Optimal preprocessing Butterworth-Wiener filter for Tl-201 myocardial SPECT

The optimal frequency characteristic of Butter-worth-Wiener filters (BWF) for improving the image quality of ²⁰¹ Tl myocardial SPECT was determined by a phantom experiment. Thirty two projection images of the phantom containing 11.1 MBq of ²⁰¹Tl with 4 different cold lesions were collected during a 180° arc of a gamma camera. A set of the projection images were processed with each of 27 different BWFs, and SPECT images were reconstructed by Shepp-Logan filtered backprojection. The SPECT images were evaluated for their diagnostic ability to visibly detect the cold lesions by four nuclear medicine physicians. The lesion contrasts were used as an adjunctive tool to determine the optimum filter. The optimal combination of the parameters determining BWF characteristics (for the data of about 100 count/pixel at the myocardium) is: 1) cutoff of 0.25/pixel, 2) FWHM of 3 pixels, 3) noise/signal ratio of 0.02. FWHM and noise/signal ratio affected lesion contrast much less than cutoff frequency. Clinical myocardial SPECT images processed with the optimal BWF showed less noise and sharper delineation of the myocardium.Part of this investigation was presented at the 34th annual meeting of the Society of Nuclear Medicine [Toronto, J Nucl Med (1987) 28:1068]     

Quantitative evaluation of myocardial viability using Tl-201 myocardial SPECT]

In order to evaluate myocardial viability, we developed a new method for quantification of redistributed area in Tl-201 myocardial SPECT, and it was applied to 71 patients with LAD lesion. Initial image was subtracted from delayed image, and redistributed area was displayed as an unfolded map (viability map). Extent and viability score, which correspond to extent and degree of the viable area, was also calculated. In the cases with prior myocardial infarction, viability score was widely distributed and extent score was smaller, while the cases with angina pectoris had larger extent score. Visual assessment of redistribution to the infarcted area was compared with % score, which was calculated as ratio to initial defect score. When the criteria of viability was defined as % viability score greater than 36 or % extent score greater than 16, quantitative evaluation agreed with visual assessment, and corresponded to clinical course. This method was considered to be effective for evaluation of extent and degree of myocardial viability, but further evaluation need to be done in comparison with reinjection, PET study, and so on, and usefulness in multi-vessel disease.     

Utility of rest Tl-201 myocardial SPECT images for estimating myocardial viability]

Rest Tl-201 myocardial SPECT images were underwent in 19 patients with anterior wall myocardial infarction under PTCR one month after the onset of acute myocardial infarction. The relationship between shortening rate (SR) of the left ventricle estimated by radial method and corresponding %Tl-201 uptake obtained by circumferential profile analysis was studied. For each patients 10 points on the anterior wall were taken into consideration. Seven patients showed depressive flat profile curve and 12 patients showed slant curve, in which %Tl-201 uptake continuously decreased from base to apex. Well correlation was obtained between SR and %Tl-201 uptake (SR = -41.2 +/- 1.03% Tl-201 uptake, r = 0.54, p less than 0.001). Average %Tl-201 uptake corresponding to SR = 0 was 46.3 + 6.8% (36-58). The sensitivity of %Tl-201 uptake greater than or equal to 60% for SR greater than or equal to 20% was 97% (87/90) and specificity was 69% (31/45). Tl-201 myocardial SPECT images were useful for estimating myocardial viability and %Tl-201 uptake was one of excellent parameters for quantitatively estimating myocardial viability.     

The optimum Butterworth-Wiener filter for I-123 IMP brain SPECT

The optimum Butterworth-Wiener filter (BWF) for the preprocessing of N-isopropyl-p-[I-123]-iodoamphetamine (I-123 IMP) SPECT was determined by a simulation experiment. Sixty-four images of the brain phantom containing 14.8 MBq of I-123 IMP were collected with a gamma camera equipped with a slant hole collimator during a 360-degree rotation. The images were processed with 27 BWFs of different shapes, followed by SPECT image reconstruction and visual comparison. The optimum BWF had a cutoff frequency of 0.25/pixel, FWHM of four pixels, and constant of 0.05. The image quality was greatly affected by the cutoff frequency of BWF used for preprocessing.     

SPECT imaging with Tl-201 and Ga-67 in myocardial sarcoidosis

Two patients with myocardial sarcoidosis are presented, both of whom underwent SPECT imaging with Tl-201 and Ga-67. The first had Ga-67 myocardial uptake with a Tl-201 defect, which disappeared with corticosteroid therapy. The second had multiple Tl-201 defects without Ga-67 uptake, which persisted despite corticosteroid therapy. Therefore, the combination of Tl-201 and Ga-67 imaging may be useful for recognizing myocardial sarcoidosis and for predicting the response to corticosteroid therapy.     

Q-wave regression after acute myocardial infarction assessed by Tl-201 myocardial perfusion SPECT

BACKGROUND: The actual relationship between the interval change of myocardial thallium 201 (Tl-201) radioactivity in the infarct area and the pattern of Q-wave regression is still unknown. This study was conducted to evaluate their relationship after acute myocardial infarction (AMI). METHODS AND RESULTS: A total of 30 patients who had a first Q-wave AMI (11 without Q-wave regression and 19 with Q-wave regression) were retrospectively included. Two sets of 12-lead surface electrocardiograms and Tl-201 myocardial perfusion images were obtained 0 to 2 months and 14 to 84 months after the AMI event, respectively. The acute/subacute redistribution Tl-201 radioactivity was similar between the patients with and those without Q-wave regression. However, the patients with Q-wave regression had higher chronic redistribution Tl-201 radioactivity than those without Q-wave regression. Moreover, the patients with Q-wave regression presented a higher gradient in the redistribution Tl-201 radioactivity between the chronic and acute/subacute images than those without Q-wave regression. CONCLUSIONS: This study supports the role of functional recovery of stunning and/or hibernating myocardium in the disappearance of Q waves after AMI.     

Incidental detection of breast cancer during Tl-201 myocardial SPECT study

A case of left breast cancer which was detected incidentally by Tl-201 SPECT performed to evaluate the status of myocardial perfusion, is reported. Both stress and redistribution Tl-201 SPECT clearly delineated the tumor. It was confirmed later as scirrhous carcinoma of the breast.     

Diagnostic value of the transesophageal atrial pacing stress for Tl-201 myocardial SPECT

The stress study for Tl-201 myocardial SPECT (single photon emission computed tomography) of a patient with old myocardial infarction, who had occasionally felt a chest pain for the last 8 months was performed with the transesophageal atrial pacing. The examination was fastly started and regular pacing rates were completely obtained for every pacing rate (50-100/min). In spite of a little amount of the pacing stress, the finding of stress induced ischemia and MI were obtained on this patient. This result suggests that the transesophageal atrial pacing stress might be useful for the evaluation of ischemic heart disease by Tl-201 myocardial SPECT, and is easily applied to the old and the patient with disorder of leg movement.     

Clinical evaluation of Tl-201 ECG-gated myocardial SPECT--comparison with ECG-gated blood pool SPECT

In order to evaluate the clinical usefulness of the Tl-201 ECG-gated myocardial single photon emission computed tomography (SPECT), we compared the wall motion and the grade of the Tl-201 uptake of the ECG-gated myocardial SPECT with the wall motion of the ECG-gated blood pool SPECT. Materials were 87 patients of 50 old myocardial infarctions (OMIs), 19 hypertrophic cardiomyopathies (HCMs), 2 dilated cardiomyopathies (DCMs) and 16 others. After intravenous injection of 111-185 MBq (3-5 mCi) of Tl-201 at rest, the projection data were acquired using a rotating gamma-camera through 180 degrees, from RAO 45 degrees in 24 directions, each of which consisted of 80-100 beats. For the reconstruction of ED, ES and non-gated images, R-R interval was divided into about 20 (18-22) fractions. In 348 regions of interest (anterior, septal, lateral and inferior wall) in 87 cases, wall motion and the Tl-201 uptake were evaluated to three grades (normal, hypokinesis and akinesis; normal, low and defect, respectively), which were compared with the wall motion of the ECG-gated blood pool SPECT. The wall motion and the grade of the Tl-201 uptake of the ECG-gated myocardial SPECT correlated well with the wall motion of the ECG-gated blood pool SPECT (96.6% and 87.9%, respectively). In conclusion, the ECG-gated myocardial SPECT can provide clear perfusion images and is a very useful diagnostic strategy to evaluate the regional wall motion and perfusion simultaneously.     

Tl-201 myocardial SPECT in patients with Duchenne's muscular dystrophy: a long-term follow-up

Tl-201 SPECT was used to evaluate myocardial involvement in 13 patients with Duchenne's muscular dystrophy. Serial studies of 9 patients were done at two-year intervals. The hypoperfused areas of the left ventricle became more prominent with age and severity.     

Three dimensional model constructed from Tl-201 myocardial SPECT in combination with bull's-eye mapping

Three dimensional images (3D Model) and Bull's-eye maps of Tl-201 stress and redistribution scintigrams were reconstructed from average distances and relative accumulations per unit area. 3D Models viewed from different angles were studied in cine mode, in conjunction with the Bull's-eye map. The accumulations of Tl-201 were classified into five different ranks. ROC curves for 3D Model were computed. The coronary artery stenoses estimated by 3D Model were found to have statistical correlations with the results of coronary angiography, in one and two coronary vessel disease, but not in three. Concerning the areas and the locations of abnormal Tl-201 distributions, 3D Model images offer more comprehensible informations than the conventional Bull's-eye method, especially around the left ventricular outlet.     

Reproducibility of Tl-201 and Tc-99m sestamibi gated myocardial perfusion SPECT measurement of myocardial function

BACKGROUND: We compared the reproducibility of thallium 201 and technetium 99m sestamibi (MIBI) gated single photon emission computed tomography (SPECT) measurement of myocardial function using the Germano algorithm (J Nucl Med 1995;36:2138-47). METHODS AND RESULTS: Gated SPECT acquisition was repeated in the same position in 30 patients who received Tl-201 and in 26 who received Tc-99m-MIBI. The quantification of end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) on Tl-201 and Tc-99m-MIBI gated SPECT was processed independently with Cedars-Sinai QGS (Quantitative Gated SPECT) software. The reproducibility of the measurement of ventricular function on Tl-201 gated SPECT was compared with that of Tc-99m-MIBI gated SPECT. Correlation between the 2 measurements for volumes and EF was excellent for the repeated gated SPECT studies of Tl-201 (r = 0.928 to 0.986, P <.05) and Tc-99m-MIBI (r = 0.979 to 0.997, P <.05). However, Bland-Altman analysis revealed the 95% limits of agreement (2 SDs) for volumes and EF were narrower by repeated Tc-99m-MIBI gated SPECT (EDV 14.1 mL, ESV 9.4 mL, EF 5.5%) than by repeated Tl-201 gated SPECT (EDV 24.1 mL, ESV 18.6 mL, EF 10.3%). The root-mean-square values of the coefficient of variation for volumes and EF were smaller by repeated Tc-99m-MIBI gated SPECT (EDV 2.1 mL, ESV 2.7 mL, EF 2.3%) than by repeated Tl-201 gated SPECT (EDV 3.2 mL, ESV 3.5 mL, EF 5.2%). CONCLUSIONS: QGS provides an excellent correlation between repeated gated SPECT with Tl-201 and Tc-99m-MIBI. However, Tc-99m-MIBI provides more reproducible volumes and EF than Tl-201. Tc-99m-MIBI gated SPECT is the preferable method for the clinical monitoring of ventricular function.     

Evaluation of ischemia by exercise stress Tl-201 myocardial SPECT in silent and symptomatic ischemia

Forty patients with ischemic heart disease confirmed by coronary arteriography were performed Tl-201 stress myocardial scintigraphy using SPECT. Fifteen patients had anginal attack during exercise Tl-201 myocardial perfusion study (symptomatic group), and 25 patients had horizontal or downsloping ST segment depression more than 0.1 mV without angina (asymptomatic group). The washout maps were derived from circumferential profile analyses of tomographic short-axis slices, and the data were plotted as a bull's eye map. The patient's washout map was compared with the lower limit of normal (mean--2 SD), and the extent and severity scores were calculated. On visual analysis 87% (13/15) of symptomatic patients showed redistribution, while only 56% (14/25) of asymptomatic patients showed redistribution (p less than 0.05). The extent score was significantly higher in the symptomatic group than in asymptomatic group (37.2 + 23.6 vs. 19.6 + 20.8, p less than 0.05), but severity score was slightly higher in symptomatic group (56.1 + 59.4 vs. 30.0 + 54.8, NS). In conclusion, symptomatic ischemia may be more severe than asymptomatic one and the degree of ischemia may be one of the factors that determine the presence of angina during ischemia.     

Clinical evaluation of coronary territory map by using unfolded map of Tl-201 myocardial SPECT

Coronary territory map was developed on unfolded map of exercise Tl-201 myocardial SPECT. Each coronary territory was determined by summing the each unfolded map of 54 cases of single vessel disease respectively, and standardizing with normal pattern obtained from normal patients. The diagnostic accuracy of coronary territory map to identify the diseased coronary artery was analyzed in 104 clinical cases and was compared with that of planar and SPECT visual diagnosis, simple unfolded map (raw map) and extent & severity map. The results were as follows; 1) Territory map showed excellent diagnostic accuracy in single or double vessel disease, especially in diagnosis of left circumflex coronary artery lesion. 2) In triple vessel disease, the diagnostic accuracy of territory map or other unfolded maps was 30% at best, and was inferior to planar or SPECT visual analysis. The cause of this inferiority seemed that the quantitatively analyzed map had no information about the degree of Tl-uptake into lung or myocardium, which give useful information in visual diagnosis. 3) The diagnostic agreement ratio in two observers was the highest in territory map diagnosis, so that the territory map diagnosis seemed to be the most objective one. 4) The unfolded map diagnosis with apical display obtained from long-axis tomogram was useful to diagnose left anterior descending coronary (LAD) lesion, which improve not only the sensitivity of LAD but also specificity of right coronary artery single vessel disease.     

Consideration of perfusion reserve in viability assessment by myocardial Tl-201 rest-redistribution SPECT: A quantitative study with dual-isotope SPECT

BACKGROUND: To optimize the use of thallium 201 rest-redistribution study in Tl-201/technetium 99m sestamibi dual-isotope single photon emission computed tomography (SPECT), the predictability of Tl-201 rest-redistribution for viable myocardium was examined according to the degree of perfusion reserve. METHODS AND RESULTS: Twenty patients with both unstable angina and left ventricular dysfunction were enrolled. Tl-201 rest-dipyridamole stress Tc-99m sestamibi gated SPECT/Tl-201 24-hour redistribution SPECT was performed before and 3 months after coronary artery bypass grafting. Through use of a 20-segment model, segmental stress perfusion, rest perfusion, and systolic thickening were quantified on gated SPECT by means of automatic quantitation software. Perfusion was expressed as the average percentage of maximal radioactivity uptake. To represent perfusion reserve, the perfusion difference score (PDS) was defined as rest perfusion minus stress perfusion. A low PDS indicated little or no inducible ischemia, and a high PDS indicated inducible ischemia. In dysfunctional myocardium, viability was defined by the improvement of thickening after coronary artery bypass grafting. The overall predictability of Tl-201 redistribution for viability was 0.709 of the area under the curve (AUC) in receiver operating characteristic analysis. With a cutoff of 7, predictability was significantly better in the low PDS group (AUC = 0.785) than in the high PDS group (AUC = 0.582). CONCLUSIONS: The predictability of Tl-201 rest-redistribution for viability differs according to perfusion reserve. It was more reliable for dysfunctional myocardium with persistent perfusion decrease. On the basis of the continuum hypothesis of chronic stunning and hibernation, we suggest that dysfunctional myocardium with persistent perfusion decrease should be assessed by Tl-201 redistribution SPECT.