Intravenous Administration Of Gadopentetate Dimeglumine Research Articles

Case 273.

HistoryA 55-year-old man with a history of chronic pancreatitis secondary to chronic alcohol abuse presented to the hospital with acute abdominal pain, generalized weakness, weight loss, and pyrexia. A clinical examination revealed he was tender to touch in the upper abdomen. Laboratory tests revealed a serum alkaline phosphatase level of 370 U/L (6.1 µkat/L) (normal range, 30-130 U/L [0.5-2.2 µkat/L]), a lipase level of 172 U/L (2.9 µkat/L) (normal range, 0-60 U/L [0-1.0 µkat/L]), a C-reactive protein level of 159 mg/L (1514 nmol/L) (normal value, <8.0 mg/L [76.2 nmol/L]), and a white cell count of 7 × 109/L (normal range, [4-11] × 109/L). During the present admission, the patient underwent urgent CT for his acute symptoms. His relevant medical history included a hospital admission 2 months earlier for abdominal discomfort. Given his history of chronic pancreatitis, baseline abdominal MRI was performed to determine the cause of his symptoms and to assess the pancreas (Figs 1-3).Figure 1a:(a, b) Images from axial fat-suppressed T2-weighted MRI (repetition time msec/echo time msec, 1000/87; section thickness, 6 mm) of the upper abdomen obtained 2 months prior to admission. (c, d) Images from axial fat-suppressed T1-weighted MRI (3.69/1.62; section thickness, 4 mm) of the upper abdomen acquired 60 seconds after intravenous administration of gadopentetate dimeglumine (0.1 mL per kilogram of body weight; Magnevist; Bayer Healthcare, East Mississauga, Ontario) during the current admission.Figure 1b:(a, b) Images from axial fat-suppressed T2-weighted MRI (repetition time msec/echo time msec, 1000/87; section thickness, 6 mm) of the upper abdomen obtained 2 months prior to admission. (c, d) Images from axial fat-suppressed T1-weighted MRI (3.69/1.62; section thickness, 4 mm) of the upper abdomen acquired 60 seconds after intravenous administration of gadopentetate dimeglumine (0.1 mL per kilogram of body weight; Magnevist; Bayer Healthcare, East Mississauga, Ontario) during the current admission.Figure 1c:(a, b) Images from axial fat-suppressed T2-weighted MRI (repetition time msec/echo time msec, 1000/87; section thickness, 6 mm) of the upper abdomen obtained 2 months prior to admission. (c, d) Images from axial fat-suppressed T1-weighted MRI (3.69/1.62; section thickness, 4 mm) of the upper abdomen acquired 60 seconds after intravenous administration of gadopentetate dimeglumine (0.1 mL per kilogram of body weight; Magnevist; Bayer Healthcare, East Mississauga, Ontario) during the current admission.Figure 1d:(a, b) Images from axial fat-suppressed T2-weighted MRI (repetition time msec/echo time msec, 1000/87; section thickness, 6 mm) of the upper abdomen obtained 2 months prior to admission. (c, d) Images from axial fat-suppressed T1-weighted MRI (3.69/1.62; section thickness, 4 mm) of the upper abdomen acquired 60 seconds after intravenous administration of gadopentetate dimeglumine (0.1 mL per kilogram of body weight; Magnevist; Bayer Healthcare, East Mississauga, Ontario) during the current admission.Figure 2:Coronal T2-weighted MRI (repetition time msec/echo time msec, 1000/89; section thickness, 4 mm) of the upper abdomen obtained 2 months prior to admission.Figure 3:Coronal CT image of the abdomen acquired 60 seconds after administration of intravenous contrast material (100 mL of iohexol, Omnipaque 350; GE Healthcare, Princeton, NJ). This CT examination was performed during the current admission.

Neurotoxic Manifestations of an Overdose Intrathecal Injection of Gadopentetate Dimeglumine

The intravenous administration of gadopentetate dimeglumine (GD) is relatively safe and rarely causes systemic toxicity in the course of routine imaging studies. However, the general safety of intrathecal GD has not been established. We report a very rare case of an overdose intrathecal GD injection presenting with neurotoxic manifestations, including a decreased level of consciousness, global aphasia, rigidity, and visual disturbance.

MR Imaging of Prostate after Treatment with High-Intensity Focused Ultrasound

To prospectively evaluate magnetic resonance (MR) imaging findings after high-intensity focused ultrasound (HIFU) treatment of the prostate and to correlate them with clinical and histologic findings. Local ethics committee approval and informed consent were obtained. Fifteen consecutive men aged 46-70 years with organ-confined prostate cancer underwent ultrasonographically guided ablation of the whole prostate. Postoperative MR images were obtained within 1 month (12 patients), at 1-3 months (five patients), and in all patients at 6 months. Prostate volume was measured on T2-weighted images, and enhancing tissue was measured on dynamic images after intravenous administration of gadopentetate dimeglumine. Prostate-specific antigen (PSA) level was measured at regular intervals, and transrectal biopsy was performed in each patient at 6 months after treatment. Initial post-HIFU images showed a central nonenhancing area, surrounded by an enhancing rim. At 6 months, the prostate was small (median volume reduction, 61%) and was of predominantly low signal intensity on T2-weighted images. The volume of prostate enhancing on the initial posttreatment image correlated well with serum PSA level nadir (Spearman r = 0.90, P < .001) and with volume at 6 months (Pearson r = 0.80, P = .001). The three patients with the highest volume of enhancing prostate at the initial posttreatment acquisition had persistent cancer at 6-month biopsy. MR imaging results of the prostate show a consistent sequence of changes after treatment with HIFU and can provide information to the operator about completeness of treatment.

Imaging meningiomas: Is there a need for post-contrast FLAIR?

The aim of this study was to compare post-contrast fluid-attenuated inversion recovery (FLAIR) imaging with post-contrast T1-weighted images (T1WI) in depicting meningiomas. Twenty-nine patients with 46 meningiomas were included in this study. FLAIR and T1WI were obtained before and after intravenous administration of gadopentetate dimeglumine. The contrast enhancement degree, contrast enhancement pattern, lesion conspicuity, and the detection of the dural sign were compared between post-contrast FLAIR images and post-contrast T1WI. The enhencement degree on FLAIR was equal or less than T1WI for all meningiomas. Among 46 meningiomas 38 (83%) enhanced homogeneously and eight (17%) inhomogeneously on T1WI. On contrast-enhanced FLAIR images, of the total 46 meningiomas 22 (48%) enhanced homogeneously, eight (17%) inhomogeneously, whereas 14 (30%) meningiomas showed a peripheral rim enhancement not observed on T1WI. Two (5%) meningiomas showed no contrast enhancement on post-contrast FLAIR images. Among the 14 meningiomas showing rim enhancement using FLAIR imaging, 12 (85%) were measured to be 2 cm or more in diameter. A dural tail sign was found in 16 (35%) and 23 (50%) meningiomas on post-contrast T1WI and FLAIR images, respectively. In contrast to other extra-axial diseases, post-contrast FLAIR sequence was not found to be a valuable adjunct to contrast-enhanced T1WI in the depiction of meningiomas.

Neural network approach to the segmentation and classification of dynamic magnetic resonance images of the breast: Comparison with empiric and quantitative kinetic parameters 1

An artificial neural network (ANN)-based segmentation method was developed for dynamic contrast-enhanced magnetic resonance (MR) imaging of the breast and compared with quantitative and empiric parameter mapping techniques. The study population was composed of 10 patients with seven malignant and three benign lesions undergoing dynamic MR imaging of the breast. All lesions were biopsied or surgically excised, and examined by means of histopathology. A T1-weighted 3D FLASH (fast low angle shot sequence) was acquired before and seven times after the intravenous administration of gadopentetate dimeglumine at a dose of 0.1 mmol/kg body weight. Motion artifacts on MR images were eliminated by voxel-based affine and nonrigid registration techniques. A two-layered feed-forward back-propagation network was created for pixel-by-pixel classification of signal intensity-time curves into benign/malignant tissue types. ANN output was statistically compared with percent-enhancement (E), signal enhancement ratio (SER), time-to-peak, subtracted signal intensity (SUB), pharmacokinetic parameter rate constant (k(ep)), and correlation coefficient to a predefined reference washout curve. ANN was successfully applied to the classification of breast MR images identifying structures with benign or malignant enhancement kinetics. Correlation coefficient (logistic regression, odds ratio [OR] = 12.9; 95% CI: 7.7-21.8), k(ep) (OR = 1.8; 95% CI: 1.2-2.6), and time-to-peak (OR = 0.45; 95% CI: 0.3-0.7) were independently associated to ANN output classes. SER, E, and SUB were nonsignificant covariates. ANN is capable of classifying breast lesions on MR images. Mapping correlation coefficient, k(ep) and time-to-peak showed the highest association with the ANN result.

Transvenous Embolization of Dural Arteriovenous Fistula of the Cavernous Sinus

We reviewed magnetic resonance (MR) images and digital subtraction angiograms (DSA) from eight patients with dural arteriovenous fistula of the cavernous sinus (DAVFCS) to clarify the fistulous points and to evaluate the venous access routes into the cavernous sinus for transvenous embolization (TVE). Multiplanar reconstruction of the MR images was achieved using three-dimensional fast spoiled gradient-recalled acquisition in the steady state (3-D fast SPGR) after the intravenous administration of gadopentetate dimeglumine (Gd-DTPA). TVE was performed using microcoils via the inferior petrosal sinus (IPS) using the transfemoral approach in five patients, via the facial vein and superior ophthalmic vein (SOV) using the transfemoral approach in 1 patient, and by SOV puncture in two patients. Most fistulas were detected in the posterior portion of the cavernous sinus or in the posterior intercavernous sinus in all of the patients. Fistulas identified as hyperintense dots or lines on contrast-enhanced 3-D fast SPGR images and were replaced with the microcoils. Target embolization of the fistulas was feasible in three patients treated via the SOV and in one patient treated via the IPS. Contrast- enhanced 3-D fast SPGR can help to identify the fistulous points of DAVFCS. Precise identification of fistulous points and selection of the adequate access route are mandatory for efficient TVE of DAVFCS.

Magnetic resonance imaging in the diagnosis of melanoma: in vivo preliminary studies with dynamic contrast-enhanced subtraction.

The aim of this study was to analyse the potential of fast dynamic subtraction magnetic resonance (MR) imaging in differentiating in vivo melanomas from benign melanocytic lesions. Dynamic MR imaging was performed after intravenous administration of gadopentetate dimeglumine (Gd-DTPA) in 18 patients with melanocytic skin lesions. Using a post-processing algorithm, time-signal intensity curves were obtained for the lesions and classified according to their shapes as type I (steady enhancement increase), type II (plateau of signal intensity) or type III (wash-out of signal intensity). Other parameters evaluated for their potential to differentiate melanomas from benign lesions were the enhancement rate (percentage of signal intensity increase) in the first minute after Gd-DTPA administration, the peak value of the enhancement rate, and the wash-out slope. The pigmented lesions were then surgically excised and the MR results compared with the histological assessment. In melanomas, the mean value of the enhancement rate in the first minute was 611%, whereas in benign lesions it was 131% (P = 0.001). The distribution of curve types was also different: seven of the nine naevi showed type I curves, while eight of the nine melanomas displayed a type III curve. In addition, distinctive wash-out dynamics were observed: the enhancement rate began to decrease between the first and third minutes for melanomas, but continued to increase until the sixth minute for naevi (P = 0.000). These findings, which are most likely related to the neoangiogenesis present in melanomas, indicate that dynamic MR imaging can be helpful in the differential diagnosis of pigmented skin lesions.

Noninvasive measurement of extraction fraction and single-kidney glomerular filtration rate with MR imaging in swine with surgically created renal arterial stenoses.

To test whether magnetic resonance (MR) imaging enables accurate measurement of extraction fraction (EF) in swine with unilateral renal ischemia and to evaluate effects of renal arterial stenosis on EF and single-kidney glomerular filtration rate. High-grade unilateral renal arterial stenoses were surgically created in eight pigs. Direct measurements of renal venous and arterial inulin concentration provided reference standard estimates of single-kidney EF. Pigs were imaged with a 1.5-T imager to estimate EF, renal blood flow, and glomerular filtration rate. A breath-hold inversion-recovery spiral sequence was used to measure T1 of blood in the infrarenal inferior vena cava and renal veins after intravenous administration of gadopentetate dimeglumine, and these data were used to calculate EF. Cine-phase contrast material-enhanced imaging of the renal arteries provided quantitative renal blood flow measurements. Bilateral single-kidney glomerular filtration rate was then determined: glomerular filtration rate = renal blood flow x (1 - hematocrit level) x EF. A statistically significant linear correlation was found between EF, as determined with MR imaging, and inulin (r = 0.77). As compared with kidneys without renal arterial stenosis, kidneys with renal arterial stenosis showed 50% (0.14/0.28) EF reduction (P <.01) and 59% glomerular filtration rate reduction (P <.01). MR imaging shows promise for in vivo measurement of EF and glomerular filtration rate, which may be useful in assessing the clinical importance of renal arterial stenosis.

Scaphoid blood flow and acute fracture healing

We have investigated whether assessment of blood flow to the proximal scaphoid can be used to predict nonunion in acute fractures of the scaphoid. We studied 32 fractures of the scaphoid one to two weeks after injury, by dynamic fat-suppressed T1-weighted gradient-echo MRI after the intravenous administration of gadopentetate dimeglumine (0.1 mmol/kg body-weight). Steepest slope values (SSV) and percentage enhancement values (%E) were calculated for the distal and proximal fragments and poles. All the fractures were treated by immobilisation in a cast, and union was assessed by CT at 12 weeks. Nonunion occurred in four fractures (12%), and there was no statistically significant difference between the proximal fragment SSV and %E values for the fractures which united and those with nonunion. The difference between the proximal pole SSV and %E values for the union and nonunion groups reached statistical significance (p &lt; 0.05), but with higher enhancement parameters for the nonunion group. Our results suggest that poor proximal vascularity is not an important determinant of union in fractures of the scaphoid.

Scaphoid blood flow and acute fracture healing. A dynamic MRI study with enhancement with gadolinium.

We have investigated whether assessment of blood flow to the proximal scaphoid can be used to predict nonunion in acute fractures of the scaphoid. We studied 32 fractures of the scaphoid one to two weeks after injury, by dynamic fat-suppressed T1-weighted gradient-echo MRI after the intravenous administration of gadopentetate dimeglumine (0.1 mmol/kg body-weight). Steepest slope values (SSV) and percentage enhancement values (%E) were calculated for the distal and proximal fragments and poles. All the fractures were treated by immobilisation in a cast, and union was assessed by CT at 12 weeks. Nonunion occurred in four fractures (12%), and there was no statistically significant difference between the proximal fragment SSV and %E values for the fractures which united and those with nonunion. The difference between the proximal pole SSV and %E values for the union and nonunion groups reached statistical significance (p < 0.05), but with higher enhancement parameters for the nonunion group. Our results suggest that poor proximal vascularity is not an important determinant of union in fractures of the scaphoid.

MR Appearance of Metastatic Melanotic Melanoma in the Breast: Case Reports

A 34-year-old Chinese woman complaining of multiple breast lumps was referred to a local Breast Clinic. She had malignant melanoma of the left middle finger and amputation had been performed 3 months earlier. Fine needle aspiration was performed on two of the breast lumps and they were diagnosed as melanotic melanoma. The pleomorphic malignant cells were immunoreactive for S100 protein and HMB 45. Ultrasound (US) was later performed which showed more than five well circumscribed hypoechoic masses, ranging in size from 0.5 to 1.5 cm, in both breasts. Mammography was performed, which showed three medium density well circumscribed masses in the right breast. There was no axillary adenopathy. Magnetic resonance imaging (MRI) of both breasts was performed with a 1.5T superconductive MR imager (Signa Advantage, GE Medical Systems, Milwaukee, U.S.A.) and a bilateral phased array breast coil. Pre-contrast medium axial T1-weighted spin-echo (TR/TE 1⁄4 500/12) with fat saturation and sagittal T2-weighted fast spin-echo (TR/TE 1⁄4 3440/126, ETL 1⁄4 12) images were acquired with 4 mm thick sections, 1 mm gap, a 256 × 192 matrix and two excitations. After intravenous administration of gadopentetate dimeglumine (0.2 mmol/kg), fat-suppressed axial T1-weighted spinecho images were taken. There were more than five abnormal masses in both breasts, ranging in size from 0.5 to 1.5 cm. The masses yielded high signal on T1-weighted (Fig. 1), low signal on T2-weighted (Fig. 2) and showed decreased signal intensity after contrast medium injection (Fig. 3). In the clinical work-up, there was no evidence of other metastases. Bilateral mastectomy was performed. A specimen photograph was taken (Fig. 4) and MRI was performed (Fig. 5). The patient was followed-up in the Breast Clinic.

Pulmonary disorders: ventilation-perfusion MR imaging with animal models.

To demonstrate the capability of magnetic resonance (MR) imaging to assess alteration in regional pulmonary ventilation and perfusion with animal models of airway obstruction and pulmonary embolism. Airway obstruction was created by inflating a 5-F balloon catheter into a secondary bronchus. Pulmonary emboli were created by injecting thrombi into the inferior vena cava. Regional pulmonary ventilation was assessed with 100% oxygen as a T1 contrast agent. Regional pulmonary perfusion was assessed with a two-dimensional fast low-angle shot, or FLASH, sequence with short repetition and echo times after intravenous administration of gadopentetate dimeglumine. Matched ventilation and perfusion abnormalities were identified in all animals with airway obstruction. MR perfusion defects without ventilation abnormalities were seen in all animals with pulmonary emboli. Ventilation and perfusion MR imaging are able to provide regional pulmonary functional information with high spatial and temporal resolution. The ability of MR imaging to assess both the magnitude and regional distribution of pulmonary functional impairment could have an important effect on the evaluation of lung disease.

Uniform fat suppression in hands and feet through the use of two-point Dixon chemical shift MR imaging.

To assess the potential of two-point Dixon chemical shift magnetic resonance imaging to achieve uniform fat suppression in the distal parts of the extremities. Two-point Dixon chemical shift imaging was performed in 31 consecutive patients clinically suspected to have bone marrow disease. In some patients, Dixon studies were performed before and after the intravenous administration of gadopentetate dimeglumine, and in some patients follow-up examinations were performed, for a total of 64 studies. Areas of interest were the hand, wrist, foot, ankle, and lower leg. There was a special interest in the neuropathic foot and osteomyelitis. The uniformity of fat suppression in the entire field of view, the frequency of displacement artifacts, and the applicability of the technique in routine patient treatment were evaluated. In 64 (100%) Dixon studies, uniform fat suppression was achieved. In 59 (92%) studies, there were no displacement artifacts. In five (8%) studies, displacement artifacts occurred; however, in only one (2%) study did they severely hamper the reading. Thus, in 63 (98%) studies, adequate diagnostic quality was obtained. Two-point Dixon chemical shift imaging is a good technique for achieving uniform fat suppression in the distal parts of the extremities. Because the frequency of displacement artifacts is low, the technique is applicable in a routine clinical setting.

Detection of mass lesions with MR colonography: preliminary report.

To evaluate the performance of magnetic resonance (MR) colonography in the detection of colorectal mass lesions. Twenty-three patients underwent MR colonography preceding colonoscopy. The colon was filled with a gadolinium-water mixture (1:100) with MR imaging guidance, and the patient was imaged prone and supine with a breath-hold three-dimensional spoiled gradient-recalled sequence. In addition, two-dimensional spoiled gradient-recalled images were acquired before and after intravenous administration of gadopentetate dimeglumine. Images were interactively analyzed on the basis of multiplanar reconstruction by two radiologists. For regions that were not conclusively assessable with multiplanar reconstruction, virtual intraluminal endoscopic images of the colon were reconstructed. MR findings were correlated with colonoscopic results. Two patients were excluded from the analysis. Findings in eight of 11 patients were correctly assessed as normal and in six of 10 as mass-positive. In the four patients with false-negative findings, one had two 8-mm polyps and the other three had polyps smaller than 5 mm. All nine mass lesions larger than 10 mm, as well as four of the 10 polyps ranging between 5 and 10 mm, were detected, but all polyps smaller than 5 mm were missed. In contrast to the polyps less than 5 mm, the four missed polyps (5-10 mm) could be identified retrospectively on virtual intraluminal endoscopic images. Contrast enhancement was documented in 13 polyps. Three-dimensional MR colonography provided virtual colonoscopic viewing and helped detection of colonic polyps.

MRI of the TMJ disc with intravenous administration of gadopentetate dimeglumine.

The purpose of this study was to ascertain whether MR imaging with intravenous administration of gadopenetate dimeglumine (Gd-DTPA) is useful in the demonstration of the temporomandibular joint (TMJ) disc. Sagittal T1-weighted MR images of 50 TMJs (25 patients) were obtained using a 0.5-T system both before and after intravenous injection of Gd-DTPA. The authors depicted the TMJ in which intravenous injection of Gd-DTPA improved visulization of the disc. Intravenous injection of Gd-DTPA increased intensity in the retrodiscal space, the pterygoid venous plexus, as well as joint effusion by diffused Gd-DTPA. The technique improved visualization of 10 (50%) of 20 normal discs and 20 (67%) of 30 anterior disc displacements in closed-mouth position, and also 23 (74%) of 31 normal discs and 12 (63%) of 19 anterior disc displacements in open-mouth position. There were 12 TMJs (24% of the 50 TMJs) in which equivocal findings became highly diagnostic. The incidence in marked contrast effect was higher in TMJs with severe internal derangement than in those with normal or mild internal derangement (p < 0.005). Using a 0.5-T MR imager, T1-weighted imaging with intravenous injection of Gd-DTPA showed more anatomic details than imaging without the contrast agent.

Differentiation of benign and malignant breast lesions: MR imaging versus Tc-99m sestamibi scintimammography.

To compare the accuracies of magnetic resonance (MR) imaging and scintimammography in differentiating benign from malignant breast lesions. MR imaging was performed in 66 women with 75 lesions during intravenous administration of gadopentetate dimeglumine. Planar and single photon emission computed tomographic (SPECT) scintimammography were performed (with 740 MBq technetium-99m sestamibi administered intravenously) in all 66 patients with 75 lesions and in 64 patients with 73 lesions, respectively. MR imaging and scintimammographic studies were independently evaluated by using signal intensity measurements versus time or focal tracer uptake to differentiate benign from malignant lesions. Histopathologic proof was obtained in 63 lesions. Twelve lesions were monitored with follow-up. MR imaging was false-negative in one and false-positive in nine lesions. Planar scintimammography was false-negative in 10 and false-positive in six lesions. SPECT scintimammography was false-negative in four and false-positive in 10 lesions. Sensitivities and specificities for malignancy were, respectively, 96% and 82% for MR imaging, 62% and 88% for planar scintimammography, and 83% and 80% for SPECT scintimammography. Both MR imaging and scintimammography are useful in the evaluation of breast cancer. MR imaging is more sensitive and as specific as scintimammography.

MR imaging of the adult elbow.

Magnetic resonance (MR) imaging can provide important diagnostic information in the evaluation of the adult elbow. Optimal imaging technique should include the use of proper positioning, surface coils, and appropriate sequences and imaging planes as indicated by the suspected abnormalities. A familiarity with the anatomy of the normal elbow is crucial to identifying pathologic entities correctly and avoiding diagnostic pitfalls. Disruption of the collateral ligaments can best be demonstrated with thin-section coronal gradient-echo MR images. Injuries to the flexor and extensor muscle groups, biceps muscles, and triceps muscles require T2-weighted or short-inversion-time inversion recovery (STIR) MR images in the long and short axes of the affected muscle. The evaluation of osteochondral lesions and intraarticular bodies is optimized with T1-weighted and STIR MR images. Synovial processes usually necessitate the intravenous administration of gadopentetate dimeglumine to distinguish joint fluid from pannus. The contents of the cubital tunnel are best visualized on axial T1-weighted and STIR MR images. Masses arising in or near the elbow should be imaged with multiple sequences in at least two planes, and involvement of adjacent vital structures should be carefully evaluated.

Detecting pulmonary abnormalities on magnetic resonance images in patients with usual interstitial pneumonitis: Effect of varying window settings and gadopentetate dimeglumine

We examined the effect of varying window settings and contrast enhancement on detecting pulmonary abnormalities on magnetic resonance (MR) images in patients with usual interstitial pneumonitis (UIP). HRCT scans and MR images from 10 patients with UIP were evaluated. T1-weighted MR images were obtained before and after administration of gadopentetate dimeglumine and were photographed at conventional windows and at windows chosen to increase the conspicuity of the lung parenchyma ("lung windows"). The four MR image configurations were mixed with the high-resolution computed tomography (HRCT) scans of these patients and randomized. Corresponding scan levels in each patient were evaluated conjointly by two thoracic radiologists for the presence of "honeycomb lung," ground-glass opacity, parenchymal bands, and reticular abnormalities. Lung signal intensity in areas containing ground-glass signal intensity was measured on MR images using regions of interest. The administration of gadopentetate dimeglumine significantly improved the detection of honeycomb lung on scans photographed at lung windows, but it did not significantly influence the detection of ground-glass abnormalities. The use of lung windows improved the detection of ground-glass abnormalities for both enhanced and unenhanced scans, but lung windows improved the detection of honeycomb lung only for enhanced scans. All MR image configurations were insensitive compared with HRCT scans for detecting parenchymal bands and reticular abnormalities. There was a good correlation between measured lung signal intensity and visual ground-glass profusion score. The visibility of pulmonary abnormalities on MR images of patients with UIP is limited compared with that of HRCT scans. The improved visibility of some parenchymal abnormalities after intravenous administration of gadopentetate dimeglumine and with the use of lung windows is insufficient to warrant their routine use in thoracic MR imaging.

Failure of gadopentetate dimeglumine-enhanced, high-resolution magnetic resonance imaging to differentiate among melanin-containing skin tumors.

We evaluated the diagnostic potential of gadopentetate dimeglumine-enhanced, high-resolution magnetic resonance (MR) imaging to differentiate benign from malignant melanin-containing skin tumors. Forty-five patients were prospectively examined using high-resolution MR imaging at 1.5 T using a 2.5-cm surface coil. For tumor assessment, T1-weighted and T2-weighted transverse spin-echo sequences were acquired. After intravenous administration of gadopentetate dimeglumine (0.1 mmol/kg), the T1-weighted transverse sequence was repeated. Contrast enhancement was quantitatively determined as the percentage increase of signal intensity. Histologic findings were correlated using the Wilcoxon signed-ranks test. The quality of contrast enhancement was assessed by three independent investigators who were unaware of the patients' history and histologic data. The signal-to-noise ratio (SNR) was calculated in the T2-weighted sequence. Significance was tested using the Wilcoxon signed-ranks test. In all tumors, contrast enhancement was visually discernible. Half of the cases were enhanced inhomogeneously. The percentage of contrast enhancement did not correlate with histologic findings. Malignant melanomas could not be differentiated from benign melanocytic nevi with the use of gadopentetate dimeglumine. Determination of the SNR in T2-weighted sequences revealed no significant difference for histologic subgroups or tumor type. Gadopentetate dimeglumine-enhanced MR imaging does not differentiate malignant melanomas from benign melanocytic nevi. Determination of the SNR in the T2-weighted sequences revealed no significant difference for histologic subgroups.

Type A dissection of the thoracic aorta: use of MR imaging for long-term follow-up.

To evaluate routine magnetic resonance (MR) imaging for long-term follow-up in patients who undergo surgery for type A aortic dissection. Ninety-two MR examinations were performed in 36 patients. Standard spin-echo images were obtained with electrocardiographic gating (n = 92) and rapid images with a fast low-angle shot sequence and intravenous administration of gadopentetate dimeglumine (n = 25). All segments of the native thoracic aorta were evaluated. Anastomoses of the prosthesis and periprosthetic hematoma were carefully analyzed. Of 22 complications that occurred in 18 patients, 18 were diagnosed at MR imaging (nine false aneurysms and nine aneurysms distal to the graft). Nine patients underwent reoperation. The findings at MR imaging correlated with those at surgery. Routine follow-up with MR imaging should improve long-term survival in patients who survive emergency surgical repair of type A aortic dissection.