Pitfalls of adrenal imaging with chemical shift MRI.

Chemical shift (CS) MRI of the adrenal glands exploits the different precessional frequencies of fat and water protons to differentiate the intracytoplasmic lipid-containing adrenal adenoma from other adrenal lesions. The purpose of this review is to illustrate both technical and interpretive pitfalls of adrenal imaging with CS MRI and emphasize the importance of adherence to strict technical specifications and errors that may occur when other imaging features and clinical factors are not incorporated into the diagnosis. When performed properly, the specificity of CS MRI for the diagnosis of adrenal adenoma is over 90%. Sampling the in-phase and opposed-phase echoes in the correct order and during the same breath-hold are essential requirements, and using the first echo pair is preferred, if possible. CS MRI characterizes more adrenal adenomas then unenhanced CT but may be non-diagnostic in a proportion of lipid-poor adenomas; CT washout studies may be able to diagnose these lipid-poor adenomas. Other primary and secondary adrenal tumours and supra-renal disease entities may contain lipid or gross fat and mimic adenoma or myelolipoma. Heterogeneity within an adrenal lesion that contains intracytoplasmic lipid could be due to myelolipoma, lipomatous metaplasia of adenoma, or collision tumour. Correlation with previous imaging, other imaging features, clinical history, and laboratory investigations can minimize interpretive errors.

Clinical features and natural history of hepatocellular adenomas: the impact of obesity.

BACKGROUND: Hepatocellular adenoma is a benign tumour associated with bleeding and malignant transformation. Obesity has been linked to hepatic tumourigenesis. AIM: To evaluate the presentation of hepatocellular adenoma in obesity, and the impact of obesity on the clinical course. METHODS: Records of 60 consecutive patients (between 2005 and 2010) with a diagnosis of hepatocellular adenoma from a single tertiary centre were analysed. RESULTS: Fifty six of 60 patients were women, median age was 36years, 75% had history of contraceptive use, 18% were overweight and 55% were obese (BMI ≥30kg/m(2) ). Majority (63%) were asymptomatic; seven patients presented with bleeding. Single (28%) and multiple adenomas (72%) were encountered; size ranged from 1 to 19.7cm. Obesity was more often associated with multiple adenomas (85% vs. 48%, P=0.005), bilobar distribution (67% vs. 33%, P=0.01), lower serum albumin (P=0.007) and co-morbidities of fatty liver (P=0.006), diabetes (P=0.003), hypertension (P=0.006) and dyslipidemia (P=0.03). During median follow-up of 2.6years, there were no instances of bleeding, malignant transformation or death. Thirty four patients underwent therapeutic intervention (17 surgical resection, nine transarterial embolization and eight both interventions sequentially). The rate of complete resection of adenoma(s) was significantly lower in obese patients (8% vs. 69%, P=0.004). In the 26 patients without intervention, tumour size progression was more frequently observed in obese patients (33% vs. 0%, P=0.05). Three of 15 obese patients (20%) lost ≥5% body weight and there was no progression in the liver lesions. CONCLUSIONS: Obesity and features of metabolic syndrome were frequently observed in hepatocellular adenoma. Multiple and bilobar adenomas were more frequent in obese patients. Among patients who were conservatively managed, tumour progression was more often associated with obesity.

Paraovarian cyst: MR imaging features.

BACKGROUND: Paraovarian cysts are common intrapelvic neoplasms, but the magnetic resonance (MR) findings of paraovarian cyst have never been reported. We investigated the spectrum of MR imaging features of paraovarian cyst. METHODS: MR images of 18 paraovarian cysts in 16 patients were reviewed retrospectively. MR images were evaluated for the size and location of paraovarian cysts, single or multicystic, signal intensity on T1- and T2-weighted images, and visualization of the normal ovary on the affected side. RESULTS: The normal ovary of the affected side was recognized in 13 lesions. Four of these 13 cysts were separated from the ipsilateral ovary. In seven cysts, the normal ovary was abutted by cysts but maintained its shape. In two cysts, the beak sign was recognized at the interface between the cyst and the ovary. Most other MR features were nonspecific. CONCLUSION: Most paraovarian cysts were homogeneous cystic masses near the ipsilateral round ligament and the uterus. Demonstration of a normal ipsilateral ovary close to, but separated from, the adnexal cyst may be an important MR finding for the diagnosis of paraovarian cysts.

Complications of renal transplantation: MR findings.

Because of its direct multiplanar capability, superb soft tissue contrast and ability to obtain dynamic three-dimensional angiograms using contrast agents without nephrotoxicity, magnetic resonance (MR) imaging and magnetic resonance angiography are ideal techniques for evaluating renal transplants. The following pictorial essay reviews the normal MR appearance of the transplant kidney as well as parenchymal, vascular, and peritransplant complications.

The evaluation of human breast lesions with magnetic resonance imaging and proton magnetic resonance spectroscopy.

PURPOSE: MR spectroscopy (MRS) assists in lesion characterization and diagnosis when combined with magnetic resonance imaging (MRI). Cancerous lesions demonstrate elevated composite choline levels arising from increased cellular proliferation. Our study investigated if MR spectroscopy of the breast would be useful for characterizing benign and malignant lesions. MATERIALS AND METHODS: Single voxel proton MR spectroscopy (MRS) was acquired as part of an MR imaging protocol in 38 patients referred upon surgical consultation. The MR spectra were read independently in a blinded fashion without the MR images by three spectroscopists. The MRI exam was interpreted in two settings: (a) as a clinical exam with detailed histories and results from previous imaging studies such as mammography or ultrasound included and (b) as a blinded study without prior histories or imaging results. RESULTS: Elevated choline levels were demonstrated by MRS in 19 of the 23 confirmed cancer patients. The sensitivity and specificity for determining malignancy from benign breast disease with MRS alone were 83 and 87%, respectively, while a blinded MRI review reported 95 and 86%, respectively. CONCLUSIONS: Proton MR spectroscopy provides a noninvasive, biochemical measure of metabolism. The technique can be performed in less than 10 min as part of an MRI examination. MRI in combination with MRS may improve the specificity of breast MR and thereby, influence patient treatment options. This may be particularly true with less experienced breast MRI readers. In exams where MRI and MRS agree, the additional confidence measure provided by MRS may influence the course of treatment.

MR imaging of the penis.

The signal intensity of the corpora cavernosa of the penis at magnetic resonance (MR) imaging may vary from that of the corpus spongiosum; this difference is dependent on the rate of blood flow within the cavernous spaces that constitute the corporal bodies. Also visible at MR imaging are the layers of fibrous tissue that envelop the corporal bodies, the deep arteries and veins, subcutaneous connective tissue, tunica dartos, epidermis, and urethra. While the iliac, pudendal, perineal, and common penile arteries can be evaluated with three-dimensional MR angiography, the smaller end arteries of the penis have not yet been reliably demonstrated. MR imaging may be used to detect and stage penile and urethral cancers, identify and characterize benign penile masses, evaluate arteriogenic impotence, identify penile fractures, evaluate penile prostheses, localize periurethral abscesses, and identify plaques of Peyronie disease. With its direct multiplanar imaging capabilities, superb soft-tissue contrast, and excellent spatial resolution, high-field surface coil MR imaging can show the soft-tissue and vascular anatomy of the penis, as well as the appearance of many penile diseases.

Imaging of hepatic steatosis.

Hepatic steatosis is a common finding encountered during cross-sectional imaging examinations. This article reviews the imaging findings of hepatic steatosis as revealed by sonography, computed tomography, magnetic resonance imaging, and magnetic resonance spectroscopy. Focal fatty sparing and focal hepatic steatosis are conditions that can create potential diagnostic challenges for the radiologist. The typical findings, distribution, and etiology of these focal processes are presented. In the setting of diffuse hepatic steatosis, hepatic mass lesions can be difficult to discern on both computed tomography and sonography, with reported decreased sensitivity and specificity of lesion detection. In such cases, magnetic resonance imaging may be the imaging procedure of choice for the detection and characterization of both hepatic steatosis and coexistent hepatic masses. Some hepatocellular neoplasms, particularly hepatic adenoma and well-differentiated hepatocellular carcinoma, can have intratumoral lipid. By demonstrating the lipid content of these masses, imaging can add specificity in characterizing them as hepatocellular in origin because nonhepatocellular neoplasms in general do not contain intracellular lipid.

Magnetic resonance imaging of the ovary.

Magnetic resonance imaging (MRI) of the pelvis can characterize a wide variety of ovarian lesions. We discuss MRI strategies for identification and characterization of ovarian neoplasms and correlate MRI findings with lesion gross pathological and histopathological structure.

Pulmonary arteriovenous malformations: three-dimensional gadolinium-enhanced MR angiography-initial experience.

PURPOSE: To determine whether three-dimensional gadolinium-enhanced magnetic resonance (MR) angiography could be used to identify pulmonary arteriovenous malformations (PAVMs) and to accurately identify the size and number of feeding arteries. MATERIALS AND METHODS: Eight patients suspected of having PAVM were examined with three-dimensional MR angiography at 1.5 T. Images were reviewed by a single radiologist blinded to conventional angiographic findings who evaluated each image for the size, number, and location of PAVMs, as well as for the size and number of feeding arteries. Five patients underwent conventional angiography with embolization therapy, and one patient underwent lobectomy. Two patients did not undergo either surgery or angiography. RESULTS: Three-dimensional MR angiography revealed nine (90%) of 10 PAVMs that were confirmed at conventional angiography (n = 9) or examination of a surgical specimen (n = 1). The single PAVM that was not identified prospectively at MR angiography was small (3-4 mm) and peripheral. Two additional PAVMs were identified in the two patients who did not undergo surgery or angiography. CONCLUSION: Three-dimensional MR angiography is a promising technique for use in the diagnosis of PAVM, although small (<5-mm) PAVMs may be more difficult to identify with the technique. The technique is a particularly useful means of noninvasively demonstrating the size and number of feeding arteries prior to treatment.

Ovarian teratomas: tumor types and imaging characteristics.

Ovarian teratomas include mature cystic teratomas (dermoid cysts), immature teratomas, and monodermal teratomas (eg, struma ovarii, carcinoid tumors, neural tumors). Most mature cystic teratomas can be diagnosed at ultrasonography (US) but may have a variety of appearances, characterized by echogenic sebaceous material and calcification. At computed tomography (CT), fat attenuation within a cyst is diagnostic. At magnetic resonance (MR) imaging, the sebaceous component is specifically identified with fat-saturation techniques. The US appearances of immature teratoma are nonspecific, although the tumors are typically heterogeneous, partially solid lesions, usually with scattered calcifications. At CT and MR imaging, immature teratomas characteristically have a large, irregular solid component containing coarse calcifications. Small foci of fat help identify these tumors. The US features of struma ovarii are also nonspecific, but a heterogeneous, predominantly solid mass may be seen. On T1- and T2-weighted images, the cystic spaces demonstrate both high and low signal intensity. Familiarity with the US, CT, and MR imaging features of ovarian teratomas can aid in differentiation and diagnosis.

Metastatic prostate cancer to the spine and a PSA of 5666: a case report.

Prostate cancer is the most commonly diagnosed cancer and the second most common cause of cancer death among American men. To our knowledge, the highest reported prostate specific antigen (PSA) level on initial presentation is 3280 ng/mL. In this case report, we discuss a 46-year-old African-American man with back pain of 1-month's duration. A magnetic resonance imaging study of the lumbar spine revealed numerous osseous metastatic lesions, and the PSA level was found to be 5666 ng/mL. He was treated with oral narcotics and a Duragesic patch to achieve analgesia and bicalutamide (Casodex) and leuprolide acetate (Lupron) therapy for androgen blockade. Later in his course, he required chemotherapy due to hormone-refractory prostate cancer. The patient has done well as shown at his latest follow-up at 48 months. The objective of this report is to discuss the first patient with metastatic prostate cancer to the spine with PSA level greater than 3,500 ng/mL.

MRI of the knee: value of short echo time fast spin-echo using high performance gradients versus conventional spin-echo imaging for the detection of meniscal tears.

OBJECTIVE: Fast spin-echo (FSE) sequences reduce imaging time compared with conventional spin-echo (CSE) sequences, but may result in blurring. High-performance gradients permit shorter interecho spacing and use of the second echo as the effective TE (20 ms); both improvements reduce blurring. This randomized observer study compared a short TE, second-echo FSE sequence obtained using high-performance gradients and a CSE sequence with similar TR/TE for the detection of meniscal tears in the knee. DESIGN AND PATIENTS: One hundred consecutive MR examinations of the knee using FSE and CSE sequences at 1.5 T were evaluated. The FSE sequence used an effective TE of 20 ms (centered on the second echo at 2 times minimal interecho spacing) and an echo train length of 4. FSE and CSE parameters were otherwise similar. Four independent, masked readers reviewed randomized sagittal FSE and CSE sequences. RESULTS: Cases were assessed for the presence or absence of meniscal tears and, if present, whether tears were medial or lateral and anterior or posterior. Sequence concordance was 93.5% (1496 of 1600 meniscal segments); the intermethod kappa value was 0.78. Sequence quality was graded from 1 to 5. Average quality of CSE images was slightly but statistically significantly preferred by three of the four readers. CONCLUSION: There was no statistically significant difference between CSE imaging and FSE imaging centered on the second echo (20 ms) using high-performance gradients for the detection of meniscal tears in the knee. There was a small preference for the quality of CSE images.

Suppression of intravascular signal on fat-saturated contrast-enhanced thoracic MR arteriograms.

PURPOSE: To assess the prevalence of artifactual signal intensity loss within the aortic arch and proximal branch vessels on fat-saturated contrast material-enhanced magnetic resonance (MR) arteriograms of the thoracic aorta and to hypothesize about the cause of the loss of signal intensity. MATERIALS AND METHODS: Between January and June 1998, 105 consecutive MR arteriograms of the thoracic aorta were acquired in 103 patients at 1.5 T. Imaging included an arterial phase three-dimensional (3D) fat-saturated contrast-enhanced gradient-echo (GRE) sequence followed by a delayed two-dimensional (2D) transverse fat-saturated GRE sequence. All MR images were reviewed by two radiologists who were blinded to patient history and results of imaging studies and who evaluated the images for the presence of intraluminal loss of signal intensity in the aortic arch and the proximal branch vessels. RESULTS: Intravascular loss of signal intensity was present in at least one vessel on 23 of the 105 arterial phase 3D studies. Seventy-one of 91 left subclavian arterial segments had loss of signal intensity on the delayed 2D studies. CONCLUSION: Intravascular signal intensity loss can be present on contrast-enhanced fat-saturated images of the aortic arch and proximal branch vessels, particularly the left subclavian artery. This phenomenon, which is to the authors' knowledge previously unreported and which is hypothesized to result from undesired water saturation, should not be misinterpreted as stenotic or occlusive vascular disease.

Role of endoscopic ultrasound and magnetic resonance imaging in the preoperative staging of pancreatic adenocarcinoma.

OBJECTIVE: Endoscopic ultrasound (EUS) and magnetic resonance imaging (MRI) have both been assessed individually as staging modalities for pancreatic cancer. The aim of our study was to assess whether tumor staging by both EUS and MRI in the same cohort of patients could predict resectability and unresectability in patients with pancreatic cancer. METHODS: A review of 63 patients evaluated preoperatively with both EUS and MRI for pancreatic adenocarcinoma between January 1995 and December 1998 was done. Patients were staged as resectable or unresectable by predefined criteria. Preoperative staging by both modalities was compared to surgical outcome and the sensitivity and predictive values of each modality for determining resectability and unresectability was determined. RESULTS: EUS did not allow for complete T- and N-staging in 10 patients; therefore, for EUS, the final analysis was done on 63 of 73 patients (86%). EUS correctly staged 22 of 36 patients with resectable tumors. The sensitivity of EUS for resectability was 61%, with a positive predictive value of 69%. All 73 patients had complete MRI examinations; therefore, the final analysis was done on all 73 patients. MRI correctly staged 30 of 41 patients with resectable tumors. The sensitivity of MRI for predicting resectability was 73% with a positive predictive value of 77%. MRI and EUS both predicted resectability in 18 patients, of whom 16 (89%) were found to be resectable on surgical exploration. MRI and EUS both predicted unresectability in 17 (27%) patients, of whom 4 (24%) were found to be resectable on surgical exploration. When both MRI and EUS agreed on resectability, the positive predictive value for resectability was 89%. When both MRI and EUS agreed on unresectability, the positive predictive value for unresectability was 76%. CONCLUSIONS: Neither MRI nor EUS alone were highly sensitive or predictive of resectability. However, when both tests agreed on resectability, nearly all patients were found to be resectable on surgical exploration.

MR imaging in patients with nipple discharge: initial experience.

PURPOSE: To investigate the potential of magnetic resonance (MR) imaging in patients with nipple discharge. MATERIALS AND METHODS: Between February 1992 and December 1998, 23 patients with nipple discharge underwent contrast material-enhanced MR imaging at 1.5 T. Mammographic findings were negative in 22 of 23 patients and revealed asymmetry in one patient. Galactography was attempted in two patients, with negative findings in one patient and no success in the other. Fifteen of 23 patients underwent excisional biopsy-seven of 15 with MR imaging-guided localization, and one of 15 with mammographic localization. Eight of 23 patients were followed up clinically (range, 7-24 months; mean, 20 months). RESULTS: In 11 of the 15 (73%) patients who underwent excisional biopsy, MR imaging findings correlated with histopathologic findings. MR imaging demonstrated four of six benign papillomas and one of two fibroadenomas as circumscribed, enhancing subareolar masses. Findings of one MR imaging examination were negative, and benign tissue was found at excisional biopsy. MR imaging findings were suspicious in six of the seven patients with excisional biopsy findings of malignancy (regional enhancement [n = 2], ductal enhancement [n = 2], peripherally enhancing mass [n = 1], and spiculated mass [n = 1]). In one of the seven patients, a benign-appearing intraductal mass was identified at MR imaging; excisional biopsy revealed a benign papilloma with an adjacent focus of DCIS. CONCLUSION: MR imaging can help identify both benign and malignant causes of nipple discharge. It potentially offers a noninvasive alternative to galactography.

MR imaging features of pelvic mucinous carcinomas.

Mucinous carcinomas in the pelvis differ from non-mucinous tumors because of the differences in clinical outcome and imaging appearance. Mucinous rectal carcinomas, for example, are to be higher in stage at the time of the diagnosis because they are more likely to be infiltrative and show a greater tendency for recurrence. These factors may lead to a poorer prognosis in patients with the mucinous as compared with non-mucinous carcinomas. Mucinous carcinomas of all types typically show high signal intensity on T2-weighted MR images, and therefore mimic other conditions such as necrotic tumors, fluid collections, cysts, or liver hemangiomas. To familiarize readers with the MRI appearance, and to avoid pitfalls, this paper illustrates the MRI features of the mucinous adenocarcinomas in various pelvic organs.