestinal malignancies.

Positron emission tomography with (18)F-fluoro-2-deoxyglucose is an imaging technology that is demonstrating increasing utility in the evaluation of gastrointestinal malignancies.

A minimally invasive method for creating coronary stenosis in a swine model for MRI and SPECT imaging.

RATIONALE AND OBJECTIVES: To develop a less-invasive method for creating coronary stenosis in an animal model for the study of myocardial perfusion defects by using magnetic resonance imaging (MRI) and single-photon-emission computed tomography (SPECT). METHODS: Eleven farm pigs were instrumented with an MR-compatible coronary flow-reduction fitting in the left anterior descending coronary artery (LAD). These fittings were turned from a nylon rod, tapered from a maximum outer diameter of 3 mm, and drilled to a specified inner diameter (depending on the degree of coronary stenosis desired). The flow-reducing fittings were delivered over a coronary guidewire and advanced to a wedge position in the proximal LAD with an angioplasty catheter via a carotid artery approach. Perfusion determined by contrast-enhanced MRI at peak dipyridamole stress was compared with that obtained by 99mTc sestamibi SPECT. Radiolabeled microspheres were injected at rest, after stenosis implantation, and at peak pharmacological stress to establish the severity of the coronary lesion. RESULTS: Coronary stenosis was successfully created in seven animals. Mild coronary stenoses (<60%) were created in four animals. Significant coronary stenoses (80%-90%) were created in three animals. Thrombosis of the coronary flow-reducing fittings was observed in four animals, leading to sudden death in three animals and myocardial infarction in one animal. CONCLUSIONS: This method of angioplasty-guided, LAD coronary stenosis creation in a swine model presents a less-invasive alternative to open-chest techniques such as hydraulic occluders and ameroid constrictors.

The value of a baseline bone scan in patients with newly diagnosed prostate cancer.

PURPOSE: This study evaluated the role of bone scans in managing newly diagnosed, untreated prostate cancer. METHODS: Two hundred seventy consecutive staging bone scans in patients (mean age, 69 years) with newly diagnosed prostate cancer who had serum prostate-specific antigen (PSA) determinations and biopsies between January 1995 and October 1997 were evaluated retrospectively. RESULTS: The bone scans were positive for metastatic bone disease in 24 patients and negative in 246. Serum PSA levels, the number of positive biopsy cores, the extent of tumor in the prostate gland, and Gleason scores were all significantly correlated with scintigraphic bone metastases (P < 0.0001 for each). Of the 177 patients with PSA levels less than 10 ng/ml, three had bone metastases. Bone metastases were found in 2 of 34 patients with PSA levels of 10.1 to 20 ng/ml, in 3 of 29 patients with PSA values of 20.1 to 50 ng/ml, and in 16 of 30 patients with PSA levels greater than 50.1 ng/ml. Only one patient had a bone metastasis when the prostate cancer involved fewer than 2 biopsy cores (1 of 135) or when disease was confined to one lobe (1 of 131), but the incidence increased significantly when the malignancy involved three or more biopsy cores (20 of 114) or disease was present in both prostate lobes (20 of 118). Four of 160 patients with Gleason scores less than 6 had bone metastases, whereas 20 of 110 patients with Gleason scores greater than 7 had bone metastases. CONCLUSIONS: The likelihood of bone metastases is low in patients with newly diagnosed, untreated prostate cancer when the initial PSA level was less than 10 ng/ml, the number of positive biopsy cores was less than 2, tumor was confined to one lobe, or the Gleason score was less than 6. However, none of these criteria can be used to exclude metastatic bone disease. A baseline bone scan is an important staging procedure and should be obtained to provide maximum data for clinical management of the disease.

Somatostatin receptor scintigraphy and somatostatin therapy in the evaluation and treatment of malignant thymoma.

PURPOSE: This report illustrates the potential diagnostic and therapeutic utility of somatostatin receptor scintigraphy and therapy with somatostatin. METHODS: In-111 pentetreotide (In-111 octreotide), a somatostatin analog, was used to define the receptor status and the extent of disease in a case of malignant thymoma. RESULTS: Subsequent treatment with nonradioactive somatostatin inhibited tumor growth. CONCLUSION: In-111 octreotide may be useful to define tumor receptor status and may provide prognostic information useful in determining subsequent therapy.

Nonsegmental ventilation-perfusion scintigraphy mismatch after radiation therapy.

PURPOSE: This report illustrates the utility of ventilation-perfusion scintigraphy in differentiating radiation pneumonitis from other causes of dyspnea, including pulmonary embolism, heart failure, obstructive tumor, and chronic obstructive pulmonary disease. METHODS AND RESULTS: A nonsegmental mismatched perfusion abnormality, which exactly conformed to a radiation port, was diagnostic of radiation pneumonitis. CONCLUSION: In patients with lung tumors presenting with dyspnea, ventilation-perfusion scintigraphy may be useful in diagnosing radiation pneumonitis and effectively excluding other causes of dyspnea.

Progressive multifocal leukoencephalopathy demonstrating contrast enhancement on MRI and uptake of thallium-201: a case report.

We describe a patient with AIDS who presented with focal neurological symptoms, and who had contrast-enhancing brain lesions on MRI which demonstrated increased thallium-201 uptake on SPECT. These findings were consistent with lymphoma; however, brain biopsy established a diagnosis of progressive multifocal leukoencephalopathy (PML). To our knowledge, this is the first reported case of PML with increased thallium-201 uptake on brain SPECT.

Resting Tl-201 scintigraphy in the evaluation of myocardial sarcoidosis.

In patients with sarcoidosis, myocardial involvement is common and may be fatal. With extensive disease, the primary manifestations may include conduction abnormalities and arrhythmias, which may lead to sudden death. Myocardial perfusion scintigraphy may be the most accurate method to assess extent of myocardial involvement and response to therapy.

Right and left ventricular volume and ejection fraction by tomographic gated blood-pool scintigraphy.

UNLABELLED: Tomographic techniques separate overlying structures, permitting measurements of absolute ventricular volumes. The purpose of this study was to determine absolute right and left ventricular volume and ejection fraction measurements with tomographic gated equilibrium blood-pool scintigraphy (TMUGA) compared to MRI and conventional planar scintigraphy. METHODS: Eighteen patients were studied. Ventricular volumes for TMUGA and MRI were calculated by modified Simpson's rule. TMUGA regions were defined by constraints including phase analysis, intensity threshold and visual inspection. MRI studies were acquired with a fast gradient-echo, ECG-gated, breath-hold technique and boundaries were defined by a semiautomated contour method. Conventional gated first-pass radionuclide angiography (FP) and planar gated equilibrium blood-pool scintigraphy (PMUGA) were performed for RV EF and LV EF, respectively. RESULTS: TMUGA absolute right ventricular volumes showed excellent-correlation with MRI for both right ventricular volumes (r = 0.91, slope = 0.90, s.e.e. = 15.7) and left ventricular volumes (r = 0.96, slope = 0.88, s.e.e. = 18.2). For left ventricular ejection fraction, TMUGA also showed excellent correlation with MRI (r = 0.94, slope = 1.10, s.e.e. = 9.0) and planar MUGA (r = 0.97, slope = 1.23, s.e.e. = 6.2). For right ventricular ejection fraction, TMUGA showed good correlation with both MRI (r = 0.88, slope = 0.79, s.e.e. = 6.0) and first-pass planar scintigraphy (r = 0.86, slope = 1.2, s.e.e. = 7.9). CONCLUSION: Tomographic gated blood-pool scintigraphy absolute right and left ventricular volumes and ejection fractions show good correlation with accepted techniques. Further studies are necessary to define the reproducibility of this method.