Bolus Injection Of Gadopentetate Dimeglumine Research Articles

MRI evaluation of microvascular obstruction in experimental reperfused acute myocardial infarction using a T1 and T2 preparation pulse sequence

To investigate a T1 and T2 preparation pulse sequence to evaluate microvascular obstruction (MO) in a porcine model of reperfused acute myocardial infarction (AMI). A total of 14 pigs with reperfused AMI underwent MRI examinations at baseline and three to four hours after reperfusion. MRI scans included a left ventricular functional study, T1 and T2 measurement on a 1.5T MRI system. At reperfusion, first-pass myocardial perfusion (FPMP) images were obtained after bolus injection of gadopentetate dimeglumine followed by an intravenous drip. Delayed contrast-enhanced MRI (DE-MRI) and T1 measurements were performed 30 and 45 minutes, respectively, after the bolus, during a constant infusion of gadopentetate dimeglumine. In 11 pigs MO was hypoenhanced in FPMP and DE-MRI. In later T1 preparation difference images postcontrast, MO was hyperenhanced while delayed hyperenhanced (DHE) regions appeared dark. MO areas on DE-MRI and T1 images were comparable. T1 reduction (%) postcontrast in MO was small compared to measurements from DHE regions (P < 0.0001) and similar to those from control segments (P = 0.66). Precontrast T1 and T2 values at reperfusion from MO and DHE regions were larger than in control regions. Using T1 preparation under a constant gadopentetate dimeglumine (Gd-DTPA) infusion, delayed imaging at 30 to 45 minutes demonstrates MO as a positive contrast with larger T1 values. Elevated T1 and T2 values in MO precontrast may also help to differentiate them from both control and DHE regions.

Dynamic Contrast-Enhanced MRI of Prostate Cancer at 3 T: A Study of Pharmacokinetic Parameters

The objectives of our study were to determine whether dynamic contrast-enhanced MRI performed at 3 T and analyzed using a pharmacokinetic model improves the diagnostic performance of MRI for the detection of prostate cancer compared with conventional T2-weighted imaging, and to determine which pharmacokinetic parameters are useful in diagnosing prostate cancer. This prospective study included 50 consecutive patients with biopsy-proven prostate cancer who underwent imaging of the prostate on a 3-T scanner with a combination of a sensitivity-encoding (SENSE) cardiac coil and an endorectal coil. Scans were obtained at least 5 weeks after biopsy. T2-weighted turbo spin-echo images were obtained in three planes, and dynamic contrast-enhanced images were acquired during a single-dose bolus injection of gadopentetate dimeglumine (0.1 mmol/kg). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were estimated for T2-weighted and dynamic contrast-enhanced MRI. The following pharmacokinetic modeling parameters were determined and compared for cancer, inflammation, and healthy peripheral zone: K(trans) (forward volume transfer constant), k(ep) (reverse reflux rate constant between extracellular space and plasma), v(e) (the fractional volume of extracellular space per unit volume of tissue), and the area under the gadolinium concentration curve (AUGC) in the first 90 seconds after injection. Pathologically confirmed cancers in the peripheral zone of the prostate were characterized by their low signal intensity on T2-weighted scans and by their early enhancement, early washout, or both on dynamic contrast-enhanced MR images. The overall sensitivity, specificity, PPV, and NPV of T2-weighted imaging were 94%, 37%, 50%, and 89%, respectively. The sensitivity, specificity, PPV, and NPV of dynamic contrast-enhanced MRI were 73%, 88%, 75%, and 75%, respectively. K(trans), k(ep), and AUGC were significantly higher (p < 0.001) in cancer than in normal peripheral zone. The ve parameter was not significantly associated with prostate cancer. MRI of the prostate performed at 3 T using an endorectal coil produces high-quality T2-weighted images; however, specificity for prostate cancer is improved by also performing dynamic contrast-enhanced MRI and using pharmacokinetic parameters, particularly K(trans) and k(ep), for analysis. These results are comparable to published results at 1.5 T.

The Cisterna Chyli: Enhancement on Delayed Phase MR Images after Intravenous Administration of Gadolinium Chelate

To retrospectively evaluate cisterna chyli (CC) enhancement on magnetic resonance (MR) images obtained after intravenous administration of a gadolinium-based contrast agent. This retrospective HIPAA-compliant study of 1.5-T MR imaging findings was institutional review board approved; informed patient consent was waived. All MR examinations involved the acquisition of heavily T2-weighted single-shot fast spin-echo (SSFSE) images and three-dimensional (3D) gradient-echo images obtained before and during the arterial, venous, and 3-5-minute delayed phases after intravenous bolus injection of gadopentetate dimeglumine. Included were the data of 59 patients (37 men, 22 women; mean age, 59 years) who had a CC 4 mm or greater in transverse diameter, which was identified as a tubular structure with fluid signal intensity (SI) on SSFSE images. The SI of the CC relative to the spinal canal (SC) was noted and was measured on 3D gradient-echo images obtained during all phases. The Student t test was performed for statistical evaluations. Mean CC-SC SI ratios on nonenhanced, arterial phase, venous phase, and delayed phase images were 0.92, 0.98, 0.99, and 2.13, respectively. The CC had low SI on all 3D gradient-echo images obtained during the nonenhanced, arterial, and venous phases and high SI, similar to the azygos vein SI, on all delayed phase images. The CC-SC SI ratio during the delayed phase was significantly higher than that during the other phases (P<.001). The CC has minimal or no enhancement on arterial phase and venous phase images but intense enhancement--similar to the enhancement of veins--on delayed phase images. Comparison of delayed phase images with SSFSE and venous phase images may help to distinguish the CC seen on delayed phase images from lymph nodes, the azygos vein, or esophageal varices.

Dynamic MRI of Solitary Pulmonary Nodules: Comparison of Enhancement Patterns of Malignant and Benign Small Peripheral Lung Lesions

The purpose of this study was to compare the dynamic contrast-enhanced MRI enhancement characteristics of malignant and benign solitary pulmonary nodules. The characteristics of 202 solitary pulmonary nodules (diameter, 1-3 cm; 144 cases of primary lung cancer, 31 cases of focal organizing pneumonia, 15 tuberculomas, 12 hamartomas) were reviewed retrospectively. In all cases dynamic MR images were obtained before and 1, 2, 3, 4, 5, 6, and 8 minutes after bolus injection of gadopentetate dimeglumine. Maximum enhancement ratio, time at maximum enhancement ratio, slope of time-enhancement ratio curves, and washout ratio were assessed. Statistical analyses were performed with the Kruskal-Wallis test with Bonferroni correction, chi-square test, and receiver operating characteristic curves. For 122 (85%) of 144 primary lung cancers, time at maximum enhancement ratio was 4 minutes or less. For all tuberculomas and hamartomas, time at maximum enhancement ratio was greater than 4 minutes or gradual enhancement occurred without a peak time (p < 0.0001). Lung cancers had different maximum enhancement ratios and slopes than benign lesions (all p < 0.005). With 110% or lower maximum enhancement ratio as a cutoff value, the positive predictive value for malignancy was 92%; sensitivity, 63%; and specificity, 74%. With 13.5%/min or greater slope as a cutoff value, sensitivity, specificity, positive predictive value, and negative predictive value for malignancy were 94%, 96%, 99%, and 74%, respectively. Dynamic contrast-enhanced MRI is helpful in differentiating benign from malignant solitary pulmonary nodules. Absence of significant enhancement is a strong predictor that a lesion is benign.

Comprehensive MR Imaging of Acute Gynecologic Diseases

Rapid advances in techniques of magnetic resonance (MR) imaging have enabled diagnosis of acute gynecologic conditions, which are characterized by sudden onset of lower abdominal pain, fever, genital bleeding, intraperitoneal bleeding, or symptoms of shock. The chemical-selective fat-suppression technique not only helps establish the characteristics of lesions that contain fat components but also increases the conspicuity of inflammatory lesions. When a T2-weighted image is obtained with a very long effective echo time (>250 msec), even a small amount of ascites can be easily identified and the contrast between urine and complex fluid becomes more conspicuous. T2*-weighted images are useful for identification of hemorrhagic lesions by demonstrating deoxyhemoglobin and hemosiderin. Contrast material-enhanced dynamic subtraction MR imaging performed with a three-dimensional fast field-echo sequence and a rapid bolus injection of gadopentetate dimeglumine allows evaluation of lesion vascularity and the anatomic relationship between pelvic vessels and a lesion and allows identification of the bleeding point by demonstrating extravasation of contrast material. To optimize the MR imaging examination, attention should be given to the parameters of each pulse sequence and proper combination of the sequences.

THE POTENTIAL INFLUENCE OF FINE-NEEDLE ASPIRATION ON MR IMAGING OF THE BREAST

The aim of this study was to determine whether fine-needle aspiration biopsy (FNAB) of breast lesions causes structural changes or changes in contrast enhancement, that could impair the evaluation of these lesions at MR investigation of the breast. Fifteen patients with 17 lesions were examined with MR imaging of the breast both before and after the FNAB with a mean interval of 7.1 days. At both examinations, signal intensities were measured pre- and post-contrast enhancement in the lesions as well as in surrounding breast parenchyma and muscle. Imaging with contrast enhancement was performed semidynamically with two images obtained in rapid sequence (acquisition time 6.23 min) immediately after bolus injection of gadopentetate dimeglumine, 0.1 mmol/kg b.w., and the contrast enhancement in both images was calculated. The diagnostic value of MR images was unimpaired by FNAB, and no statistical difference between contrast enhancement in corresponding images obtained before and after FNAB was found, either within the lesions or in the breast parenchyma or muscle. FNAB of the breast can be performed without impairing the diagnostic outcome of MR investigation.

The Potential Influence of Fine-Needle Aspiration on MR Imaging of the Breast

The aim of this study was to determine whether fine-needle aspiration biopsy (FNAB) of breast lesions causes structural changes or changes in contrast enhancement, that could impair the evaluation of these lesions at MR investigation of the breast. Fifteen patients with 17 lesions were examined with MR imaging of the breast both before and after the FNAB with a mean interval of 7.1 days. At both examinations, signal intensities were measured pre- and post-contrast enhancement in the lesions as well as in surrounding breast parenchyma and muscle. Imaging with contrast enhancement was performed semidynamically with two images obtained in rapid sequence (acquisition time 6.23 min) immediately after bolus injection of gadopentetate dimeglumine, 0.1 mmol/kg b.w., and the contrast enhancement in both images was calculated. The diagnostic value of MR images was unimpaired by FNAB, and no statistical difference between contrast enhancement in corresponding images obtained before and after FNAB was found, either within the lesions or in the breast parenchyma or muscle. FNAB of the breast can be performed without impairing the diagnostic outcome of MR investigation.

Dynamic Contrast Enhanced MRI of Prostate Cancer: Correlation with Morphology and Tumour Stage, Histological Grade and PSA

AIM: To quantify MRI enhancement characteristics of normal and abnormal prostatic tissues and to correlate these with tumour stage, histological grade and tumour markers.MATERIALS AND METHODS: Quantitative gradient recalled echo MR images were obtained following bolus injection of gadopentetate dimeglumine in 48 patients with prostate cancer. Turbo spin-echo T2-weighted images at the same anatomical position were reviewed for the presence of tumours (45 regions), normal peripheral zone (33 regions), and normal appearing central gland (30 regions). Time-signal intensity parameters (onset time, mean gradient and maximal amplitude of enhancement and wash-out score) and modelling parameters (permeability surface area product, lesion leakage space and maximum gadolinium concentration) were correlated with tumour stage, histological grade (Gleason score) and serum prostatic specific antigen (PSA) levels.RESULTS: Significant differences were noted between peripheral zone and tumour with respect to signal intensity and modelling parameters (P=0.0001), except onset time. No differences between central gland and tumour enhancement values were seen. There was weak correlation between MRI tumour stage and tumour vascular permeability (r2=12%;P=0.02) and maximum tumour gadolinium concentration (r2=14%;P=0.015). However, no significant correlations were seen with Gleason score or PSA levels.CONCLUSION: Quantification of MR contrast enhancement characteristics allows tissue discrimination in prostate cancer consistent with known variations in microvessel density estimates.Padhani, A. R. (2000). Clinical Radiology55, 99–109.

Contrast-enhanced three-dimensional MR portography.

Three-dimensional (3D) magnetic resonance (MR) portography with contrast material enhancement is a fast means of evaluating the portal venous system that has some advantages over currently used modalities, such as digital subtraction angiography, helical computed tomography, ultrasonography, and nonenhanced MR angiography with time-of-flight and phase-contrast techniques. With contrast-enhanced 3D MR portography, a first-pass study of the mesenteric vasculature is performed after rapid bolus injection of gadopentetate dimeglumine; a 3D fast field echo sequence is used, which can demonstrate the intrahepatic and extrahepatic portal venous system clearly. Repeated sequences after administration of gadopentetate dimeglumine allow separate demonstration of the splanchnic arteries and portomesenteric veins. The images are reconstructed by means of maximum-intensity projection postprocessing, and a subtraction technique can be used to eliminate arterial enhancement and demonstrate portosystemic shunts. The coronal source images simultaneously demonstrate parenchymal lesions of the liver, pancreas, biliary tract, and spleen. This technique is clinically indicated in portosystemic shunt, portal vein thrombosis, hepatocellular carcinoma, pancreatobiliary tumor, hepatic vein obstruction, differentiation of splanchnic arterial from portal venous disease, and gastrointestinal hemorrhage. Its limitations include allergic reactions to contrast media, inappropriate positioning of the 3D acquisition slab, respiratory motion artifacts, and pseudodissection.

Effects of Subcortical Cerebrovascular Lesions on Cortical Hemodynamic Parameters Assessed by Perfusion Magnetic Resonance Imaging

A simultaneous decrease of cerebral blood volume (CBV) and cerebral blood flow (CBF) has been described after subcortical stroke with positron emission tomography. However, this imaging modality cannot be applied routinely to stroke patients. Dynamic susceptibility contrast-enhanced MRI techniques (DSC-MRI) might be interesting in the assessment of these effects. Dynamic T₂-weighted echo planar imaging was used to produce DSC-MR images during an intravenous bolus injection of gadopentetate dimeglumine in 9 patients who experienced a subcortical stroke involving thalamus or basal ganglia and in 8 control subjects. A series of 50 consecutive images at 1-second intervals was acquired at the anatomic level of the centrum semiovale quite distant from the subcortical lesion, rCBF and rCBV were determined over frontal and parietal regions of interest and through the entire cortical mantle. DSC-MRI enabled the detection of hemodynamic changes induced by subcortical stroke. Analysis of rCBV and rCBF values showed that the hemodynamic parameters were significantly decreased on the affected side. In controls mean rCBF and rCBV values recorded over the whole cortical mantle of each hemisphere showed no significant interhemispheric asymmetry.

Effects of thalamic hemorrhage on cortical hemodynamic parameters assessed by perfusion MR imaging: Preliminary report

Thalamic lesions may induce a diffuse hypometabolism and subsequent decrease of cortical cerebral blood flow (rCBF) and cerebral blood volume (rCBV). Up to now PET was used to assess these changes. However this latter method cannot be applied routinely to stroke patients because it is expensive and not currently available. The purpose of this preliminary study was to evaluate the effects of `pure metabolic depression' induced by thalamic stroke on rCBV and rCBF by using a non invasive method perfusion-MRI. Two patients experienced aphasia, with motor and sensory impairment related to thalamic hemorrhage. Four weeks later, dynamic T2*-weighted echo planar imaging was used to produce perfusion-MR images during an intravenous bolus injection of gadopentetate dimeglumine. A decrease of cortical rCBV and rCBF mainly confined to sensorimotor cortex was observed in both cases ipsilateral to the lesion. Although a sequential assessment of this abnormalities is needed in a larger series of patients in order to establish relevant correlations with neurological status, this preliminary study indicates that perfusion-MRI might be a practical and promising tool in the assessment of cortical rCBV and rCBF changes.

Contrast-enhanced magnetic resonance imaging for the detection of acute haemorrhagic necrotizing pancreatitis

Eleven piglets with haemorrhagic necrotizing pancreatitis and nine piglets with oedematous pancreatitis were imaged using a multi-breath-hold TurboFLASH (TR 6.5 ms, TE 3 ms, TI 300 ms, flip angle 8 degrees , three slices) pre-excited T1-weighted sequence with an IV bolus injection of gadopentetate dimeglumine (Gd-DTPA, 0. 3 mmol/kg) as a contrast agent to show dynamic contrast enhancement of the pancreas by MRI. All piglets were imaged according to the same protocol before inducing the disease. Following the IV Gd-DTPA bolus, time-enhancement curve of the pancreas during haemorrhagic necrotizing pancreatitis was significantly lower than during oedematous pancreatitis. The enhancement curves for the healthy piglets and piglets with oedematous pancreatitis did not differ significantly. Each piglet served as its own control. Because the results of this initial study are similar to those obtained with contrast-enhanced CT, we conclude that our results may encourage further clinical trials, and contrast-enhanced dynamic MRI may be an alternative to the established method of CT for diagnosing acute haemorrhagic necrotizing pancreatitis.

Dual dynamic contrast-enhanced MR imaging.

A method was devised for obtaining dynamic contrast-enhanced T1-weighted and relaxation rate (delta R2*) images simultaneously to evaluate regional hemodynamics of the brain tumors. On a 1.5-T MR system, dual dynamic contrast-enhanced images were obtained using a gradient echo (dual echo fast field echo) pulse sequence with the keyhole technique to improve temporal and spatial resolution during a rapid bolus injection of gadopentetate dimeglumine. The dynamic T1 contrast images were obtained from the first echo: moreover. integral delta R2*dt values were calculated from the first and the second echo images. The dynamic T1 contrast images provided information about characteristic enhancement pattern (vascularization and disruption of blood-brain barrier), and the integral delta R2*dt values provided a map of regional blood pool in tumor site, peritumoral edema, and other surrounding regions of the brain. The ability to obtain dynamic contrast-enhanced T1 contrast and delta R2* imaging at the same time allows optimization of the advantages of each and thereby more information about the microvascular circulation of the brain lesions.

Hilar cholangiocarcinomas: T2-weighted spin-echo and gadolinium-enhanced FLASH MR imaging.

To investigate the use of magnetic resonance (MR) imaging with dynamic gadopentetate dimeglumine enhancement in hilar cholangiocarcinoma. Twenty-four patients (14 men, 10 women; aged 27-78 years; mean age, 51 years) with hilar cholangiocarcinoma underwent T2-weighted spin-echo MR imaging in the axial plane and multisection, breath-hold, fast low-angle shot (FLASH) MR imaging in the coronal oblique plane before and at 30, 60, 90, and 120 seconds after bolus injection of gadopentetate dimeglumine. Morphologic features were recorded, and contrast medium enhancement characteristics and contrast-to-noise ratios were calculated for each sequence. All the lesions were hyperintense on T2-weighted spin-echo images and hypointense on FLASH images. On dynamic gadolinium-enhanced images, progressive heterogeneous enhancement was seen in all patients. Intrahepatic ductal dilatation was present in every patient. Intraluminal components were seen in 11 patients, lobar atrophy in 12, and segmental portal venous occlusion or stenosis in 13. Satellite lesions were present in four patients, and hilar lymph nodal enlargement in 11. Contrast-to-noise ratios were statistically significantly higher on T2-weighted spin-echo images than on all other images. Hilar cholangiocarcinomas have consistent enhancement and morphologic features that can be demonstrated with dynamic contrast-enhanced MR imaging.

Hepatic malignancies: usefulness of acquisition of multiple arterial and portal venous phase images at dynamic gadolinium-enhanced MR imaging.

To determine whether liver tumor detection is increased by acquiring multiple dynamic arterial phase and portal venous phase magnetic resonance (MR) images. Dynamic MR imaging was performed in 205 patients at 1.5 T with use of a fast spoiled gradient-echo technique (repetition time, 9-12 msec; echo time, 2.1-3.0 msec; flip angle, 30 degrees). During intravenous bolus injection of gadopentetate dimeglumine or gadoteridol (0.1 mmol/kg), nine images were acquired at each of 10-12 locations over approximately 120 seconds. The number of tumors detected on arterial phase and portal venous phase images and unenhanced T1- and T2-weighted spin-echo (SE) images was evaluated separately. Data obtained in 75 patients with proved malignancies were analyzed. At imaging, 220 malignant tumor nodules were depicted. At prospective review of all images, 110 hepatocellular carcinomas (HCCs) were detected: 82 (75%) on unenhanced T1-weighted SE images, 83 (75%) on unenhanced T2-weighted SE images, 92 (84%) on arterial phase images, and 76 (69%) on portal venous phase images. At prospective review, eight HCCs were detected on only arterial phase images, one on only portal venous phase images, nine on both arterial and portal venous phase images, and 11 on only unenhanced SE images. The 18 additional HCCS detected prospectively on only dynamic images increased HCC detection by 21% over prospective detection on only SE images. Detection of non-HCC tumors (including metastases) did not increase with dynamic images. Acquisition of multiple dynamic arterial phase and portal venous phase images increased detection of HCC but not metastases.

Cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease: assessment with dynamic susceptibility contrast-enhanced MR imaging and the acetazolamide stimulation test.

To quantitatively assess cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease. In 21 symptomatic patients with occlusive cerebrovascular disease, magnetic resonance (MR) imaging was performed with a 1.5-T system. Before, during, and after a brief bolus injection of gadopentetate dimeglumine into the antecubital vain, a series of 32 rapid T2*-weighted gradient-echo images of two different sections were acquired simultaneously to measure the concentration-time-curves in the brain tissue and in the brain-feeding arteries. Principles of indicator dilution analysis were applied to compute regional cerebral blood flow (rCBF) and volume. Each patient underwent two examinations, the first before and the second after acetazolamide stimulation. In the asymptomatic hemisphere, a mean increase in rCBF value of 47.1% was observed after acetazolamide stimulation. In the affected areas of the symptomatic hemisphere, a statistically significantly reduced response to acetazolamide stimulation was found, indicating a severely compromised cerebrovascular reserve capacity. MR imaging with the described techniques provides quantitative information about the cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease.

Pancreatic adenocarcinoma: assessment of vascular invasion with high-field MR imaging and a phased-array coil.

We performed this study to determine the value of MR imaging for assessing vascular invasion in preoperative staging of pancreatic carcinoma. In 73 consecutive patients with an established diagnosis of pancreatic duct adenocarcinoma, spin-echo T1-weighted and breath-hold multiplanar gradient-recalled (MPGR) images were obtained at 1.5 T with a phased-array coil before and after bolus injection of gadopentetate dimeglumine. Major peripancreatic vessels were evaluated for contiguity with tumor and tumor encasement. All patients subsequently underwent surgery. Results of unenhanced and enhanced MR imaging studies were compared with the histologic findings in the resected specimens of 49 tumors and with the surgical findings of 24 nonresected tumors. In 39 patients, tumor contiguity with adjacent vessels was found at pathologic examination. Of the remaining 34 patients, 10 had vascular encasement by tumor seen on pathologic examination of the resected specimen; the other 24 had unresectable tumors encasing adjacent vessels at surgical evaluation. In the assessment of vascular tumor contiguity, the accuracy was 85% for unenhanced spin-echo T1-weighted imaging, 87% for enhanced spin-echo T1-weighted imaging, 67% for unenhanced MPGR imaging, and 69% for enhanced MPGR imaging. In the assessment of vascular tumor encasement, the accuracy was 91% for unenhanced spin-echo T1-weighted imaging, 94% for enhanced spin-echo T1-weighted imaging, 74% for unenhanced MPGR imaging, and 76% for enhanced MPGR imaging. MR imaging is helpful for preoperative assessment of vascular involvement caused by pancreatic carcinoma. For this purpose, unenhanced and enhanced spin-echo T1-weighted images seem to be more accurate than images obtained with other pulse sequences.

Use of magnetization transfer contrast to improve single breath-hold three-dimensional MR-portography with bolus injection of gadopentetate dimeglumine: a preliminary report.

We investigated whether better visualization of the intrahepatic portal system could be obtained by adding magnetization transfer contrast (MTC) to three-dimensional MR portography (3D-MRP). In 15 healthy volunteers, 3D fast low-angle shot images combined with an off-resonance pulse were obtained after bolus injection of gadopentetate dimeglumine during one period of breath-holding. Within 1 week after injection, MR images without MTC were obtained using the same scanning condition. MRPs with and without the MTC pulse were compared quantitatively and qualitatively. The contrast-to-noise ratio of the portal vein-liver was significantly higher in the group imaged with the addition of MTC. Qualitatively, the use of MTC improved peripheral portal branch depiction on maximum-intensity projection images. Even when the MTC pulse was added to the conventional method of 3D data collection, it was possible to obtain images within one period of breath-holding. In conclusion, the use of MTC can substantially enhance the quality of 3D-MRPs.

Measurement of renal transit of gadopentetate dimeglumine with echo-planar MR imaging.

Times of peak gadolinium concentration ([Gd]) after intravenous (IV) and left ventricular (LV) bolus injection of gadopentetate dimeglumine were determined in renal cortex and medulla in normal rabbits and in rabbits after saline load (overhydration) or hemorrhage (dehydration). Magnetic resonance images were obtained with echo-planar inversion-recovery sequences, and signal intensity-versus-time curves in cortical and medullary regions of interest were converted to [Gd]-versus-time curves. Cortical perfusion measured with microspheres demonstrated that the three physiologic states were significantly different. There were three separate [Gd] peaks in both the cortex and medulla as the bolus moved from one anatomic compartment to the next. The first cortical peak occurred sooner after LV than after IV bolus injection (P < .05) and later in dehydrated than in normal and overhydrated rabbits (P < .05). The first medullary peak always followed the first cortical peak by about 6-10 seconds and mirrored the cortical patterns. The second and third cortical peaks were consistent with proximal and distal tubular transit. These peaks similarly showed faster response to LV than IV injection and were delayed by hemorrhage. The authors conclude that quantitative physiologic information can be obtained with dynamic contrast-enhanced MR imaging of the kidney.

Comparative signal intensity measurements in dynamic gadolinium-enhanced MR mammography.

Increases in signal intensity enhancement were measured in defined regions of interest (ROIs) to allow distinction between malignant and benign tumors with dynamic gadolinium-enhanced magnetic resonance (MR) mammography. Twenty patients with palpable breast lesions (15 malignant, five benign) underwent MR mammography. The dynamic gradient-echo sequence was performed with intravenous bolus injection of gadopentetate dimeglumine and consisted of 25 images with a time resolution of 30 seconds. Contrast enhancement was calculated by comparing user-defined ROIs on pre- and postcontrast images. An increase in signal intensity of 70% or more on the 1-minute postcontrast image was used as the criterion of malignancy. MR mammographic results correlated with histopathologic findings in all patients when the defined ROI was in the most enhancing part of the tumor. For the ROI in areas of submaximal enhancement or when the ROI surrounded the whole lesion, only five and nine tumors, respectively, fulfilled the malignancy criterion. All malignant tumors showed large variations in signal intensity enhancement that depended on the position of the ROI in the tumor. Dynamic, gadolinium-enhanced MR mammography allows distinction of benign from malignant breast tumors when the selected ROI is in the most enhancing part of the lesion.