Thallium-201 myocardial imaging during pharmacologic coronary vasodilation: comparison of oral and intravenous administration of dipyridamole.

Although the diagnostic utility of thallium-201 myocardial imaging after dipyridamole infusion is well established, the intravenous form of the drug is not yet commercially available in North America. Fifty patients referred for coronary angiography were prospectively studied. Within a 2 week period, each patient underwent cardiac catheterization and thallium-201 myocardial imaging after both oral and intravenous dipyridamole administration. For the oral protocol, patients were randomly assigned to treatment with either 200 or 400 mg of dipyridamole in tablet form. Coronary artery stenoses of 70% or greater were considered significant. For the 25 patients who received a 200 mg oral dose of dipyridamole, the scintigraphic study showed perfusion defects in 65% of patients with significant coronary artery disease after the oral dose and in 85% of patients after the intravenous dose. For the 25 patients who received a 400 mg oral dose, the sensitivity of the scintigram was 84% after the oral dose and 79% after the intravenous dose. Except for headache and nausea, side effects were less severe and less frequent with oral (either 200 or 400 mg) than with intravenous dipyridamole. Because of the delayed and variable absorption of dipyridamole tablets, the oral studies required a longer period of medical supervision (45 to 60 minutes), and aminophylline was empirically administered after completion of the first set of thallium-201 images. It is concluded from this study that thallium-201 myocardial imaging after coronary vasodilation with a 400 mg oral dose of dipyridamole is a safe, widely available and reliable alternative for the evaluation of coronary artery disease in patients unable to achieve an adequate exercise level on stress testing.

The role of single photon emission computed tomography brain imaging with 99mTc-bicisate in the localization and definition of mechanism of ischemic stroke.

99mTc-bicisate (99mTc-ECD) is a new brain perfusion imaging agent formulated from a radiochemically stable kit (Neurolite). A multicenter trial was conducted to determine the sensitivity and specificity of single photon emission computed tomography (SPECT) imaging with 99mTc-bicisate in the localization of ischemic stroke; 170 subjects were enrolled, 128 patients with stroke and 42 controls. Imaging results from 148 subjects (107 stroke patients and 41 controls) were considered evaluable. In the evaluable subjects, SPECT brain imaging with 99mTc-bicisate (21.0 +/- 2.5 mCi) was interpreted without clinical information and was compared with a final assessment using all clinical, diagnostic, and laboratory procedures except the 99mTc-bicisate SPECT results. 99mTc-bicisate was safe and well-tolerated. SPECT imaging with 99mTc-bicisate demonstrated a specificity of 98% and a sensitivity of 86% for localization of strokes (kappa, 0.75; 95% confidence interval, 0.64-0.86). Results were unchanged over time and were similar for all stroke mechanisms except for lacunar disease (sensitivity, 58%). In a secondary analysis, a normal image or small, deep (e.g., subcortical) perfusion defect was highly predictive of a lacunar mechanism. Defects involving the cortical surface were strongly associated with nonlacunar mechanisms. SPECT imaging with 99mTc-bicisate is a sensitive marker in the localization of perfusion defects associated with ischemic stroke and may assist in the determination of the underlying mechanism of a stroke.

Intrasubject comparison between technetium-99m-ECD and technetium-99m-HMPAO in healthy human subjects.

The pharmacokinetics and quality of planar and SPECT brain imaging of two 99mTc-labeled brain perfusion agents, d,l-hexamethyl propylene amine oxime (HMPAO) and ethyl cysteinate dimer (ECD), were compared in seven healthy, normal subjects. Both radiopharmaceuticals showed rapid brain uptake and had a net brain washout of less than 5% during the first 20 min after drug administration. However, during the same time period, 99mTc-ECD images of the head showed significantly less background facial uptake and retention when compared to 99mTc-HMPAO images. The brain-to-background contrast ratio of 99mTc-ECD (brain/neck) continued to improve over time and by 5 hr postadministration was 17 to 1 versus 2 to 1 for 99mTc-HMPAO. SPECT brain images of both agents show gray/white matter ratios that were unchanged over time and an intracerebral distribution consistent with blood flow. A blind read of these SPECT images also shows 99mTc-ECD to produce images that were "easier to interpret" with less extracerebral activity as compared to 99mTc-HMPAO. Repeat, whole-body planar spot imaging suggests that 99mTc-ECD was cleared more rapidly from the body than was 99mTc-HMPAO.

Comparison between thallium-201, technetium-99m-sestamibi and technetium-99m-teboroxime planar myocardial perfusion imaging in detection of coronary artery disease.

Technetium-99m-sestamibi (MIBI) and 99mTc-teboroxime (TEBO) are two new myocardial perfusion imaging agents. The purpose of this prospective study was to compare MIBI and TEBO to 201TI planar imaging. Eighteen patients with significant coronary artery disease on coronary angiogram were submitted to three treadmill stress tests performed within 3 mo and were imaged with the three radiopharmaceuticals as follows. 1. TI: 2.2 mCi, immediate and delayed views (4 hr later, 8 min/view). 2. TEBO: 15-20 mCi at stress (1 min/view) and a second injection was repeated 4 hr later at rest (20-25 mCi). 3. MIBI: 15-18 mCi at stress (8 min/view) and 1-4 days later, 15-18 mCi at rest. Patients achieved similar levels of exercise. A blinded reading was performed by three observers. The left ventricle was divided into three segments/view and ischemic/normal wall ratios were also determined. Segmental comparison showed an agreement in 85% (138/162) of the segments between TI and TEBO, in 92% (149/162) between TI and MIBI and in 84% (136/162) between MIBI and TEBO. Abnormal TI, MIBI and TEBO studies were seen in 16 (89%), 16 (89%) and 15 (83%) patients, respectively, detecting 77, 75 and 65 abnormal segments. Ischemic-to-normal wall ratios were 0.75 +/- 0.06, 0.73 +/- 0.08 and 0.78 +/- 0.08 for TI, MIBI and TEBO, respectively. In conclusion, although the biologic characteristics of these agents are different, this study showed a good correlation between them in detection of significant coronary artery disease (high pretest likelihood population).

Technetium-99m glucoheptonate in brain-tumor detection: an important advance in radiotracer techniques.

We have compared [Tc-99m] sodium pertechnetate with Tc-99m glucoheptonate in 52 patients studied for various brain lesions. Flow studies as well as delayed scans were performed in all. Especially in primary and metastatic lesions of the posterior fossa, the diagnostic yield was improved by the delayed glucoheptonate (GH) scans. In contrast, no advantage of GH over pertechnetate could be detected in the study of infarcts or other ischemic lesions. Various hypotheses are discussed to explain the observed differences in behavior between the two tracers.

Technetium-99m-sestamibi myocardial perfusion imaging in detection of coronary artery disease: comparison between initial (1-hour) and delayed (3-hour) postexercise images.

Technetium-99m-sestamibi, a new myocardial perfusion imaging agent, does not show significant or rapid myocardial redistribution following its intravenous injection at stress. The purpose of this study was to evaluate the myocardial clearance of 99mTc-sestamibi and ischemic/normal wall ratios at 1 hr and at 3 hr after injection at stress in patients with significant coronary artery disease. Twenty-five patients with ischemic defects on 201Tl scans (n = 15) and/or significant disease on coronary angiogram (n = 18) were prospectively studied. Planar images were obtained at 65 and at 190 min after an injection at stress of 20-25 mCi of 99mTc-sestamibi. A rest study was performed 1-6 days later. Ischemic/normal wall ratios were 0.73 +/- 0.10 and 0.83 +/- 0.12 (p less than 0.05) at 1 and 3 hr, respectively (0.98 +/- 0.15 at rest). Myocardial washout was 26% +/- 12% for normal walls and 15% +/- 8% for ischemic walls (p less than 0.001). Segmental analysis showed 48 and 46 ischemic segments at 1 and 3 hr, respectively. In conclusion, although only a few ischemic segments were missed at 3 hr, significantly lower ischemic/normal wall ratios were found at 1 hr. Faster myocardial washout from normal walls is responsible for the partial reduction of this ratio.

Metastatic axillary lymph node technetium-99m-MIBI imaging in primary breast cancer.

UNLABELLED: Technetium-99m-MIBI scintimammography has been shown to be useful in the detection of primary breast cancer. The purpose of this study was to evaluate the potential role of scintimammography in detecting axillary lymph node involvement in patients undergoing scintimammography to detect primary breast cancer. METHODS: A group of 100 women with breast cancer who were scheduled for a Level I-II axillary dissection were prospectively studied. Scintimammography was performed in all patients before histopathologic confirmation of breast cancer. Two lateral (prone imaging) views and one anterior (supine) planar thoracic view were obtained 10-15 min after the injection of 25-30 mCi 99mTc-MIBI (10 min/view) by using a special breast positioning device (foam cushion) placed over the imaging table. Both of the axilla were included in the field-of-view. Two experienced blinded observers reviewed all cases both from films and from the computer screen with contrast adjustment when needed. The site of intravenous injection of 99mTc-MIBI was known to the interpreters in order to avoid reading any false-positive uptake in the axilla ipsilateral to the injection site. RESULTS: A total of 52 patients had no axillary lymph node involvement (611 negative nodes) while 48 patients had at least one axillary lymph node with metastatic involvement (180/502 positive nodes). The sensitivity of scintimammography in detecting metastatic axillary lymph node involvement was 79.2% (38/48), and the specificity was 84.6% (44/52). The positive and the negative predictive values were 82.6% (38/46) and 81.5% (44/54), respectively. CONCLUSION: This study shows that scintimammography has good diagnostic accuracy for detecting axillary lymph node involvement in patients with breast cancer. This information should be added to the result of standard scintimammography, which requires very minor modifications in order to simultaneously evaluate both of the axilla.

Radionuclide captopril renography in postpartum renal artery aneurysms.

We report the case of a young woman with three left renal artery aneurysms, diagnosed immediately postpartum, associated with a de novo high blood pressure. To assess anatomical and functional characteristics of renal artery aneurysms, renal angiogram, MRI, intravenous pyelography, ultrasonography and radionuclide renography were performed. Two patent saccular renal artery aneurysms were demonstrated in the left kidney by renal angiogram. A larger, thrombosed aneurysm was also depicted on the left side on ultrasonography, MRI and renal angiogram. The larger aneurysm was responsible for renovascular disease of the middle third of the kidney, as demonstrated by captopril and baseline radionuclide renographic studies. It also impeded drainage of the lower pyelocalyceal group, without obstructing it, as shown by concomitant furosemide (Lasix) evaluations.

Characterization of technetium-99m-L,L-ECD for brain perfusion imaging, Part 2: Biodistribution and brain imaging in humans.

The safety, biodistribution and kinetics of a new perfusion imaging agent [99mTc-L,L]-ethyl cysteinate dimer (ECD) was evaluated in normal volunteers. Technetium-99m-L,L-ECD is a neutral, lipophilic complex, which is radiochemically pure and stable. Twelve healthy adults were injected with 25-30 mCi of 99mTc-L,L-ECD and imaged periodically for up to 24 hr. Planar imaging showed rapid brain uptake with a peak concentration of 4.9% injected dose and very slow brain washout (approximately 6% per hour during the first 6 hr). Repeat or dynamic tomographic imaging of the brain using either a rotating gamma camera or a multidetector system was performed up to 6 hr postinjection. The distribution of 99mTc-L,L-ECD in the brain did not change and was similar to the pattern seen with other perfusion agents. Background facial areas and lungs cleared rapidly. Peak blood activity was below 10% injected dose at all times and 99mTc-L,L-ECD cleared rapidly through the kidneys. Vital signs, blood and urine chemistries were normal in all volunteers and no adverse reactions were noted. These results suggest that 99mTc-L,L-ECD should be useful for routine assessment of cerebral perfusion in humans.

Biodistribution, dosimetry, and clinical evaluation of technetium-99m ethyl cysteinate dimer in normal subjects and in patients with chronic cerebral infarction.

Technetium-99m ethyl cysteinate dimer (ECD) has high initial cerebral uptake with slow clearance in nonhuman primates suggesting ideal characteristics for single photon emission computer tomography (SPECT) imaging. We evaluated the biodistribution, dosimetry and scintigraphic pattern of [99mTc]ECD in normal subjects and the accuracy of SPECT imaging in patients with chronic cerebral infarction. Sixteen normal subjects were injected with approximately 10 mCi of [99mTc]ECD. Anterior and posterior single-pass whole-body images were obtained at multiple times after injection. Blood clearance of the radiotracer was rapid, falling to 10.0 +/- 6.6% and 4.9 +/- 1.1% of the injected dose at 2 and 60 min, respectively. Brain uptake was 6.4 +/- 2.1% of the injected dose 5 min after injection. The critical organ was the urinary bladder. Technetium-99m ECD SPECT was performed with a rotating gamma camera in ten of the 16 normal subjects and 34 patients with clinical and CT evidence of chronic stroke. Thirty-three of the thirty-four patients had focal [99mTc]ECD abnormalities on SPECT (97.1%) based on visual inspection of the SPECT images. In summary, we obtained high quality SPECT images as a result of the optimal physical and biologic characteristics of the tracer. Technetium-99m ECD SPECT shows promise for the evaluation of patients with stroke.

Comparison between technetium-99m-teboroxime and thallium-201 dipyridamole planar myocardial perfusion imaging in detection of coronary artery disease.

Technetium-99m (TC-99m)-teboroxime is a new myocardial perfusion imaging agent. The purpose of this prospective study was to compare Tc-99m-teboroxime with thallium-201 imaging after the administration of dipyridamole. Thirty patients referred for the evaluation of chest pain were studied with both thallium-201 and Tc-99m-teboroxime dipyridamole scans (mean interval 2 days). Dipyridamole was administered at 0.142 mg/kg/min for 4 minutes. Planar imaging (3 standard views) was obtained at 5 and 240 minutes after the injection of 2.2 mCi of thallium-201. Tc-99m-teboroxime (18 to 25 mCi) was injected after dipyridamole infusion. A second injection, at rest, was repeated 4 hours later. Planar imaging (3 standard views of 1 minute/view for the first 2 views, and 90 seconds for the last view) was obtained 2 minutes after Tc-99m-teboroxime injection. Blinded reading was performed by 3 observers. Thallium-201 showed perfusion defects in 182 myocardial segments corresponding to 33 of 45 (73%) significantly stenosed coronary arteries (greater than or equal to 70% reduction in endoluminal diameter), and Tc-99m-teboroxime detected 160 abnormal segments corresponding to 29 of 45 (64%) stenosed arteries. Thallium-201 and Tc-99m-teboroxime studies were normal in 3 patients. In conclusion, this study shows that there is a good correlation in the imaging results found with thallium-201 and Tc-99m-teboroxime using dipyridamole infusion on both a segmental and a diagnostic comparison.

In vivo measurement of atrial natriuretic peptide receptors using nuclear imaging.

We have successfully visualized atrial natriuretic peptide (ANP) receptors in vivo using nuclear imaging. 123I-Labelled ANP, injected in green vervet monkeys, was rapidly bound to ANP receptors in the kidneys and lungs. That the observed uptake was receptor mediated was demonstrated with competition studies using simultaneous injection of unlabelled ANP 99-126. It was possible to distinguish between the ANP receptor subtypes by the use of selective antagonists. Thus coinjection of ANP 102-121-des[Gln, Ser, Gly, Leu, Gly] (C-ANP), an ANP analog that selectively binds to the ANP C-receptor, decreased uptake in the kidneys by 50% but increased relative uptake in the lungs and soft tissues. This method permits for the first time, the dynamic in vivo analysis of ANP receptors and their interaction with endogenous ligand. Differences and changes in local ANP receptor concentrations and occupancy could be detected. Since ANP receptor density and affinity are influenced by various physiological and pathological conditions, clinical and diagnostic applications seem possible.

Case study: dreamy state and temporal lobe dysfunction in a migrainous adolescent.

Symptoms of migraine can be very atypical during childhood and adolescence. This article describes a case in which the symptoms of migraine were mainly psychiatric: dreamy state, intermittent confusion, partial amnesia, and childlike regressive behavior with depressive features. Although the results from neurological examinations and electroencephalographic recordings were normal when the individual was symptomatic or not, temporal lobe dysfunction, determined by 99mTc-hexamethyl-propyleneamine oxamine single-photon emission computed tomography, was evident during the migraine.

Neuropsychological functioning in unilateral cerebellar damage.

A woman had a left superior cerebellar artery infarct associated with reduced hexamethylpropileneamine oxime uptake on SPECT scan of the basal ganglia and frontoparietal areas of the opposite hemisphere performed poorly in some neuropsychological tests indicating right hemisphere dysfunction. There was a lengthening of reaction and movement times with the hand ipsilateral to the lesion. These deficits were temporary. A unilateral cerebellar lesion can produce neuropsychological deficits, possibly because of hypoperfusion in contralateral frontoparietal regions, but spontaneous neuropsychological remissions may occur.

Parkinsonism--dementia complex, hydrocephalus and Paget's disease.

A 65-year-old female patient with Paget's disease displayed dementia, a bilateral Parkinsonian syndrome, gait ataxia, bilateral grasp reflex of the feet, urinary incontinence and a left hemicerebellar syndrome. She had a marked basilar impression; the radionuclide cisternogram was suggestive of a communicating hydrocephalus with ventricular dilatation. After a shunting procedure there was improvement in both neurological and mental function.

Comparative evaluation of technetium-99m glucoheptonate and gallium-67 citrate thoracic imaging in detection of mediastinal and hilar involvement in primary lung cancer.

Fifty-two patients with proven primary lung cancer who were referred for mediastinoscopy were prospectively studied with Tc-99m glucoheptonate and Ga-67 citrate thoracic scintigraphy. Primary lung tumors concentrated Ga-67 in 92% of cases, compared to 88% for Tc-99m glucoheptonate. Mediastinoscopy confirmed the presence of mediastinal metastases in 23 patients. The sensitivity of Tc-99m glucoheptonate and Ga-67 scans for mediastinal involvement detection is respectively 52% and 83%, for a specificity of 100% (Tc-99m glucoheptonate) and 88% (Ga-67). Twenty-nine patients underwent thoracotomy after a negative mediastinoscopy. Hilar metastatic involvement was present in eight patients. The sensitivity and the specificity for detection of hilar involvement were respectively 63% and 95% for Tc-99m glucoheptonate and 88% and 78% for Ga-67. Although more specific than Ga-67 scan, Tc-99m glucoheptonate thoracic imaging cannot be recommended in the staging of lung cancer because of its low sensitivity in the detection of intrathoracic metastatic spread of primary lung carcinoma.

"Cold" reflex sympathetic dystrophy in an adult.

The classical presentation of acute reflex sympathetic dystrophy (RSD) or triple-phase bone scintigraphy usually consists of increased periarticular uptake in each phase. The authors present a rare case of acute adult RSD characterized by bone hypofixation of Tc-99m MDP. Reflex sympathetic dystrophy in adults and children is reviewed.

A physiologic approach to renal scintigraphy. Application to evaluation of hypertension.

The aim of this study was to define the use of the triple radiopharmaceutical renal study (TRRS) for renal scintigraphy as a physiological tool for renal evaluation, and to determine if the sensitivity and/or specificity of a renal study for the diagnosis of renovascular hypertension (RVH) could be improved by the combination of three radiopharmaceuticals (i.e., I-131 OIH, Tc-99m DTPA, and Tc-99m glucoheptonate). One hundred ninety-five patients with suspected RVH underwent TRRS, standard Tc-99m DTPA renal studies, and renal angiography. One hundred eighty-nine patients were hypertensive and ischemic nephropathy was suspected in six. Ninety-one, including three patients with ischemic nephropathy, had a renal artery stenosis of 70% or more (66 unilateral, 25 bilateral). Effective renal plasma flow (ERPF), glomerular filtration rate (GFR) (from plasma clearance of I-131 OIH and Tc-99m DTPA), and geometric renal masses (from Tc-99m glucoheptonate study) were compared to normal values corrected for body surface, to determine the severity of renal dysfunction. For the TRSS, RVH criteria included: 1) differential Tc-99m DTPA function minus differential Tc-99m glucoheptonate function of affected kidney ( < -5% or > 5%) and 2) functional parameters: ERPF = 1.6-2.0 ml/g/minute, GFR = 0.25-0.4 ml/g/minute, and filtration fraction (i.e., GFR/ERPF = 0.15-0.20) on the affected side.

Myocardial perfusion imaging with a new radiotracer, technetium-99m-hexamibi (methoxy isobutyl isonitrile): comparison with thallium-201 imaging.

Technetium-99m-hexamibi (methoxy isobutyl isonitrile) is a Tc-99m-hexakis analog that can be used as a myocardial perfusion imaging agent. This is a report of an initial study that was performed in four institutions to assess the feasibility of Tc-99m-hexamibi myocardial imaging for the detection of coronary artery disease in patients undergoing treadmill stress test. Thirty-three patients referred for evaluation of chest pain had two exercise stress tests, one with Tl-201 and at least 24 hours after, and a second one with Tc-99m-hexamibi. Myocardial planar imaging started 60 minutes after injection at stress of 10-20 mCi of Tc-99m-hexamibi. Because this agent does not redistribute in myocardium after a stress injection, a second injection of 10-20 mCi of Tc-99m-hexamibi was performed with the patient at rest a few days later. Qualitative assessment of both Tl-201 and Tc-99m-hexamibi myocardial distribution was performed in 297 left ventricle segments (three segments of each of three views). There was a good correlation for the presence of normality, scar, or ischemia with the two radiopharmaceuticals, both on a segment by segment (259/297, or 87.2%) and patient-by-patient basis (29/33, or 87.9%). The number of segments found ischemic with Tl-201 and with Tc-99m-hexamibi were nearly equal, as were the number that were normal with one radiopharmaceutical and ischemic by the other. This initial study demonstrates that it is possible to detect stress-induced abnormalities of myocardial perfusion with Tc-99m-hexamibi similar to Tl-201 imaging.