Biomedical subjects

G Germano

Publications and source records attributed to G Germano.

At least 73 records · Page 4Linked to original sources

PubMed1995

Automatic reorientation of three-dimensional, transaxial myocardial perfusion SPECT images.

UNLABELLED: We developed a completely automatic technique to reorient transaxial images into short-axis (oblique) myocardial perfusion SPECT images. METHODS: The algorithm starts by isolating (segmenting) the left ventricle (LV) myocardium using a combination of iterative clusterification and rule-based location/size/shape criteria. The three-dimensional, mid-myocardial LV surface is initially estimated as the locus of the trilinearly interpolated maxima for the count profiles originating from the center of mass of the segmented LV. The final mid-myocardial surface is obtained by iteratively applying this process, incorporating additional constraints of shape and texture and using the nonsegmented, nonthresholded transaxial image to obtain information on hypoperfused areas of the myocardium. It is then fitted to an ellipsoid, of which the major axis is assumed to represent the long axis of the LV, and the three-dimensional image volume is resliced perpendicularly to it. RESULTS: The algorithm was retrospectively applied to 400 dual-isotope studies (200 rest 201TI, 200 stress 99mTc-sestamibi) from 200 consecutive patients. Segmentation was successful in 394/400 (98.5%) of the patients. The reproducibility of computer-based reorientation was perfect and significantly better than either intraobserver or interobserver reproducibility. CONCLUSION: Automatic reorientation offers the potential for consistently faster and more accurate image processing and analysis and is an important step towards totally operator-less management of myocardial perfusion SPECT data.

Algorithms↗

PubMed1994

Pharmacologic stress dual-isotope myocardial perfusion single-photon emission computed tomography.

Separate-acquisition rest thallium-201/exercise technetium-99m sestamibi (sestamibi) dual-isotope single-photon emission computed tomography (SPECT) has been shown to be effective for assessment of myocardial perfusion and viability. The present study was designed to validate the dual-isotope approach when used in conjunction with pharmacologic stress. All patients had rest 201TI SPECT followed immediately by adenosine (n = 82) or dipyridamole (n = 50) infusion and sestamibi injection. Sestamibi SPECT was performed 1 hour later. The entire study lasted < 2.5 hours. The patient population was categorized into three groups: 51 consecutive patients with coronary angiography and no previous myocardial infarction (group I), 58 consecutive patients with a low prescintigraphic test likelihood of coronary artery disease (group II), and 23 consecutive catheterized patients with remote Q-wave myocardial infarction (group III). For group I patients, the sensitivity and specificity for dual-isotope SPECT were 92% (35 of 38) and 85% (11 of 13), respectively, when > or = 50% coronary artery narrowing was considered significant and were 97% (34 of 35) and 81% (13 of 16) respectively, when > or = 70% narrowing was considered significant. The normalcy rate among the 58 patients of group II was 96%. Comparisons for pattern of stress-defect reversibility demonstrated that of the 97 stress defects within the infarct zones (group III), 15% were reversible and 85% were nonreversible. In contrast, of the 227 stress defects within the diseased (> or = 50% stenosis) vessel zones of the group I patients, 93% were reversible and 7% were noreversible (p < 0.001 vs group III). In conclusion, separate acquisition rest 201-TI/pharmacologic stress sestamibi dual-isotope SPECT is an efficient myocardial perfusion imaging protocol with high accuracy for detection and assessment of angiographically significant coronary artery disease.

Adenosine↗

PubMed1994

Gated technetium-99m sestamibi for simultaneous assessment of stress myocardial perfusion, postexercise regional ventricular function and myocardial viability. Correlation with echocardiography and rest thallium-201 scintigraphy.

OBJECTIVES: This study compares technetium-99m sestamibi (sestamibi) electrocardiographic (ECG) gated single-photon emission computed tomography (gated SPECT) and echocardiography for the evaluation of myocardial function and assesses the feasibility of single-injection, single-acquisition stress perfusion/rest function technetium-99m sestamibi-gated SPECT as an alternative to conventional stress/rest imaging for assessment of myocardial perfusion and viability. BACKGROUND: Simultaneous assessment of stress perfusion and rest function is possible with gated SPECT acquisition of stress-injected technetium-99m sestamibi. METHODS: Rest thallium-201 SPECT followed by stress sestamibi-gated SPECT (acquired 0.5 to 1 h after sestamibi injection) was performed in 58 patients. Echocardiography was performed immediately after or before gated SPECT in 43 of the patients. All studies were analyzed by semiquantitative visual scoring. Sestamibi-gated SPECT studies were read for stress perfusion and rest wall motion and thickening. Reversibility on sestamibi-gated SPECT was defined as the presence of a definite stress defect with normal or mildly impaired wall motion or thickening on gated SPECT: RESULTS: There was high segmental score agreement between gated SPECT and echocardiography for wall motion (91%, kappa = 0.68, p < 0.001) and thickening (90%, kappa = 0.62, p < 0.001). Correlation for global wall motion (r = 0.98, p < 0.001) and thickening (r = 0.96, p < 0.001) scores between the two modalities was excellent. In 32 patients without previous myocardial infarction, there was excellent agreement for reversibility between stress sestamibi-gated SPECT and rest thallium-201/stress sestamibi (98%, kappa = 0.93, p < 0.01). However, in 26 patients with previous infarction, discordance between the two approaches was frequent, with 26% (20 of 78) of nonreversible defects by stress sestamibi-gated SPECT being reversible by rest thallium-201/stress sestamibi and 21% (23 of 112) of reversible defects by stress sestamibi-gated SPECT being nonreversible by rest thallium-201/stress sestamibi. CONCLUSIONS: Gated SPECT of stress-injected sestamibi correlates well with echocardiographic assessment of regional function and thus adds information to perfusion SPECT: In patients without previous myocardial infarction, a single-injection stress perfusion/rest function approach using sestamibi-gated SPECT can substitute for conventional stress/rest myocardial perfusion imaging, adding a rest perfusion study only if there are nonreversible defects or consideration of attenuation artifacts. In patients with previous myocardial infarction, the gated SPECT approach does not replace the need for a rest perfusion study.

Aged↗

PubMed1994

Temporal image fractionation: rejection of motion artifacts in myocardial SPECT.

METHODS: We have developed a protocol, termed "temporal image fractionation," in which static myocardial perfusion SPECT studies are acquired as three-interval dynamic studies (three temporal frames, each consisting of a full projection set), utilizing continuous alternating detector rotation and a multi-detector camera. The frames are individually examined for motion by cine display, then summed together into a static SPECT file which is reconstructed with standard procedure. This approach offers three potential advantages in reducing or eliminating image artifacts resulting from patient or organ motion: (1) If severe motion occurs in one frame, only the remaining two are summed and reconstructed (motion-purging); (2) Alternating detector rotation reduces artifacts from mono-directional, drifting motion during acquisition (i.e., upward creep of the heart); and (3) Generally, with multiple rotations, motion is spread over a larger angular range and therefore has a lesser effect of the final reconstructed images. RESULTS: These advantages are demonstrated and quantified in this paper using clinical data (A) and simulated motion on phantom data (B and C). In the phantom experiments, fractionated images were found to be 48.9%, 35.8% and 35.9% "more similar" to the original images than nonfractionated images for simulated 1.67-cm upward creep, 1.1-cm nonreturning axial motion and 1.65-cm lateral motion, respectively. CONCLUSION: This protocol requires little extra processing and no final extra data storage compared to standard acquisition, and it has nearly eliminated instances in which a study had to be repeated due to patient motion. Step-and-shoot acquisition is not recommended in conjunction with this protocol, as it would lengthen the time necessary to obtain the same count statistics as in nonfractionated acquisition.

Artifacts↗

PubMed1994

Dual-isotope myocardial perfusion SPECT with rest thallium-201 and stress Tc-99m sestamibi.

The commercial availability of Tc-99m-labeled myocardial perfusion agents had added choices in the noninvasive clinical assessment of coronary artery disease. Preferential use of Tc-99m sestamibi has been advocated principally due to improved image quality, which results from the combined physical and biological characteristics of this agent. This article reports upon the investigation of another approach for Tc-99m sestamibi SPECT--dual-isotope rest-stress myocardial perfusion SPECT, which takes advantage of the Anger camera's ability to collect date in different energy windows. For the dual-isotope approach, separate radiopharmaceuticals are employed for the rest injection and the stress injection.

Coronary Disease↗

PubMed1994

Comparative feasibility of separate or simultaneous rest thallium-201/stress technetium-99m-sestamibi dual-isotope myocardial perfusion SPECT.

UNLABELLED: Separate or simultaneous rest 201Tl/stress 99mTc-sestamibi dual-isotope SPECT are potentially efficient myocardial perfusion imaging protocols which combine the use of a high-resolution 99mTc tracer for stress perfusion assessment and 201Tl, the current single-photon agent of choice, for viability assessment. METHODS: To investigate the feasibility of dual-isotope myocardial perfusion SPECT protocols using rest 201Tl and stress sestamibi, 201Tl crosstalk into the 99mTc acquisition window (Group 1, n = 26 patients) and 99mTc crosstalk into 201Tl windows (Group 2, n = 25) were studied. For Group 1, treadmill exercise with sestamibi injection and poststress SPECT ("virgin" sestamibi images) were performed, followed by rest 201Tl injection and SPECT acquisition using dual-isotope windows (contaminated or "dual" images). For Group 2, the order was reversed: rest 201Tl SPECT (virgin 201Tl images) was performed first, followed by exercise sestamibi injection and dual-isotope SPECT. RESULTS: The contribution of 201Tl scatter to the dual sestamibi images (Group 1) was measured to be 2.9% +/- 2.1%, while 99mTc crosstalk contributed 26.7% +/- 13.0% to the dual 201Tl images (Group 2). Image quality was considered good to excellent in 92% of the sestamibi (virgin and dual) images and 88% of the virgin 201Tl SPECT, but only in 23% of the dual 201Tl studies. CONCLUSIONS: Technetium-99m crosstalk into 201Tl windows is substantial; therefore, simultaneous dual-isotope protocols, which involve assessment of 201Tl images contaminated by 99mTc, are not recommended. On the other hand, because of the small amount of 201Tl crosstalk into the 99mTc window, a separate acquisition dual-isotope approach employing the rest 201Tl (virgin)/stress sestamibi sequence is acceptable.

Aged↗

PubMed1994

Myocardial perfusion imaging with technetium-99m-sestamibi: comparative analysis of available imaging protocols.

Several protocols for rest and stress myocardial perfusion imaging with 99mTc-sestamibi have been developed, each with distinct advantages and disadvantages. The various approaches have similar sensitivities and specificities for detection of coronary artery disease (CAD), but differ mainly in their ability to identify defect reversibility. The dual-isotope approach, with a rest 201Tl study and a stress 99mTc-sestamibi study, permits optimal evaluation of both stress perfusion and defect reversibility. Gated SPECT may be added to any of the protocols and aids in identifying artifacts, defining regional wall thickening and assessing ventricular function. First-pass 99mTc-sestamibi radionuclide angiography can add exercise ventricular function data to the study. Clinical trials have shown that the various protocols for 99mTc-sestamibi provide diagnostic and prognostic information comparable to that derived from traditional 201Tl imaging, with the added advantage of higher quality images and increased certainty in interpretation.

Coronary Circulation↗

PubMed1994

A quantitative phantom analysis of artifacts due to hepatic activity in technetium-99m myocardial perfusion SPECT studies.

UNLABELLED: We have observed that filtered backprojection may cause artifactual decreased myocardial wall uptake in the reconstructed images if the hepatic-to-cardiac activity ratio (HCR) in 99mTc clinical myocardial SPECT studies is sufficiently high (> 1). METHODS: To quantitatively relate hepatic uptake to this phenomenon, a commercial chest and heart phantom was modified with the addition of a customized liver insert, which was filled with various concentrations of 99mTc to simulate HCRs of 0:1, 1:1 and 2:1. The phantom was imaged with a high-sensitivity, three-detector camera, low-energy, high-resolution (LEHR) collimation and 180 degrees noncircular orbits. RESULTS: Quantitative circumferential profile analysis of the reoriented SPECT images demonstrated artifactual inferior/inferoseptal maximal activity decreases of 17.8% and 46.2% for the 1:1 and 2:1 HCRs, compared to the 0:1 HCR. Hepatic scatter probably partly mitigates the decrease. Smoothing the projection data before reconstruction worsened the artifacts' severity. Using Butterworth filters of order 5 and cutoff frequencies of 0.1, 0.2 and 0.215 Nyquist (clinical standard) resulted in artifactual inferior wall activity decreases of 5%, 8% and 16%, compared to using the same filter with a cutoff of 0.3 for an HCR of 2:1. CONCLUSION: These data indicate that if count statistics are good and liver uptake is high, higher frequency cutoffs in pre-reconstruction filters may improve specificity in 99mTc-labeled myocardial perfusion SPECT studies.

Artifacts↗

PubMed1993

Separate acquisition rest thallium-201/stress technetium-99m sestamibi dual-isotope myocardial perfusion single-photon emission computed tomography: a clinical validation study.

OBJECTIVES: This study assessed the validity of a novel approach to myocardial perfusion scintigraphy that provides the opportunity to avoid the drawbacks of standard same-day rest/stress technetium-99m sestamibi myocardial perfusion studies by using separate-acquisition dual-isotope rest thallium-201 and exercise technetium-99m sestamibi single-photon emission computed tomography (SPECT). BACKGROUND: Standard same-day rest/stress technetium-99m sestamibi myocardial perfusion studies are cumbersome, associated with a potential decrease in perceived stress defect severity compared with thallium-201 due to the presence of rest technetium-99m sestamibi and may be unable to differentiate hibernating from infarcted myocardium. METHODS: The dual-isotope procedure was performed in 63 patients without previous myocardial infarction undergoing coronary angiography to evaluate sensitivity and specificity for coronary artery disease and in 107 patients with a low (< 5%) likelihood of coronary artery disease to evaluate normalcy rate. To validate defect reversibility, the dual-isotope SPECT study was compared with stress/rest technetium-99m sestamibi SPECT studies in a separate group of 31 patients with previous documented myocardial infarction who underwent a rest technetium-99m sestamibi study in addition to the dual-isotope SPECT study. RESULTS: In angiographic correlations, dual-isotope SPECT demonstrated high sensitivity for detecting patients with > or = 50% stenosis (91%, 55 patients) and > or = 70% stenosis (96%, 52 patients). In a small group of patients, high specificity was also observed (75% for < 50% stenosis [8 patients] and 82% for < 70% stenosis [11 patients]). A very high normalcy rate of 95% was also found. In the patient group assessed for defect reversibility, in zones with no previous myocardial infarction, segmental agreement for defect type between rest thallium-201 and rest technetium-99m sestamibi studies was 97% (kappa = 0.79, p < 0.001). In myocardial infarct zones, segmental agreement for defect type was 98% (kappa = 0.93, p < 0.001). Image quality was generally good to excellent. CONCLUSIONS: Our findings demonstrate that separate-acquisition dual-isotope myocardial perfusion SPECT is accurate for coronary artery disease detection, correlates well with rest-stress sestamibi studies for assessment of defect reversibility and results in good to excellent image quality. This approach provides an excellent method for the combined assessment of stress myocardial perfusion and myocardial viability.

Aged↗

PubMed1993

Technetium-99m teboroxime regional myocardial washout in subjects with and without coronary artery disease.

The aim of this study was to test the hypothesis that regional myocardial washout of technetium-99m teboroxime is slowed in the presence of coronary stenosis. Washout was assessed in 33 catheterized patients and in 13 with a low likelihood of coronary artery disease, using a triple detector camera and dynamic single-photon emission computed tomography, with serial 1-minute acquisitions after injection of 20 to 25 mCi of teboroxime at the third minute of adenosine-induced hyperemia. Washout was measured as the percent change in counts between the first, second and third minutes after injection, as measured in 6 short-axis myocardial regions of interest. Myocardial regions were classified as ischemic (> or = 50% diameter stenosis and no prior myocardial infarct), infarcted, normal (no significant coronary stenosis) or "low likelihood" (from the 13 patients with a low likelihood of coronary artery disease). Teboroxime washout was significantly (p < 0.001) slowed in the ischemic myocardium (12.7 +/- 8.3%) compared with the normal (18.5 +/- 5.7%), low-likelihood (17.8 +/- 6.1%) and infarcted (17.8 +/- 4.4%) zones. There was regional variability in washout rates (% washout/min), with the anterior wall having the lowest (13.8 +/- 3.4%/min) and the inferior wall the highest (20.7 +/- 7.9%/min) values. In regard to individual coronary territories, 21 of 41 ischemic, noninfarcted territories (51%) had abnormal washout compared with 3 of 43 normal territories (7%) (p = 0.001). In conclusion, regional washout of teboroxime is detectably slowed in ischemic, noninfarcted myocardium. The clinical value of washout analysis in teboroxime single-photon emission computed tomography warrants further investigation.

Cohort Studies↗

PubMed1993

Quantitative severity of stress thallium-201 myocardial perfusion single-photon emission computed tomography defects in one-vessel coronary artery disease.

The relation between the quantitative myocardial perfusion defect severity of exercise thallium-201 single-photon emission computed tomography (SPECT) and the quantitative degree of coronary stenosis was examined in 18 patients with 1-vessel disease (> or = 50% diameter stenosis), and abnormal thallium-201 SPECT. A total of 26 vessels were analyzed. Thallium-201 SPECT quantitative defect severity score was derived by summing the number of pixels in a coronary territory in which counts fell below the normal mean and multiplied by the number of SDs by which they fell below the normal mean. The thallium-201 defect severity score was significantly (p < 0.001) related to the maximal percent luminal diameter narrowing (r = 0.93), percent area narrowing (r = 0.89), absolute stenotic area (r = 0.79), and absolute stenotic diameter (r = 0.81). As expected, the strongest relation between thallium-201 defect severity and quantitative angiographic indexes was in the low and high ranges of coronary stenosis, with more variability and lower correlation coefficients (percent diameter: r = 0.75, p < 0.02, percent area stenosis: r = 0.63, p < 0.05) in the middle ranges (50 to 80% diameter stenosis). This observation is likely to be due to the complex flow characteristics across stenotic lesions. The findings suggest that in a select population, thallium-201 defect severity is potentially useful for noninvasive characterization of the functional severity of coronary artery stenosis and may complement coronary angiography in predicting functionally significant stenosis.

Adult↗

PubMed1993

Early nocturnal blood pressure changes in diabetic autonomic neuropathy assessed by Fourier series.

The 24 h periodic pattern of blood pressure was studied in 44 patients with diabetes mellitus (14 type 1, 30 type 2; mean duration of disease 6.5 +/- 1.8 years) in good metabolic control but with abnormal cardiovascular reflex responses; of these 21 were normotensive and 23 hypertensive. All had abnormal responses to at least two out of four tests: deep breathing, lying to standing, Valsalva manoeuvre and postural hypotension. Two sex- and age-matched groups, consisting of 20 normotensive and 20 hypertensive diabetic patients without dysautonomia, were studied as controls. Each patient underwent ambulatory blood pressure monitoring for at least 24 h, using an auscultatory automatic device. Data were analysed using the sum of three periodic functions (Fourier partial sum). In the diabetic normotensive groups, the absolute blood pressure fell to its night-time minimum more rapidly, and increased to its morning maximum more slowly, in those with abnormal cardiovascular reflexes than in the controls (nightly blood pressure decrease -5.8/-4.7 vs. -3.8/-4.0 mmHg/h; increase 4.7/3.6 vs. 5.9/6.1 mmHg/h). The same behaviour was found in both hypertensive groups but the amplitude of the differences was more marked (blood pressure nocturnal decrease -7.7/-7.1 vs. -4.3/-3.9 mmHg/h; increase 3.2/2.1 vs. 5.8/4.3 mmHg/h). This analysis of 24 h ambulatory blood pressure data may be of value in diagnosis and evaluation of autonomic deficits.

Adult↗

PubMed1993

Detection and correction of patient motion in dynamic and static myocardial SPECT using a multi-detector camera.

We have developed a method for the detection and correction of translational patient motion in dynamic and static myocardial SPECT studies. The method uses a low activity 99mTc point source and is especially designed for multi-detector cameras. The source's centroid coordinates are measured or derived for all projection images in a temporal frame. The coordinate curves fitted to predicted distributions and the projection images shifted to realign measured to fitted values, with sub-pixel accuracy. In dynamic studies, the frame with the best fits serves as reference for all others. The accuracy of this method, measured with cardiac phantom experiments, was found to be +/- 0.37 mm and +/- 0.44 mm in the axial and transaxial dimension, respectively. By comparison, overall motion in 42 patients undergoing 99mTc-teboroxime dynamic cardiac SPECT studies was +/- 1.6 mm and +/- 1.2 mm, respectively (average on 39,272 projection views). Application of the method to phantom experiments, 99mTc-sestamibi and 99mTc-teboroxime human studies visually eliminated artifactual perfusion defects from simulated phantom motion and actual patient motion.

Gamma Cameras↗

PubMed1993

Rapid back to back adenosine stress/rest technetium-99m teboroxime myocardial perfusion SPECT using a triple-detector camera.

Technetium-99m-teboroxime is characterized by a high extraction fraction over a wide range of blood flow rates, rapid myocardial clearance and avid hepatic uptake. This study determined the imaging parameters and examined the clinical efficacy of a rapid back to back adenosine stress/rest teboroxime myocardial perfusion SPECT protocol using a triple-detector camera. Acquisition parameters were determined using cardiac phantom studies which were then applied in SPECT studies of 51 catheterized patients (22 with prior myocardial infarction) and 20 patients with a "low" (7.9% +/- 4.3%) likelihood of coronary artery disease. Technetium-99m-teboroxime (20-25 mCi) was injected at the third minute of adenosine infusion. Teboroxime (20-25 mCi) was also injected at rest, 15 min later. Stress followed by rest SPECT were completed within 25 min using a triple-detector camera and sequential, 1-min continuous rotations in alternating directions. Summed raw data from the first to second (1-2 min), second to third (2-3 min) and second to fifth (2-5 min) minutes of imaging following stress teboroxime injection were reconstructed and compared for image quality, degree of liver interference, and accuracy for diagnostic efficacy. In a subgroup of 30 patients, 2-8-min summed images were also reconstructed to compare this more conventional imaging protocol with our rapid acquisition. Image quality was fair to good in 75% of the 1-2-min, 84% of the 2-3-min and 2-5-min studies and 53% of the 2-8-min scans. The frequency of severe liver interference appeared to increase with the duration of imaging time (1-2 min: 3%; 2-3 min: 7%; 2-5 min: 8%) and was greatest (30%, p = 0.08) with 2-8-min images. Three patients (4%) had uninterpretable studies due to intense hepatic uptake. Overall sensitivity (95%) and specificity (71%) were equal for the 2-3-min and 2-5-min stress images and appeared better than in the 1-2-min images (84% and 57%, respectively). For the 2-8-min scans, vessel sensitivity (69%) and specificity (63%) appeared poorer than with 2-3-min studies (83% and 81%, respectively). Normalcy rates were 89% for the 2-3-min and 2-5-min and 79% for 1-2-min images. The back to back adenosine stress/rest teboroxime SPECT can be performed in 30 min using a triple-detector camera. Although overall high sensitivity and normalcy rates were achieved, the protocol is technically demanding. Interference due to intense liver uptake remains problematic.

Adenosine↗

PubMed1993

Quantitative same-day rest-stress technetium-99m-sestamibi SPECT: definition and validation of stress normal limits and criteria for abnormality.

Gender-matched stress normal limits and criteria for abnormality for rest-stress 99mTc-sestamibi same-day myocardial perfusion imaging were developed and validated in 160 patients who were imaged using previously developed optimized acquisition, processing and quantitative protocols. The gender-matched mean and standard deviation of the normal response were calculated using 35 male and 25 female patients with a < 5% likelihood of coronary artery disease. Receiver-operating curve analysis using expert visual interpretation as the "gold standard" was used to determine the optimal criteria for abnormality detection, in terms of standard deviations from the mean and minimum defect size for each of the four major zones of the polar map, in a pilot population consisting of an additional 35 male and 25 female patients with a variety of perfusion defects. The optimum standard deviations resulted in the following true-positive/true-negative rates when quantitative results were compared to visual analysis for the anterior, septal, lateral, and inferior segments in the combined male and female pilot populations: 84%/86%, 70%/75%, 86%/76% and 69%/76%, respectively. The final criteria were then applied to a prospective population consisting of 33 male and 7 female patients. This analysis resulted in the following true-positive/true-negative rates for overall perfusion abnormalities and abnormalities of the LAD, LCX and RCA vascular territories: 97%/67%, 94%/73%, 73%/90% and 72%/91%, respectively. The optimized 99mTc-sestamibi stress normal limits and criteria for abnormality correlate well with expert visual interpretation of stress myocardial perfusion defects.

Coronary Disease↗

PubMed1992

Ambulatory blood pressure recording in diabetic patients with abnormal responses to cardiovascular autonomic function tests.

The aim of our study was to analyse the 24-h periodic pattern of blood pressure (BP) in diabetic patients with abnormal responses to cardiovascular reflexes, in order to evaluate the extent of the initial autonomic damage. We studied 44 patients with diabetes mellitus (14 insulin-dependent, 30 non-insulin-dependent; mean duration of disease 6.5 +/- 1.8 years) in good metabolic control (fasting glycaemia less than 140 mg/dl, postprandial glycaemia less than 180 mg/dl, fructosamine less than 285 mg/dl), divided into two subgroups, containing 21 normotensives (13 males and 8 females aged 28-72 years) and 23 hypertensives (13 males and 10 females aged 32-70 years) respectively. All patients showed abnormal responses to at least two out of four tests: deep breathing, lying to standing, Valsalva manoeuvre and postural hypotension. Two sex- and age-matched control groups were recruited, comprising 20 normotensive and 20 hypertensive diabetic patients without dysautonomia, respectively. The reference group consisted of 248 normotensives (135 males and 113 females, aged 18-76 years) and 212 mild-moderate hypertensives (130 males and 82 females, aged 27-66 years). Each patient underwent ambulatory BP monitoring for at least 24 h, using an auscultatory automatic device. Data concerning biological rhythms were analysed by means of periodic functions. We limited the Fourier partial sums to the first three harmonics.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

A new noninvasive quantification of renal blood flow with N-13 ammonia, dynamic positron emission tomography, and a two-compartment model.

In order to determine if dynamic positron emission tomography (PET) and N-13 ammonia can be used to quantitate regional RBF (rRBF) noninvasively, six anesthetized dogs were examined with PET imaging after an iv bolus administration of 5 mCi of N-13 ammonia. Renal time activity curves and the arterial input function were derived from regions of interest drawn over the renal cortex and abdominal aorta, respectively. For calculation of rRBF, less than 120 s of the initial data were used to minimize contamination by plasma metabolites of N-13 radioactivity. rRBF was quantitated with a two-compartment model, and the results were compared with simultaneously acquired microsphere blood flow measurement. Fourteen experiments were performed in six dogs, and four regions of interest on renal cortex were selected on each PET image. RBF derived from dynamic PET imaging with N-13 ammonia was linearly related to microsphere (MS) values (rRBF = 1.06 x MS - 0.17; r = 0.91). Mean rRBF in the canine experiments was 4.0 mL/min/g. The results indicate that dynamic N-13 ammonia renal PET can provide noninvasively quantitative rRBF.

Ammonia↗

PubMed1992

Use of the abdominal aorta for arterial input function determination in hepatic and renal PET studies.

A method using the activity in the abdominal aorta of human and animal subjects to noninvasively estimate blood-pool input function in dynamic, abdominal PET scans is proposed and validated in this paper. Partial volume effects due to the aorta's dimensions are corrected by a semi-automated algorithm based on the transaxial resolution in the reconstructed images. The technique was validated by comparing PET measurements of abdominal aortic activity to well counter measurements of arterial blood samples (eight canine renal studies) and to PET measurements of left ventricular cavity activity (eight human hepatic studies). In renal studies, correlation analysis of the areas subtended by the two input functions yielded an essentially unitary slope (1.03 +/- 0.09), with high correlation (R2 greater than 0.95, p less than 0.001). In hepatic studies, similar values (0.99 +/- 0.03 and R2 greater than 0.85, p less than 0.001) were found. Correlation of the blood flow estimates based on the two input functions and a two-compartment model produced slopes of 1.07 +/- 0.16 and 1.03 +/- 0.07, and correlations of (R2 greater than 0.98, p less than 0.001) and (R2 greater than 0.97, p less than 0.001) for the renal and hepatic studies, respectively. We conclude that noninvasive, accurate measurements of the arterial input function by dynamic PET imaging are possible and represent a clinically viable alternative to arterial blood sampling.

Animals↗