Rectal carcinoma: Prospective comparison of conventional and gadopentetate dimeglumine enhanced fat-suppressed MR imaging

The purpose of this study is to compare the usefulness of conventional MR imaging and gadopentetate dimeglumine enhanced fat-suppressed MR imaging for the depiction and staging of rectal carcinoma. Thirty-two patients were prospectively evaluated by MR imaging using a 1.5-T unit. Based on the results of a barium study and/or digital examination, a balloon catheter was inserted to the level of the lesion before examination. Both conventional T1- and T2-weighted images and gadopentetate dimeglumine enhanced fat-suppressed T1-weighted images were obtained for all patients. The kappa statistics were performed for the evaluation of interobserver agreement and the McNemar test was performed for the analysis of staging accuracy. When only T1- and T2-weighted images were used, 5 of 32 tumors were not detected and the extent of 18 of 32 tumors were unclear. However, when gadopentetate dimeglumine enhanced fat-suppressed imaging was added, 24 of 32 tumors were well defined and only one tumor was not detected. In determining the depth of invasion, the staging accuracy was 72% for conventional imaging and 68% for all images combined. There was no significant difference between with gadopentetate dimeglumine fat-suppressed imaging and conventional imaging (P > .05). Use of gadopentetate dimeglumine (fat-suppressed imaging) resulted in overestimation of muscular invasion, peri-rectal fat invasion, and adjacent organ invasion in 12 patients, whereas nine patients were overestimated without the use of gadopentetate dimeglumine. In the detection of metastatic lymph nodes, gadopentetate dimeglumine enhanced fat-suppressed imaging also was not useful. Tumor detection was excellent using gadopentetate dimeglumine enhanced fat-suppressed images. However, the accuracy of staging was not improved by obtaining such images.     

Preliminary clinical trial of gadodiamide injection: a new nonionic gadolinium contrast agent for MR imaging.

The safety and efficacy of a newly developed intravenous formulation of the nonionic contrast agent gadolinium diethylenetriaminepentaacetic acid-bis(methylamide), formulated as gadodiamide injection, was investigated. In 30 patients who underwent spin-echo magnetic resonance (MR) imaging before and after contrast agent enhancement, the enhanced images had characteristics judged similar to those of images enhanced by means of available gadolinium compounds. In 15 patients, contrast agent administration was of major diagnostic help, either revealing lesions not apparent without enhancement or providing important lesion characterization. In 12 patients, the lack of abnormal enhancement patterns was important in excluding the presence of disease. In three patients, the contrast agent did not provide information additional to that obtained with the unenhanced T1- and T2-weighted images. No clinically significant changes were observed in vital signs, neurologic status, or laboratory results. The authors conclude that, in this limited series, gadodiamide injection proved to be a safe and useful MR imaging contrast agent for evaluation of the central nervous system and surrounding structures.     

Diagnostic value of gadopentetate dimeglumine for 1.5-T MR imaging of musculoskeletal masses: comparison with unenhanced T1- and T2-weighted imaging.

Three magnetic resonance (MR) imaging techniques (T1-weighted, T2-weighted, and T1-weighted gadopentetate dimeglumine--enhanced) were compared in 32 consecutive MR imaging studies of 26 patients with suspected musculoskeletal masses. T2-weighted images were superior to T1-weighted enhanced images with respect to detection and definition of lesions in 12% of cases (n = 4) and were equal in 88% of cases (n = 28). T2-weighted images were also superior to T1-weighted images in 38% of cases (n = 12). In no cases were T1-weighted enhanced images superior to T2-weighted images. In two cases, T1-weighted images were superior to both T1-weighted enhanced and T2-weighted images. The authors conclude that gadopentetate dimeglumine did not provide much value in lesion detection above that obtained with T2-weighted images. They also conclude that T1-weighted images were occasionally superior to T1-weighted enhanced images and T2-weighted images because of loss of definition between fat and lesion on the latter.     

High-dose gadoteridol in MR imaging of intracranial neoplasms.

Twelve patients with a high suspicion of brain metastases by previous clinical or radiologic examinations were studied in a phase III investigation with magnetic resonance (MR) imaging at 1.5 T after a bolus intravenous injection of 0.1 mmol/kg gadoteridol followed at 30 minutes by a second bolus injection of 0.2 mmol/kg gadoteridol. All lesions were best demonstrated (showed greatest enhancement) at the 0.3-mmol/kg (cumulative) dose, with image analysis confirming signal intensity enhancement in the majority of cases after the second gadoteridol injection. More lesions were detected with the 0.3-mmol/kg dose than with the 0.1-mmol/kg dose, and more lesions were detected with the 0.1-mmol/kg dose than on precontrast images. In this limited clinical trial, high-dose gadoteridol injection (0.3-mmol/kg cumulative dose) provided improved lesion detection on MR images specifically in intracranial metastatic disease.     

MR imaging of normal rat brain at 0.35 T and correlated histology.

A custom-built small-animal transceiver was used for in vivo imaging of normal rat brain at 0.35 T, with the objective of identifying anatomic components by comparison of images with corresponding histologic sections. The cerebrum, cerebellum, brain stem, ventricles, hippocampus, and subarachnoid space were identified and cerebrospinal fluid (CSF) was differentiated from gray matter and white matter on coronal and transaxial magnetic resonance (MR) images. These images compare favorably with those obtained by others at higher field strengths in regard to delineating major neuroanatomic structures. It is concluded that this technique will be useful for investigating small-animal models of human neurologic disease involving morphologic and morphometric changes in gray matter, white matter, and CSF-filled spaces.     

MR imaging of soft-tissue masses: Role of gadopentetate dimeglumine

To assess the effectiveness of gadopentetate dimeglumine in the magnetic resonance (MR) imaging evaluation of soft-tissue masses without osseous involvement, 30 patients underwent MR imaging before and after administration of contrast material (0.1 mmol/ kg) of the 30 lesions, 22 were benign and eight were malignant; histologic confirmation was available in all lesions except one benign lesion. Overall, enhancement was detected in 26 (87%) of 30 lesions: 18 (82%) of the 22 benign lesions and eight (100%) of eight malignant lesions. Enhancement was characterized as homogeneous (two [11%] benign lesions, two [25%] malignant lesions), inhomogeneous (11 [61%] benign lesions, six [75%] malignant lesions), or peripheral (five [28%] benign lesions, no malignant lesions) of the 19 lesions assessed for a change in enhancement over time, seven (37%) showed an increase and two (11%) showed a decrease in signal intensity. The authors conclude that benign and malignant soft-tissue lesions could not be differentiated solely on the basis of enhancement (pattern, degree, or time course).     

Theoretical analysis of gadopentetate dimeglumine enhancement in T1-weighted imaging of the brain: Comparison of two-dimensional spin-echo and three-dimensional gradient-echo sequences

By using a theoretical model, the signal difference-to noise ratios between simulated lesions and normal white matter and gray matter were calculated as a function of lesion concentration of gadopentetate dimeglumine (GD) for two-dimensional (2D) T1-weighted spin-echo (SE), three-dimensional (3D) steady-state spoiled gradient-echo (GRE) (FLASH [fast low-angle shot]), and 3D magnetization-prepared rapid gradient echo (MP-RAGE) pulse sequences. The 3D GRE sequences provided greater contrast enhancement at relatively high [GD], and the 2D SE sequence demonstrated greater enhancement and a higher rate of enhancement at low [GD]. The results predict that at low [GD], certain lesions could probably be detected with the 2D SE sequence but possibly not with one or both of the 3D GRE sequences. At high [GD], certain lesions could probably be detected with one or both of the 3D GRE sequences but possibly not with the 2D SE sequence. This provides a potential explanation for the clinical observation that certain contrast agent enhanced lesions appear less conspicuous on 3D GRE images than on 2D SE images and vice versa. Modified parameter values were derived for the 3D FLASH and 3D MP-RAGE sequences that are predicted to produce contrast enhancement behavior equivalent or superior to that of a conventional 2D SE sequence.     

Quantitation of structural distortion of the cervical neural foramina in gradient-echo MR imaging

Quantitative errors (due to magnetic susceptibility artifacts) in the measurement of the cervical spinal neural foramina with fast gradient-echo (GRE) magnetic resonance imaging were assessed. Cylindric phantoms of different materials were used to demonstrate the nature of magnetic susceptibility artifacts, emphasizing the dependence of the artifact on tissue geometry. Neural foramina diameters measured on thin, sagittal GRE and spin-echo (SE) images through the neural foramina of a fresh human cervical spine specimen were then compared with direct measurements with calipers. The GRE images showed more apparent narrowing than did the SE images. The absolute distortion of seven neural foramina was rather constant (less than two pixels) on the GRE images; therefore, the relative distortion was inversely proportional to the size of the neural foramen, ranging up to 10% in the upper cervical region at a short TE. The absolute and relative distortion increased as TE increased. At a constant TE, the structural distortion did not change with different TRs or flip angles. The shortest possible TE is recommended in evaluation of the cervical spine.     

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.     

Dynamic MR imaging of human brain oxygenation during rest and photic stimulation.

Dynamic FLASH (fast low-angle shot) magnetic resonance (MR) imaging was used to monitor changes in brain oxygenation in the human visual cortex during photic stimulation. The approach exploits the sensitivity of the gradient-echo signal to susceptibility changes induced by varying concentrations of paramagnetic deoxyhemoglobin in the cerebral blood pool. After the onset of binocular photic stimulation (10 Hz, red light, checker-board), there was a distinct increase in the MR signal in the calcarine cortex within 6-9 seconds, indicating a decrease in the total deoxyhemoglobin concentration. After the stimulation was switched off, the MR signal returned to a basal value within a similar period of time. Assuming enhanced blood flow and only a minor increase in oxygen consumption (production of deoxyhemoglobin) during physiologic activation, the results reflect an enhanced supply of diamagnetic oxyhemoglobin and an increase in the partial oxygen pressure in the capillary and venous blood pools. In addition, a decrease in the basal MR signal in the calcarine cortex was observed during the first 60-90 seconds of persistent activation, which may be understood as an autoregulatory adaptation to increased overall brain activity associated with information processing due to continuous perception of visual stimuli.     

Routine quantitative analysis of brain and cerebrospinal fluid spaces with MR imaging.

A computerized system for processing spin-echo magnetic resonance (MR) imaging data was implemented to estimate whole brain (gray and white matter) and cerebrospinal fluid volumes and to display three-dimensional surface reconstructions of specified tissue classes. The techniques were evaluated by assessing the radiometric variability of MR volume data and by comparing automated and manual procedures for measuring tissue volumes. Results showed (a) the homogeneity of the MR data and (b) that automated techniques were consistently superior to manual techniques. Both techniques, however, were affected by the complexity of the structure, with simpler structures (eg, the intracranial cavity) showing less variability and better spatial correlation of segmentation results between raters. Moreover, the automated techniques were completed for whole brain in a fraction of the time required to complete the equivalent segmentation manually. Additional evaluations included interrater reliability and an evaluation that included longitudinal measurement, in which one subject was imaged sequentially 24 times, with reliability computed from data collected by three raters over 1 year. Results showed good reliability for the automated segmentation procedures.     

Assessing response to therapy of spinal metastases with gadolinium-enhanced MR imaging.

The utility of gadolinium-enhanced magnetic resonance (MR) imaging in assessing the response of spinal metastases to therapy was evaluated. Fifteen patients (62 affected vertebral bodies) with spinal metastases were evaluated with gadopentetate dimeglumine-enhanced imaging before and after irradiation or chemotherapy. Signal intensities of the lesions and of adjacent normal vertebral bodies were compared. Before therapy, metastatic foci enhanced significantly more than did normal vertebral bodies. After therapy, the lesions were divided into 37 responding lesions (group 1) and 25 nonresponding lesions (group 2). In group 1, lesion enhancement diminished considerably and the patients with these lesions remained clinically asymptomatic for 2-6 months. In group 2, lesion enhancement did not diminish much, and the difference between the groups was significant. Gadolinium-enhanced MR imaging may thus be a useful method for assessing the effectiveness of therapy for spinal metastases.     

Phase III clinical evaluation of Gd-HP-DO3A in head and spine disease.

As part of a phase III clinical trial, 25 patients with suspected intracranial or spinal disease underwent magnetic resonance (MR) imaging before and after intravenous injection of 0.1 mmol/kg Gd-HP-DO3A (1,4,7-tris[carboxymethyl]-10-[2' hydroxypropyl]-1,4,7,10- tetraazacyclododecane), a neutral (nonionic) gadolinium chelate. Laboratory analysis included a complete blood count; blood chemistry; measurement of electrolyte levels; hepatic function, clotting function, and iron metabolism panels; and urinalysis both before and 24 hours after contrast agent administration. No statistically significant changes related to contrast agent administration were noted in laboratory values after administration of the contrast agent. In this selected group of patients, the contrast agent-enhanced study provided greater diagnostic information than did the precontrast study in 69% of head cases and 67% of spine cases. These initial clinical trials demonstrate that Gd-HP-DO3A is a safe, efficacious agent for head and spine examinations.     

MR imaging of the central nervous system in divers.

A group of 70 professional divers and 47 healthy control subjects who had never dived were examined with magnetic resonance (MR) imaging to determine the prevalence of focal white matter changes in the brain. Spots of high signal intensity in white matter on proton density- and/or T2-weighted spin-echo images were detected in 42% of the control subjects and in 34% of the divers. In the control subjects, the prevalence of more than three changes was related to smoking, use of alcohol, head trauma, age of more than 35 years, and a combination of several cerebrovascular risk factors. This relationship was not present in the divers. The prevalence of changes in divers was inversely related to diving depth, amount of diving, participation in "unsafe diving," and decompression sickness. The reasons for these results could not be ascertained. The results are compared with those of MR imaging studies of white matter changes recently presented by other research groups.     

MR portography: Preliminary comparison with CT portography and conventional MR imaging

Magnetic resonance (MR) imaging with arterial portography (MRAP) was compared with computed tomography with arterial portography (CTAP) and conventional MR imaging for preoperative evaluation of hepatic masses in eight patients (nine studies). Twenty contiguous, 10-mm-thick-section CTAP images were obtained. MR imaging included T1- and T2-weighted spin-echo and fast multiplanar SPGR (spoiled gradient-recalled acquisition in the steady state) techniques. For MRAP, 0.1 mmol/kg gadopentetate dimeglumine was injected into the superior mesenteric artery. Portographic-phase, 8-mm-thick-section, axial SPGR images were first obtained, followed by “systemic phase” SPGR images. Lesions were seen best on the portographic-phase MRAP images and were less conspicuous on the systemic-phase MRAP, CTAP and conventional MR images. Of 19 visualized lesions, 18 were seen with MRAP; however; five subcentimeter lesions seen with MRAP were not seen with conventional MR imaging or CTAP. Systemic recirculation of iodinated contrast material from the bolus and from previous angiography is a potential limitation of CTAP. For both CTAP and MRAP, optimal results are expected if all images are obtained during a single breath hold, within seconds of the onset of contrast agent administration.     

Comparison of Gadomer-17 and gadopentetate dimeglumine for differentiation of benign from malignant breast tumors with MR imaging

RATIONALE AND OBJECTIVES: This study compared gadopentetate dimeglumine (molecular weight, 0.5 kD), a standard contrast medium, and Gadomer-17 (apparent molecular weight, approximately 35 kD), a new, clinically applicable, large-molecular contrast medium, with respect to their microvascular characterizations of experimentally induced breast tumors at magnetic resonance (MR) imaging. MATERIALS AND METHODS: A spectrum of breast tumors, benign through highly malignant, was induced in Sprague-Dawley rats (n = 30) by intraperitoneal administration of N-ethyl-N-nitrosourea (ENU), a potent carcinogen. All animals underwent three-dimensional spoiled gradient-recalled MR imaging, with precontrast imaging and dynamic postcontrast imaging after injection of gadopentetate dimeglumine (0.1 mmol/kg) and Gadomer-17 (0.03 mmol/kg), administered in a random order at a 24-hour interval. Several microvascular parameters were compared: the endothelial transfer coefficient (K(PS)), a measure of microvascular permeability; the fractional plasma volume (fPV), and the plasma equivalent volume. Each MR imaging parameter was correlated with histopathologic findings. RESULTS: With Gadomer-17, the mean values for K(PS) and fPV were significantly greater in carcinomas than in fibroadenomas (P < .004 and .04, respectively). With gadopentetate dimeglumine, the mean values for fPV and PEV were significantly greater in carcinomas (P <. 004 and .02, respectively). Because of the high variability within both fibroadenoma and carcinoma groups, however, there were no significant correlations between K(PS), fPV, or PEV and histopathologic tumor grade as indicated by the Scarff-Bloom-Richardson score, for either agent. CONCLUSION: Although the K(PS) and fPV estimates obtained from dynamic MR imaging data with Gadomer-17 enhancement offer some potential for characterizing breast tumors, none of the quantitative microvascular parameters derived with either agent were significantly correlated with histopathologic tumor grade.     

Efficacy of nonionic low-osmolar gadodiamide injection in animals with intracranial mass lesions.

Gadodiamide injection is a nonionic, low-osmolar formulation of a paramagnetic metal chelate complex consisting of gadodiamide and caldiamide sodium. The efficacy of gadodiamide injection as a magnetic resonance (MR) imaging enhancement medium was evaluated by imaging intracranial 9L-glioma lesions induced in rats and naturally occurring lesions in dogs. T1- and T2-weighted spin-echo images were obtained before and after administration of gadodiamide injection at doses of 0.1 and 0.2 mmol/kg. On the precontrast T1-weighted images, the intracranial lesions were not well seen, appearing isointense to normal brain parenchyma. Although the presence of disease was shown unequivocally on the T2-weighted images, the margins of the masses could not be delineated. Postcontrast T1-weighted images were characterized by marked enhancement of the tumor, with no change in signal intensity in the surrounding edematous brain tissue. Gadodiamide injection was efficacious in identifying areas of blood-brain barrier breakdown associated with intracranial masses.     

Dynamic gadopentetate dimeglumine-enhanced MR imaging of hepatocellular carcinoma

Nineteen patients with 28 histologically proven hepatocellular carcinomas (HCCs) were examined using T1- and T2-weighted spin-echo sequences and dynamic gadopentetate dimeglumine-enhanced magnetic resonance imaging (MRI) performed by fast T1-weighted gradient-echo sequence (100/5/80°) which was performed before and repeatedly (12 sets of images) after intravenous bolus injection of gadopentetate dimeglumine (Gd-DTPA) over a period of 10 min. Enhancement of HCC was heterogeneous in 24 lesions (85.7%). Intra-lesional non-enhancing areas were seen in 18 cases (64%). A late-enhancing pseudocapsule was seen in 12 lesions (42.9%). In addition, two groups were distinguished in the examined HCCs: 16 lesions (57.1%) showed stronger enhancement compared to liver parenchyma with maximum positive lesion-to-liver contrast on the 15-s images, while 12 lesions (42.9%) had an enhancement less than normal liver with a maximum negative contrast on the 15-s images. We conclude that the morphologic features most frequently encountered in HCC on dynamic Gd-DTPA-enhanced MRI are inhomogeneity of enhancement, intra-lesional non-enhancing areas, and relatively late enhancement of a pseudocapsule. Taking the degree of enhancement to be representative of the degree of vascularity, we also conclude that HCC can appear either hypervascular or hypovascular in the early phase of the dynamic study. Correspondence to: B. Hamm     

MR imaging of head and neck vascular malformations.

Between 1980 and 1990, 150 patients with cervicofacial vascular malformations were studied at the authors' institution with computed tomography, plain radiography, and angiography. Since 1989, 34 of these patients have also undergone magnetic resonance (MR) imaging. Capillary-venous hemangiomas seem to be the best indication for the adjunctive use of MR imaging. The venous pouches, characteristic of this type of lesion, cause elevated signal intensity, well seen on the T2-weighted images. Excellent fat and muscle differentiation with MR imaging allows appreciation of the depth of extension of these lesions and their delimitation from normal tissue. Arteriovenous malformations (AVMs) are characterized by serpentine signal voids, indicative of the high flow rate of these lesions. Delimitation of the AVM nidus in the midst of the afferent and efferent dilated vessels is often difficult. Study of immature angiomas with MR imaging should be restricted to lesions in specific locations (eg, orbital, laryngeal). Lymphatic malformations showed either tissular or cystic signal intensity changes. MR imaging does not replace other studies but represents an important complementary study for the delineation and diagnosis of deep extensions of vascular malformations, allowing better planning of therapy.     

Intracranial and Spinal Ependymomas: Review of MR Images in 61 Patients

Objective

To compare the age distribution and characteristic MR imaging findings of ependymoma for each typical location within the neuraxis.

Materials and Methods

During a recent eleven-year period, MR images of 61 patients with histologically proven ependymomas were obtained and retrospectively reviewed in terms of incidence, peak age, location, size, signal intensity, the presence or absence of cyst and hemorrhage, enhancement pattern, and other associated findings.

Results

Among the 61 patients, tumor location was spinal in 35 (57%), infrartentorial in 19 (31%), and supratentorial in seven (12%). In four of these seven, the tumor was located in brain parenchyma, and in most cases developed between the third and fifth decade. Approximately half of the infratentorial tumors occurred during the first decade. The signal intensity of ependymomas was non-specific, regardless of their location. A cystic component was seen in 71% (5/7) of supratentorial, 74% (14/19) of infratentorial, and 14% (5/35) of spinal cord tumors. Forty-nine percent (17/35) of those in the spinal cord were associated with rostral and/or caudal reactive cysts. Intratumoral hemorrhage occurred in 57% (4/7) of supratentorial, 32% (6/19) of infratentorial, and 9% (3/35) of spinal cord tumors. In 17% (6/35) of spinal ependymomas, a curvilinear low T2 signal, suggesting marginal hemorrhage, was seen at the upper and/or lower margins of the tumors. Peritumoral edema occurred in 57% (4/7) of supratentorial, 16% (3/19) of infratentorial and 23% (8/35) of spinal cord tumors. Seventy-two percent (5/7) of supratentorial and 95% (18/19) of infratentorial tumors showed heterogeneous enhancement, while in 50% (17/34) of spinal cord tumors, enhancement was homogeneous.

Conclusion

Even though the MR imaging findings of ependymomas vary and are nonspecific, awareness of these findings, and of tumor distribution according to age, is helpful and increases the likelihood of correct preoperative clinical diagnosis.