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Biomedical subjects

P Lanzer

Publications and source records attributed to P Lanzer.

At least 19 recordsLinked to original sources
PubMed1991

Sequential 2D inflow venography: initial clinical observations.

Sequential 2D inflow NMR (SDI) venography was employed to define venous anatomy and pathology in five healthy subjects and five patients, mean age 48 +/- 7 years, with documented deep vein thrombosis. SDI images were graded independently by two observers on a scale of 1,2 nondiagnostic and 3,4 diagnostic categories. All iliac and femoropopliteal SDI venograms were diagnostic. In contrast, only one out of nine calf SDI venograms was diagnostic. SDI is a promising new method to assess the proximal peripheral venous system. Improved imaging strategy is needed to produce flow images of the calf veins.

Femoral Vein↗
PubMed1991

Peripheral arterial occlusive disease: prospective comparison of MR angiography and color duplex US with conventional angiography.

Conventional angiography, two-dimensional inflow magnetic resonance (MR) angiography, and color duplex ultrasound (US) were performed on 12 patients in a blinded, prospective study. The ability to grade arterial lesions and plan revascularization interventions were compared. Arterial lesions were categorized as nonsignificant (0%-49% diameter reduction) or significant (50%-100% diameter reduction). Determination of nonsignificant and significant lesions with MR angiography was in agreement with that at conventional angiography in 100 of 140 lesions (71%). Agreement between results of conventional angiography and color duplex US occurred with 114 of 123 infrainguinal lesions (93%). Twenty-one vascular interventions were planned by using conventional angiography; there was agreement with color duplex US in 11 cases and MR angiography in five. Color duplex US performed well in the assessment of infrainguinal disease but was limited in the evaluation of iliac segments because of nonvisualization. The iliac region was visualized in more patients with MR angiography than with color duplex US, but image quality with MR angiography was inconsistent. Strategies to improve MR angiography of the peripheral vasculature merit further study.

Aged↗
PubMed1991

[Peripheral spin exchange nuclear spin resonance angiography: Studies of the effect of blood flow on contrast].

Sequential two-dimensional (2-D) inflow MR-angiography (SDSMRA) utilizes the bloodflow-induced changes in the MR-signal for intraluminal vessel contrast. To assess the effect of the peripheral arterial flowpulse on the average intraluminal MR-signalintensity (MIMRSI) seven healthy subjects, mean age 31 +/- 4 years, were studied using color Doppler flow mapping and SDSMRA. In each subject the regional MIMRSI was measured in 21 vascular segments and correlated with the regional flowpulse in a simple regression model. MIMRSI ranged from 915 +/- 299 in the right profunda femoris to 1378 +/- 283 in the distal abdominal aorta: distally, the trifurcation it was, with the exception of the posterior tibial artery in three subjects (MIMRSI = 545 +/- 64), not measurable. The regional differences in the peripheral flowpulse were without statistically measurable effect on MIMRSI. MIMRSI was best correlated to the systolic forward flow in 14, to the backward flow in 3, and to the mean forward flow in 1 vascular segment, respectively. The mean correlation coefficient (r) was 0.56, ranging from r = 0.11 in the right popliteal artery to r = 0.93 in the right superficial femoral artery. In the distal abdominal aorta no positive correlation between the blood flow and MIMRSI was determined. The regional differences in the peripheral arterial flow-pulse have no significant effect on MIMRSI in healthy men. MIMRSI correlates best with the systolic forward flow. However, on the average, 44% of the MIMRSI appear to be related to flow-independent yet unidentified factors. Optimal design of SDSMRA pulse sequences will require a better characterization of flow-dependent and flow-independent MIMRSI parameter.

Adult↗
PubMed1990

Quantitation of abdominal aortic wall dynamics in man by gradient echo NMR imaging.

To determine the magnitude of the pulsatile (P), translational (T), and composite (C) aortic wall motion and to predict its effect on endothelial edge definition in vascular NMR imaging, 10 healthy volunteers, mean age 42.5 +/- 13 years, were studied. In each subject a series of transverse high-resolution (0.6 X 0.6 mm; TR = 40 ms) gradient echo images spanning the cardiac cycle were generated and the aortic wall motion dynamics were analyzed. The group data expressed as a mean +/- SD in millimeters, P = 0.87 +/- 0.34 (mm), T = 2.71 +/- 1.07, and C = 3.39 +/- 1.081, indicate that a significant displacement of the endothelial aortic edge (up to 5.6 pixels in high-resolution imaging) occurs during the cardiac cycle in normotensive healthy volunteers. The displacement of this magnitude suggests that cardiac cycle synchronized aortic NMR imaging should be used to improve endothelial edge definition.

Aorta, Abdominal↗
PubMed1990

Aortoiliac and femoropopliteal phase-based NMR angiography: a comparison between FLAG and RSE.

To assess the performance of FLAG and RSE NMR angiography 22 aortoiliac (AI) and 22 femoropopliteal (FP) angiograms in 11 healthy males, mean age 38 +/- 7.6 years, were acquired. The image quality was graded in a blinded fashion by two independent readers. The readers grades were not statistically different (kappa = 0.5696). The representation of diagnostic images was 6/11 FLAG and 8/11 RSE AI as well as 8/11 FLAG and 8/11 RSE FP. On back-to-back comparison six RSE AI and seven RSE FP were graded better than their FLAG counterparts. Although these differences did not achieve a statistical significance RSE NMR angiography provided consistently better images and appears preferable for imaging of the peripheral vascular system in normal subjects.

Adult↗
PubMed1990

Aortoiliac imaging by projective phase sensitive MR angiography: effects of triggering and timing of data acquisition on image quality.

To assess the ability of projective phase sensitive magnetic resonance (MR) angiography to visualize the aortoiliac vascular segment, and to determine the effects of triggering and timing of data acquisition om image quality, we studied 18 healthy volunteers, mean age 33.3 +/- 11 years, by color Doppler imaging and by MR angiography. MR angiography was performed at 1.5 T using a flow-adjustable gradient-echo (FLAG) sequence operated in both ECG-triggered and non-triggered acquisition modes. The images were graded in a blinded fashion by two independent observers. The data were analyzed using Pearson's chi-square analysis. Eighteen triggered time-resolved and 17 non-triggered, time-averaged MR angiograms consisting of 252 and 17 angiographic images, (AI) respectively, were analyzed. In the triggered mode 69 (27.4%) AI and in the non-triggered mode 2 (11.8%) AI were diagnostic. At least one triggered diagnostic AI was obtained in each subject. The image grades were not statistically different between observers (kappa = 0.6686). In the triggered mode diagnostic images were acquired within +/- 90 msec of the peak systolic flow velocity determined by Doppler. The proportion of diagnostic images in the triggered mode was highest (73.3%) within a 30-msec interval before the peak flow. In healthy subjects the aortoiliac segment is reliably visualized by FLAG MR angiography. The optimum results are achieved using the triggered acquisition mode and timing acquisition to the initial 180 msec of the abdominal aortic systolic flow pulse.

Adult↗
PubMed1990

Timing of data acquisition determines image quality in femoropopliteal phase-sensitive MR angiography.

To study the effects of timing of data acquisition on quality of femoropopliteal magnetic resonance (MR) angiograms, the authors studied 16 healthy men, mean age 34.3 +/- 6 years, by color Doppler imaging and by phase-sensitive (PS) MR angiography. PS MR imaging was performed at 1.5T using a flow adjustable gradient (FLAG) pulse sequence. The images were graded in a blinded fashion by two independent observers. Of 16 MR angiograms consisting of 141 angiographic images (AI), 45 (31.9%) were diagnostic. At least 1 diagnostic AI was obtained in each subject, and 38 (84.4%) of the diagnostic images were acquired within the first 120 milli-seconds (ms) of the systolic flow pulse. The highest yield of diagnostic images (90.9%) was obtained in the interval of thirty to sixty ms before the peak flow velocity. In healthy man diagnostic PS MR angiography requires triggering to the femoropopliteal systolic flow pulse. The highest yield of diagnostic images is acquired during the flow pulse acceleration.

Adult↗
PubMed1990

[Nuclear magnetic resonance angiography: principles and uses].

Nuclear magnetic resonance (NMR) angiography is a novel concept in vascular imaging. The method is noninvasive and contrast agents are not required. As in radiographic arteriography, the morphology of the intima is defined indirectly by visualizing the vessel lumen. Similar to vascular ultrasound, the blood flow and the arterial wall dynamics can be studied. NMR angiography is based on a modulation of the amplitude or the phase of the resonance signal due to the motion of the blood in conjunction with a modified two- or three-dimensional (2D; 3D) imaging pulse sequence. Based on the currently available evidence, neurovascular pathology is optimally visualized using the nontriggered 3D inflow angiography. The peripheral vascular pathology was successfully imaged using the sequential 2D inflow approach. Suboptimal definition of vascular lesions currently represents the most important limitation of the available angiographic technology. Due to the limited clinical experience it would be premature to predict the future role of NMR angiography in vascular medicine. The efforts to further develop and clinically test this highly promising technology are, however, fully justified.

Angiography↗
PubMed1988

In vivo alterations of high-energy phosphates and intracellular pH during reversible ischemia in pigs: a 31P magnetic resonance spectroscopy study.

Phosphorus-31 magnetic resonance spectroscopy was used to study the relationship between metabolic and functional alterations during acute regional ischemia in vivo. Phosphocreatine, adenosine triphosphate (ATP), inorganic phosphate, and intracellular pH (pHi) were monitored in 11 pigs at 2-minute intervals during 4 and 20 minutes of acute left anterior descending coronary artery occlusion followed by 20 minutes of reperfusion. In a parallel series of experiments, segment shortening was continuously monitored by sonomicrometry during the early ischemic period. Segment shortening decreased precipitously after coronary occlusion, and systolic expansion was noted within 30 seconds. Phosphocreatine levels decreased rapidly and reached a minimum value of 44 +/- 13% (mean +/- SE) of the control value by 20 minutes of ischemia. Ischemia-induced reduction of ATP was small and not statistically significant. Inorganic phosphate increased rapidly to a peak level of 158 +/- 9% of the control value by 4 minutes of ischemia. Intracellular pH decreased 0.76 +/- 0.04 units during the initial 10 minutes of ischemia and subsequently stabilized. After reperfusion, phosphocreatine, inorganic phosphate, and pHi recovery occurred within 4 minutes and was similar in the 4- and 20- minute ischemia groups. These results indicate that the changes in high-energy phosphates and pHi observed during both 4 and 20 minutes of coronary occlusion are rapidly reversible. The temporal course of metabolic and functional alterations during early ischemia suggests that if these are causally related the decline in contractility is mediated by an increase in inorganic phosphate, a decrease in pHi, or both rather than by loss of ATP.

Adenosine Triphosphate↗
PubMed1986

Quantitation of regional myocardial function by cine computed tomography: pharmacologic changes in wall thickness.

To determine the capability of high speed computed transmission tomography to quantitate regional wall thickening dynamics over a wide range of physiologic states, left ventricular wall thickening was studied in nine anesthetized mongrel dogs in the control state and during separate infusions of dobutamine (10 micrograms/kg per min) and phenylephrine (25 micrograms/kg per min). After an intravenous bolus of contrast medium the heart was imaged from base to apex with serial transverse images in eight short-axis cine computed tomographic planes. In each dog during each experimental condition, 50 ms scans spanning the cardiac cycle were acquired at each anatomic level. Left ventricular epicardial and endocardial boundaries were identified on end-diastolic and end-systolic images at the equatorial left ventricular planes by an objective threshold contour method validated in a series of experiments performed on ex vivo anatomic specimens. End-diastolic and end-systolic frames were automatically realigned by superposition of epicardial centers of gravity and then rotated using a cross correlation function. The left ventricular wall thickness was measured manually at 16 points around the circumference by two independent observers. For the group of dogs the average percent wall thickening was 40.5 +/- 28.2% and varied among segments from 18 to 70% in the control state. After dobutamine was administered, significant increases in heart rate and cardiac output (p less than or equal to 0.01) were accompanied by an increase in the average wall thickening (73.6 +/- 51.2%; p less than or equal to 0.001) in the left ventricle; the average wall thickening among segments ranged from 46 to 97%. After phenylephrine administration, significant increases in mean blood pressure and cardiac output (p less than or equal to 0.01) were noted along with a significant increase in average left ventricular wall thickening (60.3 +/- 52.5%; p less than or equal to 0.001). Despite an overall increase in the percent wall thickening, no statistically significant changes in segmental contraction pattern between control and drug intervention states were observed. The wall thickness measurements were highly reproducible between the two independent readers (reliability coefficient = 0.99). Cine computed tomography-derived measurements can potentially be used for quantitative assessment of left ventricular wall thickening dynamics of a single heartbeat during acute interventions, such as the administration of drugs.

Animals↗
PubMed1985

Measurement of cardiac output by cine computed tomography.

High-speed computed transmission tomography (cine CT) is a new noninvasive technique that may be useful for the rapid, accurate quantitation of cardiac function. The capability of cine CT to assess cardiac output was examined 10 mongrel dogs as an initial step in validating this method. After the dogs were anesthetized, femoral arterial pressure and pulmonary artery thermodilution catheters were inserted. After intravenous injection of a bolus of contrast medium, cine CT scans were performed in the flow mode, in which 50-ms scans were triggered electrocardiographically at end-diastole at 8 levels during sequential cardiac cycles. Scans and thermodilution measurements of cardiac output were obtained at rest and during altered hemodynamic states induced by separate infusions of dobutamine and phenylephrine. Time-density analysis was performed over the left ventricular cavity and curves were fitted to the CT flow data by gamma-variate analysis. Using the Stewart-Hamilton equation established for indicator dilution techniques, the cardiac output was calculated. The results established a direct linear correlation (r = 0.92) between cine CT cardiac output and thermodilution cardiac output over a wide range of cardiac outputs (1.5 to 6.3 liters/min). This study demonstrates that cine CT can provide a reliable estimate of cardiac output noninvasively using contrast medium as an indicator in dogs.

Cardiac Output↗
PubMed1985

Magnetic resonance imaging in hypertrophic cardiomyopathy.

Gated magnetic resonance imaging (MRI) was performed using a 0.35-Tesla cryogenic system in 14 patients with hypertrophic cardiomyopathy (HC) in order to define the site and extent of abnormal wall thickness. These studies were compared with 2-dimensional (2-D) echocardiograms. Gated magnetic resonance imaging studies in 12 normal volunteers were used for comparison. In normal subjects and in patients with HC, the sharp demarcation of the myocardial wall permitted measurement of wall thickness. The thickness of the septal and posterolateral walls in normal subjects was 10.2 +/- 0.4 mm (+/- standard deviation) and 10.8 +/- 0.5 mm, respectively, whereas septal thickness in all but 1 patient with HC was 15.0 mm or greater. In patients with HC, septal and posterolateral wall thickness were 2.2 +/- 0.8 cm and 1.3 +/- 0.17 cm, respectively, by MRI. The 2-D echocardiographic measurements for septal and posterolateral walls were 2.4 +/- 0.6 cm and 1.4 +/- 0.7 cm, respectively. The severity and distribution of abnormal wall thickness were comparable on 2-D echo and MRI. Gated MRI is an effective and completely noninvasive technique for demonstrating the presence, site and extent of abnormal wall thickness in HC. The large field of view, ability to image directly in multiple planes, and discrete blood-endocardial interfaces are advantages for cardiovascular imaging.

Adult↗
PubMed1985

Interaction of "supplementary" scintigraphic indicators of ischemia and stress electrocardiography in the diagnosis of multivessel coronary disease.

Lung uptake, ventricular cavitary dilation and basal myocardial uptake represent abnormalities that have been associated with myocardial ischemia on stress thallium-201 images, but that are supplementary to the conventional assessment of perfusion distribution. These "supplementary" indicators of ischemia were related to the coronary distribution of perfusion abnormalities, the results of electrocardiographic stress testing and to the findings on coronary angiography in 73 patients. Forty patients had multivessel coronary disease; 19 of these had three vessel disease. Perfusion abnormalities were seen in 39 of these 40 patients but were indicative of multivessel coronary disease in only 28 and of three vessel disease in only 6. However, supplementary indicators were present in 33 of 40 patients with multivessel disease and in 15 of 19 with three vessel disease. Furthermore, they were seen in 16 of 22 patients with multivessel disease in whom conventional perfusion abnormalities underestimated the extent of disease, but in only 4 of 12 patients in whom the extent of disease was overestimated. The presence of either perfusion abnormalities in a multivessel distribution or supplementary indicators identified 38 (95%) of 40 patients with multivessel disease. A markedly positive electrocardiographic treadmill test was a less sensitive indicator of multivessel disease, appearing in only 15 of 40 patients. However, it was present in only 4 of 33 patients without multivessel coronary disease and was more specific for that diagnosis than were supplementary scintigraphic indicators (88 versus 67%, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Assessment of cardiac anatomy using nuclear magnetic resonance imaging.

Nuclear magnetic resonance imaging has emerged in the past few years as a completely noninvasive method for medical imaging of internal organs. Because of the loss of signal intensity by motional nuclei (hydrogen) using most proton imaging techniques, flowing blood within the cardiovascular system generates little or no signal and consequently there is high natural contrast between blood and the walls of blood vessels or cardiac chambers. However, motion during imaging also complicates cardiac imaging because signal is lost from the nuclei in the moving cardiac structures. Consequently electrocardiographic gating of data acquisition is required for nuclear magnetic resonance imaging of the heart. Distinct advantages of nuclear magnetic resonance imaging in relation to other imaging modalities are good contrast between soft tissues and the capability for characterization of specific tissues by estimation of magnetic relaxation times. Early in vitro studies measuring relaxation times of myocardial tissue samples of excised hearts indicate that nuclear magnetic resonance imaging will be capable of discriminating infarcted from normal myocardium. Recent studies using electrocardiographically gated nuclear magnetic resonance imaging of dogs with acute infarction showed the infarct as a region of high intensity on spin-echo images. Initial clinical experience with electrocardiographically gated nuclear magnetic resonance imaging (0.35 tesla) in patients has clearly defined internal cardiac anatomy without the use of contrast media. This technique has demonstrated the consequence of previous myocardial infarction such as regional wall thinning, aneurysm, thrombus and contractile dysfunction, a number of pericardial abnormalities and the morphology of hypertrophic and congestive cardiomyopathies.

Coronary Circulation↗
PubMed1985

Effects of intravenous administration of a new nonionic dimeric contrast medium on the coronary circulation. Comparison with monomeric ionic and nonionic media.

Contrast media injected into the circulation produce a variety of cardiovascular effects. Agents with low osmolality and low concentrations of cations cause considerably less hemodynamic effects. This study compared the effects of a nonionic dimer, iotrol, which has an osmolality (340 mosm/kg) close to that of serum (290 mosm/kg), with a standard ionic monomer, meglumine diatrizoate, and a nonionic monomer, iosimide. The effects of intravenous bolus injection of these three contrast agents on coronary and systemic hemodynamics were studied in eight anesthetized dogs. The influence of the contrast media on subendocardial and subepicardial perfusion was assessed by injecting radioactive microspheres into the left atrium 30 seconds after injection of the media. Alterations in coronary hemodynamics occurred with both iosimide and meglumine diatrizoate. Iotrol produced minimal changes in coronary hemodynamics. Thus, iotrol is the least perturbing contrast indicator and seems the best for use in quantitative digital subtraction and dynamic computed tomography studies designed to measure myocardial perfusion.

Animals↗
PubMed1985

Magnetic resonance imaging of the heart: a review of the experience in 172 subjects.

Gated magnetic resonance (MR) imaging was used to evaluate central cardiovascular anatomy in 172 subjects, 31 of whom were healthy volunteers. Using the spin-echo technique, images of diagnostic quality were obtained in 93% of cases with TE = 28 msec and in 65% of cases with TE = 56 msec. Transverse multisection sequences encompassing most of the left ventricle required approximately 6-8 minutes. Corroborative studies were available in 134 of 141 patients who had cardiovascular disease; two dimensional echocardiograms and angiography in 133 and 100 patients, respectively. Gated MR demonstrated the wall thinning and complications caused by prior myocardial infarctions and high signal intensity of the myocardium at the site of acute myocardial infarctions. MR accurately demonstrated anatomic abnormalities owing to hypertrophic and congestive cardiomyopathies, congenital abnormalities of the heart and great vessels, rheumatic heart disease, pulmonary hypertension, and cardiac and paracardiac masses. Depiction of cardiovascular anatomy and pathoanatomy was attained without the use of any contrast media. Consequently, gated MR is an effective technique for cardiac diagnosis. The short time required for tomographic examination of the entire heart using the multisection technique renders this a practical cardiac imaging modality.

Adolescent↗
PubMed1985

ECG-synchronized cardiac MR imaging: method and evaluation.

An electrocardiographic (ECG) sensing and gating device compatible with a 0.35-tesla (T) magnetic resonance (MR) imager has been developed and used to produce 802 MR images of the heart in 30 patients. The instrument consists of an isolated acquisition module, an electrically floating preamplifier, and a monitor gating module. Two spin-echo images were acquired for each of five, 0.7-cm thick, transaxial sections from the base to the apex of the heart during each ECG-synchronized imaging run. Image quality was assessed in a blind study by two investigators, on a scale from 0 to 3, as diagnostic [2-3] or nondiagnostic [0-1]. There was agreement in 91.4% of their assessments of diagnostic images (68.1% of the images studied). Resolution of heart anatomy on the MR images was adversely affected by prolonged spin-echo time delay, imaging in late diastole, image acquisition at the cardiac apex, irregular triggering, and artifacts. The synchronization of gradient pulses to the ECG at 0.35 T appears safe for patients, permits diagnostic resolution of images, allows image acquisition at distinct points during the cardiac cycle, and enables monitoring of patients during imaging.

Adult↗