Investigation of measures to reduce interfering abdominal activity on rest myocardial images with Tc-99m sestamibi

Interaction between the effects of proton pump inhibitors and aspirin on gastric wall sestamibi uptake on myocardial perfusion imaging

BACKGROUND

Increased gastric wall activity on myocardial perfusion imaging (MPI) is associated with proton pump inhibitor (PPI) therapy; however, the mechanism is unknown. We proposed a role for gastric mucosal prostaglandin synthesis and asked whether concurrent use of aspirin would antagonize this effect.

METHODS

An observational study was performed of 319 patients undergoing technetium-99m sestamibi (MIBI) rest/stress MPI. We assessed the effects of taking PPIs, aspirin and their interaction on the principle outcome of clinically significant gastric wall activity.

RESULTS

The outcome was observed in 13% of patients taking neither a PPI nor aspirin, 22% of those taking aspirin only, 51% taking a PPI only and 33% of those taking both. Adjusted odd ratios (95% confidence intervals) were 6.3 (CI 2.8-14.0; p < .001) for taking a PPI only, 1.8 (CI 0.8-3.9; p = .16) for taking aspirin only, and 3.0 (CI 1.4-6.5; p = .005) for taking the combination of a PPI and aspirin. There was evidence of negative statistical interaction between the two drug effects using additive (p = .006) and multiplicative (p = .016) scales.

CONCLUSIONS

PPI use was strongly associated with enhanced gastric wall activity on MPI; however, concurrent aspirin appears to reduce the effect. Enhanced local prostaglandin synthesis may mediate the PPI effect.

Association of use of proton pump inhibitors and H2 antagonists with stomach wall uptake in 99mTc-methoxy-isobutyl-isonitrile (MIBI) myocardial perfusion imaging

BACKGROUND

Stomach wall uptake (SWU) of tracer in 99mTc-MIBI myocardial perfusion imaging (MPI) occasionally leads to imaging artifacts, thereby lowering the diagnostic accuracy. It is less-studied phenomenon for possible link with proton pump inhibitors (PPIs) intake. This prospective work looked for association of SWU with PPI intake and compared its incidence with H2 antagonists (H2A) users and patients not on either gastroprotective medication.

METHODS

One hundred fifty-six patients undergoing one day stress/rest 99mTc-MIBI SPECT-MPI were distributed into four groups: control group (n = 48, not on any gastroprotective medication), PPI group (n = 47, on PPI treatment), H2A group (n = 19, on H2A therapy), and intervention group (N = 42, PPI discontinued for 3 days before MPI). Poststress planar images were analyzed for clinically relevant SWU.

RESULTS

Clinically relevant SWU was seen in 36% of PPI group patients compared to 8% in the control group, 10.5% in the H2A group, and 9.5% in the intervention group, respectively, with statistically significant difference. Only 1/40 patients undergoing exercise stress showed clinically relevant SWU compared to 26/116 patients undergoing adenosine stress (P = .020).

CONCLUSION

Patients on PPIs scheduled for vasodilator stress MPI may discontinue PPIs for 3 days, or replace with H2A to reduce the incidence of clinically relevant SWU associated with PPI therapy.

Image Quality and Interpretation of [18F]-FES-PET: Is There any Effect of Food Intake?

Background: High physiological 16α-[¹⁸F]-fluoro-17β-estradiol ([¹⁸F]-FES) uptake in the abdomen is a limitation of this positron emission tomography (PET) tracer. Therefore, we investigated the effect of food intake prior to PET acquisition on abdominal background activity in [¹⁸F]-FES-PET scans. Methods: Breast cancer patients referred for [¹⁸F]-FES-PET were included. Three groups were designed: (1) patients who consumed a chocolate bar (fatty meal) between tracer injection and imaging (n = 20), (2) patients who fasted before imaging (n = 20), and (3) patients without diet restrictions (control group, n = 20). We compared the physiological [¹⁸F]-FES uptake, expressed as mean standardized uptake value (SUV_mean), in the abdomen between groups. Results: A significant difference in [¹⁸F]-FES uptake in the gall bladder and stomach lumen was observed between groups, with the lowest values for the chocolate group and highest for the fasting group (p = 0.015 and p = 0.011, respectively). Post hoc analysis showed significant differences in the SUVmean of these organs between the chocolate and fasting groups, but not between the chocolate and control groups. Conclusion: This exploratory study showed that, compared to fasting, eating chocolate decreases physiological gall bladder and stomach [¹⁸F]-FES uptake; further reduction through a normal diet was not seen. A prospective study is warranted to confirm this finding.

The effects of pharmacological interventions, exercise, and dietary supplements on extra-cardiac radioactivity in myocardial perfusion single-photon emission computed tomography imaging

Myocardial perfusion imaging (MPI) as an imaging modality plays a key role in the monitoring of patients with cardiovascular disease. MPI enables the assessment of cardiovascular disease, the effectiveness of therapy, and viable myocardial tissue. However, MPI suffers from some downfalls and limitations, which can influence its clinical applications. These limitations can arise from the patient's condition, equipment, or the actions of the technologist. In this review, we mainly focused on the different effective parameters on radioactivity uptake of organs including liver, intestines, stomach, and gall bladder and how they affect the quality of the acquired images in nuclear medicine. More importantly, we cover how different suggested medicines, foods and exercise alleviative this problem.

Stomach interference in 82Rb-PET myocardial perfusion imaging

BACKGROUND

82Rubidium(82Rb)-positron-emission-tomography (PET) is prone to some of the same imaging artifacts as single-photon-emission-computed-tomography myocardial perfusion imaging (MPI) including interference from excessive subdiaphragmatic activity. Our aim was to determine associations between clinical parameters and MPI interference including any potential correlation between interference severity and stomach volume.

METHODS AND RESULTS

Two hundred men and women fasted two hours prior to standard clinical 82Rb myocardial perfusion rest/stress PET. Images were analyzed for radiotracer interference between left ventricle myocardium and extracardiac activity. Furthermore, volume of the stomach was measured. Interference, predominantly caused by 82Rb activity in the stomach, was less severe in stress PET compared to rest (absent in 46% vs 31% of patients during stress and rest, P < 0.05). In addition, a large stomach volume was associated with more severe interference in rest (P < 0.05) while a high body mass index was associated with less interference.

CONCLUSION

Among clinical parameters associated with patient size, BMI was the strongest predictor of MPI interference. Furthermore, a large stomach volume was associated with more severe MPI interference, suggesting that sufficient fasting prior to imminent 82Rb PET may be important to reduce interference from adjacent radiotracer activity and consequently improve interpretation of MPI results, especially in small patients.

Effects of Glycosylation on Biodistribution and Imaging Quality of Necrotic Myocardium of Iodine-131-Labeled Sennidins

PURPOSE

Sennidins are necrosis-avid agents for noninvasive assessment of myocardial viability which is important for patients with myocardial infarction (MI). However, high accumulation of radioactivity in the liver interferes with the assessment of myocardial viability. In this study, we compared sennidins with sennosides to investigate the effects of glycosylation on biodistribution and imaging quality of sennidins.

PROCEDURES

Sennidin A (SA), sennidin B (SB), sennoside A (SSA), and sennoside B (SSB) were labeled with I-131. In vitro binding to necrotic cells and hepatic cells and in vivo biodistribution in rats with muscular necrosis were evaluated by gamma counting, autoradiography, and histopathology. Single photon emission computed tomography/computed tomography (SPECT/CT) images were acquired in rats with acute MI.

RESULTS

The uptake of [¹³¹I]SA, [¹³¹I]SSA, [¹³¹I]SB, and [¹³¹I]SSB in necrotic cells was significantly higher than that in viable cells (p < 0.05). Hepatic cells uptake of [¹³¹I]SSA and [¹³¹I]SSB were 7-fold and 10-fold lower than that of corresponding [¹³¹I]SA and [¹³¹I]SB, respectively. The biodistribution data showed that the radioactivities in the liver and feces were significantly lower with [¹³¹I]sennosides than those with [¹³¹I]sennidins (p < 0.01). Autoradiography showed preferential accumulation of these four radiotracers in necrotic areas of muscle, confirmed by histopathology. SPECT/CT imaging studies showed better image quality with [¹³¹I]SSB than with [¹³¹I]SB due to less liver interference.

CONCLUSIONS

Glycosylation significantly decreased the liver uptake and improved the quality of cardiac imaging. [¹³¹I]SSB may serve as a promising necrosis-avid agent for noninvasive assessment of myocardial viability.

The Effect of Milk, Water and Lemon Juice on Various Subdiaphragmatic Activity-Related Artifacts in Myocardial Perfusion Imaging

Background:

Subdiaphragmatic activity can produce subdiaphragmatic-related artifacts, which can degrade the quality of myocardial perfusion imaging (MPI).

Objectives:

We examined the impact of drinking milk, water, and lemon juice on different subdiaphragmatic-related artifacts by using ^99mTc-sestamibi myocardial single-photon emission computed tomography (SPECT) in order to determine a feasible method for improving the image quality.

Patients and Methods:

A total of 179 patients (age 58 ± 9.6 years) were enrolled in this study. The patients were randomly divided into five groups. Ten minutes after injection of 740 MBq 99mTc-sestamibi in both pharmacologic stress and rest phases, the individuals in group 1 were given water and milk (125 mL of each); those in group 2 were given lemon juice (250 mL); group 3 was given milk (250 mL); and group 4 was given water (250 mL), whereas no intervention was performed in group 5. The study was double-blind for both subjects and data collectors. MPI was performed for all patients and image quality was controlled by 2 experienced nuclear physicians. Interfering activity was determined visually on reconstructed images and categorized as extracardiac normalization artifact, overlapping of activity, scattering of activity, and ramp filter artifact.

Results:

There were significant differences in terms of interfering activity among the five groups; group 3 (milk) had significantly lower interfering activity than other groups had, as defined by overlapping of activity (on both stress and rest images), ramp filter artifact (stress images), and scatter artifact (rest images) (P < 0.05). Furthermore, there was a significant difference in the incidence of good-quality images, with no interfering activity in group 3 in the resting state compared with the other groups in the study (P < 0.05).

Conclusions:

Drinking 250 mL of milk in either the stress phase or the rest phase of imaging diminishes interfering subdiaphragmatic-related artifacts, particularly overlapping of activity in MPI SPECT, resulting in better-quality images.

The impact of regimented aminophylline use on extracardiac radioisotope activity in patients undergoing regadenoson stress SPECT myocardial perfusion imaging: a substudy of the ASSUAGE trial

BACKGROUND

In patients undergoing regadenoson stress SPECT myocardial perfusion imaging (MPI), the impact of the regimented administration of aminophylline on the cardiac-to-extracardiac photon activity ratio is unknown.

METHODS

This is a substudy of the ASSUAGE trial (NCT01250496); a double-blinded, randomized, placebo-controlled clinical trial which investigated the attenuation of regadenoson-related adverse effects using 75 mg of intravenous aminophylline vs placebo, administered 90 seconds following (99m)Tc-tetrofosmin injection in patients undergoing regadenoson stress SPECT-MPI. In subjects with normal MPI enrolled in the trial, we sampled from the antero-posterior planar projection of the post-stress scintigraphic data the mean photon activity in the myocardium, liver, bowel, and lungs. The mean cardiac-to-extracardiac activity ratios were compared between patients randomized to aminophylline vs placebo.

RESULTS

We studied 158 eligible subjects, randomized to receive aminophylline (n = 86) or placebo (n = 72). The means of photon activity ratios of the heart-to-liver, heart-to-bowel, heart-to-lungs, inferior wall of the heart-to-liver, and inferior wall of the heart-to-bowel were not statistically different between those who received aminophylline vs placebo (P values > .30). Only the time lapse between stress (99m)Tc-tetrofosmin injection and stress SPECT acquisition independently correlated with higher heart-to-liver and heart-to-bowel activity ratios (P values ≤ .01). Patients' body mass index independently correlated with lower heart-to-lung ratio (P = .009).

CONCLUSION

The regimented intravenous aminophylline use following regadenoson stress does not significantly improve the cardiac-to-extracardiac photon activity ratio in patients undergoing regadenoson stress (99m)Tc-tetrofosmin SPECT-MPI.

Pharmacokinetics and biodistribution of 99mTc N-MPO in healthy human volunteers

PURPOSE

Tc N-MPO ([Tc N(MPO)(PNP5)]: HMPO = 2-mercaptopyridine N-oxide, and PNP5 = N-ethoxyethyl-N,N-bis[2-(bis(3-methoxypropyl)phosphino)ethyl]amine) is a new Tc radiotracer useful for myocardial perfusion imaging. This study was designed to determine its pharmacokinetics and biodistribution in healthy volunteers.

PATIENTS AND METHODS

Ten healthy volunteers were involved in this study. Each subject was administered approximately 925 MBq of Tc N-MPO under rest or stress conditions (n = 5 per group). Whole-body planar images were obtained at 10, 30, 60, 240, and 1440 minutes after injection. Organ uptake was quantified by region-of-interest analysis. The blood clearance and urine excretion kinetics were determined by collecting blood and urine samples at different time points.

RESULTS

Tc N-MPO showed significant accumulation in myocardium with prolonged retention. At rest, its percentage of injected dose (%ID) uptake in the heart, lungs, and liver at 10 minutes after injection was 2.47% (0.64%), 1.84% (0.64%), and 20.88% (5.23%), respectively. The liver uptake decreased to 6.79%ID (1.60%ID) at 60 minutes after injection and 4.50%ID (1.86%ID) at 240 minutes after injection. Under stress conditions, the heart uptake was slightly increased (2.57%ID [0.21%ID]). The rapid liver clearance led to favorable heart-to-liver ratios, reaching values of 0.27%ID (0.07%ID) under rest condition and 0.28%ID (0.05%ID) under stress condition at 60 minutes after injection.

CONCLUSIONS

Tc N-MPO demonstrates a highly favorable biodistribution in humans. The high heart uptake and the fast liver washout of Tc N-MPO will allow SPECT images of the left ventricle to be acquired as early as 10 minutes after injection.

Diagnostic value of myocardial SPECT to detect in-stent restenosis after drug-eluting stent implantation

Different angiographic patterns and restenosis rate may affect diagnostic value of single-photon emission computed tomography (SPECT) in the era of drug-eluting stents (DES). We aimed to determine the ability of myocardial SPECT to detect in-stent restenosis (ISR) in patients treated with DES compared to that of patients treated with bare metal stent (BMS). We evaluated 228 consecutive patients who underwent 6 months follow-up SPECT and coronary angiography (CAG) after stent implantation. In 228 patients, 354 vessels were treated with stent implantation (BMS, n = 105; DES, n = 249) and 65 (18.4%) vessels showed ISR (angiographic % diameter stenosis ≥ 50%) at the 6-month follow-up CAG. In patients with BMS-ISR (n = 37), restenosis was primarily diffuse (70.3%), whereas patients with DES-ISR (n = 28) exhibited more focal restenosis (53.6%, p = 0.028). The sensitivity and specificity of myocardial SPECT did not differ significantly between patients with BMS and those with DES (BMS vs. DES: sensitivity 56.8 vs. 39.3%, p = 0.163; specificity 72.1 vs. 76.5%, p = 0.460). Evaluation of 71 false positive and 33 false negative lesions showed that the most common cause of false-positive results in SPECT was the perfusion decrease which improved but not disappeared compared with the baseline (46 among 71 vascular territories). Despite different patterns of restenosis and ISR rates, the diagnostic value of SPECT did not differ between BMS and DES. Further study looking at ISR in larger number of patients and using other protocol such as Fleming-Harrington Redistribution Wash-in Washout may give additional information.

Kinetic characterization of a novel cationic (99m)Tc(I)-tricarbonyl complex, (99m)Tc-15C5-PNP, for myocardial perfusion imaging

BACKGROUND

Intense liver uptake of (99m)Tc-sestamibi (MIBI) often interferes with visualization of myocardial perfusion in the inferior wall of the left ventricle. To develop improved myocardial perfusion agents, crown ether-containing dithiocarbamates and bisphosphines have been introduced in recent years. This study was designed to investigate the myocardial imaging properties and in vivo kinetics of a cationic (99m)Tc(I)-tricarbonyl complex, (99m)Tc-15C5-PNP, in comparison with MIBI.

METHODS

Dynamic cardiac images were acquired for 60 minutes after intravenous tracer injection using a small-animal SPECT system in healthy control rats and rats with myocardial infarcts. Myocardial and liver time-activity curves were generated for radiopharmaceutical kinetic analysis.

RESULTS

Good visualization of the left ventricular wall and perfusion defects could be achieved 20 minutes after (99m)Tc-15C5-PNP administration. (99m)Tc-15C5-PNP images in all hearts with infarcts showed perfusion defects, which were comparable to MIBI images. The kinetic curves plotted from 1 to 60 minutes demonstrated that (99m)Tc-15C5-PNP has a shorter washout half-life (6.4 ± 3.2 vs 124 ± 30.5 minutes, P < .01) in the liver, lower residual liver activity (14.5 ± 10.2% vs 36.5 ± 28.9%, P < .01), and higher heart/liver ratio than MIBI.

CONCLUSIONS

(99m)Tc-15C5-PNP has potential for rapid myocardial perfusion imaging with low liver uptake.

The effects of early and late scanning on image quality and functional parameters in myocardial perfusion imaging

MATERIALS AND METHODS

Timing of acquisition is a factor that may influence the subdiaphragmatic activity in myocardial perfusion scintigraphy (MPS). According to the instructions of tetrofosmin, scintigraphy may already be started 15 minutes postinjection. The aim of the present study was to compare the image quality and the functional parameters between early and late scanning. Eventually, 49 consecutive patients underwent a 2-day MPS protocol in which 15 and 45 minutes after the injection of 500 MBq of technetium-99m-tetrofosmin scintigraphy both at stress and rest were performed. The amount of subdiaphragmatic tracer activity was scored from "no tracer activity" to "severe." Moderate and severe subdiaphragmatic tracer activity was considered relevant for the interpretation of the myocardial perfusion scan.

RESULTS

Two-thirds of the patients (64%) showed a considerable amount of subdiaphragmatic activity on the 15 minutes rest images, whereas only 9 patients (18%) had considerable subdiaphragmatic activity on the late images. Stress imaging showed comparable results, however, subdiaphragmatic activity was generally less frequent and less prominent following stress. The value of the ejection fraction was significantly lower during early imaging comparing with late imaging. Lower ejection fraction was exclusively noticed in imaging with moderate and severe subdiaphragmatic tracer activity related wrong border estimation.

CONCLUSIONS

Acquisition 15 minutes after the injection of Tetrofosmin shows a significant and clinically relevant subdiaphragmatic activity in most myocardial perfusion scans leading to poorer image quality and to an erroneous measurement of the ejection fraction. Therefore, early acquisition in MPS is not recommended in clinical practice.

Randomized, single-blind, factorial design study of the interaction of food and time on intestinal activity in 99mTc-tetrofosmin stress myocardial perfusion scintigraphy

PURPOSE

Intestinal activity at the inferior myocardial wall represents an issue for assessment of myocardial perfusion imaging (MPI) with 99mTc-labelled tracers. The aim of this study was to investigate the effect of time and food on upper abdominal activity in 99mTc-tetrofosmin MPI.

METHODS

The study population consisted of 152 consecutive patients referred for routine MPI. All patients underwent 2-day stress-rest 99mTc-tetrofosmin single-photon emission computed tomography MPI. Before stress testing, patients were randomized in a factorial design to four different regimens. Group A: early scan (image acquisition initiated within 15 min after injection of the tracer) and no food; group B: early scan and food (two pieces of white bread with butter and a minimum of 450 ml of water); group C: late scan (image acquisition 30-60 min after injection of the tracer) and no food; and group D: late and scan with food. Patients underwent standard bicycle exercise or pharmacological stress test. The degree of upper abdominal activity was evaluated by trained observers blinded to the randomization code. The primary endpoint was the proportion of accepted scans in the intention-to-treat population in stress MPI.

RESULTS

The results showed statistical significant impact on both time and food on upper abdominal activity. The primary endpoint showed that the acceptance rate improved from 55% in group A to 100% success rate in group D. An early scan reduced the acceptance rate by 30% versus a late scan [hazard ratio 0.70, 95% confidence interval 0.58-0.84; P<0.0001], whereas the addition of food improved the success rate versus no food by 27% (hazard ratio 1.27, 95% confidence interval 1.07-1.51; P=0.006). No significant interaction between food and time was observed. An analysis of accepted scans according to the actual scan time and food consumption confirmed the findings of the intention-to-treat analysis. In addition, similar findings were seen in 116 of 152 patients with a rest MPI (success rate of 53% in group A vs. 96% in group D).

CONCLUSION

A combination of solid food and water administered after injection of the tracer and delayed image acquisition led to significant and clinically relevant decrease of interfering upper abdominal activity in 99mTc-tetrofosmin MPI.

Assessment of 18F-labeled mitochondrial complex I inhibitors as PET myocardial perfusion imaging agents in rats, rabbits, and primates

PURPOSE

Myocardial extractions of mitochondria complex I (MC-I) inhibitors were high and well correlated with flow. This study assessed the potential of MC-I inhibitors to be developed as myocardial perfusion imaging (MPI) agents.

METHODS

RP1003, RP1004, and RP1005 representing three classes of MC-I inhibitor were synthesized and radio-labeled with (18)F. These agents were evaluated for IC(50) values, tissue biodistribution, and cardiac PET imaging. (18)F-RP1004 was further examined for first-pass extraction and by imaging in non-human primates (NHP) and rats following coronary ligation.

RESULTS

RP1003, RP1004, and RP1005 exhibited high MC-I inhibitory activity with IC(50) of 3.7, 16.7, and 14.4 nM. Heart uptakes in rats (percent injected dose per gram tissue) at 15 and 60 min after injection were 3.52 +/- 0.36 and 2.68 +/- 0.20 for (18)F-RP1003, 2.40 +/- 0.21 and 2.67 +/- 0.27 for (18)F-RP1004, and 2.28 +/- 0.12 and 1.81 +/- 0.17 for (18)F-RP1005. The heart to lung and liver uptake ratios were favorable for cardiac imaging with these agents. In isolated perfused rabbit hearts, the uptake of (18)F-RP1004 increased from 0.74 +/- 0.19 to 1.68 +/- 0.39 mL/min/g at flow rates of 1.66 to 5.06 mL/min/g. These values were higher than or similar to that of (99m)Tc-sestamibi. Cardiac imaging with these agents in rats and rabbits allowed visualization of the heart with minimal lung interference and rapid liver activity clearance. Imaging with (18)F-RP1004 also showed clear myocardium and marked liver activity washout in the NHP and clear detection of the perfusion-deficit area associated with left coronary artery ligation in the rat.

CONCLUSION

MC-I inhibitors have the potential to be a new class of MPI agent.

Influence of the different biokinetics of sestamibi and tetrofosmin on the interpretation of myocardial perfusion imaging in daily practice

AIM

Digestive activity can interfere with the interpretation of myocardial perfusion single photon emission computed tomography using sestamibi or tetrofosmin. Compared with sestamibi, the liver clearance of tetrofosmin is more rapid, but its absolute cardiac uptake is lower. In this study, the activity of sestamibi and tetrofosmin was quantified after exercise or pharmacological stress and at rest to objectify the biokinetic differences and to evaluate whether there is a correlation between quantitative measurements and the visual assessment of image quality.

METHODS

Left ventricular activity and five ratios (R1-R5) of cardiac to adjacent extra-cardiac activity were quantified in 204 sestamibi (68 exercise stress/56 pharmacological stress/80 rest) and 221 tetrofosmin (67 exercise stress/59 pharmacological stress/95 rest) studies. Image quality was assessed by a three-point score (1, good; 2, moderate; 3, poor) and correlated with the heart to left supra-diaphragmatic region (R1) and heart to right supra-diaphragmatic region (R2) ratios.

RESULTS

The mean left ventricular activity was higher for sestamibi, especially at rest (sestamibi, 0.21+/-0.05 counts/pixel/injected MBq; tetrofosmin, 0.16+/-0.042 counts/pixel/injected MBq; P<0.001). By contrast, most ratios were higher with tetrofosmin, particularly for the exercise stress and rest studies. Using the three-point quality scoring, more sestamibi than tetrofosmin studies were scored as 3 (12.2% versus 6.3%), also particularly for the exercise stress and rest studies. A highly significant relationship was found between decreasing R1 and R2 and an increasing quality score, regardless of the radiopharmaceutical used (P values between 0.02 and <0.001).

CONCLUSIONS

Despite a lower cardiac uptake, the more rapid liver clearance of tetrofosmin than sestamibi significantly improves the ratios of cardiac to digestive activity, especially after exercise or at rest. These quantitative differences in biokinetics result in less poor scans with tetrofosmin in daily practice.

Can administration of metoclopramide reduce artefacts related to abdominal activity in myocardial perfusion SPECT?

OBJECTIVES

Myocardial perfusion SPECT is frequently affected by artefacts related to abdominal activity. Metoclopramide has been suggested to relieve this, but two previous studies have shown conflicting results.

METHODS

Ninety-five patients received 10 mg metoclopramide orally after injection of 99mTc-tetrofosmin for the stress scan and 86 patients had metoclopramide after their rest injection. A control group of 82 patients did not receive metoclopramide. Scans were evaluated visually by three readers.

RESULTS

Metoclopramide given before the stress scan led to abdominal activity being visually better in 16 scans, worse in 10, and unchanged in 67 scans, compared to the same patient's rest scan without metoclopramide administration. Metoclopramide administered before the rest scan resulted in abdominal activity in 11 scans being visually better, in 19 worse, and 53 scans were deemed unchanged. These differences were not significant. The number of repeat stress or rest scans was not significantly different between patients who had received metoclopramide and those who had not. The administration of metoclopramide, irrespective of whether it was given before the stress or rest scan, made no significant difference to inferior wall-to-abdomen count ratio.

CONCLUSION

Neither qualitative nor quantitative analysis showed an effect of metoclopramide on abdominal activity in myocardial perfusion SPECT.

Efficacy of milk versus water to reduce interfering infra-cardiac activity in 99mTc-sestamibi myocardial perfusion scintigraphy

OBJECTIVE

Interference from infra-cardiac radionuclide activity prevents accurate interpretation of true myocardial perfusion. The study aim was to compare the efficacy of milk versus water in reducing infra-cardiac activity in myocardial perfusion scintigraphy.

METHODS

We prospectively randomized 198 patients undergoing stress-rest (99m)Tc-sestamibi SPECT with exercise or pharmacological stress to drink 300 ml of water or milk prior to imaging. A semi-quantitative grading of the relative intensity of infra-cardiac activity compared to the myocardial activity and a qualitative assessment of the effect on the overall interpretation was performed.

RESULTS

For stress images, there was no infra-cardiac activity in 37.9%, less intense infra-cardiac activity in 40.8%, equal in 11.7% and greater than infra-cardiac activity in 9.7% with milk, compared with 20.0%, 49.5%, 20.0% and 10.5%, respectively, with water (P=0.038). For rest images, there was also less intense infra-cardiac activity with milk compared to water (P=0.014). However, no change in subsequent image interpretation was seen.

CONCLUSION

Administration of milk resulted in a significant decrease in the intensity of infra-cardiac activity compared to water. However, this did not translate into an improvement in image interpretation.

Acceleration of hepatobiliary excretion by lemon juice on 99mTc-tetrofosmin cardiac SPECT

BACKGROUND

We sought to determine whether drinking lemon juice reduces extra-cardiac activity and improves image quality on (99m)Tc-tetrafosmin myocardial single photon emission computed tomography (SPECT).

METHODS

Eighty male patients were enrolled in this study and divided into four groups with 20 patients in each group. Each patient received 259-333 MBq tetrofosmin. Ten minutes after injection no action was taken for group 1 (G1), patients in group 2 (G2) each drank 250 ml of water, patients in group 3 (G3) each drank 250 ml of whole milk, and patients in group 4 (G4) each drank 250 ml diluted lemon juice. Myocardial perfusion imaging without attenuation correction was performed after a 1 day rest-stress protocol. Both rest and stress images were aligned at corresponding slices for comparison. Interfering activity was determined visually on reconstructed images, and the heart-to-liver (H/L) ratios were calculated with planar images at 25-30 min and at 45-50 min.

RESULTS

Interfering activity was seen in 80% of G1, 70% of G2, 60% of G3, and 35% of G4 (G4 vs. G1, P=0.006) on rest images, and in 70% of G1, 60% of G2, 55% of G3, and 30% of G4 (G4 vs. G1, P=0.014) on stress images at 25-30 min. It was also observed in 60% of G1, 50% of G2, 45% of G3, and 15% of G4 (G4 vs. G1, P=0.006) on rest images, and in 50% of G1, 45% of G2, 40% of G3, and 10% of G4 (G4 vs. G1, P=0.011) on stress images at 45-50 min. The mean H/L ratios of rest images were 0.47+/-0.13 for G1, 0.71+/-0.17 for G2, 0.65+/-0.12 for G3, and 0.93+/-0.23 for G4 at 25-30 min, and 0.63+/-0.14 for G1, 0.73+/-0.14 for G2, 0.85+/-0.25 for G3, and 1.15+/-0.25 for G4 at 45-50 min. On stress images, they were 0.49+/-0.11 for G1, 0.74+/-0.16 for G2, 0.69+/-0.11 for G3, and 0.98+/-0.22 for G4 at 25-30 min, and 0.66+/-0.15 for G1, 0.77+/-0.11 for G2, 0.89+/-0.26 for G3, and 1.21+/-0.19 for G4 at 45-50 min.

CONCLUSION

Drinking 250 ml of diluted lemon juice accelerates the transit of tetrofosmin through the liver parenchyma and improves image quality on (99m)Tc-tetrafosmin myocardial SPECT.

Clinical implication of reverse redistribution on99mTc-sestamibi images for evaluating ischemic heart disease

OBJECTIVE

The purpose of this study was to clarify the usefulness of 99mTc-sestamibi (MIBI) delayed imaging in the assessment of the severity of myocardial ischemia in patients with coronary artery stenosis.

METHODS

Forty-three angina pectoris with coronary stenosis of greater than 75% were enrolled in this study. Myocardial perfusion SPECT images were obtained 1 and 6 hours after an intravenous injection of MIBI at rest. Stress myocardial perfusion SPECT images were also acquired after the injection of MIBI. And myocardial fatty acid metabolism images were obtained 30 minutes after the injection of BMIPP at rest. Myocardial perfusion SPECT images were divided into 20 segments which were semiquantitatively assessed according to a 4-level defect score scale: score 0 (normal) to score 3 (severely); then the extent score (ES) and severity score (SS) were calculated.

RESULTS

The sensitivity for myocardial ischemia showed the highest rate at 88.3% with MIBI delayed SPECT. According to the coronary angiography findings, MIBI stress SPECT and MIBI delayed SPECT detected the severity and extent of ischemia with more sensitivity than MIBI early SPECT in 12 patients (group A) with stenosis of more than 75% but less than 90% (p < 0.01). Even though MIBI stress SPECT detected the severity and extent of ischemia in 31 patients (group B) with stenosis of more than 90% but less than 100%, there was no significant difference between MIBI stress SPECT and MIBI delayed SPECT. BMIPP SPECT revealed significant differences between group A and group B regarding the severity of myocardial ischemia. MIBI reverse redistribution was observed in 33 patients and no significant difference existed between groups A and B.

CONCLUSIONS

Myocardial washout of MIBI was frequently observed in patients with angina pectoris and the detection accuracy for ischemia was high. MIBI imaging is considered useful for assessment not only of myocardial perfusion but also mitochondrial function. The imagings with BMIPP and delayed MIBI could serve to determine the severity of myocardial ischemia more accurately.

The prevalence and significance of increased gastric wall radiotracer uptake in sestamibi myocardial perfusion SPECT

BACKGROUND

Limited available data indicate that a specific pattern of increased gastric wall radiotracer uptake is associated with dyspepsia. Our purpose was to evaluate the frequency of this finding and its relation with dyspeptic evidences.

METHOD

1056 consecutive outpatients referred for myocardial perfusion SPECT were interviewed concerning the dyspeptic symptoms, current gastric medications and previous gastroduodenal interventions. The intensity of gastric wall activity was graded qualitatively as G1 or hyperactive gastric wall (equivalent to the patient's heart activity) and G2 (less than heart activity).

RESULTS

The pattern of gastric wall hyperactivity was identified in 1.9% of patients. Dyspeptic symptoms were present in 80 and 18.6% of G1 and G2 patients, respectively (p<0.001). The dyspeptic symptoms were classified as ulcer-like in 37.5%, dysmotility-like in 43.75% and GERD-like in 18.75% of the dyspeptic G1 patients. Considering the classification of dyspepsia, there was no significant difference between the dyspeptic patients of groups. The history of previous gastroduodenal interventions and current use of gastric medications was significantly higher among G1 patients.

CONCLUSION

The infrequent pattern of gastric wall hyperactivity could be clinically important and can identify a category of patients, who require additional diagnostic gastrointestinal investigation to specify another possible noncardiac origin of complaints.

EANM/ESC procedural guidelines for myocardial perfusion imaging in nuclear cardiology

The European procedural guidelines for radionuclide imaging of myocardial perfusion and viability are presented in 13 sections covering patient information, radiopharmaceuticals, injected activities and dosimetry, stress tests, imaging protocols and acquisition, quality control and reconstruction methods, gated studies and attenuation-scatter compensation, data analysis, reports and image display, and positron emission tomography. If the specific recommendations given could not be based on evidence from original, scientific studies, we tried to express this state-of-art. The guidelines are designed to assist in the practice of performing, interpreting and reporting myocardial perfusion SPET. The guidelines do not discuss clinical indications, benefits or drawbacks of radionuclide myocardial imaging compared to non-nuclear techniques, nor do they cover cost benefit or cost effectiveness.

The volume effect of the stomach on intestinal activity on same-day exercise--rest Tc-99m tetrofosmin myocardial imaging

PURPOSE

The aim of this study was to investigate quantitatively the volume effect of the stomach on the prevention of intestinal artifacts in the rest phase on same-day exercise--rest Tc-99m tetrofosmin myocardial perfusion scintigraphy.

MATERIALS AND METHODS

The study was performed in 81 consecutive patients (43 men, 38 women; mean age, 57 +/- 9 years) who were referred for routine Tc-99m tetrofosmin exercise--rest SPECT myocardial perfusion imaging with normal scintigrams or completely normal inferior wall perfusion on visual assessment of SPECT images. Group A (control group, n = 41) and group B (n = 40) were given 200 ml milk to enhance the hepatobiliary clearance of tetrofosmin 30 minutes before the exercise SPECT acquisition study and just after the injection for the rest SPECT acquisition study. For the rest SPECT acquisition study, patients in group B were given, in addition to milk, a standard solid and fluid meal to enhance the volume of the stomach after the injection of Tc-99m tetrofosmin. In all patients, both exercise and rest SPECT acquisitions were started 45 minutes after the injection of Tc-99m tetrofosmin. Myocardial and abdominal activity were assessed on three separate views in the rest phase of the study, and the mean myocardium-to-abdomen count ratios were calculated. In addition, the presence of interfering intestinal activity was assessed visually on SPECT images. Infracardiac activity was described as absent when it was equal to lung background.

RESULTS

The myocardial-to-abdominal ratios were 1.38 +/- 0.05 and 1.95 +/- 0.04 in groups A and B, respectively (P < 0.0001). Interfering intestinal activity with varying degrees of intensity was seen in 20 patients in group A (49%) and in 5 patients in group B (13%; P < 0.001).

CONCLUSIONS

These results suggest that filling of the stomach with some fluid and solid food before rest acquisition on the same-day stress--rest protocol, because of its volume effect, may provide a high target-to-nontarget ratio for myocardial imaging and thus may reduce the frequency of intestinal artifacts.

Comparing the image quality of myocardial perfusion agents in the clinical laboratory: small test groups and large reference populations

Myocardial perfusion studies have been performed for 6 years using technetium-99m (99Tcm)-sestamibi (MIBI). In this study we evaluated a newer agent, 99Tcm-tetrofosmin (TF), on a trial basis for 2 weeks, and compared the results from each week to those in an adjacent week of MIBI use. The routine protocol included weight-based dosing, frequent dipyridamole use, and separate-day rest and stress wherever possible. During the first week, TF was used with 'usual' image timing, i.e. stress tomography performed 30-60 min after stress, and ancillary immediate images performed 4 min after injection. For the second week, 'early' tomography was performed 15-30 min after stress. TF scans (n = 53) were compared with MIBI scans for the adjacent weeks (n = 54) and with a historical reference series (n = 1800). Blinded analysis was made of tomographic image quality, peak myocardial counts and background activity (lung and abdomen) on immediate and delayed acquisitions and on tomographic reconstructions. The TF and MIBI test groups were similar with respect to gender, weight, stress protocol, tracer doses, imaging times and scintigraphic findings. Using analysis of variance, the tomographic quality scores were similar for the two observers, with stress>rest (P<0.0001), 'usual'>'early' (P<0.001) and MIBI>TF (P<0.05). Myocardial counts were approximately 20% higher with the MIBI test group than with TF at all times after stress (P=0.001), and were similar to the reference population. MIBI with usual timing gave more favourable stress abdominal background ratios than the other three agent/timing combinations. Satisfactory images could be obtained with TF, but no apparent advantage over MIBI could be attained with earlier post-stress imaging. Subtle advantages for MIBI over TF were suggested by comparison of the small test groups. In our local imaging context, these conclusions were reinforced by a large control series.

Myocardial perfusion imaging: clinical experience and recent progress in radionuclide scintigraphy and magnetic resonance imaging

In the past 20 years, radionuclide scintigraphy has proven to be a sensitive clinical tool in the assessment of myocardial perfusion abnormalities. Magnetic resonance imaging may also be used to study myocardial perfusion, but its potential value still has to emerge in the clinical setting. This review addresses the potential and achievements of both methods in clinical cardiology.