Impact of exercise single-photon emission computed tomographic imaging on appropriateness of coronary revascularization

This study examined the predictors of early coronary revascularization in 816 patients with chest pain syndromes who had coronary artery disease by angiography and exercise single-photon emission computed tomography (SPECT) thallium imaging. Multivariate analysis of clinical, stress, nuclear, and catheterization variables revealed the presence of SPECT reversibility as the most powerful predictor (chi-square = 43) of early revascularization.     

Myocardial [18F]FDG tomography using a conventional gamma camera and a seven pinhole collimator

Interventional radiology is a rapidly expanding subspecialty in radiology in which the imaging specialist can diagnostically and therapeutically access many organ systems percutaneously, simplifying the treatment of many conditions previously managed surgically. It minimises patient discomfort, renders general anaesthesia unnecessary, reduces morbidity and mortality and decreases the length and cost of hospitalisation. It can also play a role in the management of inoperable cases. Radiologists today are not just "shadow gazers" but can actively participate in patient care and management. In a modern teaching hospital, interventional radiology has an increasingly important role in patient management and is changing the practice of clinical medicine. With advances in imaging, bio-technology and innovation, there has been an explosive development in interventional radiology for the past 15 years and it is hard to keep abreast of what is happening in this field. This article is a brief summary of the state of the art in interventional radiology in 1993 and our experience in Westmead, Sydney, Australia, in some of the many procedures that have recently evolved.     

Simultaneous acquisition of iodine-123 emission and technetium-99m transmission data for quantitative brain single-photon emission tomographic imaging

The aim of this study was to obtain quantitative iodine-123 brain single-photon emission tomographic (SPET) images with scatter and attenuation correction. We used a triple-headed SPET gamma camera system equipped with fan-beam collimators with a technetium-99m line transmission source placed at one of the focal lines of the fan-beam collimators. Four energy windows were employed for data acquisition: (a) 126-132 keV, (b) 132-143 keV, (c) 143-175 keV and (d) 175-186 keV. A simultaneous transmission-emission computed tomography scan (TCT-ECT) was carried out for a brain phantom containing 123I solution. The triple energy window scatter correction was applied to the 123I ECT data measured by means of the windows (b), (c) and (d) acquired by two detectors. Attenuation maps were reconstructed from 99mTc TCT data measured by means of the windows (a), (b) and (c) acquired by one detector. Chang's iterative attenuation correction method using the attenuation maps was applied to the 123I ECT images. In the phantom study cross-calibrated SPET values obtained with the simultaneous mode were almost equal to those obtained with the sequential mode, and they were close to the true value, within an error range of 5.5%. In the human study corrected images showed a higher grey-to-white matter count ratio and relatively higher uptake in the cerebellum, basal ganglia and thalamus than uncorrected images. We conclude that this correction method provides improved quantification and quality of SPET images and that the method is clinically practical because it requires only a single scan with a 99mTc external source.     

Attenuation compensation for cardiac single-photon emission computed tomographic imaging: Part 1. Impact of attenuation and methods of estimating attenuation maps

Attenuation is believed to be one of the major causes of false-positive cardiac single-photon emission computed tomographic (SPECT) perfusion images. This article reviews the physics of attenuation, the artifacts produced by attenuation, and the need for scatter correction in combination with attenuation correction. The review continues with a comparison of the various configurations for transmission imaging that could be used to estimate patient specific attenuation maps, and an overview of how these are being developed for use on multiheaded SPECT systems, including discussions of truncation, noise, and spatial resolution of the estimated attenuation maps. Ways of estimating patient specific attenuation maps besides transmission imaging are also discussed.     

Bone scintigraphy equipped with a pinhole collimator for diagnosis of avascular necrosis of the femoral head

The hypothesis that direct nursing hours correlate with the cost of a patient stay in intensive care was tested. One hundred and thirty-nine patients were studied and the data collected included: (a) direct nursing hours applied to each patient; (b) a daily TISS score: (c) a detailed costing of each patient (all costs are shown in N.Z.$). There was a strong correlation between the direct nursing hours and the total cost per patient (r2 = 0.98) (total cost = 54 x direct nursing hours + 344). Also a strong correlation existed between the total TISS scores and the total costs per patient (r2 = 0.96) (total cost = 67.13 x TISS). Direct nursing hours offer a relatively simple and logical method of allocating costs per patient.     

Cardiac single-photon emission tomography with a 90 degrees dual-head system

Dual-head single-photon emission tomography (SPET) systems which permit a 90 degrees orientation of the heads provide a twofold increase in sensitivity for 180 degrees SPET compared with single-head systems. Since such systems have additional mechanical and electrical alignment and stability requirements, clinical equivalency for myocardial perfusion SPET must be demonstrated. Accordingly, we studied 26 subjects who underwent exercise thallium scintigraphy consecutively with both single-head and dual-head systems. Image acquisition was similar, except that the dual-head study took one-half the time. Image reconstruction was identical. Images were interpreted in a blinded fashion, and rated for technical quality. All 26 studies were equivalently interpreted for the presence or absence of perfusion defects. Fourteen of the studies were judged to be technically equivalent; seven were judged to be slightly better with the single-head system; three were judged to be slightly better with the dual-head system; and two were judged to be definitely better with the dual-head system. We conclude that dual-head 90 degrees systems provide equivalent clinical performance in half the acquisition time.     

Assessment of myocardial viability: Dobutamine echocardiography and thallium-201 single-photon emission computed tomographic imaging predict the postoperative improvement of left ventricular function after bypass surgery

The aim of this study was to evaluate the usefulness of dobutamine echocardiography and quantitative thallium-201 single photon emission computed tomography myocardial scintigraphy with reinjection in the detection of viable myocardium in patients with coronary artery disease and reduced left ventricular function, which will improve after aortocoronary bypass surgery. Forty-eight patients (47 men, aged 61 +/- 6 years) with angiographically documented reduced left ventricular function (ejection fraction 35 +/- 14, 63% with chronic transmural myocardial infarction) were examined by dobutamine two-dimensional echocardiography (before and during low dosage), 201Tl, and gated radionuclide ventriculography before and 3 +/- 2 months after aortocoronary bypass surgery. Four of 55 areas classified viable before operation were revascularized inadequately and discarded. Global left ventricular ejection fraction at rest rose from 35% +/- 14% before operation to 40% +/- 13% (p < 0.05) after operation. Stress-induced perfusion defects involved 40% +/- 19% of the left ventricle circumference after stress and showed a significant reduction of size to 23% +/- 14% (p < 0.01) at rest, 4 hours later, and after reinjection. This value fell to 16% +/- 12% (p < 0.05) 3 months after aortocoronary bypass surgery. We conclude that both dobutamine echocardiography (sensitivity 95%, specificity 80%, positive predictive value 87%, negative predictive value 88%) and 201Tl studies (sensitivity 87%, specificity 98%, positive predictive value 97%, negative predictive value 93%) are suitable and comparable accurate methods for predicting improvement in systolic function 3 months after revascularization in a selected population with a high prevalence of viable but hypokinetic or akinetic myocardium.     

Accuracy of single-photon emission computed tomography myocardial perfusion imaging in patients with stents in native coronary arteries

Strategies to noninvasively evaluate patients after coronary stenting have not been evaluated. To determine the accuracy of single-photon emission computed tomography (SPECT) myocardial perfusion imaging in patients after coronary stenting, 209 patients who had undergone stenting followed by late stress SPECT myocardial perfusion imaging were evaluated. Quantitative coronary angiography was performed in 33 patients following SPECT imaging. SPECT restenosis was defined as a reversible or fixed defect within the stented vascular territory. Angiographic restenosis was examined using 2 definitions: total area narrowing > or =50% or > or =70% of the stent site or stented artery. The SPECT and angiographic findings were concordant in 22 of 33 stented vascular territories using the 50% definition of restenosis and in 29 of 33 stented territories using the 70% definition. Use of the 70% definition of restenosis resulted in improved accuracy of SPECT to detect a significant stenosis in the stented artery. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of SPECT were 95%, 73%, 88%, 89%, and 88% respectively. In patients with positive SPECT scans, the most significant stenosis in the stented artery was outside the stent site in 50% of cases. SPECT imaging appears to be accurate to predict significant stenosis in the stented artery, although the most severe stenosis is frequently distant from the stent site.     

Positron emission tomographic imaging of the cardiovascular system: an emerging clinical tool

Cyclic GMP-dependent protein kinase (cGMP kinase) is the major receptor protein for cGMP in vascular smooth muscle. Vascular smooth muscle cells (VSMC) isolated from the rat aorta express type I cGMP kinase at high levels, but expression decreases markedly upon passage of the cells. In primary or early passage, the expression of cGMP kinase is lowest when cells are plated at low density as assessed by immunological and Northern analyses. Expression increases at confluence and is maintained in postconfluent cultures. With repeated passaging, however, the levels of cGMP kinase decrease even in confluent and postconfluent cultures so that after several passages enzyme levels are undetectable. The decrease in expression in passaged cells is not due to exposure to serum-derived growth factors, but rather on the repeated exposure of cells to conditions in which cell density is reduced (i.e., subculturing). These results indicate that aortic VSMC grown at low density or those repetitively passaged have reduced expression of cGMP kinase, and thus may not represent appropriate cultures with which to investigate the role of nitric oxide and cGMP in VSMC function.     

Underestimation of extent and severity of coronary artery disease by dipyridamole stress thallium-201 single-photon emission computed tomographic myocardial perfusion imaging in patients taking antianginal drugs

OBJECTIVES: This study evaluated the diagnostic value of dipyridamole plus low level treadmill exercise (dipyridamole stress) thallium-201 single-photon emission computed tomography (SPECT) in patients taking antianginal drugs. BACKGROUND: Dipyridamole stress is the major substitute for maximal exercise in patients referred for myocardial perfusion imaging. Although antianginal drugs are commonly suspended before exercise, dipyridamole stress is usually performed without discontinuing these drugs. METHODS: Twenty-six patients underwent two dipyridamole perfusion studies: the first without (SPECT-1) and the second with (SPECT-2) antianginal treatment. Twenty-one patients (81%) received calcium antagonists, 19 (73%) received nitrates, and 8 (31%) received beta-blockers. Eighteen of the patients underwent coronary angiography. Data are presented as the mean value +/- SD. RESULTS: Visual scoring yielded significantly larger and more severe reversible perfusion defects for SPECT-1 than for SPECT-2. Quantitative analysis showed larger perfusion defects on stress images of SPECT-1 in the left anterior descending coronary artery (LAD) (25 +/- 21% vs. 17 +/- 15%, p = 0.003), left circumflex coronary artery (LCx) (56 +/- 35% vs. 48 +/- 36%, p = 0.03) and right coronary artery (RCA) (36 +/- 27% vs. 25 +/- 24%, p = 0.008) territories. Individual vessel sensitivities in the LAD, LCx and RCA territories were 93%, 79% and 100% for SPECT-1 and 64%, 50% and 70% for SPECT-2, respectively. These differences were highly significant for the LAD (p = 0.004) and LCx (p = 0.00004) territories. The overall individual vessel sensitivity of SPECT-1 was significantly higher than that of SPECT-2 (92% vs. 62%, p = 0.000003). Specificity was not significantly different in SPECT-1 compared with SPECT-2 (80% and 93%, p = 0.33). CONCLUSIONS: Continued use of antianginal drugs before dipyridamole plus low level treadmill exercise thallium-201 SPECT may reduce the extent and severity of myocardial perfusion defects, resulting in underestimation of coronary artery disease.     

Breast tumour imaging using incomplete circular orbit pinhole SPET: a phantom study

Improvements in 99Tcm-sestamibi breast lesion visualization using single photon emission tomography (SPET) may help define the clinical role of this technique alongside X-ray mammography in the diagnosis and management of breast cancer. Pinhole SPET offers the advantages of high resolution and sensitivity when compared to conventional parallel-beam collimation for sources located near the pinhole aperture. In this work, the potential of incomplete (180 degrees) circular orbit (ICO) SPET with pinhole collimation is investigated as a means to visualize small (6.4 and 9.6 mm diameter) spherical simulated tumours, at clinical count densities and tumour-to-background ratios, in a breast phantom. ICO pinhole SPET is compared to complete circular orbit (CCO) pinhole SPET for reference, and planar breast imaging (scintimammography) using parallel-beam and pinhole collimators. A prototype box-shaped pinhole collimator with a 4 mm diameter circular aperture was used to acquire projections of an 890 ml breast phantom both in isolation and mounted on a cylinder filled with a mixture of 99Tcm-pertechnetate and water. A heart phantom containing 99Tcm activity in the myocardium was placed in the cylinder. Simulated tumours containing 99Tcm were placed in the breast phantom and scanned at clinically relevant count densities and scan times with tumour-to-normal tissue concentration ratios of 5.0:1 (9.6 mm sphere) and 7.7:1 (6.4 mm sphere). Phantom data were reconstructed using pinhole filtered backprojection (FBP) and maximum likelihood-expectation maximization (ML-EM). The tumours were not visualized with scintimammography, in which lesion contrast and signal-to-noise were estimated from region of interest analysis to be < 2% and 0.01, respectively. Average (over lesion size and scan time) contrast and signal-to-noise in the ICO (CCO) SPET images were 33% and 1.72 (34% and 1.3), respectively. These values indicate that ICO pinhole SPET has the potential to improve visualization of small (< 10 mm) breast tumours when compared with scintimammography, which may be beneficial for the early classification of cancers of the breast.     

Use of 123I-BMIPP single-photon emission tomography to estimate areas at risk following successful revascularization in patients with acute myocardial infarction

PURPOSE: To determine the frequency and nature of intraoperative complications of endocapsular phacoemulsification cataract surgery. SETTING: Dalcross Private Hospital and the Departments of Ophthalmology, Concord Hospital and Prince of Wales Hospital, Sydney, Australia. METHODS: This prospective study included the first 1000 cases of planned endocapsular phacoemulsification cataract surgery performed by an experienced surgeon. A standardized proforma was completed at the time of surgery. Data recorded included pre-existing ocular abnormalities, duration of surgery, nuclear sclerosis grade, and intraoperative complications. RESULTS: Major complications comprised posterior capsule tears with vitreous loss (1.4%), isolated posterior capsule tears (0.7%), and zonulysis (0.1%). Minor complications included anterior capsule tears (3.8%), iris prolapse (0.6%), and ciliary body incision (0.2%). There was a significant trend toward complications as the nuclear sclerosis grade increased. The incidence of major complications was 9.3% in the first 150 cases and 0.9% in the last 850. This represents a relative risk of 9.9 (95% confidence interval 4.2 to 23.0) of a major complication occurring in the first 150 compared with the later 850 cases. CONCLUSION: The frequency of major and minor complications fell sharply after the first 150 operations and was maintained. This study may provide a guide for beginning phacoemulsification surgeons and a basis for experienced surgeons to compare their performance outcomes.     

MR imaging of the uterus: findings from high-resolution multisection dynamic imaging with a surface coil

MR imaging of the female pelvis with a local coil (multiple phased array coils) has been reported. With this method, the signal-to-noise ratio (S/N) is improved so that high-resolution images can be obtained. Dynamic contrast-enhanced MR imaging has been reported to be useful in diagnosing uterine neoplasms. However, dynamic MR imaging is done in only limited imaging planes. When multisection dynamic MR imaging with fast gradient-echo sequences is combined with the use of a local coil, high-resolution images can be obtained throughout the entire uterus during a single breath-hold. This pictorial essay illustrates the appearance of the normal uterus and malignant uterine neoplasms on high-resolution multisection dynamic MR images obtained with a Helmholtz-type surface coil.     

Imaging of the dopaminergic neurotransmission system using single-photon emission tomography and positron emission tomography in patients with parkinsonism

Parkinsonism is a feature of a number of neurodegenerative diseases, including Parkinson's disease, multiple system atrophy and progressive supranuclear palsy. The results of post-mortem studies point to dysfunction of the dopaminergic neurotransmitter system in patients with parkinsonism. Nowadays, by using single-photon emission tomography (SPET) and positron emission tomography (PET) it is possible to visualise both the nigrostriatal dopaminergic neurons and the striatal dopamine D2 receptors in vivo. Consequently, SPET and PET imaging of elements of the dopaminergic system can play an important role in the diagnosis of several parkinsonian syndromes. This review concentrates on findings of SPET and PET studies of the dopaminergic neurotransmitter system in various parkinsonian syndromes.     

Myocardial infarction in france: Prognosis improvement?

BACKGROUND: Cyclosporine for the treatment of psoriasis constitutes a new approach. Alternative systemic cyclosporine derivatives have been studied to find an immunosuppressive drug with fewer adverse effects. Tacrolimus is one of these new immunosuppressive drugs. Systematically, it has been proven effective in treating psoriasis. A topical formulation of tacrolimus is attractive because it has fewer adverse effects and is useful for a large group of patients. We report for the first time on the efficacy of nonocclusive topical tacrolimus in the treatment of psoriasis. OBSERVATIONS: After a washout phase of 2 weeks, patients were randomized to receive 0.005% calcipotriol ointment twice daily, placebo ointment once daily, or 0.3% tacrolimus ointment once daily. One psoriatic plaque was treated with a surface area of 40 to 200 cm2. Efficacy was estimated using the local psoriasis severity index. The reduction in the local psoriasis severity index score after 6 weeks was 62.5% in the calcipotriol group, 33.3% in the tacrolimus group, and 42.9% in the placebo group. CONCLUSIONS: There was no statistically significant difference between the efficacy of tacrolimus and placebo ointment (P = .77). Calcipotriol ointment, applied twice daily, had a better effect than tacrolimus ointment and placebo ointment once daily.     

Attenuation-corrected 99mTc-tetrofosmin single-photon emission computed tomography in the detection of viable myocardium: comparison with positron emission tomography using 18F-fluorodeoxyglucose

OBJECTIVES: The purpose of this study was to assess the efficacy of attenuation-corrected (AC) technetium-99m (99mTc)-tetrofosmin single-photon emission computed tomography (SPECT) in detecting viable myocardium compared to 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET). BACKGROUND: The role of 99mTc-labeled perfusion tracers in the assessment of myocardial viability remains controversial. Attenuation artifacts affect the diagnostic accuracy of SPECT images. METHODS: Twenty-four patients with coronary artery disease (mean left ventricular ejection fraction 30%) underwent resting 99mTc-tetrofosmin SPECT and FDG PET imaging. Both AC and non-attenuation-corrected (NC) SPECT images were generated. RESULTS: Using a 50% threshold for viability by FDG PET, the percentage of concordant segments of viability between 99mTc-tetrofosmin and FDG on the patient basis increased from 79.8%+/-14.0% (mean+/-SD) on the NC images to 90.8%+/-10.6% on the AC images (p=0.002). The percentage of 99mTc-tetrofosmin defect segments within PET-viable segments, an estimate for the degree of underestimation of viability, decreased from 19.8%+/-15.2% on the NC images to 9.7%+/-12.6% on the AC images (p=0.01). Similar results were obtained when a 60% threshold was used to define viability by FDG PET. When the anterior-lateral and inferior-septal regions were separately analyzed, the effect of attenuation correction was significant only in the inferior-septal region. CONCLUSIONS: The results indicate that AC 99mTc-tetrofosmin SPECT improves the detection of viable myocardium mainly by decreasing the underestimation of viability particularly in the inferior-septal region, although some underestimation/overestimation of viability may still occur even with attenuation correction.     

Striatal and extrastriatal imaging of dopamine D2 receptors in the living human brain with [123I]epidepride single-photon emission tomography

The complete sequence of a 36775 bp DNA segment located on the right arm of chromosome XV of Saccharomyces cerevisiae has been determined and analysed. The sequence encodes 26 open reading frames of at least 100 amino acids. Eight of these correspond to known genes, whereas 18 correspond to new genes.     

Myocardial infarction in a pregnant woman during salbutamol therapy

The authors report the case of a 31 year old woman at 30 weeks' gestation who developed a non-Q wave postero-lateral myocardial infarction during treatment with salbutamol. There were no complications and delivery took place at term normally. Coronary angiography was performed 3 months post-partum and was normal: the Methergin test was negative. Myocardial ischaemia occurring during treatment with a beta-2 mimetic in pregnancy is rare and hardly ever progresses to myocardial infarction. The usual mechanism of ischaemia is an imbalance of myocardial oxygen demand and supply. Myocardial oxygen consumption is naturally increased during pregnancy and excess intracellular calcium secondary to the beta-1 stimulation occurring with the use of beta-2 mimetic drugs further aggravates matters. This hypothesis raises the question of the value of calcium inhibitors in these forms of myocardial ischaemia.