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Respiratory and cardiac motion artefacts impair the quality and reliability of medical imaging, particularly in nuclear medicine. At worst, the interpretation of distorted images may lead to inadequate or unnecessary treatment. Image artefacts can be minimized by gating the image acquisition according to respiratory phase and cardiac contractions. However, currently there are no clinically established dual-gating methods in nuclear medicine imaging. The aim of this study is to validate a previously determined optimized bioimpedance measurement configuration against traditional respiratory and cardiac measurement systems in 12 volunteers. High agreement and excellent correlations (r = 0.944-0.999) were found between respiratory peak-to-peak amplitudes as well as temporal respiratory and cardiac intervals. Above all, good quality respiratory and cardiac gating signals were obtained from all test subjects with a fairly regular sinus rhythm. Importantly, both signals were acquired simultaneously with a single device. Due to the simplicity of this inexpensive method, the technique has high potential to be adopted for dual-gating in clinical practice in the future.

Summary Aim: Reversible or irreversible myocardial damage due to ischemia correlates with altered membrane functions of the cells. To compare myocardial free fatty acid (FFA) metabolism and flow during exercise induced ischemia we studied ten patients with coronary artery disease but without previous myocardial infarction. Methods: A series of post-exercise single-photon emission computed tomography (SPECT) measurements was performed after injection of 123I labelled heptadecanoic acid (HDA). Myocardial perfusion was estimated from the separately performed exercise-redistribution thallium study. Fatty acid metabolic rate, thallium uptake and washout were calculated for anterior, lateral, posterior and septal segments. Results: The more reduced post-exercise FFA metabolic rate (–63 ±18%, mean ±1 SD) compared to flow (–36 ±16%) was related to the severity of myocardial ischemia and wall motion abnormalities. Conclusion: In this small group of patients, the reduced post-exercise FFA metabolic rate tentatively suggests a parsimonious workload of the exercising myocardium by reducing oxygen consumption in patients with coronary artery disease.

The aim of the study was to evaluate quality of myocardial perfusion single-photon emission tomography (SPET) imaging in Finnish hospitals. Nineteen nuclear medicine departments participated in the study. A myocardial phantom simulating clinical stress and rest conditions was filled with routinely used isotope solution (technetium-99m or thallium-201). The cardiac insert included three reversible defects (simulating ischaemia): 30x30x14 mm(3) septal (90% recovery at rest), 30x20x14 mm(3) posterobasal (full recovery) and 20x20x14 mm(3) lateral (full recovery). There were two fixed defects (simulating infarct): 30x20x14 mm(3) postero-apical and 10x10x6 mm(3) apical. The phantom was imaged and interpreted as a myocardial perfusion patient. Reconstruction, printout and reporting were performed according to the clinical routine of each centre. Three nuclear medicine specialists anonymously evaluated the quality of the image sets. The visual scores of the experts were ranked from 1 to 5. Additionally, points from 0 to 8 were given to research reports according to how well perfusion defects were detected. Quantitative points were calculated by comparing background-subtracted and -normalized counts from 12 regions of interest between stress and rest images. Results for technetium studies (12 departments) were better than those for thallium (7 departments). The average visual scores of the experts were 3.7+/-0. 9 for all image sets, 3.2+/-0.5 for thallium users and 3.9+/-0.6 for technetium users (P=0.003). Five laboratories received a low score which, according to the specialists, is barely sufficient for limited clinical use. Average points for the reports were 5.6+/-2.1, 4.9+/-1.5 and 6.5+/-1.7 (P=0.051), and for the quantitation 8.2+/-1. 0, 7.9+/-0.4 and 8.4+/-1.1 (P=0.185), respectively. Seven out of 22 interpreters did not detect the lateral 20x20x14 mm(3) defect; five of them used thallium. This study demonstrated the heterogeneity of myocardial perfusion SPET in Finland. The participating laboratories used a wide scale of methods and, sometimes, inappropriate imaging protocols. The need for quality assurance in nuclear cardiology, correct use of SPET instrumentation and objective comparison of clinical studies is evident. The method described is suitable for external quality assurance and quality improvement of myocardial SPET imaging, and is recommended for regular use in nuclear medicine.

In myocardial perfusion SPET studies with 99 Tc m -Q12, we observed that some patients had high liver uptake that interfered significantly in the assessment of the inferior wall. The aim of this study was to assess the effects of the radiochemical purity of 99 Tc m -Q12 on liver uptake. Thirty-one patients undergoing routine myocardial infarction perfusion studies were evaluated. The radiochemical purity of 99 Tc m -Q12 was determined using HPLC. Venous blood samples taken 50 min after injection of 99 Tc m -Q12 during peak exercise were also analysed. Liver uptake was expressed as the liver-to-heart ratio. In addition, the SPET images were classified by two experienced nuclear medicine specialists into three groups representing high-quality images (n = 7), images with high general background activity (n = 13) and images with high liver and/or intestinal uptake (n = 11). The liver-to-heart ratio correlated inversely with the radiochemical purity of 99 Tc m -Q12 (r = -0.65, P < 0.001) and unchanged 99 Tc m -Q12 in plasma (r = -0.44, P < 0.02). The radiochemical purity of 99 Tc m -Q12 was significantly lower in the group with high liver uptake (60.1 ± 4.2%) than in the group with good-quality images (81.8 ± 5.6%, P < 0.01) or with high background activity (82.3 ± 2.5%, P < 0.01). In conclusion, the radiochemical purity of 99 Tc m -Q12 has a significant inverse correlation with the liver-to-heart ratio; thus, the high radiochemical purity of 99 Tc m -Q12 should be confirmed to prevent interference by liver uptake.

SummaryPhoton scatter is one of the most important factors degrading the quantitative accuracy of SPECT images. Many scatter correction methods have been proposed. The single isotope method was proposed by us. Aim: We evaluate the scatter correction method of improving the quality of images by acquiring emission and transmission data simultaneously with single isotope scan. Method: To evaluate the proposed scatter correction method, a contrast and linearity phantom was studied. Four female patients with fibromyalgia (FM) syndrome and four with chronic back pain (BP) were imaged. Grey-to-cerebellum (G/C) and grey-to-white matter (G/W) ratios were determined by one skilled operator for 12 regions of interest (ROIs) in each subject. Results: The linearity of activity response was improved after the scatter correction (r = 0.999). The y-intercept value of the regression line was 0.036 (p

Knowledge of the contributions of transit time heterogeneity to the cardiopulmonary system is important for understanding cardiopulmonary function in patients with intracardiac shunt. We determined the heterogeneity of blood transit times occurring between the right atrium and the left ventricle. Eighty two patients with suspected left-to right shunt were investigated with first-pass 99mTc-labelled red blood cell radiocardiography at supine rest. Forty two of them had a pulmonary-to-systemic flow ratio (Qp:Qs) of less than 1.2 and they served as a control group. The remaining study subjects had a Qp:Qs ratio of 1.7 +/- 0.3 (mean +/- SD). The patients with shunt had significantly greater (p0.001) heterogeneity of transit times (49 +/- 9%) than in the controls (39 +/- 7%). Overall heterogeneity of cardiopulmonary transit times in patients with shunt showed a curvature relationship; the highest values were centred in patients with moderate to severe shunt (1.5Qp:Qs2.5). The results suggest that the increased heterogeneity of transit times mainly occurs within the pulmonary capillary bed in patients with intracardiac shunt. This is probably due to the recruitment of the open capillaries without vessel distension.

We evaluated the physical performance of the new Siemens E.CAM gamma camera. The camera is a dual-headed, large detector system with an open gantry dedicated to planar and to multislice single photon emission tomographic (SPET) imaging of the whole body. The energy-independent digital detectors with high-quality photo-multiplier tubes seem to keep the physical performance of the E.CAM camera very stable. The imaging resolution is very good. The SPET resolution is 9.1 mm full-width at half maximum in scatter for high-resolution collimators with a rotational radius of 15 cm. Both planar (or = 2%) and SPET uniformity (or = 4%) are excellent. The detectors can be configured at variable angles which allows flexibility, especially in heart studies. Autocontouring performs whole-body and SPET scans as close to the patient as possible. The patient couch, with its very low gamma-ray attenuation, is firm and can be lowered to make patient loading easier. Camera tuning, calibration, acquisition and processing are controlled by two Power Macintosh 8500 computers. The ICON software is easy to use (a mouse-driven system). However, acquisition interrupts and autocontouring errors were noted during our initial experience. The image quality of routine bone and heart scans was excellent. The E.CAM system allows fast and accurate planar and SPET imaging both in clinical practice and research.

This review article forecasts developments in nuclear medicine instrumentation which are on the horizon. Special attention is paid to the physical properties of detectors and multiple-processor parallel processing systems needed for fast and high-quality imaging in emission tomography. Advances in detector technology will improve imaging resolution below 5 mm and will increase sensitivity and quantitative accuracy. In addition, high count rate list-mode acquisition enables 'true' four-dimensional data-sets. A sandwich-like construction of two different crystals allows the simultaneous use of conventional tracers and positron tracers (multiple emission tomography, MET). Transmission-based attenuation and scatter compensation with fast iterative reconstruction methods will further improve image quality. The clinical and scientific importance of improved images and the limits on advances in instrumentation are also reviewed.

Epidemiological studies have suggested that patients with rheumatoid arthritis (RA) have increased mortality due to cardiovascular disease. We studied cardiac performance in 12 asymptomatic male patients with RA and 14 control subjects to elucidate early disturbances in cardiac function. In echocardiography, isovolumic relaxation time was longer (64 +/- 6 vs. 49 +/- 3 ms, mean +/- SEM, P = 0.010) and peak filling rate (134 +/- 10 vs. 159 +/- 6 mm s-1, P = 0.015) lower in patients with RA than in control subjects, reflecting an impairment in left ventricular diastolic function. Left ventricular systolic function assessed by radionuclide angiocardiography at rest and during exercise was similar in both groups. There were no differences between the patients with RA and control subjects in the heart rate, systolic blood pressure and oxygen uptake during peak exercise. Left ventricular diastolic function is impaired in spite of normal left ventricular systolic function in patients with RA without clinically evident cardiovascular disease and this may contribute to the excess of cardiovascular mortality in patients with RA.

Alterations in dopaminergic and serotonergic systems have been observed in many neuropsychiatric disorders. We evaluated the reproducibility of dopamine (DAT) and serotonin transporter (SERT) binding measured with single-photon emission computed tomography (SPECT). Two repeated SPECT studies with nor-(β-CIT were performed within one year interval in 11 healthy control subjects. The intraclass correlation coefficient was 0.79 (p < 0.01) for DAT and 0.82 (p < 0.01) for SERT, respectively. The agreements between two measurements were good. Therefore we considered acceptable to use SPECT with nor-(β-CIT in measurements of DAT and SERT binding in various neuropsychiatric disorders.

The iodine-123 labelled selective ligand N-(3-iodoprop-2E-enyl)-2beta-carbomethoxy-3beta-(4-methylphe nyl)nortr opane ([(123)I]PE2I) has been developed and has been shown to be suitable for single-photon emission tomography imaging of the dopamine transporter. In this study the influence of age on ligand binding was investigated in 16 healthy males with an age range of 23- 75 years. Single-photon emission tomography (SPET) imaging was performed with a triple-headed gamma camera. A simplified reference region model, in which the input function was derived from the non-displaceable cerebellar compartment, was used to calculate the volume of distribution in the striatum. The volume of distribution was shown to decline with age (-0.4%/year; P0.005). The results were in agreement with in vivo and in vitro findings of a decline in dopamine transporter binding with age. The findings confirm the suitability of [(123)I]PE2I for SPET imaging in clinical routine but emphasize the necessity of using age-matched controls in patient studies.

To study its usefulness as a tracer for assessment of the perfusion and viability of myocardium, 15-(p-iodophenyl)pentadecanoic acid (IPPA) was compared with technetium-99m sestamibi (MIBI). Dual-tracer single-photon emission tomography rest imaging was performed no more than 2 months before and 3 months after coronary artery bypass grafting in 28 patients with previous anterior (n=13) or inferior (n=15) infarction. The size of MIBI and IPPA defects decreased from 14%+/-12% and 13%+/-9% to 10%+/-11% and 9%+/-7%, respectively (P0.001 for both). The MIBI uptake increased in the infarct zones from 35%+/-11% to 43%+/-8% (P0.001), and in the peri-infarct zones from 50%+/-11% to 55%+/-10% (P0.05). The IPPA uptake increased in the infarct zones from 37%+/-11% to 44%+/-13% (P0.001), and in the peri-infarct zones from 51%+/-11% to 57%+/-12% (P0.05). In nine patients with improved regional echocardiographic wall motion score after bypass surgery, the pre-operative uptake values of both MIBI and IPPA in the infarct and peri-infarct zones were on average slightly but not significantly higher than in 19 patients with no observed improvement in regional wall motion score. In patients with improved regional wall motion, the MIBI scans and the IPPA scans showed (non-significant) decreases in defect size and increases in infarct and peri-infarct zone uptake after bypass surgery. Similar (in some cases significant) changes were observed in the patients without improvement in wall motion. Thus IPPA and MIBI provided similar information about perfusion and viability in pre- and postoperative evaluation of patients with clinically evident myocardial infarction and with normal global ejection fraction. Regardless of the tracer used, the resolution capability of the dual-tracer method with a rest imaging protocol was not sufficient to differentiate viable from non-viable infarction defects in unselected individual patients with a normal ejection fraction.

Background and Purpose —More effective imaging methods are needed to overcome the limitations of CT in the investigation of treatments for acute ischemic stroke. Diffusion-weighted MRI (DWI) is sensitive in detecting infarcted brain tissue, whereas perfusion-weighted MRI (PWI) can detect brain perfusion in the same imaging session. Combining these methods may help in identifying the ischemic penumbra, which is an important concept in the hemodynamics of acute stroke. The purpose of this study was to determine whether combined DWI and PWI in acute ( Methods —Forty-six patients with acute ischemic stroke underwent DWI and PWI on days 1, 2, and 8. No patient received thrombolysis. Twenty-three patients underwent single-photon emission CT in the acute phase. Lesion volumes were measured from DWI, SPECT, and maps of relative cerebral blood flow calculated from PWI. Results —The mean volume of infarcted tissue detected by DWI increased from 46.1 to 75.6 cm 3 between days 1 and 2 ( P 3 after 1 week ( P r =0.699, P r =0.827, P r =0.824, P Conclusions —Combined DWI and PWI can predict infarct enlargement in acute stroke. PWI can detect hypoperfused brain tissue in good agreement with SPECT in acute stroke.

Six healthy controls and 13 patients with Parkinson’s disease in different disability stages were studied with high resolution SPET using [123I]β-CIT-FP. The caudatus­to-cerebellum and putamen-to-cerebellum ratios were calculated at 3.5 hours after injection. Patients had the significantly lower ratio than that of the controls in the putamen (3.0 ± 1.0 vs. 4.7 ± 0.4 ) and in the caudatus (3.5 ± 1.1 vs. 4.9 ± 0.5), respectively. There was a significant negative correlation between the ratio and the Hoehn and Yahr stage in the putamen (r = −0.74) and in the caudatus(r = −0.80). Reduced striatal uptake demonstrates the loss of presynaptic nerve endings in the striatum of the patients with Parkinson’s disease.