Ultrafast MR imaging of the pelvis

MR gradient systems with higher slew rates and gradient amplitude enable certain forms of imaging that are not practical with older gradient systems. These newer pulse sequences include single shot half-Fourier T2-weighted images and echo planar imaging. More important in MR imaging of the pelvis, these gradient systems benefit more conventional imaging methods such as gadolinium-enhanced 3D MR angiography, dynamic gradient echo contrast-enhanced images, and T2-weighted fast spin echo images, by shortening echo times. For most MR imaging of the pelvis, spatial resolution is paramount, and therefore sequences such as half-Fourier acquisition Turbo spin echo (HASTE) and 3D gadolinium-enhanced dynamic imaging play a less important role than in the upper abdomen. The potential of these techniques for diffusion or perfusion studies in the pelvis has not been explored.

Safety profile of ultrasmall superparamagnetic iron oxide ferumoxtran-10: phase II clinical trial data

The safety data from the phase II clinical trial of ferumoxtran-10, an ultrasmall superparamagnetic iron oxide contrast agent, are presented. One hundred and four patients with focal liver or spleen pathologies underwent ferumoxtran-10-enhanced magnetic resonance (MR) imaging at doses of 0.8, 1.1, and 1.7 mg Fe/kg. Overall, 15% patients reported a total of 33 adverse events, regardless of causality. The adverse events most frequently seen were dyspnea (3.8%), chest pain (2.9%), and rash (2.9%). No serious adverse events were reported during the 48 hour observation period. There were no clinically significant effects on vital signs, physical examination, and laboratory results. Ferumoxtran-10 is a safe and well tolerated MR contrast agent.

Aggressive angiomyxoma: findings on CT and MR imaging

OBJECTIVE

Aggressive angiomyxoma is a benign tumor affecting the pelvis and perineum, predominantly in women. Because of its variable presentation as a soft mass in the vulva, perianal region, buttock, or pelvis, the tumor is often clinically misdiagnosed and initial surgery is usually unsuccessful in extirpating it. This study describes the imaging features of these tumors.

CONCLUSION

Aggressive angiomyxomas display unusual growth patterns of translevator extension with growth around perineal structures. Both CT and MR imaging show the transdiaphragmatic extent of these tumors. High signal intensity on T2-weighted MR images may reflect the myxomatous stroma of these tumors.

Perirectal cystic paragonimiasis: endorectal coil MRI

We report the transrectal ultrasonographic (TRUS) and endorectal surface coil MR findings for paragonimiasis involving the perirectal space. The patient presented with voiding difficulty. TRUS showed a well demarcated, oval-shaped hyperechoic mass in the perirectal space. On endorectal MR images, the lesion was depicted as a well defined cystic mass with homogeneous intermediate signal intensity on T1-weighted images and heterogeneous hyperintensity on T2-weighted images. Ectopic paragonimiasis can appear as a well defined cystic mass in the peritoneum and should be included in the differential diagnosis of cystic mass in the abdomen and pelvic cavity, including the perirectal space.

Ovarian Brenner tumors: MR imaging characteristics

This study describes the appearance of Brenner tumors on MR imaging and compares quantitative signal intensity measurements of Brenner tumors with that of other ovarian tumors. A search of pathologic and MR records disclosed patients who had MRIs showing Brenner tumors prior to surgical excision. Patients (21) with other surgically proven ovarian masses were randomly selected for comparison. MR imaging was performed at 1.5 T with phased array multicoils and fast spin echo T2-weighted images. Region-of-interest measurements of signal intensity (SI) were made to calculate signal intensity ratios (SIR = mass SI/muscle SI). Brenner tumors showed significantly lower SIR than other tumors on T2-weighted images (p = 0.004) and similar SIR on T1-weighted images. Brenner tumors show lower signal intensity on T2-weighted images than other non-fibrous ovarian tumors. This lower signal intensity may result from the extensive fibrous content of these tumors.

Detection of lipid in abdominal tissues with opposed-phase gradient-echo images at 1.5 T: techniques and diagnostic importance

T1-weighted gradient-echo magnetic resonance images can be acquired with an echo time such that water and lipid spins are in phase or opposed phase. Observation of relative loss of signal intensity on opposed-phase images compared with that on in-phase images allows qualitative assessment of relatively small amounts of lipid in tissues. Conversely, frequency-selective fat saturation techniques are useful primarily for identifying predominantly fatty masses such as angiomyolipomas. Both in-phase and opposed-phase images should be acquired with similar parameters because unequivocal identification of lipid requires comparison with in-phase images to control for T1 and T2* effects. Opposed-phase imaging has been used to differentiate adrenal adenomas, which contain lipid, from adrenal metastases, which do not. The technique can be expanded to examine a spectrum of intraabdominal tumors and conditions that are characterized by intracellular lipid. These include hepatic steatosis, hepatocellular neoplasms, myelolipoma, adrenocortical carcinoma, angiomyolipoma, and renal cell carcinoma. In liver masses, the presence of lipid is largely restricted to primary hepatocellular tumors. Renal and adrenal masses may contain focal fat (angiomyolipomas and myelolipomas, respectively) or diffuse lipid (clear cell renal carcinomas and adenomas, respectively).

Sex cord-stromal and steroid cell tumors of the ovary

Gonadal cell types that derive from the coelomic epithelium (sex cords) or mesenchymal cells of the embryonic gonads include granulosa cells, theca cells, fibroblasts, Leydig cells, and Sertoli cells. Ovarian tumors of these cell types are called sex cord-stromal tumors. This group of tumors represents approximately 8% of ovarian neoplasms and affects all age groups. The more common types are granulosa cell tumors (GCTs), fibrothecomas, and Sertoli-Leydig cell tumors. Sex cord-stromal tumors are of interest partly because of their hormonal effects, which are rare for other ovarian neoplasms. These effects include estrogenic effects (pseudoprecocious puberty, endometrial bleeding, endometrial hyperplasia and carcinoma) and virilization. The variety of gross appearances of these tumors, ranging from large multicystic masses to small solid masses, would appear to preclude a specific radiologic diagnosis. However, in many patients, both clinical and radiologic clues can suggest the diagnosis, including predominantly fibrous content at ultrasound or magnetic resonance imaging (fibrothecoma), large hemorrhagic multicystic mass in a child with pseudoprecocious puberty (juvenile GCT), and associated syndromes such as Peutz-Jeghers syndrome (sex cord tumor with annular tubules) or Ollier disease and Maffucci syndrome (juvenile GCT).

Dilated fallopian tubes: MR imaging characteristics

PURPOSE

To determine the magnetic resonance (MR) imaging characteristics of hydrosalpinx and the accuracy of MR imaging for distinguishing hydrosalpinx from other adnexal masses.

MATERIALS AND METHODS

Cross-referencing of pathologic records and MR studies from two institutions disclosed 41 study patients with surgically proved dilated fallopian tubes. A set of 38 patients with surgically evaluated adnexal masses, but no hydrosalpinx, were randomly chosen as control subjects. All MR examinations included T1-weighted spin-echo and T2-weighted fast spin-echo imaging in multiple planes with a phased-array multicoil. Two blinded readers scored each adnexa for the presence of a dilated fallopian tube or thickened tubal wall and mucosal folds and the signal intensity of the intratubal fluid. Blinded readings were compared with surgical findings of dilated fallopian tube, endometriosis, and salpingitis. Radiologic-pathologic correlation was performed with adnexal specimens imaged in vitro in three study patients.

RESULTS

On a per patient basis, the blinded readers correctly identified dilated fallopian tubes in 31 of 41 study patients and correctly excluded dilated tubes in a mean 34 of 38 control subjects. On T1-weighted images, hyperintense tubal fluid was significantly correlated with the presence of endometriosis in the pelvis at surgery (P < .002, chi 2).

CONCLUSION

MR imaging can depict most dilated fallopian tubes and differentiate them from other adnexal masses on the basis of morphologic features. On T1-weighted images, high signal intensity is correlated with the presence of endometriosis affecting the tube.

Progressive viral-induced cirrhosis: serial MR imaging findings and clinical correlation

PURPOSE

To determine which magnetic resonance (MR) imaging findings of cirrhosis change as disease severity progresses.

MATERIALS AND METHODS

Seventy-six abdominal MR imaging studies in 38 patients (two per patient) with Child-Pugh grade A cirrhosis were retrospectively reviewed. All patients were followed up clinically and with MR imaging for 12 months or longer. MR images were used to determine volume indexes of the spleen and of each liver segment, as well as changes in hepatic contour, iron or fat deposition, and presence of varices and collateral vessels.

RESULTS

During follow-up in patients with progressive cirrhosis (n = 13), the volume indexes of the anterior, posterior, and medial segments of the liver decreased significantly (P = .011, .013, .002, respectively), and the number of varices and collateral vessels increased significantly (P = .018). In patients with stable cirrhosis (n = 25), the volume indexes of the spleen, caudate lobe, and lateral segment increased significantly (P = .032, .018, .003, respectively). The atrophic index was significantly greater in progressive cirrhosis than in stable cirrhosis (P = .009).

CONCLUSION

Progressive atrophy of the right hepatic lobe and the medial segment correlated with progression of clinical severity of cirrhosis, whereas increasing size of the caudate lobe and the lateral segment correlated with stability.

MR imaging techniques of the liver

This article reviews the currently available MR imaging techniques that are useful for the detection and characterization of focal and diffuse liver pathology. The implementation and clinical utility of various T1-weighted, T2-weighted, T2*-weighted, and MR angiographic sequences are described.

Magnetic resonance imaging of the pancreas and biliary tree

MRI of the pancreas and bile ducts is becoming more widely used due to recent advances in surface coils, breath-hold imaging techniques, and magnetic resonance cholangiopancreatography (MRCP). MRI provides a comprehensive and accurate examination for the detection, staging, and characterization of a variety of developmental, inflammatory, and neoplastic processes that involve the pancreas.

Magnetic resonance imaging of focal and diffuse hepatic disease

MRI is a powerful tool in the detection and characterization of both focal and diffuse liver pathology. Because of superior soft tissue characterization, direct multi-planar capabilities and lack of ionizing radiation, current state of the art MRI is useful when contrast CT is relatively contraindicated or not definitive. This article reviews the MRI findings of the most common focal and diffuse liver diseases encountered in clinical practice. Reviews of current MR techniques and MR contrast agents used in liver imaging have been recently published. For this article, discussion of specific techniques and use of contrast is addressed for each pathological entity discussed.

Median nerve hamartoma: MR imaging using chemical shift techniques

Magnetic resonance imaging findings of median nerve hamartoma are presented in three patients with palpable wrist masses and median neuropathy. Fat-suppressed T1-weighted images demonstrated adipose tissue separating the neural and fibrous tissue bundles in two of three patients, which results in the distinctive appearance of these tumors on magnetic resonance imaging. Fibrous tissue appeared as enhancing longitudinal bundles within the tumor on gadolinium enhanced fat-suppressed T1-weighted images.

Rapidly enhancing hepatic hemangiomas at MRI: distinction from malignancies with T2-weighted images

The purpose of this study is to describe a subset of atypical hepatic hemangiomas that enhance rapidly and diffusely and to determine whether heavily T2-weighted images could distinguish between atypically enhancing liver hemangiomas and hypervascular malignancies. A retrospective search of MR records identified seven patients with liver hemangiomas that demonstrated diffuse early enhancement and 23 patients with biopsy-proven malignant liver lesions that were hypervascular on dynamic gadolinium-enhanced MR images. Quantitative analysis of signal intensity measurements was performed on the T2-weighted images, heavily T2-weighted (TE > 140), and dynamic gadolinium-enhanced images. Blinded reader comparison of the T2-weighted images and gadolinium-enhanced images was performed. Hypervascular hemangiomas enhanced to a greater degree than hypervascular malignant liver lesions on the early phase gadolinium-enhanced images. Perilesional parenchymal enhancement was demonstrated in five cases of rapidly enhancing hemangiomas. Signal intensity and contrast-to-noise ratios on the heavily T2-weighted images of the hemangiomas were significantly greater than that of the hypervascular malignant lesions (P < .05). Hemangiomas were differentiated from the hypervascular malignant liver lesions with high accuracy (97-100%) by three blinded readers based on the T2-weighted images. A subset of hemangiomas have atypical rapid diffuse enhancement on dynamic gadolinium-enhanced images. These atypical hemangiomas can be distinguished from hypervascular malignant liver lesions on T2-weighted MR images.

Lipid in renal clear cell carcinoma: detection on opposed-phase gradient-echo MR images

PURPOSE

To determine if comparison of in-phase and opposed-phase gradient-echo magnetic resonance (MR) images enables detection of lipid in renal clear cell carcinoma.

MATERIALS AND METHODS

A retrospective search of MR and pathologic records identified 43 patients with biopsy-proved renal masses who underwent in-phase and opposed-phase MR imaging. Thirty-three patients had renal cell carcinoma (27 with clear cell carcinoma), and 10 patients had other renal tumors. With MR images, a region-of-interest measurement of signal intensity of the renal mass was divided by that of reference tissue. In each patient, a ratio of these region-of-interest measurements on the opposed-phase images to those on the in-phase images was calculated and termed the opposed-phase/in-phase signal intensity ratio (OIR).

RESULTS

The mean OIR of clear cell carcinomas was significantly different from that of other renal masses (P < .0002); in 16 (59%) of 27 patients with clear cell carcinoma, the OIR was less than 2 standard deviations below the mean OIR of other masses. In cases of clear cell carcinoma, focal signal intensity on opposed-phase images was less than that on in-phase images.

CONCLUSION

On opposed-phase images, some clear cell carcinomas show relative focal and diffuse loss of signal intensity. In renal masses, this signal intensity loss-which is consistent with lipid-does not necessarily indicate angiomyolipoma.

A multicenter clinical trial of Gadolite Oral Suspension as a contrast agent for MRI

The purpose of this study was to assess the effectiveness and safety of Gadolite Oral Suspension as a gastrointestinal (GI) contrast agent for MRI in a phase II and two phase III multicenter clinical trials. Gadolite was administered to 306 patients with known or suspected abdominal and/or pelvic disease. MRI with T1- and T2-weighted sequences was performed before and after ingestion. Efficacy was evaluated by having two masked readers rate the certainty of their MR diagnosis (0 = uncertain, 1 = probable, 2 = definite) on randomly presented pre- and post-Gadolite Oral Suspension enhanced images. Principal investigators also evaluated the images and established the final diagnosis. Vital signs, clinical chemistries, and adverse events were documented. Blood and urine samples were analyzed for gadolinium content to determine whether Gadolite Oral Suspension was absorbed systemically. Certainty in MR diagnosis increased significantly (P < .001) for both blinded readers between pre- and post-Gadolite images (.49-1.18 for reader 1: .46-1.53 for reader 2). Sensitivity, specificity, and accuracy also increased for both masked readers. No gadolinium was detected in blood or urine samples. There were no serious adverse events and no apparent drug-related trends in mean vital signs or laboratory values. Gadolite is a highly effective, safe, and well tolerated contrast agent for clinical use with MRI.

High-resolution MR imaging of the vagina

High-resolution magnetic resonance (MR) imaging with pelvic phased-array and endoluminal coils provides information on vaginal abnormalities heretofore not available with other imaging modalities. Congenital anomalies of the vagina can result from disorders of lateral fusion of the descending müllerian ducts and ascending urogenital sinus, developmental absence of the müllerian ducts, or disorders of vertical fusion. In these conditions, MR imaging can depict the presence or absence of the vagina, cervix, and uterus and help determine whether these structures contain a septum or are duplicated or distended with blood. Gartner duct cysts and Bartholin gland cysts have the same signal intensity characteristics, but the former are located in the anterolateral aspect of the proximal third of the vagina and the latter are in the posterolateral portion of the lower vagina. Entero-, vesico-, and ureterovaginal fistulas result from obstetric and surgical trauma, radiation therapy, or inflammatory bowel disease. MR imaging has great potential for detection and characterization of these fistulas. MR imaging can be used to detect and stage primary and secondary vaginal tumors. However, neither signal intensity nor patterns of enhancement enable confident prediction of the histologic subtype of vaginal malignancy.

Hepatic lesions: discrimination of nonsolid, benign lesions from solid, malignant lesions with heavily T2-weighted fast spin-echo MR imaging

PURPOSE

To determine whether the combined use of heavily and moderately T2-weighted fast spin-echo magnetic resonance (MR) images improves differentiation of non-solid, benign hepatic lesions from solid malignancies.

MATERIALS AND METHODS

Three radiologists reviewed moderately (n = 133) and heavily (n = 133) T2-weighted and multiphasic dynamic contrast material-enhanced (n = 93) MR images in 133 patients with proved focal hepatic lesions (95 benign, 38 malignant). The radiologists used a five-point scale to rate their confidence in determination of malignancy.

RESULTS

All three reviewers were statistically significantly better able to differentiate small (diameter less than 3 cm; n = 84) benignancies from small malignancies with the combination of moderately and heavily T2-weighted images (area under the receiver operating characteristic curve, 0.99 for each reader) than with moderately T2-weighted images alone (area, 0.88-0.90; P < .05). Confident diagnoses were rendered in 69 (82%) patients, with 100% accuracy for the combined use of moderately and heavily T2-weighted images. For larger lesions (diameter 3 cm or larger; n = 49), accurate differentiation was possible with moderately T2-weighted images alone. Additional use of multiphasic images did not improve the sensitivity, specificity, or accuracy of image interpretation.

CONCLUSION

The combined use of moderately and heavily T2-weighted fast spin-echo MR images improves differentiation of small benign hepatic lesions from small malignant lesions.

Compensated cirrhosis due to viral hepatitis: using MR imaging to predict clinical progression

OBJECTIVE

The goal of our study was to determine the relative value of multiple MR features in predicting clinical progression of disease in patients with compensated cirrhosis.

MATERIALS AND METHODS

The MR examinations of 23 patients with compensated cirrhosis (Child A) were retrospectively reviewed independently by two radiologists and correlated with clinical progression after follow-up of all patients for more than 12 months each (12-87 months: average, 39 months) by the same experienced hepatologist. Clinical progression was defined as an increase of the Child grade or the Pugh score by at least two points (5- to 15-point scale). In the initial MR study of each patient, the following MR findings were assessed by each radiologist independently: volume indexes of the spleen and each segment of the liver (based on three-axis measurements), nodular surface, regenerative nodules, ascites, iron or fat deposition, and varices or collaterals.

RESULTS

The volume index of the spleen was the most accurate predictor of clinical progression (p = .001), the next most accurate was the number of sites of varices or collaterals (p = .002), and the third most accurate was the ratio of caudate lobe to right lobe volume index (p = .02). Other MR findings failed to correlate with clinical progression.

CONCLUSION

As revealed on MR imaging, the volume index of the spleen, the severity of varices, and the volume index ratio of caudate lobe to right lobe can be used to help predict clinical progression of disease in patients with compensated cirrhosis.

Papillary projections in ovarian neoplasms: appearance on MRI

Papillary projections are distinctive pathologic features of epithelial ovarian neoplasms. We sought to determine whether these structures have recognizable features on MRI. A search of a database of 125 patients on whom MRI was performed with pelvic phased-array coil and abdominal surgical exploration was performed for suspected gynecologic disease identified 15 patients who had either MRI reports or pathology reports mentioning papillary projections in an adnexal mass. The MR images were reviewed to characterize the size, structure, and signal intensity of papillary projections. Pathologic correlation was performed on these and on four surgical specimens imaged with high resolution technique. Pathologic correlation showed that larger papillary projections had a distinctive structure of a fibrous stalk supporting clumps of edematous papillae with signal intensity similar to that of fluid on T2-weighted images. Smaller papillae showed nondescript intracystic projections of intermediate signal intensity on T2-weighted images. All papillary projections in vivo enhanced after injection of gadopentetate dimeglumine. Papillary projections have an appearance on MRI that reflects their histologic structure.

Ovarian fibromas and cystadenofibromas: MRI features of the fibrous component

Ovarian fibromas and cystadenofibromas are neoplasms that share a similar distinctive tissue component of dense fibrous tissue. We sought to describe the MRI features of these neoplasms and to determine if the fibrous component shows distinctive characteristics. Fourteen patients in whom MR images performed with multicoil and fast-spin-echo images and who subsequently underwent surgery for resection of ovarian fibromas or cystadenofibromas were identified from two institutions. Five patients had ovarian fibromas, and nine patients had fourteen cystadenofibromas. 1.5-T MR studies used T1-weighted spin echo and multiplanar T2-weighted fast-spin-echo images, with fat saturation gadolinium-enhanced fast multiplanar gradient-echo images in seven patients. Studies were reviewed for findings of low (approximately equal to skeletal muscle) signal intensity solid components on T2-weighted images, characteristics of gadolinium enhancement, and associated endometrial findings. Images were obtained ex vivo from three adnexal surgical specimens with an 8-cm field of view and correlated with histology. All five of the fibromas showed predominantly very low signal intensity, similar to skeletal muscle, on T2-weighted images. Two of five fibromas were in patients with endometrial polyps and increased amounts of fluid in the pelvis. Thirteen cystadenofibromas were multicystic masses with bands of very low signal intensity ranging from 2 to 20 mm in the wall of the mass, and one was predominantly solid fibrous tissue. Pathologic correlation with specimen images showed that the low signal intensity material was the subepithelial fibrous component of the cystadenofibromas. Fibrous components of ovarian fibromas and cystadenofibromas are demonstrable by MR as solid components representing fibrous tissue of very low signal intensity on T2-weighted images.

Correction to a previously published case: recurrence of invasive adrenocortical tumor after excision of atypical adenoma

A 74-year-old woman had hyperaldosteronemia and an adrenal adenoma that showed no evidence of lipid on in-phase and opposed-phase gradient-echo magnetic resonance (MR) images. MR images obtained 4 years after resection of the mass showed large masses of invasive tumor in the resection site, with small foci of lipid, and biopsy results confirmed the presence of an adrenocortical tumor.

MRI of benign and malignant hepatic lobar atrophy

We assessed the magnetic resonance imaging (MRI) features of hepatic lobar atrophy. Two of us reviewed MRIs of the liver in eight patients with benign or malignant forms of lobar atrophy. All atrophic lobes showed low signal intensity on T1-weighted images and high signal intensity on T2-weighted images compared with the remainder of the liver, and all showed greater enhancement compared to the nonatrophic lobe. Atrophic lobes have suggestive MRI findings and are similar for both benign and malignant etiologies.