Can the estimation of ejection fraction during gated single photon emission computed tomography at rest add information to the cardiac perfusion study?

Left ventricular function is an important prognostic indicator in patients with coronary artery disease. The electrocardiogram gated, myocardial, single photon emission tomography (SPECT) program is coming into wide use. This program permits measurement of end diastolic volume, end systolic volume, and ejection fraction. This study was designed to show whether the measurement of ejection fraction by using (99c)Tc tetrofosmin gated SPECT at rest could give additional information to the interpretation of perfusion. Exercise 99mTc tetrofosmin SPECT and gated (99c)Tc tetrofosmin SPECT at rest were performed in 33 patients with or suspected of having coronary artery disease. Left ventricular ejection fraction was calculated from reconstructed gated SPECT at rest with a software quantitative gated SPECT. The results showed a poor correlation between segmental ejection fraction and segmental perfusion in stress and rest. There was an increasing probability of reversibility as the ejection fraction increased, while there was a greater chance of a fixed defect as the ejection fraction decreased. It is concluded that gated SPECT using (99c)Tc tetrofosmin provides clinically satisfactory functional data that, in combination with the perfusion information, will improve diagnostic and prognostic accuracy without an increase in cost or radiation dose to patients.     

“W-shaped” volume curve with gated myocardial perfusion single photon emission computed tomography

OBJECTIVES: Gating errors (GEs) with ECG gated myocardial SPECT (G-SPECT) may occur irrespective of the presence or absence of arrhythmias. We evaluated the impact of GEs on both reconstructed tomograms and left ventricular ejection fraction (LVEF) derived from G-SPECT, and searched for clues to identify these errors. METHODS: We studied 2 GE patients, 10 normal subjects (NLs), and 10 atrial fibrillation patients. Stress technetium-99m sestamibi G-SPECT was performed. Left ventricular (LV) contraction was evaluated in the beating slices. LVEF was calculated with G-SPECT using QGS (Cedars-Sinai, Los Angels) and p-FAST (Sapporo Medical University, Japan), and compared with that obtained by echocardiography (ECHO). LV volume curves were created by QGS and p-FAST. The heart rates (HRs) were calculated from the acquired images, and compared with their resting HRs. The mean count density of the myocardium was measured and time-activity curves were created. RESULTS: In patients with GEs, bi-phasic LV contraction was demonstrated with fading-out towards end-diastole. G-SPECT underestimated LVEF compared to ECHO by 10% or more. The volume curves appeared "W-shaped." The HRs from the images were slower than the resting HRs. The count density decrement from frame #1 to #8 was larger than that of NLs. The time-activity curves were different in shape from those of NLs. CONCLUSIONS: G-SPECT underestimates LVEF in patients with GEs. These errors can be identified with a combination of visual inspection of beating slices, time-volume curves, and time-activity curves. Monitoring the HR is a clue for anticipating and avoiding these errors.     

Ventilation/perfusion scan and dead space in pulmonary embolism: are they useful for the diagnosis?

The diagnostic strategy for pulmonary embolism, based on the mismatch of the ventilation/perfusion scan, was developed some 30 years ago on the following assumption: since the disorder involves the pulmonary vessels, it was surmised that in the embolized regions lung alveoli are unperfused or poorly perfused but well ventilated. Hence, it was inferred that this disorder was characterized, unlike parenchymal disease, by ventilation/perfusion mismatch in the affected lung zones and by an obvious increase of wasted ventilation, i.e., dead space. As matter of fact, experimental evidence on the redistribution of ventilation away from the vascular occluded lung had been already obtained in the early 60s of the last century. More recently, the behavior of regional pulmonary ventilation (V(A)) and blood flow (Q) in patients with acute pulmonary embolism (APE) has been studied by applying the multiple inert gas elimination technique (MIGET). It has been shown that the development of lung units with high V(A)/Q ratio (those with relative prevalence of perfusion obstruction) is accompanied by substantial redistribution of ventilation away from these units. Furthermore, radioisotopic techniques, used to visualize the topographic distributions of V(A) and Q in the same patients studied by MIGET, have shown reduced or absent V(A) in the embolized regions. This may occur by different mechanisms in the various stages of APE: bronchoconstriction mediated by local hypocapnia, atelectasis (occasionally hemorrhagic) related to alteration of surfactant production, bronchiolar obstruction and pulmonary infarction ascribed to degenerative and/or necrotic changes secondary to insufficient blood flow. In dogs and humans alike, the dead space measured by MIGET does not increase and that obtained from CO2 increases far less than the amount of unperfused lung in APE thus confirming a substantial redistribution of ventilation away from the embolized lung zones. Taken together, all these observations provide the pathophysiological explanation of the unacceptedly low level of sensitivity for the diagnostic strategy of APE based on the mismatch of the ventilation/perfusion scan.     

Does lung perfusion scintigraphy continue to have a role in the clinical management of patients suspected of pulmonary embolism in the CT pulmonary angiography era?

Objective

Acute pulmonary embolism (PE) is a life-threatening disorder with high mortality. A prompt diagnosis and treatment is essential for reducing the mortality rate. The purpose of the study is to evaluate if lung perfusion scintigraphy (LPS) continues to have a role in the clinical management of patients suspected of pulmonary embolism in the CT pulmonary angiography (CTPA) era.

Methods

For this study, 1183 patients who had been subjected to LPS were retrospectively evaluated and classified into the following groups: A (positive LPS), B (negative LPS) and C (indeterminate LPS). Patients were further classified into A1 (‘PE likely’ and LPS-negative), B1 (PE unlikely and LPS-positive) and C1 (PE likely and indeterminate LPS) by combining the LPS findings and the clinical pretest probability (cpp). Subgroups A1, B1 and C1 underwent additional CTPA.

Results

Groups A, B, and C included 1086/1183, 69/1183 and 28/1183 patients, respectively. The proportion of patients with inconsistent cpp LPS findings who underwent additional CTPA was 106/1183 patients: subgroup A1 (n?=?73), B1 (n?=?21), and C1 (n?=?12). In subgroup A1, CTPA was negative in 61/73, non-diagnostic in 12/73 and positive in 0/73 patients. In subgroup B1, CTPA excluded PE in 2/21, non-diagnostic in 3/21 and positive in 16/21 patients. In group C1, CTPA was negative in 8/12, positive in 2/12 and non-diagnostic in 2/12 patients.

Conclusion

In the CTPA era, LPS continues to have a role in the clinical management of patients suspected of PE.

     

Does location matter? Prognostic value of single-photon emission computed tomography myocardial perfusion imaging by vascular territory

Background

The location of a myocardial perfusion abnormality frequently affects clinical decision making, especially if the left anterior descending artery (LAD) territory is involved. The purpose of this study was to determine whether the location of abnormalities on single-photon emission computed tomography (SPECT) imaging affects outcomes.

Methods

We retrospectively analyzed 21,294 consecutive patients with known or suspected coronary artery disease who underwent exercise or pharmacological stress SPECT over a 10-year period. Using the ASNC 17-segment model, 2 observers interpreted images with regards to defect severity, size, and reversibility. The summed stress score (SSS) was used in relation to vascular territories [LAD, right coronary artery (RCA), and left circumflex artery (LCx)]. All patients were followed over a mean period of 2.5?±?2?years for cardiac events (cardiac death or non-fatal myocardial infarction).

Results

Of the enrolled patients, 5,676 had single-vessel territory defects with a mean SSS of 4.3?±?2.8. Cardiac event-free survival curves revealed no significant difference between the 3 locations (LAD, RCA, and LCx) (P?=?.235). When compared by mild (2-3), moderate (4-8), or severe (>8) SSS, outcomes between the 3 groups were again similar. There were 2,907 patients with two-vessel territory defects with a mean SSS of 10.8. Outcomes were similar between the following 2 groups: two-vessel with LAD involvement and two-vessel without LAD involvement (P?=?.558).

Conclusion

In patients with single- or two-vessel territory perfusion abnormalities with similar size and severity of perfusion defects, the location of defect did not impact future cardiac events. Location of myocardial perfusion defect on SPECT imaging may not be helpful in clinical decision making.     

Technetium-99m MIBI single photon emission computed tomography as an indicator of prognosis for patients with lung cancer —Preliminaly report—

PURPOSE: We performed technetium-99m hexakis-2-methoxyisobutylisonitrile (Tc-99m MIBI) single photon emission computed tomography (SPECT) in 23 patients with primary lung cancer between July 1993 and March 1996. We evaluated the relationships among the uptake ratio, retention index and the prognosis after radiation therapy and/or chemotherapy. MATERIALS AND METHODS: Tc-99m MIBI SPECT was performed at 30 minutes and at 3 hours after intravenous injection of 600 MBq of Tc-99m MIBI with three gamma camera detectors (GCA-9300A/HG) on transverse SPECT images. Regions of interest were set in the area of abnormal uptake of Tc-99m MIBI and in the contralateral normal lung. The ratio of uptake in the lesion to that in the contralateral normal lung was obtained on early images (early ratio; ER) as well as delayed images (delayed ratio: DR). The retention index (RI) was calculated as follows: RI = (DR - ER)/ER x 100. The ratio was compared with survival time and prognostic factors. RESULTS: There was no correlation between ER and DR. The patients with high RI survived longer than those with low RI (median survival, 19.4 months vs. 9.4 months; p = 0.0104 by the Mantel-Cox test). CONCLUSION: These results suggest that RI is the most useful among Tc-99m MIBI indices of primary lung cancer in predicting prognosis.     

201Tl gated single photon emission computed tomographic myocardial perfusion imaging in the assessment of global and regional left ventricular function. Would it be favoured over equilibrium radionuclide angiography?

BACKGROUND: This study investigates the clinical performance of routine 201Tl gated single photon emission computed tomographic (201Tl GSPECT) myocardial perfusion imaging. Equilibrium radionuclide angiography (ERNA) was used as the standard for comparison. METHODS AND RESULTS: One hundred and seventy-two consecutive patients were submitted to both myocardial 201Tl GSPECT imaging, at stress and in redistribution, and ERNA. Left ventricular ejection fractions (LVEF) and regional wall motion were assessed from both stress and redistribution 201Tl GSPECT datasets, and from ERNA. Linear regression analysis showed a good correlation between LVEF calculated by ERNA and 201Tl GSPECT (r=0.73 at stress, r=0.75 in redistribution, P<0.0001). However, the 95% prediction intervals of 201Tl GSPECT LVEF from ERNA LVEF were wide (minimum 35.4% at stress and 33.2% in redistribution). Moreover, a difference in LVEF > or =10% between ERNA and 201Tl GSPECT was found in 26.4% of cases at stress and 28.6% of cases in redistribution. A fair agreement between ERNA and 201Tl GSPECT was found in regional wall motion assessment in segments with normal or mildly reduced tracer uptake (kappa=0.32 at stress and kappa=0.33 in redistribution). In segments with moderately to severely reduced tracer uptake, a moderate agreement was found in regional wall motion assessment between ERNA and 201Tl GSPECT (kappa=0.44 at stress and kappa=0.42 in redistribution). CONCLUSIONS: Left ventricular function may be misinterpreted in a significant proportion of patients if the calculation of LVEF is based on 201Tl GSPECT. Moreover, the evaluation of regional wall motion by 201Tl GSPECT appears unsatisfactory.     

Radioiodinated benzimidazole derivatives as single photon emission computed tomography probes for imaging of β-amyloid plaques in Alzheimer's disease

Five iodinated 2-phenyl-1H-benzo[d]imidazole derivatives were synthesized and evaluated as potential probes for β-amyloid (Aβ) plaques. One of the compounds, 4-(6-iodo-1H-benzo[d]imidazol-2-yl)-N,N-dimethylaniline (12), showed excellent affinity for Aβ(1-42) aggregates (K(i) = 9.8 nM). Autoradiography with sections of postmortem Alzheimer's disease (AD) brain revealed that a radioiodinated probe [(125)I]12, labeled Aβ plaques selectively with low nonspecific binding. Biodistribution experiments with normal mice injected intravenously with [(125)I]12 showed high uptake [4.14 percent injected dose per gram (% ID/g) at 2 min] into and rapid clearance (0.15% ID/g at 60 min) from the brain, which may bring about a good signal-to-noise ratio and therefore achieve highly sensitive detection of Aβ plaques. In addition, [(125)I]12 labeled amyloid plaques in vivo in an AD transgenic model. The preliminary results strongly suggest that [(125)I]12 bears characteristics suitable for detecting amyloid plaques in vivo. When labeled with (123)I, it may be a useful SPECT imaging agent for Aβ plaques in the brain of living AD patients.     

Is contrast material needed after treatment of malignant lymphoma in positron emission tomography/computed tomography?

Purpose  

Positron emission tomography (PET)/computed tomography (CT) with ¹⁸F-fluorodeoxyglucose is widely used for post-therapeutic surveillance of malignant lymphoma. Debate still exists as to whether intravenous contrast media during the CT stage of a PET/CT scan should be used. The purpose of this study was to investigate the clinical value of contrast agent in PET/CT in patients with lymphoma following treatment.     

Limited value of ⁹⁹mTc depreotide single photon emission CT compared with CT for the evaluation of pulmonary lesions

Objectives

A contrast-enhanced multidetector CT (MDCT) scan is the first choice examination when evaluating patients with suspected lung cancer. However, while the clinical focus is on CT, research focus is on molecular biological methods whereby radiolabelled pharmaceuticals are injected into participants and target malignant lung tumours. We examined whether a contrast-enhanced MDCT scan supplied with an additional non-contrast enhanced high-resolution CT scan, or a newer but more expensive ^99mTc depreotide single photon emission CT (SPECT) scan, was the better first-choice examination for the work-up of pulmonary lesions. Furthermore, we examined whether a ^99mTc depreotide SPECT scan was an appropriate second-choice examination for patients with indeterminate lesions.

Methods

140 participants were included in the analysis. CT images were given a malignancy potential rating of 1, 2 or 3 with higher rating being indicative of disease. ^99mTc depreotide SPECT images were graded either positive or negative. Histopathology and CT follow-up were used as reference standard. Sensitivity, specificity and diagnostic accuracy were calculated.

Results

Overall sensitivity, specificity and diagnostic accuracy of CT were 97%, 30% and 84%, respectively. Overall sensitivity, specificity and diagnostic accuracy of ^99mTc depreotide SPECT were 94%, 58% and 76%, respectively. For indeterminate lesions sensitivity, specificity and diagnostic accuracy of ^99mTc depreotide SPECT were 71%, 68% and 69%, respectively.

Conclusion

Both CT and ^99mTc depreotide SPECT made valuable contributions to the evaluation of pulmonary lesions. ^99mTc depreotide SPECT results were not superior to CT results and did not contribute further to the diagnostic work-up. Regarding indeterminate lesions, ^99mTc depreotide SPECT sensitivity was too low.Lung cancer has a poor prognosis with an overall 5-year mortality rate of approximately 84%. However, with early detection and surgery the mortality rate can be as low as 47% [1]. Lung cancer is a major indication for chest imaging. Many years of CT imaging have seen a steady evolution of methods used to evaluate lung nodules and mass lesions. A contrast-enhanced multidetector CT (MDCT) scan is the first-choice examination when lung cancer is suspected.While the clinical focus is on MDCT, the research focus is on molecular biological methods whereby radiolabelled pharmaceuticals are injected into participants to target malignant lung tumours. Examples of such functional modalities include ^99mTc depreotide single photon emission CT (SPECT) and 18-fluoro-2-deoxyglucose positron emission tomography (18-FDG PET). However, while numerous studies have been published regarding 18-FDG PET, only a limited number, including a preliminary report by our group [2], have focused on ^99mTc depreotide SPECT [3].In this study we examine whether a contrast-enhanced MDCT scan supplied with an additional non-contrast-enhanced high-resolution CT (HRCT) scan or a newer but more expensive ^99mTc depreotide SPECT scan is the better first-choice examination when dealing with the work-up of pulmonary nodules and mass lesions. Furthermore, we examined whether a ^99mTc depreotide SPECT scan is an appropriate second-choice examination for the subgroup of patients with indeterminate lesions.     

The clinical value of single photon emission computed tomography myocardial perfusion imaging in cardiac risk stratification of very elderly patients (≥80 years) with suspected coronary artery disease

Background  

The role of single photon emission computed tomography myocardial perfusion imaging (SPECT MPI) in cardiac evaluation of the very elderly patients is unclear. We investigated the clinical value of SPECT MPI in very elderly patients (≥80 years) with suspected coronary artery disease (CAD) as well as in comparison to younger patients.     

Multidetector CT: a new gold standard in the diagnosis of pulmonary embolism? State of the art and diagnostic algorithms

PURPOSE: From the early 90s, spiral CT technology has considerably changed the diagnostic capability of Pulmonary Embolism (PE), giving a direct vision of intravascular thrombi. Further technological progress has strengthened its diagnostic impact leading to an essential role in clinical practice. The advent of Multi-Detector CT (MDCT) has subsequently increased the reliability of this technique to the point of undermining the role of pulmonary angiography as the gold standard and occupying a central position in diagnostic algorithms. The aim of this paper is to appraise this evolution by means of a meta-analysis of the relevant literature from 1995 to 2004. RESULTS: The review of the literature showed the sensitivity and specificity of CT to have increased from 37-94% and 81-100% (single-detector CT) to 87-94% and 94-100% (4-channel multidetector CT), especially thanks to the possibility of depicting subsegmental clots, with an interobserver agreement of 0.63-0.94 (k). CONCLUSIONS: CT is one of the most reliable and effective methods in the diagnosis is PE, with the advantage of being extremely fast and providing alternative diagnoses. Recent improvements in MDCT technology confers the highest value of diagnostic accuracy with respect to other imaging modalities such as scintigraphy, angiography, MRI, D-dimer assay and Doppler US.     

Correlation of left ventricular dyssynchrony with myocardial stunning using dual single photon emission computed tomography of 123iodine-β-methyl iodophenyl pentadecanoic acid and 201thallium scintigraphy after reperfusion therapy

Objective  

Left ventricular (LV) dyssynchrony after reperfusion therapy has been closely examined as a cause of chronic remodeling, but the details have not been clarified. The present study measured LV dyssynchrony appearing immediately after reperfusion therapy using real-time three-dimensional echocardiography (RT-3DE), and assessed the significance of this phenomenon in relation to dual single photon emission computed tomography (SPECT) of ¹²³iodine β methyliodophenyl pentadecanoic acid (¹²³I-BMIPP) and ²⁰¹thallium (²⁰¹Tl).