Automatic detection of coronary artery disease in myocardial perfusion SPECT using image registration and voxel to voxel statistical comparisons.

The purpose of this study was to compare the performance of automatic detection of coronary artery disease (CAD) with that of expert observers. A male and female normal image template was constructed from normal stress technetium-99m single photon emission computed tomography (SPECT) studies. Mean and standard deviation images for each sex were created by registering normal studies to a standard shape and position. The test group consisted of 104 patients who had been routinely referred for SPECT and angiography. The gold standard for CAD was defined by angiography. The test group studies were registered to the respective templates and the Z-score was calculated for each voxel. Voxels with a Z-score greater than 5 indicated the presence of CAD. The performance of this method and that of three observers were compared by continuous receiver operating characteristic (CROC) analysis. The overall sensitivity and specificity for automatic detection were 73% and 92%, respectively. The area (Az) under the CROC curve (+/-1 SE) for automatic detection of CAD was 0.88+/-0.06. There was no statistically significant difference between the performances of the three observers in terms of Az and that of automatic detection (P> or =0.25, univariate Z-score test). The use of this automated statistical mapping approach shows a performance comparable with experienced observers, but avoids inter-observer and intra-observer variability.

An assessment of perfusion deficits in decompression illness using 99Tcm HMPAO SPET and statistical parametric mapping.

AIM: The aim of this study was to use statistical parametric mapping (SPM) to investigate differences in the regional cerebral blood flow (rCBF) of decompression illness (DCI) and non-diving control subjects. METHODS: Twenty DCI subjects were imaged using 99Tcm hexamethylproplylene amine oxime (HMPAO) single photon emission tomography (SPET) within days of their incident of DCI, and on a second occasion between 2 and 27 months after their DCI event. SPM was used to make a comparison between decompression illness studies and a second group of non-diving control studies for both early and late imaging of DCI. A paired comparison of early and late imaging was also performed testing for correlation between time of imaging and changes in the rCBF pattern. RESULTS: The comparison between control subjects and early imaging of decompression illness showed a large, significant (P = 0.002), irregularly shaped, multi-focal area of reduced uptake in the left occipito-parieto-temporal region of the brain. Comparisons between control and repeat decompression illness imaging studies showed two areas of reduced uptake. The first was similar to that found in the initial comparison although it was less significant (P = 0.035). The second region was similar but contra-lateral to the first region with significance P < 0.001. An attempt to correlate any changes in rCBF with the time that elapsed between each set of imaging found no areas of significant correlation. CONCLUSION: 99Tcm HMPAO SPET images of decompression illness display areas of reduced perfusion, which persist in the majority of cases.

Comparison of methods for quantification of transient ischaemic dilation in myocardial perfusion SPET.

The purpose of this study was to compare six methods of measuring the left ventricular (LV) transient ischaemic dilation (TID) ratio during stress-rest myocardial perfusion single-photon emission tomography (SPET). The TID ratio was defined as the mean LV short-axis area at stress divided by the mean LV area of similar slices at rest. The centre of the LV wall was defined as either the maximum, mean or median of the radial short-axis count profiles. The area within the endocardial wall was also calculated for each definition of the LV wall centre. We identified 50 consecutive patients undergoing dipyridamole technetium-99m-tetrofosmin SPET imaging and angiography. Continuous receiver operating characteristic (CROC) analysis showed no significant difference between the six methods in terms of identifying severe coronary artery disease (P >0.47). Algorithms using the mean or the median value in the profile were significantly more robust than those using the maximum (P <0.0005). TID measured by all the algorithms is an indicator of severe coronary disease (P < 0.05). The algorithms compared provide a repeatable, quantitative and specific measure of the TID ratio.

HMPAO SPECT imaging of Alzheimer's disease patients with similar content-specific autobiographic delusion: comparison using statistical parametric mapping.

UNLABELLED: Delusional behavior and thinking are common symptoms in Alzheimer's disease (AD). In the past, these delusions have been considered to be psychotic complications of global neurologic dysfunction. Recently, authors have suggested that content-specific delusions in AD are associated with discrete regional abnormalities of the right hemisphere. METHOD: This study compared 99mTc-hexamethyl propyleneamine oxime (HMPAO) SPECT images of a group of AD patients with a similar autobiographic delusion with a group of AD patients without delusions and a group of AD patients with a range of delusions but without autobiographic content. The reconstructed SPECT data were compared using a statistical parametric mapping technique. RESULTS: The autobiographic AD group had a significant area of hypoperfusion in the right frontal lobe when compared with the 2 other groups. The area of hypoperfusion included parts of Brodmann's areas 9 and 10. Region 9 has been identified previously as having a role in episodic memory retrieval. CONCLUSION: This result suggests that autobiographic delusions in AD may have an identifiable neuropsychologic mechanism and that it may be possible to identify an organic cause in some patients using 99mTc-HMPAO SPECT.

Changes in the rCBF images of patients with Alzheimer's disease receiving Donepezil therapy.

Alzheimer's disease is associated with a loss in presynaptic cholinergic function. It has been suggested that cholinergic inhibitors such as donepezil hydrochloride (Donepezil) could restore this function and improve some of the symptoms of Alzheimer's disease. Previous work has shown that Donepezil improves cognitive and global function in patients with mild to moderate Alzheimer's disease. This study reviewed retrospectively 12 patients who had previously had a 99Tcm-hexamethylpropylene amine oxime (99Tcm-HMPAO) single photon emission tomography (SPET) regional cerebral blood flow (rCBF) examination and had gone on to receive Donepezil therapy. These patients were recalled for a further 99Tcm-HMPAO SPET rCBF examination and the image data sets were compared. The results showed an overall increase in global cerebral blood flow (P = 0.04) averaged over the group with a percentage change in blood flow ranging from -1.8% to 6.4%. However, some patients showed a slight decrease in blood flow. When the data were analysed in terms of regional cerebral blood flow, we found that the most significant increase in blood flow occurred in the frontal lobes (P = 0.02).

Delusions in Alzheimer's disease: spet evidence of right hemispheric dysfunction.

Delusional thinking and related behaviours are common symptoms in Alzheimer's disease (AD). The aim of the study was to determine if any consistent cerebral image pattern can be identified using Tc99m-hexamethylpropyleneamine (HMPAO) SPET in AD patients with and without delusions. 18 AD patients with delusion and 15 AD patients without delusion underwent neuropsychological testing and regional cerebral blood flow imaging using Tc99m-HMPAO SPET. The reconstructed data was compared using regions of interest drawn over each cerebral lobe and a statistical parametric mapping (SPM) approach. The neuropsychological testing showed that there was no difference in the profiles of the deluded and non deluded AD patients. The imaging results showed a significant degree of image asymmetry. This took the form of a right hemisphere hypoperfusion mainly in the right frontal and limbic regions. The results do not indicate a specific focal site of hypoperfusion in the patients with delusion. They do, however, indicate that delusions in AD may be associated with areas of hypoperfusion in the right anterior hemisphere.

Correlation between 99Tcm-HMPAO-SPECT brain image and a history of decompression illness or extent of diving experience in commercial divers.

OBJECTIVES: To explore the use of 99technetiumm-hexamethyl propylene amine oxime single photon computed tomography (HMPAO-SPECT) of the brain as a means of detecting nervous tissue damage in divers and to determine if there is any correlation between brain image and a diver's history of diving or decompression illness (DCI). METHODS: 28 commercial divers with a history of DCI, 26 divers with no history of DCI, and 19 non-diving controls were examined with brain HMPAO-SPECT. Results were classified by observer assessment as normal (I) or as a pattern variants (II-V). The brain images of a subgroup of these divers (n = 44) and the controls (n = 17) were further analysed with a first order texture analysis technique based on a grey level histogram. RESULTS: 15 of 54 commercial divers (28%) were visually assessed as having HMPAO-SPECT images outside normal limits compared with 15.8% in appropriately identified non-diver control subjects. 18% of divers with a history of DCI were classified as having a pattern different from the normal image compared with 38% with no history of DCI. No association was established between the presence of a pattern variant from the normal image and history of DCI, diving, or other previous possible neurological insult. On texture analysis of the brain images, divers had a significantly lower mean grey level (MGL) than non-divers. Divers with a history of DCI (n = 22) had a significantly lower MGL when compared with divers with no history of DCI (n = 22). Divers with > 14 years professional diving or > 100 decompression days a year had a significantly lower MGL value. CONCLUSIONS: Observer assessment of HMPAO-SPECT brain images can lead to disparity in results. Texture analysis of the brain images supplies both an objective and consistent method of measurement. A significant correlation was found between a low measure of MGL and a history of DCI. There was also an indication that diving itself had an effect on texture measurement, implying that it had caused subclinical nervous tissue damage.

Decompression illness in sports divers detected with technetium-99m-HMPAO SPECT and texture analysis.

UNLABELLED: Diving for sport and recreation has increased in recent years, resulting in more incidences of diving illness. Therefore, we studied potential use of regional cerebral blood flow SPECT imaging with 99mTc-HMPAO in the management of divers who have experienced decompression illness (DCI). METHODS: A group of ten sports divers who had no experience of DCI were compared with ten sports divers who had experienced at least one episode of DCI. Transaxial SPECT images were first compared objectively using a first-order texture measure and then subjectively using a receiver operator characteristic (ROC) experiment. Experienced observers were asked to rate images subjectively in terms of the images' textural appearance. RESULTS: Both these techniques showed that there is a statistically significant difference between the two groups and the images produced by the DCI divers were generally more coarsely patchy when compared to the non DCI divers. The quantitative texture technique proved significantly better in identifying divers with DCI than the visual analysis by observers using ROC curves. CONCLUSION: Differences between the cerebral blood flow patterns of sports divers who have experienced DCI and sports divers who have no experience of DCI can be detected using 99mTc-HMPAO SPECT and a texture analysis technique.

A variable threshold edge-detector for improved quantitation of gated tomographic imaging of the left ventricular blood pool.

The accurate measurement of left ventricular volume from tomographic MUGA studies is difficult due to the limited resolving power of the gamma camera, which causes errors in the detection of the correct ventricular boundaries. Therefore, the use of fixed threshold or second-derivative edge-detectors results in overestimates at small volumes. A variable threshold edge-detection technique was developed to overcome this. Computer-simulated short-axis slices through the heart over a range of left ventricular dimensions were convolved by the Point Spread Response Function of the system to model the acquired image. The maximum pixel value and the threshold value required to detect the true ventricular edge from each simulation were then combined into a look-up table for the calculation of the required threshold value. As the dimension of the ventricle decreased, the threshold value chosen to detect the ventricular edge increased. Left ventricular volumes and ejection fraction measurements were calculated for seven patients using cine-MRI as the gold-standard technique for validation of the proposed method. The single photon emission tomographic studies were analysed using both the standard second-derivative edge-detection software and the proposed variable threshold technique. The variable threshold technique was shown to increase significantly the accuracy of ventricular volume measurements and ejection fraction calculations. The average error in the measurement of volumes was reduced from 41.4 +/- 45.1% to 18.5 +/- 14.6% and the accuracy of ejection fraction measurement was increased from 29.7 +/- 4.6% to 11.3 +/- 6.9%.

Assessment of energy-weighted acquisition in SPECT using ROC analysis.

UNLABELLED: Energy-weighted acquisition is a technique for reducing Compton scatter effects in nuclear medicine images. The effect of energy-weighted acquisition on SPECT99mTc images was evaluated by comparing the energy-weighted acquisition images with those obtained using a 20% photopeak energy window. METHODS: SPECT images were compared using receiver operator characteristic (ROC) experiments testing the observer's ability to perform a pseudoclinical task. The tasks were detecting cold lesions within a uniform background and cold lesions within images created with a tomographic brain phantom. RESULTS: ROC analysis for each phantom produced different results. No significant difference was found between the two acquisition techniques in detecting cold lesions on uniform backgrounds. Energy-weighted acquisition improved cold lesion detection significantly within the brain phantom in comparison with 20% photopeak acquisition. CONCLUSION: Lesion detection in 99mTcSPECT images can be improved using energy-weighted acquisition. This improvement, however, is dependent on the nature of the object being imaged. Images with structure show improved detection, whereas uniform images do not.

Texture analysis of divers' brains using 99Tcm-HMPAO SPET.

The potential use of regional cerebral blood flow (rCBF) single photon emission tomography (SPET) imaging with 99Tcm-hexamethylpropyleneamine oxime (HMPAO) in the management of divers who have undergone a form of decompression sickness (DCS) was investigated using texture analysis. We imaged 50 divers, 10 of whom had only experienced DCS which had been categorized as Type 1, 20 of whom had a history of DCS classified as Type 2 and 20 of whom had not suffered an episode of DCS. A number of divers who had experienced Type 2 DCS had also had incidents of Type 1. The reconstructed SPET images were pre-processed and analysed using a first-order texture analysis technique based on a grey level histogram. The results showed that there was a significant textural difference between the divers who had only suffered episodes of DCS Type 1 and the diving controls and a difference between the divers with a history of Type 2 and the diving controls. No differences were found between the two groups of divers who had a history of DCS. This result suggests that DCS produces a detectable change in 99Tcm-HMPAO SPET brain images. However, the segmentation between the groups investigated was not complete and so the usefulness of this approach appears limited in individual cases but may provide useful information about the effects of different diving practices.

Technetium-99m-1,2-bis[bis(2-ethoxyethyl) phosphino]ethane: human biodistribution, dosimetry and safety of a new myocardial perfusion imaging agent.

A novel 99mTc complex (1,2-bis[bis(2-ethoxyethyl)phosphino] ethane, 99mTc-tetrofosmin) has been developed to replace 201Tl in myocardial perfusion imaging. Biodistribution, safety and dosimetry of 99mTc-tetrofosmin were studied in 12 male volunteers, each at rest and during exercise. Safety parameters measured to 48 hr postinjection revealed no clinically significant long-term drug-related changes. Biodistribution was studied by acquiring whole-body or serial static images up to 48 hr postinjection. Technetium-99m-tetrofosmin shows good heart uptake (1.2%) with retention. Clearance is excellent from blood (< 5% by 10 min), liver (< 4.5% by 60 min) and lung. Sequestration of activity by skeletal muscle is enhanced during exercise. Radiation dosimetry calculations indicate that the effective dose, assuming a 3.5 hr bladder voiding period, is 32.9 x 10(-3) rad/mCi (8.9 x 10(-3) mSv/MBq) at rest and 26.7 x 10(-3) rad/mCi (7.1 x 10(-3) mSv/MBq) after exercise. Technetium-99m-tetrofosmin can produce high quality myocardial images from 5 min to several hours postinjection.

Alzheimer's disease in adults with Down's syndrome: the relationship between regional cerebral blood flow equivalents and dementia.

Twenty adult patients suffering from Down's syndrome (DS) were recruited from hospitals and the community, together with 14 age- and sex-matched controls of normal intelligence. Dementia was diagnosed in patients using a structured psychiatric and physical examination as well as a carer interview and case notes. All patients and controls were imaged using single photon emission computerized tomography with 99mTc-exametazime. Four patients were clinically demented and all of them showed regional cerebral blood flow (rCBF) changes commonly found in patients with Alzheimer's disease, namely bilateral temporo-parietal deficits. These changes were also observed in about half of the patients without clinical evidence of dementia, but in none of the healthy controls. Across the group of patients, temporo-parietal rCBF deficits were associated with evidence of deterioration, but not with advancing age.

The short term effects of oral labetalol in patients with chronic renal disease and hypertension.

This double-blind, controlled, crossover study compared the effects on blood pressure control, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) of labetalol, methyldopa and placebo in patients with chronic renal disease and hypertension. When compared with placebo, BP was significantly lower during treatment with both labetalol and methyldopa (P greater than 0.05) but did not differ significantly between the two active treatment periods; post-exercise heart rates were also significantly lower on labetalol than placebo (P less than 0.05). After treatment with labetalol, ERPF was significantly greater than with the placebo (P less than 0.05) but did not differ significantly between the active treatments. GFR did not differ significantly between the three groups. No significant differences were observed in haematology or liver function test results on labetalol compared with placebo. Labetalol is a safe and effective antihypertensive in patients with hypertension associated with chronic renal disease. In the short term it leads to an increase in ERPF which may be beneficial for such patients.

Regional cerebral blood flow imaging: a quantitative comparison of technetium-99m-HMPAO SPECT with C15O2 PET.

The aim of this study was to compare technetium-99m-hexamethylpropyleneamineoxime (99mTc-HMPAO) single-photon emission computed tomography (SPECT) with regional cerebral blood flow (rCBF) imaging using positron emission tomography (PET). As investigation of dementia is likely to be one of the main uses of routine rCBF imaging, 18 demented patients were imaged with both techniques. The PET data were compared quantitatively with three versions of the SPECT data. These were, first, data normalized to the SPECT cerebellar uptake, second, data linearly corrected using the PET cerebellar value and, finally, data Lassen corrected for washout from the high flow areas. Both the linearly-corrected (r = 0.81) and the Lassen-corrected (r = 0.79) HMPAO SPECT data showed good correlation with the PET rCBF data. The relationship between the normalized HMPAO SPECT data and the PET data was nonlinear. It is not yet possible to obtain rCBF values in absolute units from HMPAO SPECT without knowledge of the true rCBF in one reference region for each patient.

Multimodal imaging in Alzheimer's disease. The relationship between MRI, SPECT, cognitive and pathological changes.

Patients with a clinical diagnosis of Alzheimer's disease were studied using MRI, SPECT, and psychometric tests. Significant correlations between focal perfusion deficits and focal cognitive deficits were found. Significant correlations between regional relaxation time of white matter and psychometric tests of diffuse and focal categories were also found. Pathological examination confirmed Alzheimer's disease as the only diagnosis.

99Tcm-HMPAO single photon emission computed tomography in partial epilepsy: a preliminary report.

In the pre-operative assessment of patients being considered for temporal lobe surgery, accurate lateralization and localization of the epileptic focus is mandatory. Surface electroencephalography (EEG) can be misleading and confirmatory evidence, preferably non-invasive, of the site of the epileptic focus is valuable. Sixteen patients with partial epilepsy, six of whom were considered to be good surgical candidates, had technetium-99m hexamethylpropylene amine oxime (99Tcm-HMPAO) scanning. In those patients with poor epileptic control and a well localized EEG focus, there was a correlation between EEG and HMPAO scan abnormalities, whilst in all patients where no correlation existed, the HMPAO scan was normal. We conclude that 99Tcm-HMPAO single photon emission computed tomography may be a useful non-invasive, adjunctive investigation in the preoperative assessment of patients with partial epilepsy.