Abdominal MRI on a Commercial 0.55T System: Initial Evaluation and Comparison to Higher Field Strengths

RATIONALE AND OBJECTIVES

This study aims to assess the quality of abdominal MR images acquired on a commercial 0.55T scanner and compare these images with those acquired on conventional 1.5T/3T scanners in both healthy subjects and patients.

MATERIALS AND METHODS

Fifteen healthy subjects and 52 patients underwent abdominal Magnetic Resonance Imaging at 0.55T. Images were also collected in healthy subjects at 1.5T, and comparison 1.5/3T images identified for 28 of the 52 patients. Image quality was rated by two radiologists on a 4-point Likert scale. Readers were asked whether they could answer the clinical question for patient studies. Wilcoxon signed-rank test was used to test for significant differences in image ratings and acquisition times, and inter-reader reliability was computed.

RESULTS

The overall image quality of all sequences at 0.55T were rated as acceptable in healthy subjects. Sequences were modified to improve signal-to-noise ratio and reduce artifacts and deployed for clinical use; 52 patients were enrolled in this study. Radiologists were able to answer the clinical question in 52 (reader 1) and 46 (reader 2) of the patient cases. Average image quality was considered to be diagnostic (>3) for all sequences except arterial phase FS 3D T1w gradient echo (GRE) and 3D magnetic resonance cholangiopancreatography for one reader. In comparison to higher field images, significantly lower scores were given to 0.55T IP 2D GRE and arterial phase FS 3D T1w GRE, and significantly higher scores to diffusion-weighted echo planar imaging at 0.55T; other sequences were equivalent. The average scan time at 0.55T was 54 ± 10 minutes vs 36 ± 11 minutes at higher field strengths (P < .001).

CONCLUSION

Diagnostic-quality abdominal MR images can be obtained on a commercial 0.55T scanner at a longer overall acquisition time compared to higher field systems, although some sequences may benefit from additional optimization.

Imaging findings of the injured in the massive Beirut blast

PURPOSE

(1) Describe imaging utilization and findings within two weeks of the 2020 Beirut blast according to the mechanism of injury, (2) determine the appropriate imaging modality per organ/system, and (3) describe changes in the workflow of a radiology department to deal with massive crises.

MATERIALS AND METHODS

Two hundred sixty patients presented to the largest emergency department in Beirut and underwent imaging within 2 weeks of the blast. In this retrospective study, patients were divided into early (1) and late (2) imaging groups. Patients' demographic, outcome, type and time of imaging studies, body parts imaged, and mechanism and types of injuries were documented.

RESULTS

Two hundred five patients in group 1 underwent 502 and 55 patients in group 2 underwent 145 imaging studies. Tertiary blast injuries from direct impact and falling objects were the most common type of injuries followed by secondary (shrapnel) injuries. Both types of injuries affected mostly the head and neck and upper extremities. Plain radiographs were adequate for the extremities and CT for the head and neck. A regularly updated and practiced emergency plan is essential to mobilize staff and equipment and efficiently deliver radiology services during crises.

CONCLUSION

Because the powerful Beirut blast occurred at the port located in the periphery of the city, most injuries seen on imaging were of the upper extremities and head and neck caused by the severe blast wind or penetrating shrapnel and resulted from people using their arms to protect their heads and bodies from direct impact and falling objects.

Quality assessment of routine brain imaging at 0.55 T: initial experience in a clinical workflow

The purpose of this study was to assess the quality of clinical brain imaging in healthy subjects and patients on an FDA-approved commercial 0.55 T MRI scanner, and to provide information about the feasibility of using this scanner in a clinical workflow. In this IRB-approved study, brain examinations on the scanner were prospectively performed in 10 healthy subjects (February-April 2022) and retrospectively derived from 44 patients (February-July 2022). Images collected using the following pulse sequences were available for assessment: axial DWI (diffusion-weighted imaging), apparent diffusion coefficient maps, 2D axial fluid-attenuated inversion recovery images, axial susceptibility-weighted images (both magnitude and phase), sagittal T1 -weighted (T1w) Sampling Perfection with Application Optimized Contrast images, sagittal T1w MPRAGE (magnetization prepared rapid gradient echo) with contrast enhancement, axial T1w turbo spin echo (TSE) with and without contrast enhancement, and axial T2 -weighted TSE. Two readers retrospectively and independently evaluated image quality and specific anatomical features in a blinded fashion on a four-point Likert scale, with a score of 1 being unacceptable and 4 being excellent, and determined the ability to answer the clinical question in patients. For each category of image sequences, the mean, standard deviation, and percentage of unacceptable quality images (<2) were calculated. Acceptable (rating ≥ 2) image quality was achieved at 0.55 T in all sequences for patients and 85% of the sequences for healthy subjects. Radiologists were able to answer the clinical question in all patients scanned. In total, 50% of the sequences used in patients and about 60% of the sequences used in healthy subjects exhibited good (rating ≥ 3) image quality. Based on these findings, we conclude that diagnostic quality clinical brain images can be successfully collected on this commercial 0.55 T scanner, indicating that the routine brain imaging protocol may be deployed on this system in the clinical workflow.

MRI evaluation of the placenta from normal variants to abnormalities of implantation and malignancies

Even though the placenta has been known for millennia, it is still considered one of the most complex and least understood human organs. Imaging of the placenta is gaining attention due to its impact on fetal and maternal outcomes. MRI plays a vital role in evaluation of inconclusive cases by ultrasonography. It enables precise mapping of placental abnormalities for proper multidisciplinary planning and management. In this article we provide a comprehensive in-depth review of the role of antenatal MR in evaluating "The Placenta." We will describe the protocols and techniques used for MRI of the placenta, review anatomy of the placenta, describe MRI features of major placental abnormalities including those related to position, depth of implantation, hemorrhage, gestational trophoblastic neoplasia, and retained products of conception and discuss the added value of MRI in the management and preoperative planning of such abnormalities. Level of Evidence: 3 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2019;50:1702-1717.

Diagnostic accuracy of MRI with extracellular vs. hepatobiliary contrast material for detection of residual hepatocellular carcinoma after locoregional treatment

PURPOSE

To compare the diagnostic accuracy of extracellular gadolinium-based contrast-enhanced MRI (Gd-MRI) and gadoxetic acid-enhanced MRI (EOB-MRI) for the assessment of hepatocellular carcinoma (HCC) response to locoregional therapy (LRT) using explant correlation as the reference standard.

METHODS

Forty-nine subjects with cirrhosis and HCC treated with LRT who underwent liver MRI using either Gd-MRI (n = 26) or EOB-MRI (n = 23) within 90 days of liver transplantation were included. Four radiologists reviewed the MR images blinded to histology to determine the size and percentage of viable residual HCC using a per-lesion explant reference standard. Sensitivities, specificities, accuracies, and agreement with histology for the detection residual HCC were calculated.

RESULTS

Gd-MRI had greater agreement with histology (ICC: 0.98 [0.95-0.99] vs. 0.80 [0.63-0.90]) and greater sensitivity for viable HCC (76% [13/17 50-93%] vs. 58% [7/12; 28-85%]) than EOB-MRI; specificities were similar (84% [16/19; 60-97%] vs. 85% [23/27; 66-96%]). Areas under ROC curves for detecting residual viable tumor were 0.80 (0.64-0.92) for Gd-MRI and 0.72 (0.55-0.85) for EOB-MRI. Gd-MRI had greater inter-rater agreement than EOB-MRI for determining the size of residual viable HCC (ICC: 0.96 [0.92-0.98] vs. 0.85 [0.72-0.92]).

CONCLUSION

Gd-MRI may be more accurate and precise than EOB-MRI for the assessment of viable HCC following LRT.

Evidence Supporting LI-RADS Major Features for CT- and MR Imaging-based Diagnosis of Hepatocellular Carcinoma: A Systematic Review

The Liver Imaging Reporting and Data System (LI-RADS) standardizes the interpretation, reporting, and data collection for imaging examinations in patients at risk for hepatocellular carcinoma (HCC). It assigns category codes reflecting relative probability of HCC to imaging-detected liver observations based on major and ancillary imaging features. LI-RADS also includes imaging features suggesting malignancy other than HCC. Supported and endorsed by the American College of Radiology (ACR), the system has been developed by a committee of radiologists, hepatologists, pathologists, surgeons, lexicon experts, and ACR staff, with input from the American Association for the Study of Liver Diseases and the Organ Procurement Transplantation Network/United Network for Organ Sharing. Development of LI-RADS has been based on literature review, expert opinion, rounds of testing and iteration, and feedback from users. This article summarizes and assesses the quality of evidence supporting each LI-RADS major feature for diagnosis of HCC, as well as of the LI-RADS imaging features suggesting malignancy other than HCC. Based on the evidence, recommendations are provided for or against their continued inclusion in LI-RADS. ^© RSNA, 2017 Online supplemental material is available for this article.

Imaging Findings Within the First 12 Months of Hepatocellular Carcinoma Treated With Stereotactic Body Radiation Therapy

PURPOSE

To correlate the imaging findings of treated hepatocellular carcinoma (HCC) after stereotactic body radiation therapy (SBRT) with explant pathology and alpha-fetoprotein (AFP) response.

METHODS AND MATERIALS

From 2007 to 2015, of 146 patients treated with liver SBRT for Barcelona Clinic Liver Cancer stage A hepatocellular carcinoma, 10 were identified with inclusion criteria and had regular interval follow-up magnetic resonance imaging/triple phase computed tomography and explant pathology or declining AFP values for radiology-pathology response correlation. Reference standards for successful response were >90% necrosis on explant pathology or pretreatment AFP >75 ng/mL normalizing to <10 ng/mL within 1 year after SBRT without other treatment. Subjects were treated with 24 to 50 Gy in 3 to 5 fractions. Multiphasic magnetic resonance imaging or computed tomography performed at 3, 6, 9, and 12 months after SBRT was compared with pretreatment imaging by 2 expert radiologists. Descriptive statistics were calculated.

RESULTS

There were 10 subjects with 10 treated HCCs, classified as 3 Organ Procurement and Transplantation Network (OPTN) 5a, 4 OPTN 5b, and 3 OPTN 5x. All had successfully treated HCCs, according to explant pathology or declining AFP. Four of 10 HCCs had persistent central arterial hyperenhancement 3 to 12 months after SBRT; persistent wash-out was common up to 12 months (9 of 10). Of 10 treated HCCs, 9 exhibited decreased size at 12 months. Liver parenchyma adjacent to the lesion showed early (3-6 months) hyperemia followed by late (6-12 months) capsular retraction and delayed enhancement. No patient had a significant decline in liver function.

CONCLUSIONS

In the absence of increasing size, persistent central arterial hyperenhancement and wash-out can occur within the first 12 months after SBRT in successfully treated HCCs and may not represent residual viable tumor. Liver parenchyma adjacent to the treated lesion showed inflammation followed by fibrosis, without significant change in hepatic function. Until a radiologic signature of tumor control is determined, freedom from local progression seems to be the best measure of HCC control after SBRT.

Predicting the likelihood of a persistent bile duct stone in patients with suspected choledocholithiasis: accuracy of existing guidelines and the impact of laboratory trends

BACKGROUND

Existing guidelines aim to stratify the likelihood of choledocholithiasis to guide the use of ERCP versus a lower-risk diagnostic study such as EUS, MRCP, or intraoperative cholangiography.

OBJECTIVE

To assess the performance of existing guidelines in predicting choledocholithiasis and to determine whether trends in laboratory parameters improve diagnostic accuracy.

DESIGN

Retrospective cohort study.

SETTING

Tertiary-care hospital.

PATIENTS

Hospitalized patients presenting with suspected choledocholithiasis over a 6-year period.

INTERVENTIONS

Assessment of the American Society for Gastrointestinal Endoscopy (ASGE) guidelines, its component variables, and laboratory trends in predicting choledocholithiasis.

MAIN OUTCOME MEASUREMENTS

The presence of choledocholithiasis confirmed by EUS, MRCP, or ERCP.

RESULTS

A total of 179 (35.9%) of the 498 eligible patients met ASGE high-probability criteria for choledocholithiasis on initial presentation. Of those, 99 patients (56.3%) had a stone/sludge on subsequent confirmatory test. Of patients not meeting high-probability criteria on presentation, 111 (34.8%) had a stone/sludge. The overall accuracy of the guidelines in detecting choledocholithiasis was 62.1% (47.4% sensitivity, 73% specificity) based on data available at presentation. The accuracy was unchanged when incorporating the second set of liver chemistries obtained after admission (63.2%), suggesting that laboratory trends do not improve performance.

LIMITATIONS

Retrospective study, inconsistent timing of the second set of biochemical markers.

CONCLUSION

In our cohort of patients, existing choledocholithiasis guidelines lacked diagnostic accuracy, likely resulting in overuse of ERCP. Incorporation of laboratory trends did not improve performance. Additional research focused on risk stratification is necessary to meet the goal of eliminating unnecessary diagnostic ERCP.

A pilot study of diffusion-weighted MRI in patients undergoing neoadjuvant chemoradiation for pancreatic cancer

PURPOSE: In the current study we examined the ability of diffusion MRI (dMRI) to predict pathologic response in pancreatic cancer patients receiving neoadjuvant chemoradiation. METHODS: We performed a prospective pilot study of dMRI in patients with resectable pancreatic cancer. Patients underwent dMRI prior to neoadjuvant chemoradiation. Surgical specimens were graded according to the percent tumor cell destruction. Apparent diffusion coefficient (ADC) maps were used to generate whole-tumor derived ADC histogram distributions and mean ADC values. The primary objective of the study was to correlate ADC parameters with pathologic and CT response. RESULTS: Ten of the 12 patients enrolled on the study completed chemoradiation and had surgery. Three were found to be unresectable at the time of surgery and no specimen was obtained. Out of the 7 patients who underwent pancreaticoduodenectomy, 3 had a grade III histopathologic response (> 90% tumor cell destruction), 2 had a grade IIB response (51% to 90% tumor cell destruction), 1 had a grade IIA response (11% to 50% tumor cell destruction), and 1 had a grade I response (> 90% viable tumor). Median survival for patients with a grade III response, grade I-II response, and unresectable disease were 25.6, 18.7, and 6.1 months, respectively. There was a significant correlation between pre-treatment mean tumor ADC values and the amount of tumor cell destruction after chemoradiation with a Pearson correlation coefficient of 0.94 (P = .001). Mean pre-treatment ADC was 161 × 10^− 5 mm²/s (n = 3) in responding patients (> 90% tumor cell destruction) compared to 125 × 10^− 5 mm²/s (n = 4) in non-responding patients (> 10% viable tumor). CT imaging showed no significant change in tumor size in responders or non-responders. CONCLUSIONS: dMRI may be useful to predict response to chemoradiation in pancreatic cancer. In our study, tumors with a low ADC mean value at baseline responded poorly to standard chemoradiation and would be candidates for intensified therapy.

Respiratory motion artifact affecting hepatic arterial phase MR imaging with gadoxetate disodium is more common in patients with a prior episode of arterial phase motion associated with gadoxetate disodium

PURPOSE

To determine, in a dual-center setting, whether patients who experience transient severe motion ( TSM transient severe motion ) in the arterial phase during gadoxetate disodium-enhanced magnetic resonance (MR) imaging are at higher risk for a subsequent episode of TSM transient severe motion than patients who do not have TSM transient severe motion during initial gadoxetate disodium administration.

MATERIALS AND METHODS

Institutional review board approval was obtained for this retrospective, multi-institutional HIPAA-compliant study. The requirement for informed consent was waived. One hundred seventy patients each underwent two MR imaging examinations with bolus injection of gadoxetate disodium at one of two sites. Three radiologists reviewed the examinations at each site for TSM transient severe motion , based on severe arterial phase motion, despite minimal motion in the other dynamic phases. The occurrence rate of TSM transient severe motion in the second examination was compared between patients who had TSM transient severe motion in their first examination and those who did not by using the χ(2) or Fisher exact test, as appropriate. Relative risks and 95% confidence intervals ( CI confidence interval s) were calculated.

RESULTS

TSM transient severe motion rates in second examinations were significantly higher for patients who had TSM transient severe motion in their first examination: site 1, 67% (six of nine) vs 4% (three of 69) (P < .0001); site 2, 60% (three of five) vs 6% (five of 87) (P < .005); and both sites, 64% (nine of 14) vs 5% (eight of 156) (P < .0001). Relative risks were 15 for site 1 (95% CI confidence interval : 5, 51), 10 for site 2 (95% CI confidence interval : 3, 32), and 13 for both sites (95% CI confidence interval : 6, 27).

CONCLUSION

Patients who experience TSM transient severe motion during gadoxetate disodium-enhanced MR imaging are at significantly and substantially higher risk for TSM transient severe motion in the next gadoxetate disodium-enhanced examination compared with patients who do not have TSM transient severe motion during their initial gadoxetate disodium administration.

MR imaging of the small bowel in Crohn disease

MR enterography has an established role in evaluating patients with Crohn disease providing essential complementary information to clinical assessment, and as an indispensible adjunct to clinical tools such as colonoscopy. MR enterography examinations can establish the diagnosis of Crohn disease, evaluate disease activity and complications, and assess treatment response, thus providing support for clinical decision-making. Currently, MR imaging findings are highly predictive of tissue inflammation and can be used clinically to guide clinical care.

Magnetic resonance imaging in cirrhosis: what's new?

Cirrhosis is the main risk factor for the development of hepatocellular carcinoma (HCC). The major causative factors of cirrhosis in the United States and Europe are chronic hepatitis C infection and excessive alcohol consumption with nonalcoholic steatohepatitis emerging as another important risk factor. Magnetic resonance imaging is the most sensitive imaging technique for the diagnosis of HCC, and the sensitivity can be further improved with the use of diffusion-weighted imaging and hepatocyte-specific contrast agents. The combination of arterial phase hyperenhancement, venous or delayed phase hypointensity "washout feature," and capsular enhancement are features highly specific for HCC with reported specificities of 96% and higher. When these features are present in a mass in the cirrhotic liver, confirmatory biopsy to establish the diagnosis of HCC is not necessary. Other tumors, such as cholangiocarcinoma, sometimes occur in the cirrhotic at a much lower rate than HCC and can mimic HCC, as do other benign lesions such as perfusion abnormalities. In this article, we discuss the imaging features of cirrhosis and HCC, the role of magnetic resonance imaging in the diagnosis of HCC and other benign and malignant lesions that occur in the cirrhotic liver, and the issue of nonspecific arterially hyperenhancing nodules often seen in cirrhosis.

Matched within-patient cohort study of transient arterial phase respiratory motion-related artifact in MR imaging of the liver: gadoxetate disodium versus gadobenate dimeglumine

PURPOSE

To compare frequency and severity of arterial phase respiratory motion-related artifact following gadoxetate disodium and gadobenate dimeglumine in matched patients administered both contrast media at different times.

MATERIALS AND METHODS

Institutional review board approval was obtained, with patient consent waived, for this retrospective, HIPAA-compliant study. Ninety patients underwent gadobenate dimeglumine-enhanced abdominal magnetic resonance (MR) followed by gadoxetate disodium-enhanced abdominal MR and were matched to 90 patients who were administered the same contrast media in reverse order (180 patients). Matching was based on length of time between paired examinations. Gadobenate dimeglumine dose was weight based (0.1 mmol per kilogram body weight). Gadoxetate disodium dose was typically fixed (10 or 20 mL [off label]). Three readers blinded to contrast agent assigned a respiratory motion-related artifact score (1 [none] to 5 [nondiagnostic]) for nonenhanced, arterial, venous, and late dynamic phases. Frequency of greater new arterial phase respiratory motion-related artifact in each within-patient pair and aggregate rate of new severe transient arterial phase respiratory motion-related artifact (scores ≤ 2, nonenhanced and venous and/or late dynamic phases; ≥ 4, arterial phase) were compared (McNemar test).

RESULTS

For groups 1 and 2, respectively, mean dose (gadoxetate disodium, 16.6 mL vs 16.6 mL, P = .99; gadobenate dimeglumine, 18.0 mL vs 17.8 mL, P = .77) and mean time between examinations (191 days vs 191 days, P = .99) were not significantly different between matched populations. Gadoxetate disodium was associated with significantly higher incidence of new arterial phase respiratory motion-related artifact compared with gadobenate dimeglumine (39% vs 10%, P < .0001) and of new severe transient arterial phase respiratory motion-related artifact (18% vs 2%, P < .0001) in patients administered both agents at different times.

CONCLUSION

Fixed off-label dose (10 or 20 mL) of gadoxetate disodium is associated with arterial phase respiratory motion-related artifact that is sometimes severe and occurs significantly more often than after gadobenate dimeglumine in patients who received both contrast media.

Repeatability of diagnostic features and scoring systems for hepatocellular carcinoma by using MR imaging

PURPOSE

To determine for expert and novice radiologists repeatability of major diagnostic features and scoring systems (ie, Liver Imaging Reporting and Data System [LI-RADS], Organ Procurement and Transplantation Network [OPTN], and American Association for the Study of Liver Diseases [AASLD]) for hepatocellular carcinoma (HCC) by using magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Institutional review board approval was obtained and patient consent was waived for this HIPAA-compliant, retrospective study. The LI-RADS discussed in this article refers to version 2013.1. Ten blinded readers reviewed 100 liver MR imaging studies that demonstrated observations preliminarily assigned LI-RADS scores of LR1-LR5. Diameter and major HCC features (arterial hyperenhancement, washout appearance, pseudocapsule) were recorded for each observation. LI-RADS, OPTN, and AASLD scores were assigned. Interreader agreement was assessed by using intraclass correlation coefficients and κ statistics. Scoring rates were compared by using McNemar test.

RESULTS

Overall interreader agreement was substantial for arterial hyperenhancement (0.67 [95% confidence interval {CI}: 0.65, 0.69]), moderate for washout appearance (0.48 [95%CI: 0.46, 0.50]), moderate for pseudocapsule (0.52 [95% CI: 050, 0.54]), fair for LI-RADS (0.35 [95% CI: 0.34, 0.37]), fair for AASLD (0.39 [95% CI: 0.37, 0.42]), and moderate for OPTN (0.53 [95% CI: 0.51, 0.56]). Agreement for measured diameter was almost perfect (range, 0.95-0.97). There was substantial agreement for most scores consistent with HCC. Experts agreed significantly more than did novices and were significantly more likely than were novices to assign a diagnosis of HCC (P < .001).

CONCLUSION

Two of three major features for HCC (washout appearance and pseudocapsule) have only moderate interreader agreement. Experts and novices who assigned scores consistent with HCC had substantial but not perfect agreement. Expert agreement is substantial for OPTN, but moderate for LI-RADS and AASLD. Novices were less consistent and less likely to diagnose HCC than were experts.

Consensus report from the 6th International forum for liver MRI using gadoxetic acid

As the utility of liver-specific magnetic resonance imaging (MRI) increases, it is pertinent to optimize and expand protocols to improve accuracy and foster evolution of techniques; in turn, positive impacts should be seen in patient management. This article reports on the latest expert thinking and current evidence in the field of liver-specific MRI, as discussed at the 6(th) International Forum for Liver MRI, which was held in Vancouver, Canada in September 2012. Topics discussed at this forum described the use of gadoxetic acid-enhanced MRI for the assessment of liver function at the segmental level; to increase accuracy in the diagnosis of liver metastases; to overcome current challenges in patients with cirrhosis, including management of arterial hypo-/isovascular, hepatobiliary phase hypointense nodules; and the data which would be required in order to recommend the use of this modality in hepatocellular carcinoma management guidelines. Growing evidence suggests that gadoxetic acid-enhanced MRI can help to improve the management of patients with a number of different liver disorders; however, more data are needed in some areas, and there may be a case for developing an interpretation guideline for gadoxetic acid-enhanced MRI findings to aid standardization.

Dynamic MRI evaluation of urethral hypermobility post-radical prostatectomy

AIMS

One postulated cause of post-prostatectomy incontinence is urethral and bladder neck hypermobility. The objective of this study was to determine the magnitude of anatomical differences of urethral and bladder neck position at rest and with valsalva in continent and incontinent men post-prostatectomy based on dynamic MRI.

METHODS

All subjects underwent a dynamic MRI protocol with valsalva and non-valsalva images and a standard urodynamic evaluation. MRI measurements were taken at rest and with valsalva, including (1) bladder neck to sacrococcygeal inferior pubic point line (SCIPP), (2) urethra to pubis, and (3) bulbar urethra to SCIPP. Data were analyzed in SAS using two-tailed t tests.

RESULTS

A total of 21 subjects (13 incontinent and 8 continent) had complete data and were included in the final analysis. The two groups had similar demographic characteristics. On MRI, there were no statistically significant differences in anatomic position of the bladder neck or urethra either at rest or with valsalva. The amount of hypermobility ranged from 0.8 to 2 mm in all measures. There were also no differences in the amount of hypermobility (position at rest minus position at valsalva) between groups.

CONCLUSIONS

We found no statistically significant differences in bladder neck and urethral position or mobility on dynamic MRI evaluation between continent and incontinent men status post-radical prostatectomy. A more complex mechanism for post-prostatectomy incontinence needs to be modeled in order to better understand the continence mechanism in this select group of men.

Abdominal applications of diffusion-weighted magnetic resonance imaging: Where do we stand

Diffusion-weighted imaging (DWI) is one of the magnetic resonance imaging (MRI) sequences providing qualitative as well as quantitative information at a cellular level. It has been widely used for various applications in the central nervous system. Over the past decade, various extracranial applications of DWI have been increasingly explored, as it may detect changes even before signal alterations or morphological abnormalities become apparent on other pulse sequences. Initial results from abdominal MRI applications are promising, particularly in oncological settings and for the detection of abscesses. The purpose of this article is to describe the clinically relevant basic concepts of DWI, techniques to perform abdominal DWI, its analysis and applications in abdominal visceral MR imaging, in addition to a brief overview of whole body DWI MRI.

Effect of abrupt substitution of gadobenate dimeglumine for gadopentetate dimeglumine on rate of allergic-like reactions

PURPOSE

To evaluate the effect of abruptly substituting gadobenate dimeglumine for gadopentetate dimeglumine on allergic-like reactions.

MATERIALS AND METHODS

The institutional review board approved and waived patient consent for this HIPAA-compliant retrospective study. Allergic-like reactions related to gadolinium-based contrast media were assessed 2 years before and 3.5 years after gadobenate dimeglumine was substituted for gadopentetate dimeglumine. Reaction rates and severity were compared by using χ(2) tests, Fisher exact tests, odds ratios (ORs), and confidence intervals (CIs).

RESULTS

Allergic-like reactions (137 mild, 19 moderate, and six severe) occurred in 162 (0.15%) of 105 607 injections of gadolinium-based contrast media (gadopentetate dimeglumine, 31 540; gadobenate dimeglumine, 66 152; other, 7915). Gadobenate dimeglumine was associated with significantly more overall (0.19% [123 of 66 152] vs 0.08% [24 of 31 540]; OR, 2.4; 95% CI: 1.6, 3.8; P < .0001) and mild (0.16% [107 of 66 152] vs 0.06% [18 of 31 540]; OR, 2.8; 95% CI: 1.7, 4.7; P < .0001) allergic-like reactions than was gadopentetate dimeglumine. The reaction rate for gadobenate dimeglumine peaked (maximum per quarter, 0.38% [16 of 4262]; minimum per quarter, 0.07% [three of 4237]) in the 2nd year after it replaced gadopentetate dimeglumine (maximum per quarter, 0.10% [four of 4122]; minimum per quarter, 0.05% [two of 4222]) and then declined in the 3rd year. The final gadobenate dimeglumine reaction rate (last 3 quarters, 0.12% [17 of 14 387]) did not significantly differ from the original baseline reaction rate with gadopentetate dimeglumine.

CONCLUSION

After gadobenate dimeglumine was substituted for gadopentetate dimeglumine, a significant transient increase occurred in the frequency of reported allergic-like reactions that demonstrated a temporal pattern suggestive of the Weber effect (a transient increase in adverse event reporting that tends to peak in the 2nd year after a new agent or indication is introduced). © RSNA, 2012.

Comparison of acute transient dyspnea after intravenous administration of gadoxetate disodium and gadobenate dimeglumine: effect on arterial phase image quality

PURPOSE

To determine whether acute transient dyspnea and/or arterial phase image degradation occurs more or less often after intravenous administration of gadoxetate disodium than with intravenous administration of gadobenate dimeglumine.

MATERIALS AND METHODS

Institutional review board approval and patient consent were obtained for this prospective observational study. One hundred ninety-eight gadolinium-based contrast media administrations (99 with gadoxetate disodium [10 mL, n = 97; 8 mL, n = 1; 16 mL, n = 1] and 99 with gadobenate dimeglumine [0.1 mmol per kilogram of body weight, maximum dose, 20 mL]) for hepatobiliary indications were assessed in 192 patients. Subjective patient complaints were assessed. Objective respiratory motion degradation on T1-weighted precontrast and dynamic postcontrast (arterial, venous, or late dynamic or extracellular) magnetic resonance (MR) imaging datasets were independently assessed in a randomized, blinded fashion by five readers using a five-point scale, with mean scores of 4 or greater indicating severe motion. Comparisons between agents were made by using χ(2) or Fisher exact test, where appropriate.

RESULTS

Significantly more patient complaints of acute transient dyspnea occurred after gadoxetate disodium administration than gadobenate dimeglumine (14% [14 of 99] vs 5% [five of 99], P = .05). There were significantly more severely degraded arterial phase data sets for gadoxetate disodium than for gadobenate dimeglumine for both the general population (17% [17 of 99] vs 2% [two of 99], P = .0007) and the subpopulation with cirrhosis (19% [14 of 72] vs 3% [one of 37], P = .02). This effect did not extend to venous (1% [one of 99] vs 2% [two of 99], P > .99 [overall population]) or late dynamic or extracellular (2% [two of 99] vs 0% [zero of 99], P = .5 [overall population]) phases. No patient required treatment for self-limited dyspnea.

CONCLUSION

Intravenous gadoxetate disodium can result in acute self-limiting dyspnea that can have a deleterious effect on arterial phase MR image quality and occurs significantly more often than with intravenous gadobenate dimeglumine.

Safety of gadolinium-based contrast material in sickle cell disease

PURPOSE

To assess the safety of intravenously administered gadolinium-based contrast material in sickle cell disease (SCD) patients.

MATERIALS AND METHODS

All pediatric and adult SCD patients evaluated by magnetic resonance imaging (MRI) at our institution between January 1995 and July 2009 were identified. The medical records of SCD patients who underwent contrast-enhanced MRI as well as an equal-sized cohort of SCD patients who underwent unenhanced MRI were reviewed for adverse (vaso-occlusive and hemolytic) events within 1 week following imaging.

RESULTS

Eight (five mild and three moderate) adverse events were documented within 1 week following contrast-enhanced MRI (38 patients and 61 contrast injections), while six (five mild and one moderate) similar events occurred within 1 week following unenhanced MRI (61 patients and 61 unenhanced MRI examinations). This difference in the number of adverse events was not statistically significant (odds ratio = 1.4; 95% confidence interval [CI] 0.4, 5.2). No severe adverse event occurred in either patient cohort.

CONCLUSION

Gadolinium-based contrast materials do not appear to be associated with increased risk of vaso-occlusive or hemolytic adverse events when administered to SCD patients. Larger, prospective studies using multiple gadolinium-based contrast materials would be useful to confirm the results of our investigation.

Magnetization transfer helps detect intestinal fibrosis in an animal model of Crohn disease

PURPOSE

To determine the utility of magnetization transfer (MT) in the identification and quantification of intestinal fibrosis in a rat model of Crohn disease.

MATERIALS AND METHODS

The university committee on the use and care of animals approved this study (UCUCA 08592). Lewis rats injected subserosally with peptidoglycan-polysaccharide (PG-PS) develop bowel inflammation 1 day after laparotomy (early phase) and fibrosis starting 14 days after laparotomy (late phase). The authors performed 2.0-T magnetic resonance (MR) imaging in 25 rats injected with PG-PS and 13 injected with human serum albumin (HSA) (control animals). Imaging was performed before laparotomy and on a weekly basis thereafter for up to 28 days. The MT ratio in the bowel wall was calculated. Resected cecal tissue was scored for inflammation and fibrosis. Tissue fibrosis was determined with colorimetric analysis of trichrome-stained specimens. Collagen content was measured with Western blot analysis. Statistical analyses were performed with the Student t test for continuous bivariate comparisons, the Pearson correlation for continuous variables, and the Spearman correlation for ordinal variables.

RESULTS

All rats developed early inflammation, which subsided over time. Rats injected with PG-PS developed increased fibrosis in the late phase, whereas control rats did not. The mean MT ratio of rats injected with PG-PS with late-phase fibrosis was higher than that in rats with early phase inflammation (P = .017). In addition, the MT ratio of rats injected with PG-PS with late-phase fibrosis was higher than that of control animals that did not develop fibrosis in the late phase (P = .0001). The MT ratio of control animals remained unchanged over time as inflammation subsided. The MT ratio in rats injected with PG-PS showed correlation with tissue fibrosis (ρ = 0.63). The MT ratio showed correlation with tissue collagen (R = 0.74). The positive and negative predictive values of the MT ratio in the prediction of fibrosis were 92% (12 of 13 rats) and 83% (five of six rats), respectively.

CONCLUSION

These results indicate that MT is sensitive to bowel wall fibrosis as occurs in Crohn strictures.

Value of delayed hypointensity and delayed enhancing rim in magnetic resonance imaging diagnosis of small hepatocellular carcinoma in the cirrhotic liver

PURPOSE

To determine the diagnostic utility of delayed hypointensity and delayed enhancing rim on magnetic resonance imaging (MRI) as indicators of hepatocellular carcinoma (HCC) in arterially enhancing nodules < or =5 cm in the cirrhotic liver and determine the features that best predict HCC.

MATERIALS AND METHODS

Gadolinium-enhanced MRI studies performed from January 2001 to December 2004 in patients with cirrhosis were evaluated for arterially enhancing nodules measuring < or =5 cm. Verification was via explant correlation, biopsy, or imaging follow-up. Sensitivity and specificity of diagnostic features of HCC were calculated. Features predictive of HCC were determined using the Generalized Estimating Equation approach.

RESULTS

In all, 116 arterially enhancing nodules were identified in 80 patients (<2 cm: n = 79, 2-5 cm n = 37). Sensitivity and specificity of delayed hypointensity for HCC measuring < or =5 cm, 2-5 cm, and <2 cm were 0.54 (40 of 74) and 0.86 (36 of 42); 0.72 (23 of 32) and 0.80 (4 of 5); and 0.41 (17 of 42) and 0.87 (32 of 37). For the delayed enhancing rim sensitivity and specificity were 0.64 (47 of 74) and 0.86 (36 of 42); 0.75 (24 of 32) and 1.0 (5 of 5); and 0.55 (23 of 42) and 0.83 (31 of 37), respectively. Lesion size (> or =2 cm) and delayed enhancing rim, as main features and their interaction, were the most significant predictors of HCC.

CONCLUSION

Delayed hypointensity and enhancing rim improve the specificity of diagnosis of HCC of all sizes but are seen less frequently in small (<2 cm) HCC. Nodule size (> or =2 cm) and delayed enhancing rim are the strongest predictors of HCC.

MR imaging and CT of the biliary tract

Magnetic resonance (MR) imaging and computed tomography (CT) can be useful in the diagnosis of biliary disease, with both modalities allowing detailed evaluation of the biliary tract. Careful interrogation of the images is critical, regardless of modality. The identification of dilated bile ducts necessitates evaluation for strictures or filling defects, which is best performed with thin-section imaging. Smooth, concentric short-segment strictures favor a benign cause, whereas abrupt, eccentric long-segment strictures favor a malignancy. At MR imaging, extrabiliary entities such as crossing vessels or metallic clip artifact may mimic strictures and should not be mistaken for disease. A stone is the most common biliary filling defect and may occur in the absence of dilated ducts. Stones commonly have a lamellated, geometric shape and are found in a dependent portion of the duct. Identification of bile duct wall thickening raises concern for cholangitis or malignancy. Improved diagnosis of biliary disease can be achieved with a knowledge of the benefits and limitations of modern MR and CT cholangiographic techniques, including the use of biliary-excreted contrast material and of various postprocessing techniques. Familiarity with the radiologic appearances of the duct lumen, wall, and surrounding structures is also important for accurate image interpretation. The rapidly evolving technology for both MR imaging and CT of the biliary tract will continue to present radiologists with opportunities as well as challenges.

Diffusion-weighted MR imaging of the liver at 3.0 Tesla using TRacking Only Navigator echo (TRON): a feasibility study

PURPOSE

To assess the feasibility of TRacking Only Navigator echo (TRON) for diffusion-weighted magnetic resonance imaging (DWI) of the liver at 3.0T.

MATERIALS AND METHODS

Ten volunteers underwent TRON, respiratory triggered, and free breathing DWI of the liver at 3.0 Tesla (T). Scan times were measured. Image sharpness, degree of stair-step and stripe artifacts for the three methods were assessed by two observers.

RESULTS

Mean scan times of TRON and respiratory triggered DWI relative to free breathing DWI were 34% and 145% longer respectively. In four of eight comparisons (two observers, two b-values, two slice orientations), TRON DWI image sharpness was significantly better than free breathing DWI, but inferior to respiratory triggered DWI. In two of four comparisons (two observers, two b-values), degree of stair-step artifacts in TRON DWI was significantly lower than in respiratory triggered DWI. Degree of stripe artifacts between the three methods was not significantly different.

CONCLUSION

DWI of the liver at 3.0T using TRON is feasible. Image sharpness in TRON DWI is superior to that in free breathing DWI. Although image sharpness of respiratory triggered DWI is still better, TRON DWI requires less scan time and reduces stair-step artifacts.

Effect of contrast media on single-shot echo planar imaging: implications for abdominal diffusion imaging

PURPOSE

The goal of this study was to determine the effect of contrast media on the signal behavior of single-shot echo planar imaging (ssEPI) used for abdominal diffusion imaging.

MATERIALS AND METHODS

The signal of an ssEPI spin echo sequence in a water phantom with varying concentrations of gadolinium was modeled with Bloch equations and the predicted behavior validated on a phantom at 1.5T. Six volunteers were given gadolinium contrast and signal intensity (SI) time courses for regions of interest (ROIs) in the liver, pancreas, spleen, renal cortex, and medulla were analyzed. Student's t-test was used to compare precontrast SI to 0, 1, 4, 5, 10, and 13 minutes following contrast.

RESULTS

The results show that following contrast ssEPI SI goes through a nadir, recovering differently for each organ. Maximal contrast-related signal losses relative to precontrast signal are 20%, 20%, 53%, and 67% for the liver, pancreas, renal cortex, and medulla, respectively. The SIs remain statistically below the precontrast values for 5, 4, and 1 minute for the pancreas, liver, and spleen, and for all times measured for the renal cortex and medulla.

CONCLUSION

Abdominal diffusion imaging should be performed prior to contrast due to adverse effects on the signal in ssEPI.

Concomitant resorptive defects of the reproductive tract: a uterocervicovaginal septum and imperforate hymen

OBJECTIVE

To review a case of concomitant longitudinal uterocervicovaginal septum and imperforate hymen.

SETTING

A university-based tertiary care center.

PATIENT(S)

A 14-year-old girl with a septum spanning the length of the uterus, cervix, and upper two-thirds of the vagina, as well as an imperforate hymen.

INTERVENTION(S)

Hymenotomy with subsequent vaginal septoplasty.

MAIN OUTCOME MEASURE(S)

NA.

RESULT(S)

NA.

CONCLUSION(S)

Anatomic anomalies of the reproductive tract may be found in tandem and when suspected, a full evaluation including advanced imaging to clearly delineate the exact anatomy, should be performed before proceeding with surgical correction.

Possible biliary disease: diagnostic performance of high-spatial-resolution isotropic 3D T2-weighted MRCP

PURPOSE

To retrospectively assess the diagnostic performance of magnetic resonance cholangiopancreatography (MRCP) performed by using a high-spatial-resolution isotropic three-dimensional (3D) fast-recovery fast spin-echo (FSE) sequence with parallel imaging for the evaluation of possible biliary disease.

MATERIALS AND METHODS

This HIPAA-compliant study was approved by the institutional review board; informed consent was waived. Ninety-five patients (58 female, 37 male; mean age, 51 years; range, 15-91 years) underwent MRCP by using the respiratory-triggered isotropic 3D fast-recovery FSE sequence and endoscopic or percutaneous direct visualization between March 2003 and June 2007. Two independent readers evaluated the MRCP images for strictures, dilatation, and intraductal filling defects. Sensitivity, specificity, and interobserver agreement (kappa statistics) were determined.

RESULTS

The respective sensitivity and specificity for strictures, dilatation, and intraductal filling defects (all choledocholithiasis) were 86% (40 of 47) and 94% (45 of 48), 98% (57 of 58) and 100% (37 of 37), and 68% (19 of 28) and 97% (65 of 67) for reader 1 and 88% (41 of 47) and 94% (45 of 48), 96% (56 of 58) and 100% (37 of 37), and 75% (21 of 28) and 99% (66 of 67) for reader 2. The sensitivity for stones larger than 3 mm was 94% (15 of 16) for reader 1 and 100% (16 of 16) for reader 2, whereas the sensitivity for stones 3 mm or smaller was 33% (four of 12) for reader 1 and 42% (five of 12) for reader 2. Agreement between readers was good to excellent, with kappa values of 0.76, 0.85, and 0.98 for strictures, dilatation, and choledocholithiasis, respectively.

CONCLUSION

MRCP by using the respiratory-triggered isotropic 3D fast-recovery FSE sequence with parallel imaging demonstrates excellent diagnostic capabilities for possible biliary disease, although it is limited for stones 3 mm or smaller in size.

Apparent wall thickening of cystic renal lesions on MRI

PURPOSE

To show that cystic renal lesions that would otherwise meet criteria for simple cysts can demonstrate perceptible walls or increased wall thickness on MRI, sometimes causing these lesions to be "upgraded." It was hypothesized that thickening of cyst walls on MRI can be artifactual, due to data truncation, applied filtering, and low signal-to-noise ratio (SNR).

MATERIALS AND METHODS

k-Space data for a 4-cm cyst were created in a 40-cm field of view (FOV) (512 x 512 matrix). Additional data sets were created using the central 512 x 256 and 512 x 128 points. Noise was simulated so that the cyst SNR was approximately 7, 14, and 20, respectively. Actual wall thickness was set at 0.25 mm, and cyst:wall signal at 1:4. An inverse two-dimensional (2D) fast Fourier transform (FFT) yielded simulated images. A Fermi filter was applied to reduce ringing. Images/projections were examined for wall thickening. Seven patients with initially thick-walled cysts on fat-saturated spoiled gradient-echo (FS-SPGR) images were scanned with increasing resolution (256 x 128 and 256 x 256; four patients were also scanned with 512 x 512). Average wall thickness at each resolution was compared using a two-tailed paired Student's t-test.

RESULTS

Simulations showed apparent wall thickening at low resolution, improving with higher resolutions. Low SNR and application of the Fermi filter made it difficult to identify ringing as the cause of this thickening. The simulation results were confirmed on seven patients, whose cyst walls proved to be artifactually thickened (P < 0.01).

CONCLUSION

Thickening of cyst walls on MRI can be artifactual. Upon encountering thick-walled cystic renal lesions, high-resolution images can be acquired to exclude apparent thickening.

MR Imaging of hepatocellular carcinoma in the cirrhotic liver: challenges and controversies

The incidence of hepatocellular carcinoma (HCC) is expected to increase in the next 2 decades, largely due to hepatitis C infection and secondary cirrhosis. HCC is being detected at an earlier stage owing to the implementation of screening programs. Biopsy is no longer required prior to treatment, and diagnosis of HCC is heavily dependent on imaging characteristics. The most recent recommendations by the American Association for the Study of Liver Diseases (AASLD) state that a diagnosis of HCC can be made if a mass larger than 2 cm shows typical features of HCC (hypervascularity in the arterial phase and washout in the venous phase) at contrast material-enhanced computed tomography or magnetic resonance (MR) imaging or if a mass measuring 1-2 cm shows these features at both modalities. There is an ever-increasing demand on radiologists to detect smaller tumors, when curative therapies are most effective. However, the major difficulty in imaging cirrhosis is the characterization of hypervascular nodules smaller than 2 cm, which often have nonspecific imaging characteristics. The authors present a review of the MR imaging and pathologic features of regenerative nodules and dysplastic nodules and focus on HCC in the cirrhotic liver, with particular reference to small tumors and lesions that may mimic HCC. The authors also review the sensitivity of MR imaging for the detection of these tumors and discuss the staging of HCC and the treatment options in the context of the guidelines of the AASLD and the imaging criteria required by the United Network for Organ Sharing for transplantation. MR findings following ablation and chemoembolization are also reviewed.

3D excretory MR urography: Improved image quality with intravenous saline and diuretic administration

PURPOSE

To assess the effect of diuretic administration on the image quality of excretory magnetic resonance urography (MRU) obtained following intravenous hydration, and to determine whether intravenous hydration alone is sufficient to produce diagnostic quality studies of nondilated upper tracts.

MATERIALS AND METHODS

A total of 22 patients with nondilated upper tracts were evaluated with contrast-enhanced MRU. All patients received 250 mL of saline intravenously immediately prior to the examination. A total of 11 patients received 10-20 mg furosemide in addition to saline. Imaging was performed with a three-dimensional (3D) and two-dimensional (2D) breathhold spoiled gradient-echo sequences. Excretory MRU images were acquired five minutes after the administration of 0.1 mmol/kg gadolinium and were independently reviewed by two radiologists, who were blinded to the MRU technique. Readers evaluated the calyces, renal pelvis, and ureters qualitatively for degree of opacification, distention, and artifacts on a four-point scale. Statistical analysis was performed using a permutation test.

RESULTS

There was no significant disagreement between the two readers (P=0.14). Furosemide resulted in significant improvement in calyceal and renal pelvis distention (P<0.005), and significant artifact reduction in all upper tract segments (P<0.001) compared to the effect of saline alone.

CONCLUSION

Intravenous furosemide significantly improves the image quality of excretory MRU studies obtained following intravenous hydration. Intravenous saline alone is insufficient to produce diagnostic quality studies of the non-dilated upper tracts.

Preoperative MR Angiography in Free Fibula Flap Transfer for Head and Neck Cancer: Clinical Application and Influence on Surgical Decision Making

OBJECTIVE

We review the fibular free flap surgical procedure to illustrate the usefulness of preoperative lower limb MR angiography and to show how calf vascular anatomy on MR angiography affects patient surgical management.

CONCLUSION

With its high positive predictive value and sensitivity, preoperative MR angiography can improve the chances of a successful outcome at the recipient mandibular site. It provides the reconstructive surgeon with a road map, revealing vascular anomalies or disease that could alter or contraindicate surgery.

Lack of tumor seeding of hepatocellular carcinoma after percutaneous needle biopsy using coaxial cutting needle technique

OBJECTIVE

The objective of our study was to determine the incidence of tumor seeding after biopsy of hepatocellular carcinoma (HCC) using a coaxial cutting needle technique. Seeding along the needle track is a dreaded complication of percutaneous biopsy in patients with HCC, particularly in potential liver transplant recipients. Reported seeding rates range from 0.6% to 5.1% using various biopsy techniques. To our knowledge, the rate of seeding using a coaxial cutting needle technique has not been reported.

MATERIALS AND METHODS

Retrospective review identified 128 patients with imaging-guided percutaneous liver biopsies positive for HCC. A coaxial cutting needle technique was uniformly used with a 17-gauge introducer and 18-gauge biopsy needle. Radiology and clinical reports were reviewed, and findings at clinical and imaging follow-up were assessed.

RESULTS

During the 6-year study period, 1,012 liver mass biopsies were performed, with 128 positive for HCC (100 men and 28 women; average age, 58.4 years). One hundred one patients had more than 30 days of clinical or imaging follow-up (or both) after biopsy (mean, 410 days; range, 33-1,989 days) and constituted the study population. The remaining 27 were excluded because of inadequate follow-up. No suspected or confirmed tumor seeding on imaging, physical examination, or laparotomy was identified.

CONCLUSION

We found no tumor seeding after percutaneous biopsy of HCC using a coaxial cutting needle technique. This rate, 0%, is lower than those reported with other techniques. The use of a needle introducer that remains in position during multiple cutting needle passes protects normal tissue along the track and may reduce seeding. This has particular importance for patients with stage I-II HCC, for whom liver transplantation may be curative.

MRI of sonographically indeterminate adnexal masses

OBJECTIVE

The purpose of this study was to assess the ability of MRI to characterize sonographically indeterminate adnexal masses and to define the sonographic features contributing to indeterminate diagnoses.

MATERIALS AND METHODS

Two blinded radiologists retrospectively reviewed the MRI examinations of 87 patients with 95 sonographically indeterminate adnexal masses. Reviewers determined the origin of a mass, its tissue content (cystic, solid, complex cystic, or cystic and solid), tissue characteristics (fat, blood, fibrous, or leiomyomatous), and benignity versus malignancy. Sonograms were reviewed by three reviewers to determine the origin of a mass, its tissue content, and reasons for an indeterminate diagnosis. Sensitivity and specificity of MRI were calculated, and agreement of sonography and MRI with the final diagnosis was determined using kappa statistics. The final diagnosis was determined by histopathology, surgical findings, or imaging or clinical follow-up.

RESULTS

The sensitivity of MRI for identifying malignancy (n = 5) was 100% and its specificity for benignity (n = 90) was 94%. Excellent agreement was seen between MRI and the final diagnosis for determining the origin (kappa = 0.93), tissue content (kappa = 0.98), and tissue characteristics (kappa = 0.91) of a mass. Sonography had poor agreement with the final diagnosis for the origin (kappa = 0.19) and tissue content (kappa = 0.33) of a mass. The main reasons for indeterminate sonographic diagnoses were the inability to determine origin because of location and large mass size and the appearances of purely solid or complex cystic masses.

CONCLUSION

Sonographically indeterminate adnexal masses of uncertain origin and solid or complex cystic content benefit from further evaluation with MRI, which is highly accurate for identifying the origin of a mass and characterizing its tissue content, obviating surgery.

Levator plate angle in women with pelvic organ prolapse compared to women with normal support using dynamic MR imaging

OBJECTIVE

The purpose of this study was to determine whether the levator plate is (1) horizontal in women with normal support, (2) different between women with and without prolapse, (3) related to levator hiatus and perineal body descent.

STUDY DESIGN

Cohorts of cases with prolapse at least 1 cm below the hymen and normal controls with all points 1 cm or more above the hymen were prospectively enrolled in a study of pelvic organ support to be of similar age, race, and parity. Subjects underwent supine midsagittal dynamic magnetic resonance imaging (MRI) during Valsalva. Levator plate angle (LPA) was measured relative to a horizontal reference line. Levator hiatus length (LH) and perineal body location (PB) were also measured. Student t tests and Pearson correlation coefficients (r) were performed.

RESULTS

Sixty-eight controls and 74 cases were analyzed. During Valsalva, controls had a mean LPA of 44.3 degrees . Cases, compared to controls, had 9.1 degrees (21%) more caudally directed LPA (53.4 degrees vs 44.3 degrees , P < .01), 15% larger LH length (7.8 cm vs 6.8 cm, P < .01), and 24% more caudal PB location (6.8 cm vs 5.5 cm, P < .01). Increases in LPA were correlated with increased LH length (r = 0.42, P < .0001) and PB location (r =.51, P < .0001).

CONCLUSION

The measured levator plate angle in women with normal support is 44.3 degrees . During Valsalva, women with prolapse have a modest (9.1 degrees) though statistically greater levator plate angle compared to controls. This larger angle showed moderate correlation with larger levator hiatus length and greater displacement of the perineal body in women with prolapse compared to controls.

The relationship between anterior and apical compartment support

OBJECTIVE

The purpose of this study was to determine whether the degree of anterior compartment (bladder) and apical compartment (cervix) prolapse are correlated, and whether 2 anterior compartment elements (urethra and bladder) are related at maximal Valsalva.

STUDY DESIGN

Women with a complete spectrum of pelvic support were recruited for a pelvic support study. Dynamic magnetic resonance scans were taken during Valsalva. A convenience sample of 153 women with a mean age of 53.3 +/- 12.5 (SD) years with a uterus in situ was studied. Anterior compartment status was assessed by the most caudal bladder point and the internal urinary meatus. The external cervical os was used to assess the apical compartment. The position of the bladder, urethra, and uterus were determined in 20 nulliparous women to determine their reference locations. The distances of each structure below the reference positions were calculated at maximum Valsalva.

RESULTS

Average distances of the bladder base, urethra, and uterus from the reference positions at maximal Valsalva were 4.1 +/- 2.4 cm, 3.1 +/- 1.3 cm, and 4.3 +/- 2.4 cm, respectively. The Pearson correlation coefficient of the relationship between the bladder base and uterine distances was r = 0.73 (r2 = 0.53). The Pearson correlation coefficient of the bladder distance and urethral distance was r = 0.82 (r2 = 0.67).

CONCLUSION

Half of the observed variation in anterior compartment support may be explained by apical support.

Hepatic fat fraction: MR imaging for quantitative measurement and display--early experience

The institutional review board approved this HIPAA-compliant study. After all five patients with nonalcoholic fatty liver disease signed a consent, they underwent magnetic resonance (MR) imaging for hepatic fat quantification. The purpose of this study was to develop a fast and accurate method to acquire and display quantitative maps of the percentage of hepatic fat. In-phase and out-of-phase gradient-echo MR imaging was performed with dual flip angles (70 degrees, 20 degrees) to resolve ambiguity of the dominant constituent. T2* corrections were also estimated and applied to generate color-coded maps of the estimated percentage of hepatic fat. MR imaging results were compared with biopsy results in two of five patients, and the technique was validated qualitatively and quantitatively with a water-oil phantom. Results of the phantom study confirmed that the dual-flip angle algorithm can be used to correctly identify the dominant constituent, allowing depiction of 0%-100% of fat content. The estimated liver fat fraction was comparable to quantitative fat measurements at biopsy in both patients (MR imaging, 18.3% +/- 2.8 [standard deviation] and 28.6% +/- 2.4, vs quantitative histopathologic analysis, 11.2% and 28.5%, respectively).

SUPPLEMENTAL MATERIAL

radiology.rsnajnls.org/cgi/content/full/2373041639/DC1

Improving the prediction of hepatocellular carcinoma in cirrhotic patients with an arterially-enhancing liver mass

In the United States, cirrhotic patients with known or suspected hepatocellular carcinoma (HCC) are prioritized for liver transplantation. Noninvasive criteria for the diagnosis of HCC rely on arterial enhancement of a mass. The aim of this study was to determine whether clinical, laboratory, and / or radiologic data can improve the prediction of HCC in cirrhotic patients with an arterially-enhancing mass. Between May 2002 and June 2003, dynamic gadolinium-enhanced magnetic resonance imaging (MRI) of consecutive patients with liver cirrhosis and a solid mass were reviewed by 2 radiologists blinded to the clinical diagnosis. Clinical, laboratory, and radiologic data were recorded for all patients. A total of 94 patients with cirrhosis and an arterially-enhancing liver mass were studied, 66 (70%) of whom had HCC. Alpha-fetoprotein (AFP) >20 ng/mL (P = .029), tumor size >2 cm (P = .0018), and delayed hypointensity (P = .0001) were independent predictors of HCC. Delayed hypointensity of an arterially-enhancing mass had a sensitivity of 89% and a specificity of 96% for HCC. The presence of delayed hypointensity was the only independent predictor of HCC among patients with arterially-enhancing lesions <2 cm (odds ratio, 6.3; 95% confidence interval [CI], 1.8-13), with a sensitivity of 80% and a specificity of 95%. In conclusion, delayed hypointensity of an arterially-enhancing mass was the strongest independent predictor of HCC, regardless of the size of the lesion. If additional studies confirm our results, the noninvasive criteria utilized to make a diagnosis of HCC should be revised.

MR imaging of the adrenal glands

MR imaging is used commonly for imaging the adrenal glands. Its high-contrast resolution and multiplanar imaging capability enables the detection and characterization of many adrenal masses. The advent of chemical-shift imaging revolutionized the role of MR imaging in characterizing adrenal masses. In this article, the authors discuss the range of MR appearances of common and uncommon adrenal masses, focusing on the nonfunctioning incidentally discovered mass and its characterization methods. MR imaging is continuously improving. The increasing use of higher strength magnets and the introduction of newer coils, sequences, and techniques will help detect and characterize very small adrenal masses, quantify their fat content, and provide exquisite morphologic images of the gland and its vascular supply.