Free-breathing cardiac MR imaging: study of implications of respiratory motion--initial results.

The respiratory motion of several anatomic regions (right hemidiaphragm, left ventricle of the heart, chest wall, abdominal wall) was investigated during free breathing in 10 healthy volunteers by using multinavigator technology and real-time magnetic resonance (MR) imaging. The respiratory motion shows hysteretic effects, which are strongly subject dependent and might have some effect on the quality of cardiac MR images.

Unilateral lung edema: effects on pulmonary gas exchange, hemodynamics, and pulmonary perfusion distribution.

Two types of unilateral lung edema in sheep were characterized regarding their effects on pulmonary gas exchange, hemodynamics, and distribution of pulmonary perfusion. One edema type was induced with aerosolized HCl (0.15 M, pH 1.0) and the other with NaCl (0.15 M, pH 7.4). Both aerosols were nebulized continuously for 4 h into left lungs. In HCl-treated animals, pulmonary gas exchange deteriorated [from a partial arterial O(2) pressure-to-inspired O(2) fraction ratio (Pa(O(2))/FI(O(2))) of 254 at baseline to 187 after 4 h HCl]. In addition, pulmonary artery pressure and total pulmonary vascular resistance increased (from 16 to 19 mmHg and from 133 to 154 dyn. s. cm(-5), respectively). In NaCl-treated animals, only the central venous pressure significantly increased (from 7 to 9 mmHg). Distribution of pulmonary perfusion (measured with fluorescent microspheres) changed differently in both groups. After HCl application, 6% more blood flow was directed to the treated lung, whereas, after NaCl, 5% more blood flow was directed to the untreated lung. HCl and NaCl treatment both induce an equivalent lung edema, but only HCl treatment is associated with gas exchange alteration and tissue damage. Redistribution of pulmonary perfusion maintains gas exchange during NaCl treatment and decreases it during HCl inhalation.

On the performance and accuracy of 2D navigator pulses.

The purpose of this study was to investigate and to optimize the performance of two-dimensional spatially selective excitation pulses used for navigator applications on a clinical scanner. The influence of gradient imperfections, off-resonance effects, and incomplete k-space covering on the pencil beam-shaped spatial excitation profile of the 2D RF pulse was studied. The studies involved experiments performed on phantoms and in vivo. In addition, simulations were carried out by numerical integration of the Bloch equations. The accuracy of positioning of the pencil beam was increased by a factor of three by employing a simple correction scheme for the compensation of gradient distortions. The spatial selectivity of the 2D RF pulse was improved by taking sampling density corrections into account. The 2D RF pulse performance was found to be sufficient to monitor the diaphragm motion even at moderate gradient strength. For applications, where a high spatial resolution is required or a less characteristic contrast is present a strong gradient system is recommended.

[The extracapsular spread of cervical lymph node metastases: the diagnostic value of computed tomography]. / Kapseldurchbrüche zervikaler Lymphknotenmetastasen: diagnostischer Stellenwert der Computertomographie.

OBJECTIVE: To assess the value of computed tomography in the determination of extracapsular neoplastic spread and soft tissue infiltration of cervical lymph nodes. MATERIALS AND METHODS: Prospectively 165 CT reports of patients with squamous cell carcinoma in the head-neck region were compared with the histologic specimens after neck dissection. RESULTS: CT reached a sensitivity of 80.9% in the determination of extra-capsular neoplastic spread. The infiltration of cervical muscles and the jugular vein was always determined but-often diagnosed false-positive. Therefore, the overall specificity in determining extracapsular neoplastic spread was low with 72.7%. CONCLUSIONS: The accuracy of computed tomography (76.3%) in the determination of extracapsular neoplastic spread, infiltration of cervical muscles and the jugular vein is only partially satisfying.

Differential diagnosis of lymph node lesions: a semiquantitative approach with colour Doppler ultrasound.

The aim of this study was to evaluate reactively enlarged cervical lymph nodes and nodal metastases in patients with squamous cell carcinoma, as well as nodes involved by malignant lymphoma, by means of colour Doppler ultrasound (CDUS) and to describe perfusion sites for each nodal group in order to determine if typical flow patterns exist for nodes with different pathology. In a prospective study, 63 untreated patients with palpable cervical lymph node enlargement (n = 208) underwent examination with CDUS. The sites of perfusion were subdivided into three groups: central, peripheral and hilar perfusion. The intensity of perfusion was subjectively quantified in a semiquantitative scale from 0 (no perfusion) to III (high perfusion). Finally, the overall perfused area of the lymph nodes was measured and the percentage of perfused nodal area was calculated. CDUS showed perfusion in 178 of 208 lymph nodes. Histological examination showed 49 reactively enlarged lymph nodes, 82 containing metastases and 47 with lymphoma. Reactively enlarged lymph nodes showed characteristically intense hilar perfusion (91.8%), whereas nodal metastases had mainly peripherally located flow (84.1%) of intensity grades I-III. Lymph nodes invaded by malignant lymphoma were highly perfused, showing colour signals in the centre as well as in the nodal periphery (78.7%). In conclusion, perfusional patterns may provide useful additional information in the differential diagnosis of cervical lymphadenopathy.

Differences in predominant enhancement mechanisms of superparamagnetic iron oxide and ultrasmall superparamagnetic iron oxide for contrast-enhanced portal magnetic resonance angiography. Preliminary results of an animal study original investigation.

RATIONALE AND OBJECTIVES: To determine the effect of particle size of superparamagnetic iron oxide (SPIO) contrast agents on magnetic resonance angiography of the portal venous system. METHODS: We studied eight beagle dogs by a T1-weighted 3D turbo-gradient echo magnetic resonance (MR) angiography sequence (TE 4 milliseconds, TR 11 milliseconds, flip angle 25 degrees, coronal imaging plane) before and after administration of either Resovist (SHU555A), a superparamagnetic iron oxide contrast agent with a mean particle size of 60 nm and a relaxivity ratio R2/R1 of approximately 7, or a new ultrasmall superparamagnetic iron oxide (USPIO) contrast agent with a mean particle size of approximately 20 nm and a R2/R1 ratio of approximately 2. Images were acquired on a 1.5-T MR body scanner. Both agents were injected as a peripheral bolus of 40 mumol Fe/kg body weight. Repeated scans were acquired before, immediately after, and 10, 20, 30, and 40 minutes after administration of the agent. RESULTS: After administration of Resovist, portal venous signal increased to 237% of control immediately after injection, while hepatic parenchymal signal intensity decreased to 86% of control. The maximal CNR increase to 177% was achieved immediately after injection of the agent. After USPIO, portal venous signal increased to 401% of the precontrast value immediately after injection, while hepatic parenchymal signal intensity also increased to 131% of control at this time. Hepatic signal then decreased progressively to 49% of control after 40 minutes. The maximal CNR increase to 326% was achieved 10 minutes after injection of the agent. CONCLUSIONS: It is concluded that superparamagnetic iron oxide particles of different sizes have different R2/R1 ratios and, consequently, different mechanisms of contrast improvement in T1-weighted portal MR angiograms.

[Use of high resolution color Doppler sonography in diagnosis of temporal arteritis]. / Einsatz der hochauflösenden Farb-Doppler-Sonographie in der Diagnostik einer Arteriitis temporalis.

PURPOSE: To define sonographic signs of arteritis temporalis using color coded duplex sonography. METHODS: 20 patients with clinically suspected temporal arteritis were examined with color coded Doppler ultrasound prior to temporalis biopsy. The investigation included the temporal artery on both sides and documentation was performed with color prints of the longitudinal orientation of both temporal arteries. All patients had an unilateral biopsy of the temporal artery. RESULTS: 6/20 patients had histologically confirmed temporal arteritis. All patients showed a paravasal zone of lower echogenicity (halo-sign) along the temporal artery. 12/14 patients without temporal arteritis showed no halo-sign. However, a halo-sign was found in 2/14 patients without temporal arteritis which could not be distinguished from the halo-sign observed in patients with temporal arteritis. CONCLUSIONS: A halo-sign could be detected in the majority of patients with arteritis temporalis in concordance with the recent published findings of Schmidt et al. However, a definite specificity of this halo-sign must be rejected.

Hemodynamic tolerance of intravascular contrast agents for magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Intravascular contrast agents for magnetic resonance imaging (MRI) facilitate the quantification of tissue perfusion. The authors determined the hemodynamic tolerance of these agents. METHODS: Doses of 0.05, 0.15, and 0.45 mmol/kg of the polymeric intravascular contrast agent gadolinium-DTPA-polylysine, and di-nitrobenzyl-gadolinium-DTPA, a non-polymeric intravascular contrast agent with high protein binding, and gadolinium-DTPA dimeglumine, a paramagnetic contrast agent with extracellular distribution, were injected into 18 normal male rats as a peripheral intravenous bolus. Systolic, diastolic, and mean blood pressure, left ventricular end-diastolic and developed pressure, positive rate of pressure change (+dP/dt), dP/dt, the rate-pressure product, and heart rate were recorded during a period of 20 minutes. Hemodynamic effects were established by analysis of variance for repeated measurements. RESULTS: There was a transient increase of all blood pressure parameters and contractility for Gd-DTPA-polylysine at the dose of 0.45 mmol/kg only. Di-nitrobenzyl-Gd-DTPA increased blood pressure parameters at 0.45 mmol/kg only. At doses of 0.05 and 0.15 mmol/kg, no significant hemodynamic effects were observed. CONCLUSIONS: The authors conclude that Gd-DTPA-polylysine is hemodynamically safe at doses to 0.15 mmol/kg and acts like a plasma expander at higher doses after peripheral bolus injection in normal rats. Additional investigations are indicated to elucidate the mechanism of a nonsignificant and satiable transient hemodynamic depression after injection of 0.05 mmol/kg DNB-Gd-DTPA.

Magnetic resonance imaging of pulmonary ventilation. Initial experiences with a gadolinium-DTPA-based aerosol.

RATIONALE AND OBJECTIVES: The authors investigate whether a modified gadolinium (Gd)-DTPA formulation can be aerosolized and used as a contrast agent for magnetic resonance (MR) ventilation imaging of the lungs. METHODS: Gadolinium-DTPA (gadopentetate dimeglumine, Schering AG, Berlin, Germany, 100 mmol Gd/L) was modified by addition of mannitol (Sigma, Deisenhofen, Germany, 10 mg/mL) and the surface active detergent Lutrol F68 (BASF, Mannheim, Germany, 2 mg/mL). The imaging was performed in an anesthetized rat model after inhalation of the contrast agent aerosol (PulmoSonic, De Vilbiss, Germany, 10-minute nebulization). T1-weighted spin echo images (repetitive time [TR]/echo time [TE] = 40/3 mseconds) were acquired at 2 T (SIS 85; Sisco, Fremont, CA) before and as long as 120 minutes after administration of the contrast agent. RESULTS: The modified Gd-DTPA aerosol elicited high and relatively homogeneous enhancement of the lung directly after nebulization. The enhancement was more pronounced than that obtained with a Gd-DTPA formulation without additives. CONCLUSIONS: Gadolinium-DTPA-based aerosol appears to be a suitable contrast agent for MR ventilation imaging in an experimental animal model. Modification by mannitol (to increase proton density through a slight additional osmotic effect) and a detergent (to reduce droplet size by decreasing surface tension) is suitable and effective in increasing signal intensity compared with Gd-DTPA without modification.

[Experimental validation of a semi-quantitative single-layer procedure for proton-spin tomographic imaging of regional cerebral perfusion]. / Tierexperimentelle Validierung eines semiquantitativen Einzelschichtverfahrens zur kernspintomographischen Erfassung der regionalen zerebralen Perfusion.

PURPOSE: The aim of the present study was to validate a simple MRI-procedure for semiquantitative assessment of regional cerebral blood flow. MATERIALS AND METHODS: Unilateral cerebral ischaemia (30 minutes) in the territory of the middle cerebral artery was induced in 14 anesthetised rates. The MRI-experiment consisted in an intravenous bolus injection of gadolinium-DTPA, recording of the cerebral contrast kinetics with a T2*-weighted pulse sequence, and measurement of the maximal concentration change at a chosen reference point of time. To measure perfusion quantitatively, a microsphere technique, an accepted reference technique was used. With both methods a perfusion index related to the contralateral side was calculated. RESULTS: In all cases decreased perfusion was detected by the MRI technique. The perfusion indices correlated with a coefficient of correlation of r = 0.89 (p < 0.001). CONCLUSION: The results demonstrate that contrast-enhanced MRI with bolus injection can be implemented with clinical potential as a semiquantitative instrument for the assessment of cerebral perfusion. Regional cerebral blood volume and collateral blood flow may interfere with the estimate of blood flow.

Young Investigator Award presentation at the 13th annual meeting of the ESMRMB, September 1996, Prague. Quantification of pulmonary water compartments by magnetic resonance.

The purpose of this study was to quantify pulmonary water compartments of total, intravascular, and extravascular lung water in excised and perfused sheep lungs with the use of magnetic resonance imaging techniques. Total lung water was measured by proton density maps calculated from multi-spin-echo images. Intravascular lung water was evaluated by magnetic resonance angiography before and after injection of gadolinium diethylenetriamine penta-acetic acid polylysine, a macromolecular paramagnetic contrast agent. Intravascular lung water was calculated from signal intensity histogram changes comparing pre- and postcontrast angiograms. Extravascular water was calculated as the difference between total and intravascular lung water. Quantities of total and intravascular lung water measured by magnetic resonance techniques were compared to reference results obtained from wet/dry weight gravimetry and Evans blue dilution performed after imaging. Magnetic resonance and reference results correlated significantly (total lung water: r = 0.93, p < 0.001; intravascular lung water: r = 0.80, p < 0.001; extravascular lung water: r = 0.89, p < 0.001). Therefore, we conclude that quantitative magnetic resonance techniques are potentially useful for the clinical evaluation of pulmonary water compartments.

[Iron oxide contrast media improve the magnetic resonance imaging of the portal vein system--an animal experimental study]. / Eisenoxydkontrastmittel verbessern die kernspintomographische Darstellung des portalvenösen Systems--eine tierexperimentelle Untersuchung.

PURPOSE: The aim was to demonstrate that intravenous superparamagnetic iron oxide contrast agents improve the delineation of the portal venous system. MATERIAL AND METHODS: The portal venous system of 8 minipigs was demonstrated by a FLASH 2-D MRA-sequence. Scans were acquired before and after intravenous administration of 10 and 20 mumol/kg of a superparamagnetic iron oxide contrast agent (SHU 555 A). Signal intensities were measured in the portal vein and hepatic parenchyma and contrast-to-noise ratios were calculated. RESULTS: Following a cumulative dose of 10 mumol iron oxide, hepatic parenchymal signal intensity decreased to 67 +/- 6%, following 20 mumol to 29 +/- 4%, and following 40 mumol to 13 +/- 2% of control (p < 0.0001). These effects improved the contrast-to-noise ratio of the portal vein (469 +/- 114%, 858 +/- 243%, and 957 +/- 272% of control in the left portal vein main branch, p = 0.02). CONCLUSION: A decrease in hepatic parenchymal signal due to a magnetic susceptibility effect accounts for an improvement of portal venous conspicuity following intravenous administration of iron oxide contrast medium.

Evaluation of portal MR angiography using superparamagnetic iron oxide.

The purpose of our research was to determine the effects of superparamagnetic iron oxide on MR imaging of the portal venous system. Eight piglets were examined in deep anaesthesia and respiratory arrest using a time-of-flight magnetic resonance fast low angle shot, two-dimensional angiography sequence at 1.5T, MR angiograms were acquired precontrast and after intravenous administration of a cumulative dose of 10, 20 and 40 mumol/kg SHU 555A, a superparamagnetic iron oxide contrast agent for MR imaging with a particle size of 60 nm. For each dose, two subsequent sets of scans were obtained and reconstructed by a maximum-intensity-projection algorithm. Hepatic parenchymal and portal venous signal intensities were measured, and portal vein contrast calculated for each set of scans. All examinations were visually rated as to portal vein contrast and homogeneity by two blinded observers. Receiver operating characteristics of both observers were analyzed. The contrast agent reduced hepatic parenchymal signal in a dose-dependent way. After a cumulative dose of 10 mumol iron oxide, hepatic parenchymal signal intensity decreased to 63 +/- 6% (average of measurements at 4 and 14 minutes, mean +/- standard error of the mean), after 20 mumol to 24 +/- 3%, and after 40 mumol to 12 +/- 1% of control. Intravascular signal in the left main portal vein branch increased to 117 +/- 6%, 127 +/- 10%, and 133 +/- 9% of control, respectively. The contrast-to-noise ratio of the portal vein improved (521 +/- 90%, 891 +/- 178%, and 995 +/- 201% of control in the left portal vein main branch). Intravascular signal intensities increased slightly. The combined effect improved contrast of the portal vein stem and its branches. Receiver operating characteristics analysis documented dose-dependency of contrast medium effects on portal venous contrast and intravascular homogeneity. Visual rating also indicated a positive effect on portal venous contrast. The superparamagnetic iron oxide agent improved portal venous contrast with surrounding hepatic parenchyma in this normal animal model, and could potentially result in more accurate diagnosis of portal venous pathology.

[Magnetic resonance imaging of the degree of pulmonary edema using a macromolecular contrast medium]. / Kernspintomographische Quantifizierung des Lungenödemgrades mit Hilfe eines makromolekularen Kontrastmittels.

PURPOSE: Development and experimental validation of a method tor the quantification of pulmonary oedema by measurement of total lung water and intravascular lung water and by calculation of extravascular lung water. MATERIAL AND METHODS: Isolated sheep lung preparations with unilateral pulmonary oedema were perfused (pulsatile pump) and examined under ventilatory arrest and during ventilation. Total lung water was calculated from proton density obtained from a multi-spin echo sequence and gravimetrically (reference method). Pulmonary intravascular volume was calculated from signal intensity histograms obtained from 3D-TOF MR-angiograms before and after application of the macromolecular contrast medium gadolinium-DTPA-polylysine. The reference method was a dye-dilution technique. Extravascular lung water was calculated as the difference between total lung water and pulmonary intravascular volume. RESULTS: Under ventilatory arrest, the magnetic resonance technique for the measurement of extravascular lung water correlated well with the reference technique (r = 0.89, n = 42 lungs). In 10 lungs the correlation coefficients were r = 0.95 (ventilatory arrest) and r = 0.92 (ventilated lungs). CONCLUSION: The results demonstrate that magnetic resonance imaging enhanced by a macromolecular contrast medium may be applicable for quantification of pulmonary oedema.

[MR imaging of experimental pulmonary embolism using a macromolecular contrast medium]. / Kernspintomographische Darstellung der experimentellen Lungenarterienembolie mit einem makromolekularen Kontrastmittel.

PURPOSE: To evaluate macromolecular contrast-enhanced MR-angiography for the detection of experimentally induced pulmonary artery embolism and to determine the size of the smallest detectable embolised vessel. METHODS: Pulmonary artery embolism was artificially induced in eight isolated perfused sheep lungs by injecting room air into the main pulmonary artery. The pulmonary vascular system enhanced by macromolecular gadolinium-DTPA-polylysine was imaged with a flow-sensitive gradient-echo technique. RESULTS: Pulmonary artery embolism was demonstrated in all eight lungs by an obvious cut-off phenomenon in the contrast-enhanced arteries proximal to the pulmonary air emboli. The smallest detectable embolised artery measured 1.6 mm in diameter and was located in the 6th generation of the pulmonary vascular system. CONCLUSIONS: In this experimental study MR angiography enhanced by a macromolecular contrast agent allowed noninvasive diagnosis of pulmonary artery embolism.

Fourier phase mapping of the human heart. The use of spatial modulation of magnetization cine magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Fourier phase mapping of cine cardiac magnetic resonance (MR) imaging offers noninvasive analysis of temporal cardiac activation patterns. The aim of our investigation was to extend this analysis to intramyocardial dynamics. METHODS: A fast-imaging with steady-state precision (FISP) two-dimensional gradient echo spatial modulation of magnetization (SPAMM) sequence and a segmented two-dimensional FISP-SPAMM sequence were applied to acquire cine MR images of the complete cardiac cycle on a 1.5-tesla imager. Signal intensity data were submitted to pixel-wise Fourier phase analysis. Color-encoded amplitude and phase maps were displayed for visual analysis. RESULTS: Using the unsegmented SPAMM two-dimensional FISP sequence, a more consistent tag-to-myocardium contrast and a higher number of cardiac phases was achieved than by using the segmented version of this sequence. The typical tag displacement reflected complex intramyocardial dynamics, including rotation. Phase mapping displayed a pattern of contraction consistent with electrophysiologic concepts of cardiac activation. In contrast, the segmented sequence did not reflect any differences in the onset of cardiac contraction, although tag displacement was apparent with this sequence as well. CONCLUSIONS. Fourier phase mapping of cardiac MR imaging tagging studies allows for noninvasive analysis of intramyocardial activation patterns. A temporal resolution of 50 mseconds per image at a heart rate of 75 beats per minute allows for an assessment of spatial differences in the onset of myocardial activation.

Comparison of gadolinium-DTPA and macromolecular gadolinium-DTPA-polylysine for contrast-enhanced pulmonary time-of-flight magnetic resonance angiography.

RATIONALE AND OBJECTIVES: The authors investigated the enhancing effect of low-dose administration of the macromolecular, paramagnetic contrast medium gadolinium (Gd)-DTPA-polylysine (average molecular weight, 40,000-50,000 dalton [D]) compared with Gd-DTPA (molecular weight, 547 D) in time-of-flight magnetic resonance angiography of unilaterally damaged sheep lungs. MATERIALS AND METHODS: Thirteen heart-lung preparations were examined in the head coil of a 1.5-tesla imager (Magnetom SP, Siemens, Erlangen, Germany). The authors performed time-of-flight angiograms (coronal; repetition time, 35 mseconds; echo time, 6 mseconds; 20 degrees flip angle; pixel size 1.0 x 1.0 x 1.5 mm3) before and after application of the contrast agents. Gadolinium-DTPA-polylysine was used in a dose of 0.027 mmol/kg body weight while Gd-DTPA was injected in variable doses. RESULTS: After Gd-DTPA-polylysine, signal intensity increased by 118% in pulmonary arteries in healthy lungs and by 121% in damaged lungs (P < 0.001). In addition, the contrast-to-noise ratio measured between pulmonary arteries and perivascular parenchyma increased significantly (P < 0.01). On three-dimensional angiograms, two more generations of vascular branches could be detected. A dose of Gd-DTPA 6.1 times higher than the Gd-DTPA-polylysine dose was necessary to obtain the same contrast enhancing effect as Gd-DTPA-polylysine in healthy lungs. In damaged lungs, none of the administered doses of Gd-DTPA reached the average contrast enhancement of Gd-DTPA-polylysine. CONCLUSIONS: The authors' measurements demonstrate significant improvement of time-of-flight angiograms by low-dose administration of Gd-DTPA-polylysine.

Cardiac activation mapping by MRI.

To establish cardiac MRI as a tool for noninvasive evaluation of activation patterns, 10 healthy volunteers were examined by cine segmented turboFLASH imaging sequences. Sequence modifications for low signal blood-pool appearance were applied, i.e., bilateral spatial saturation for segmented turboFLASH imaging. Pixelwise calculation of first-harmonic Fourier phase values (displayed as color-encoded maps) reveal either anterior septal or left ventricular free-wall sites as areas of earliest phase spreading towards posterior paraseptal sites in segmented turboFLASH scans. Phase scatter is lower in unsaturated than spatially presaturated segmented turboFLASH studies. Phase standard deviation in areas of endocardial displacement is higher in basal than apical slice positions in these scans. Early results indicate that first-harmonic Fourier phase analysis of cardiac-segmented turboFLASH MRI cine studies may provide a tool for noninvasive studies of cardiac activation sequence.

Magnetic resonance perfusion imaging with gadolinium-DTPA. A quantitative approach for the kinetic analysis of first-pass residue curves.

RATIONALE AND OBJECTIVES: To present a mathematic approach for the analysis of first-pass gadolinium (Gd)-DTPA kinetics and to validate the numerical tools using simulated and measured kinetics. METHODS: In a capillary plasma filter, pulsatile flow was varied between 7.4 and 12.6 mL/second. After contrast bolus injection, the arterial input curve and the residue curve were recorded simultaneously. Signal intensity versus time curves were converted to concentration versus time curves. By deconvolution of these curves and tracer kinetic analysis, the mean transit time of the contrast medium through the organ model was calculated. RESULTS: A satisfactory correlation (r = 0.98) between the inverse of mean transit time and flow measured volumetrically was demonstrated. CONCLUSIONS: The kinetic analysis of first-pass curves in an organ model indicates that this approach might be useful for in vivo assessment of organ blood flow.

Gd-DTPA-polylysine-enhanced pulmonary time-of-flight MR angiography.

The enhancing effect of gadolinium diethylenetriaminepentaacetic acid (DTPA) polylysine (a macromolecular paramagnetic contrast agent) in time-of-flight magnetic resonance (MR) angiography of isolated perfused sheep lungs was studied. Unilateral lung damage was induced with hydrochloric acid in eight sheep. The heart and lungs were removed from the thoracic cavity, and after cannulation of the trachea and both ventricles, pulsatile perfusion and ventilation were initiated. The heart-lung preparations were placed in the head coil of a 1.5-T imager. Time-of-flight pulmonary MR angiography was performed during respiratory arrest, before and after administration of 0.02 mmol/kg Gd-DTPA-polylysine. On the postcontrast angiograms, the signal intensity increased by 120% in pulmonary arteries (P < .01). The contrast-to-noise ratio between pulmonary arteries and parenchyma increased significantly (P < .01). The number of visualized generations of pulmonary artery branches increased from four to six in normal lungs and from three to five in edematous lungs. Low-dose Gd-DTPA-polylysine significantly improves the conspicuity of the pulmonary vascular tree in time-of-flight pulmonary MR angiography.