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Upper-extremity venous thrombosis often presents as unilateral arm swelling. The differential diagnosis includes lesions compressing the veins and causing a functional venous obstruction, venous stenosis, an infection causing edema, obstruction of previously functioning lymphatics, or the absence of sufficient lymphatic channels to ensure effective drainage. The following recommendations are made with the understanding that venous disease, specifically venous thrombosis, is the primary diagnosis to be excluded or confirmed in a patient presenting with unilateral upper-extremity swelling. Contrast venography remains the best reference-standard diagnostic test for suspected upper-extremity acute venous thrombosis and may be needed whenever other noninvasive strategies fail to adequately image the upper-extremity veins. Duplex, color flow, and compression ultrasound have also established a clear role in evaluation of the more peripheral veins that are accessible to sonography. Gadolinium contrast-enhanced MRI is routinely used to evaluate the status of the central veins. Delayed CT venography can often be used to confirm or exclude more central vein venous thrombi, although substantial contrast loads are required. The ACR Appropriateness Criteria((R)) are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment. [ABSTRACT FROM AUTHOR]

Lower-extremity arteriopathy patients can be managed nonsurgically, but there is no standard algorithm for follow-up. The authors present a consensus on appropriate postangioplasty studies in the setting of claudication or a threatened limb. Physical examination with measurements of the ankle-brachial index should be the first step in patients with recurrent symptoms. When there is high clinical suspicion for a threatened limb, the patient should proceed directly to catheter angiography for possible reintervention. However, in the setting of claudication alone, segmental Doppler pressures and pulse volume recordings are the initial test of choice. Magnetic resonance angiography or ultrasound can be used in conjunction to further characterize lesions with more detail. Computed tomographic angiography may also be used to image lower-extremity vasculature but is limited by the presence of large amounts of vascular calcifications. Novel techniques, including dual-energy computed tomographic angiography and noncontrast magnetic resonance angiography, may provide clinicians with alternative approaches in patients with large amounts of vascular calcifications and renal insufficiency, respectively. [ABSTRACT FROM AUTHOR]

Advances in MRI technology have led to the development of low-field-strength (hereafter, "low-field") (0.55 T) MRI systems with lower weight, fewer shielding requirements, and lower cost than those of traditional (1.5-3 T) systems. The trade-offs of lower signal-to-noise ratio (SNR) at 0.55 T are partially offset by patient safety and potential comfort advantages (eg, lower specific absorption rate and a more cost-effective larger bore diameter) and physical advantages (eg, decreased T2* decay, shorter T1 relaxation times). Image reconstruction advances leveraging developing technologies (such as deep learning-based denoising) can be paired with traditional techniques (such as increasing the number of signal averages) to improve SNR. The overall image quality produced by low-field MRI systems, although perhaps somewhat inferior to 1.5-3 T MRI systems in terms of SNR, is nevertheless diagnostic for a broad variety of body imaging applications. Effective low-field body MRI requires (a) an understanding of the trade-offs resulting from lower field strengths, (b) an approach to modifying routine sequences to overcome SNR challenges, and (c) a workflow for carefully selecting appropriate patients. The authors describe the rationale, opportunities, and challenges of low-field body MRI; discuss important considerations for low-field imaging with common body MRI sequences; and delineate a variety of use cases for low-field body MRI. The authors also include lessons learned from their preliminary experience with a new low-field MRI system at a tertiary care center. Finally, they explore the future of low-field MRI, summarizing current limitations and potential future developments that may enhance the clinical adoption of this technology. © RSNA, 2023 Supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Venkatesh in this issue.

Background: Although studies have described factors associated with failed magnetic resonance elastography (MRE), little is known about what factors influence usable elastography data., Purpose: To identify factors that have a negative impact on percent measurable liver volume (pMLV), defined as the proportion of usable liver elastography data relative to the volume of imaged liver in patients undergoing MRE., Study Type: Retrospective., Subjects: A total of 264 patients (n = 132 males, n = 132 females; mean age = 57 years) with suspected or known chronic liver disease underwent MRE paired with a liver protocol MRI., Field Strength/sequence: MRE was performed on a single 1.5 T scanner using a two-dimensional gradient-recalled echo phase-contrast sequence with a passive acoustic driver overlying the right hemiliver., Assessment: Stiffness maps (usable data at 95% confidence) and liver contours on magnitude images of the MRE acquisition were manually traced and used to assess mean stiffness and pMLV. Hepatic fat fraction and R 2 * values were also calculated. The distance from the acoustic wave generator on the skin surface to the liver edge was measured. Two radiologists performed the MR analyses with 50 overlapping cases for inter-reader analysis., Statistical Tests: Linear regression was performed to identify factors significantly associated with pMLV. Intraclass correlation was performed for inter-reader reliability., Results: pMLV was 31% ± 20% (range 0%-86%). Complete MRE failure (i.e. pMLV = 0%) occurred in 10 patients (4%). Multivariate linear regression identified higher hepatic fat fraction, R 2 *, BMI, and driver-to-liver surface distance; male sex; and lower mean liver stiffness was significantly independently associated with lower pMLV. Intraclass correlation for pMLV was 0.96, suggestive of excellent reliability., Data Conclusion: Higher fat fraction, R 2 *, BMI, driver-to-liver surface distance, male sex, and lower mean liver stiffness were associated with lower pMLV. Optimization of image acquisition parameters and driver placement may improve MRE quality, and pMLV likely serves as a diagnostic utility quality control metric., Level of Evidence: 3 TECHNICAL EFFICACY STAGE: 2., (© 2021 International Society for Magnetic Resonance in Medicine.)

OBJECTIVE. The purpose of this article was to assess the reliability and accuracy of hepatic periportal space widening and other qualitative imaging features for the prediction of hepatic fibrosis. MATERIALS AND METHODS. This single-center retrospective study identified consecutive patients who had undergone liver MR elastography. Two abdominal radiologists independently reviewed anatomic images, assessing multiple qualitative features of chronic liver disease (CLD) including periportal space widening. Each reader also measured the periportal space at the main portal vein (MPV) and right portal vein (RPV). Interrater reliability analysis was then performed. Sensitivity and specificity were determined for the detection of any hepatic fibrosis (stage I or higher) and of advanced fibrosis (stage III or higher) using stiffness on MR elastography as the reference standard. RESULTS. Of 229 subjects, 157 (69%) had fibrosis and 78 (34%) had advanced fibrosis. Agreement for periportal space widening was moderate (κ = 0.47), and agreement for remaining features was moderate to substantial (κ = 0.42-0.80). Agreement for the periportal space at the MPV was moderate (ICC, 0.55), and agreement for the periportal space at the RPV was near perfect (ICC, 0.83). Periportal space widening had the highest sensitivity (83.0%) for any fibrosis, with limited specificity (61.3%). Surface nodularity had the highest specificity (94.4%) for any fibrosis, with limited sensitivity (51.6%). Periportal space widening plus one or more additional imaging feature of CLD or the presence of surface nodularity alone had sensitivity of 72.6% and specificity of 76.1%. A periportal space at the MPV greater than 9.5 mm had substantial agreement with qualitative periportal space widening (κ = 0.74). CONCLUSION. Periportal space widening has a high sensitivity for hepatic fibrosis, with moderate specificity when combined with additional anatomic features of CLD.

Scheduling of CT and MR exams requires reasonable estimates for expected scan duration. However, scan-time variability and efficiency gains from combining multiple exams are not quantitatively well characterized. In this work, we developed an informatics approach to quantify typical duration, duration variability, and multiple-procedure efficiency on a large scale, and used the approach to analyze 48,766 CT- and MR-based neuroradiological exams performed over one year. We found MR exam durations demonstrated higher absolute variability, but lower relative variability and lower multiple-procedure efficiency, compared to CT exams (p < 0.001). Our approach enables quantification of real-world operational performance and variability to inform optimal patient scheduling, efficient resource utilization, and sustainable service planning.

Spontaneous rupture of the inferior vena cava (IVC) is a rare entity. We report a case of a spontaneous IVC rupture associated with IVC filter thrombosis in a patient presenting with severe atraumatic back pain. Computed tomography (CT) identified a retroperitoneal hematoma and suggested IVC thrombosis. Magnetic resonance (MR) imaging confirmed the presence of IVC filter thrombosis and demonstrated a large defect in the infrarenal IVC, with the vessel lumen in free communication with the adjacent hematoma. The patient was managed conservatively and discharged in stable condition. MR imaging played an important role in characterizing the CT findings, which were unclear., (Copyright Journal of Radiology Case Reports.)

Objective: Tertiary care practices increasingly provide second-opinion consultations on reports from outside practices or institutions. This practice of providing a second opinion has been studied in a variety of subspecialties; however, its potential effect on the management of hepatopancreaticobiliary (HPB) disease is not known. The purpose of this study was to assess the rate of significant discrepancies between the initial report and the consultation report, the source of discrepancies, and the frequency of repeat imaging recommendations., Materials and Methods: Retrospective chart review was performed for 480 consecutive CT and MRI consultation reports interpreted between January 2014 and December 2015 for patients with HPB diseases whose initial CT and MRI reports were generated at outside facilities. The initial report and the consultation report were independently reviewed and compared by two abdominal radiologists. Discrepancies between the initial report and the consultation report were divided into minor and major differences in the detection or interpretation of abnormalities. Clinical importance was defined as a change in a finding or interpretation that directly impacted management of the patient., Results: A major discrepancy between the reports was identified in 27-28% of cases split evenly between detection and interpretation of abnormalities. Interreader agreement for categorization was moderate (weighted kappa value, 0.49). In consensus review, the rate of a major discrepancy occurring increased to 32%. Common sources of discrepancy were interpretation of findings as malignant versus benign (49% of cases) and accuracy of staging (15% of cases). Imaging limitations were described in 16% of cases, commonly as a result of an insufficient protocol or poor image quality., Conclusion: Discrepancies in interpretation resulting in direct implications for clinical management are seen in almost one-third of HPB consultation cases. Second-opinion imaging consultation in the tertiary care setting can frequently impact management.

The treatment of cancer using targeted radionuclide therapy is of interest to nuclear medicine and radiation oncology because of its potential for killing tumor cells while minimizing dose-limiting toxicities to normal tissue. The ionizing radiations emitted by radiopharmaceuticals deliver radiation absorbed doses over protracted periods of time with continuously varying dose rates. As targeted radionuclide therapy becomes a more prominent part of cancer therapy, accurate models for estimating the biologically effective dose (BED) or equieffective dose (EQD2 α/β ) will become essential for treatment planning. This study examines the radiobiological impact of the dose rate increase half-time during the uptake phase of the radiopharmaceutical. MDA-MB-231 human breast cancer cells and V79 Chinese hamster lung fibroblasts were irradiated chronically with 662 keV γ rays delivered with time-varying dose rates that are clinically relevant. The temporal dose-rate patterns were: 1. acute, 2. exponential decrease with a half-time of 64 h (T d = 64 h), 3. initial exponential increase to a maximum (half time T i = 2, 8 or 24 h) followed by exponential decrease (T d = 64 h). Cell survival assays were conducted and surviving fractions were determined. There was a marked reduction in biological effect when T i was increased. Cell survival data were tested against existing dose-response models to assess their capacity to predict response. Currently accepted models that are used in radiation oncology overestimated BED and EQD2 α/β at low-dose rates and underestimated them at high-dose rates. This appears to be caused by an adaptive response arising as a consequence of the initial low-dose-rate phase of exposure. An adaptive response function was derived that yields more accurate BED and EQD2 α/β values over the spectrum of dose rates and absorbed doses delivered. Our experimental data demonstrate a marked increase in cell survival when the dose-rate-increase half-time is increased, thereby suggesting an adaptive response arising as a consequence of this phase of exposure. We have modified conventional radiobiological models used in the clinic for brachytherapy and external beams of radiation to account for this phenomenon and facilitate their use for treatment planning in targeted radionuclide therapy.

Background & Objectives: Multidisciplinary tumor boards (MDTBs) are frequently employed in cancer centers but their value has been debated. We reviewed the decision-making process and resource utilization of our MDTB to assess its utility in the management of pancreatic and upper gastrointestinal tract conditions., Methods: A prospectively-collected database was reviewed over a 12-month period. The primary outcome was change in management plan as a result of case discussion. Secondary outcomes included resources required to hold MDTB, survival, and adherence to treatment guidelines., Results: Four hundred seventy cases were reviewed. MDTB resulted in a change in the proposed plan of management in 101 of 402 evaluable cases (25.1%). New plans favored obtaining additional diagnostic workup. No recorded variables were associated with a change in plan. For newly-diagnosed cases of pancreatic ductal adenocarcinoma (n = 33), survival time was not impacted by MDTB (p = .154) and adherence to National Comprehensive Cancer Network guidelines was 100%. The estimated cost of physician time per case reviewed was $190., Conclusions: Our MDTB influences treatment decisions in a sizeable number of cases with excellent adherence to national guidelines. However, this requires significant time expenditure and may not impact outcomes. Regular assessments of the effectiveness of MDTBs should be undertaken., (Copyright © 2016 International Hepato-Pancreato-Biliary Association Inc. Published by Elsevier Ltd. All rights reserved.)

Primary aortic neoplasms are rare. Aortic sarcoma arising after endovascular aneurysm repair (EVAR) is a scarce subset of primary aortic malignancies, reports of which are infrequent in the published literature. The diagnosis of aortic sarcoma is challenging due to its non-specific clinical presentation, and the prognosis is poor due to delayed diagnosis, rapid proliferation, and propensity for metastasis. Post-EVAR, aortic sarcomas may mimic other more common aortic processes on surveillance imaging. Radiologists are rarely knowledgeable about this rare entity for which multimodality imaging and awareness are invaluable in early diagnosis. A series of three pathologically confirmed cases are presented to display the multimodality imaging features and clinical presentations of aortic sarcoma arising after EVAR.

Picture archiving and communication systems (PACS) play a critical role in radiology. This paper presents the criteria important to PACS administrators for selecting a PACS. A set of criteria are identified and organized into an integrative hierarchical framework. Survey responses from 48 administrators are used to identify the relative weights of these criteria through an analytical hierarchy process. The five main dimensions for PACS selection in order of importance are system continuity and functionality, system performance and architecture, user interface for workflow management, user interface for image manipulation, and display quality. Among the subdimensions, the highest weights were assessed for security, backup, and continuity; tools for continuous performance monitoring; support for multispecialty images; and voice recognition/transcription. PACS administrators' preferences were generally in line with that of previously reported results for radiologists. Both groups assigned the highest priority to ensuring business continuity and preventing loss of data through features such as security, backup, downtime prevention, and tools for continuous PACS performance monitoring. PACS administrators' next high priorities were support for multispecialty images, image retrieval speeds from short-term and long-term storage, real-time monitoring, and architectural issues of compatibility and integration with other products. Thus, next to ensuring business continuity, administrators' focus was on issues that impact their ability to deliver services and support. On the other hand, radiologists gave high priorities to voice recognition, transcription, and reporting; structured reporting; and convenience and responsiveness in manipulation of images. Thus, radiologists' focus appears to be on issues that may impact their productivity, effort, and accuracy.

Combined hepatocellular-cholangiocarcinoma (CHC), also referred to as primary liver carcinoma (PLC) with biphenotypic differentiation, is an increasingly recognized subtype of malignant PLC encompassing varying morphologic forms thought to arise either from progenitor cell lineage or dedifferentiation of mature liver cells. Tumor cells express both biliary and hepatocellular markers by immunohistochemistry, and may also express progenitor cell and stem cell markers. Due to the relative rarity of this tumor type, little is known about the risk factors, imaging appearance, or prognosis. Few studies have demonstrated risk factors that overlap with hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC), though not all appear to arise in the background of cirrhosis. The imaging appearances of these tumors may overlap with those of HCC and CC and discriminating features such as classic enhancement patterns and biliary ductal dilation are not universally present. Serum tumor markers, such as alpha-fetoprotein and carbohydrate antigen 19-9, may be helpful when they are discordant with imaging or if both are elevated to a significant degree. In regards to management and prognosis, most studies demonstrate worse outcomes compared with HCC or CC. In the United States, the diagnosis of HCC is frequently made with imaging alone, and subsequent management decisions, including organ allocation for transplantation, rely upon the radiological diagnosis. Given the importance of radiological diagnosis, awareness of this tumor type is essential for appropriate management.

The purpose of this article is to introduce the underlying challenges associated with the incorporation of magnetic resonance imaging (MRI) into the new hybrid imaging modality simultaneous positron emission tomography (PET)/MR and their impact on attenuation correction, sequence optimization, and protocol development. Many adjustments to MR sequences are necessary for optimal whole-body and fused image results., (Copyright © 2013 Wiley Periodicals, Inc.)

Purpose: To compare [(18)F]fluorodeoxyglucose (FDG)/positron emission tomography (PET)/computed tomography (CT) and magnetic resonance imaging (MRI) for evaluating patients with cervical cancer. We compared tumor characteristics on FDG-PET and apparent diffusion coefficient (ADC) maps on diffusion-weighted MRI (DWI) to evaluate concordance of two functional imaging techniques., Materials and Methods: Twenty women with cervical cancer underwent pretreatment FDG-PET/CT and pelvic MRI. Images were rigidly fused by pelvic anatomy using coregistration software. Tumor contours on PET images were generated by autosegmentation of the region containing at least 40% of the maximum standardized uptake value (SUV). DWI contours were generated by manual segmentation. Tumor volume similarity was evaluated using the [PET]/[ADC] volume proportion, Dice's coefficient, and the mean SUV isothreshold at the surface of each ADC contour. Tumor subvolume similarity was evaluated with analysis of variance (ANOVA)., Results: The [PET]/[ADC] volume proportion was 0.88 ± 0.14. Dice's coefficient between PET and ADC tumor contours was 0.76 ± 0.06. The mean SUV isothreshold at the ADC-delineated tumor surface was 34 ± 4%. Subvolumes with increased metabolic activity on FDG-PET also had more restricted diffusion on DWI (P < 0.0001, ANOVA)., Conclusion: Concordance of functional imaging was observed between FDG-PET and DWI for cervical cancer. Tumor subvolumes with increased metabolic activity on FDG-PET also have greater cell density by DWI., (Copyright © 2012 Wiley Periodicals, Inc.)

Purpose: To determine which measurement of donor renal size on computed tomographic (CT) angiograms has the greatest correlation with renal function preoperatively in the donor and postoperatively in the transplant recipient., Materials and Methods: Informed consent was waived for this retrospective HIPAA-compliant study approved by the institutional review board. Renal length, total volume, and cortical volume were measured on renal donor CT angiograms in 111 patients. Preoperative serum creatinine values for donors and postoperative creatinine values for recipients at hospital discharge and 6, 12, 24, and 36 months after transplant were collected, and estimated glomerular filtration rate (eGFR) was calculated. Correlation coefficients with 95% confidence intervals (CIs) were obtained for renal measures and donor eGFR and for renal measures adjusted to recipient body habitus and posttransplant creatinine level in the recipient. Thresholds were set for adjusted length and volumes, and the odds ratio (OR) for creatinine level less than 1.5 mg/dL at 36 months was calculated., Results: Renal volumes and length were correlated with donor eGFR (r=0.58 [95% CI: 0.44, 0.69] for cortical volume, 0.56 [95% CI: 0.42, 0.68] for total volume, and 0.43 [95% CI: 0.27, 0.57] for renal length). All three measures, adjusted to recipient body habitus, were correlated with recipient renal function from discharge (r=-0.41 to -0.43) up to 36 months after transplantation (r=-0.33 to -0.41). By using a threshold of 1.5 for cortical volume to recipient weight, 2.25 for total volume to recipient weight, and 0.175 for renal length to recipient weight, the odds of creatinine level greater than 1.5 mg/dL were four times as great for smaller kidney-to-recipient weight ratios, a statistically significant pattern for cortical volume (OR, 4.07; 95% CI: 1.10, 15.09) but not total volume (OR, 4.24; 95% CI: 0.90, 20.01) or renal length (OR, 4.08; 95% CI: 0.48-34.29)., Conclusion: Renal length and volumes correlated with recipient renal function up to 36 months after transplant. A low ratio of cortical volume to recipient weight was associated with diminished renal function at 36 months after transplant., (© RSNA, 2012.)

Because of its lack of ionizing radiation and excellent soft-tissue contrast, magnetic resonance (MR) imaging is being increasingly used in the evaluation of acute abdominal pain in the pregnant patient. Roughly 2% of all pregnancies are ectopic. Although ectopic pregnancy is usually diagnosed on the basis of a combination of clinical, laboratory, and ultrasonographic findings, it occasionally is initially identified at MR imaging. Thus, it is imperative that the radiologist should be familiar with the variable appearance of ectopic pregnancy at MR imaging and should evaluate for ectopic pregnancy at any time when (a) a patient has positive results of a pregnancy test and (b) an intrauterine pregnancy is not definitively seen. Because of potential issues of fetal safety, a conservative approach should be used for MR imaging in pregnancy. An MR imaging protocol for the evaluation of possible appendicitis in pregnant women is detailed. Specific findings that can aid in the diagnosis of ectopic pregnancy are the lack of an intrauterine pregnancy, isolated hemoperitoneum, tubal masses, hematosalpinx, and interstitial masses. In the differential diagnosis of acute abdominal pain in pregnancy, consideration should be given to the more unusual forms of ectopic pregnancy, such as angular pregnancy, cornual pregnancy, and abdominal pregnancy. Potential mimics of ectopic pregnancy include placental abnormalities, ovarian neoplasms, and corpus luteum cysts.

Purpose: T2-weighted (T2W) magnetic resonance imaging (MRI) has been used for target delineation in cervix cancer brachytherapy. The objective of this study was to examine the feasibility of using diffusion-weighted magnetic resonance imaging (DWI) for target delineation as compared against T2W imaging., Material and Methods: Fifteen cervix cancer patients, implanted with tandem and ovoid applicators, underwent T2W turbo-spin echo imaging and DWI with a maximum diffusion factor of 800 sec/mm(2) on a 1.5-T MR scanner. Apparent diffusion coefficient (ADC) maps were derived from the DWI. The gross tumor volume was manually delineated on the T2W and ADC datasets for each patient. The agreement between T2W- and ADC-delineated volumes was assessed using the Dice similarity coefficient (DSC). An algorithm was developed to compare the edge contrast of the delineated volumes on T2W images and ADC maps by calculating the percentage difference in the intensity values of selected regions of pixels inside versus outside the target contour., Results: ADC-delineated volumes were generally smaller than T2W-delineated volumes, yielding a low DSC of 0.54 ± 0.22. ADC maps were found to display superior definition of the target volume edge relative to T2W images, yielding a statistically significant difference between the mean edge contrast on ADC (12.7 ± 7.7%) versus that on T2W images (4.6 ± 3.2%; p = 0.0010)., Conclusions: These results suggest that incorporating the use of DWI for cervix cancer brachytherapy may yield gross tumor volumes that are different from those based on T2W images alone.

This article is a review of magnetic resonance imaging (MRI) of incidental focal liver lesions. This review provides an overview of liver MRI protocol, diffusion-weighted imaging, and contrast agents. Additionally, the most commonly encountered benign and malignant lesions are discussed with emphasis on imaging appearance and the diagnostic performance of MRI based on a review of the literature., (Copyright © 2011 American Association for the Study of Liver Diseases.)

Background: Symptomatic Crohn's disease (CD) patients often undergo diagnostic imaging studies for evaluation of disease activity or complications including bowel strictures and obstruction. Magnetic resonance enterography (MRE) provides information regarding disease activity, chronicity, and stricture formation without using ionizing radiation., Aim: Examine the use of MRE among CD patients presenting with symptoms suggesting obstruction in a tertiary care practice setting., Methods: We performed a retrospective study of all CD patients undergoing MRE at a tertiary IBD referral center over a 3-year study period including a subgroup analysis of patients presenting obstructive symptoms. Positive and negative findings from MRE were correlated with medical and surgical decision outcomes over the subsequent 90-day period., Results: In the study, 119 CD patients underwent 133 MRE scans, including 40 scans on individuals presenting with obstructive symptoms. Positive findings of CD including active inflammation, stricturing, and penetrating disease were more frequent in MREs ordered to evaluate obstructive symptoms (87.5%) compared other indications (58.1%, p = 0.001). In patients presenting with obstructive symptoms, MRE findings assisted in directing a change of clinical management towards escalation of medical therapy in 55% and surgery in 32.5%. Review of surgical resection specimens corroborated MRE findings of disease activity and fibrosis in 92% of cases going to surgery., Conclusions: In practice-based use at a tertiary IBD referral center, MRE provided an effective, radiation-free alternative to computed tomography by providing valuable diagnostic information for evaluating and directing care in Crohn's disease, particularly for patients presenting with obstructive symptoms.

Picture archiving and communication systems (PACS) are being widely adopted in radiology practice. The objective of this study was to find radiologists' perspective on the relative importance of the required features when selecting or developing a PACS. Important features for PACS were identified based on the literature and consultation/interviews with radiologists. These features were categorized and organized into a logical hierarchy consisting of the main dimensions and sub-dimensions. An online survey was conducted to obtain data from 58 radiologists about their relative preferences. Analytical hierarchy process methodology was used to determine the relative priority weights for different dimensions along with the consistency of responses. System continuity and functionality was found to be the most important dimension, followed by system performance and architecture, user interface for workflow management, user interface for image manipulation, and display quality. Among the sub-dimensions, the top two features were: security, backup, and downtime prevention; and voice recognition, transcription, and reporting. Structured reporting was also given very high priority. The results point to the dimensions that can be critical discriminators between different PACS and highlight the importance of faster integration of the emerging developments in radiology into PACS.

Lower extremity deep vein thrombosis (DVT) is a common clinical concern, with an incidence that increases with advanced age. DVT typically begins below the knee but may extend proximally and result in pulmonary embolism. Pulmonary embolism can occur in 50% to 60% of patients with untreated DVT and can be fatal. Although clinical examination and plasma d-dimer blood evaluation can often predict the presence of DVT, imaging remains critical for the diagnostic confirmation and treatment planning of DVT. Patients with above-the-knee or proximal DVT have a high risk for pulmonary embolism and are recommended to receive anticoagulation therapy. On the other hand, patients with below-the-knee or distal DVT rarely experience pulmonary embolism, and anticoagulation therapy in these patients remains controversial. However, one sixth of patients with distal DVT may experience extension of their thrombus above the knee and therefore are recommended to undergo serial imaging assessment at 1 week to exclude proximal DVT extension if anticoagulation therapy is not initiated. Ultrasound is the preferred imaging method for evaluation of patients with newly suspected lower extremity DVT. Magnetic resonance and CT venography can be especially helpful for the evaluation of suspected DVT in the pelvis and thigh. Contrast x-ray venography, the historic gold standard for DVT assessment, is now less commonly performed and primarily reserved for patients with more complex presentations such as those with suspected recurrent acute DVT., (Published by Elsevier Inc.)

Purpose: To study the magnetic resonance imaging characteristics of adrenal and extra-adrenal pheochromocytomas in the abdomen and pelvis., Methods: We retrospectively reviewed 18 cases of pathologically proven cases of pheochromocytomas in the abdomen and pelvis. These patients have undergone magnetic resonance imaging evaluation before surgery. The study population included 10 men and 7 women (age range, 19-68 years; mean, 38 years). A consensus review of the magnetic resonance images was performed by 2 blinded expert observers. A qualitative evaluation was completed, and the tumors were classified by anatomical location, shape, T2 signal, contrast enhancement, and signal dropout on chemical shift pulse sequences., Results: On T2-weighted images, most lesions demonstrated mild to moderate increased signal intensity (SI) (n = 12), 5 lesions demonstrated a markedly increased SI, and only 1 lesion demonstrated an isointense SI on T2-weighted images.Five lesions demonstrated marked postcontrast enhancement. Three lesions demonstrated moderate enhancement, and 5 lesions demonstrated mild postcontrast enhancement.The pattern of enhancement was variable: 4 salt and pepper, 4 homogeneous, 3 heterogeneous, and 2 target with central necrosis and hemorrhage. None of the lesions contained significant amount of intracellular lipid, as no lesions demonstrated greater than 16.5% signal dropout on out-of-phase compared with in-phase pulse sequences.

The contrast provided by diffusion-sensitive magnetic resonance offers the promise of improved tumor localization in organ-confined human prostate cancer (PCa). Diffusion tensor imaging (DTI) measurements of PCa were performed in vivo, in patients undergoing radical prostatectomy, and later, ex vivo, in the same patients' prostatectomy specimens. The imaging data were coregistered to histological sections of the prostatectomy specimens, thereby enabling unambiguous characterization of diffusion parameters in cancerous and benign tissues. Increased cellularity, and hence decreased luminal spaces, in peripheral zone PCa led to approximately 40% and 50% apparent diffusion policy (ADC) decrease compared with benign peripheral zone tissues in vivo and ex vivo, respectively. In contrast, no significant diffusion anisotropy differences were observed between the cancerous and noncancerous peripheral zone tissues. However, the dense fibromuscular tissues in prostate, such as stromal tissues in benign prostatic hyperplasia in central gland, exhibited high diffusion anisotropy. A tissue classification method is proposed to combine DTI and T2-weighted image contrasts that may provide improved specificity of PCa detection over T2-weighted imaging alone. PCa identified in volume rendered MR images qualitatively correlates well with histologically determined PCa foci.

Benign hepatic neoplasms constitute a heterogeneous group of neoplasms with characteristic histology and variable tumor biology. Based on the cell of origin, benign hepatic neoplasms are classified into epithelial, nonepithelial, and miscellaneous categories according to the 2000 World Health Organization classification system. Benign hepatic neoplasms demonstrate a wide spectrum of imaging findings that reflect the histomorphologic changes. Some neoplasms show pathognomic imaging findings that permit accurate characterization and optimal management.

Cholangiocarcinoma is the second most common primary malignant hepatobiliary neoplasm, accounting for approximately 15% of liver cancers. Diagnosis of cholangiocarcinoma is challenging and the prognosis is uniformly poor, with recurrence rates of 60%-90% after surgical resection. A wide spectrum of neoplastic and nonneoplastic conditions of the biliary tract may masquerade as cholangiocarcinoma, adding to the complexity of management in patients suspected to have cholangiocarcinoma. Mimics of cholangiocarcinoma constitute a heterogeneous group of entities that includes primary sclerosing cholangitis, recurrent pyogenic cholangitis, acquired immunodeficiency syndrome cholangiopathy, autoimmune pancreatitis, inflammatory pseudotumor, Mirizzi syndrome, xanthogranulomatous cholangitis, sarcoidosis, chemotherapy-induced sclerosis, hepatocellular carcinoma, metastases, melanoma, lymphoma, leukemia, and carcinoid tumors. These entities demonstrate characteristic histomorphology and variable clinicobiologic behaviors. The imaging findings of these disparate entities are protean and may be indistinguishable from those of cholangiocarcinoma. In most cases, a definitive diagnosis can be established only with histopathologic examination of a biopsy specimen.

Objectives: The results of treatment for subclavian vein effort thrombosis were assessed in a series of competitive athletes., Methods: A retrospective review was conducted of high-performance athletes who underwent multidisciplinary management for venous thoracic outlet syndrome in a specialized referral center. The overall time required to return to athletic activity was assessed with respect to the timing and methods of diagnosis, initial treatment, operative management, and postoperative care., Results: Between January 1997 and January 2007, 32 competitive athletes (29 male and 3 female) were treated for venous thoracic outlet syndrome, of which 31% were in high school, 47% were in college, and 22% were professional. The median age was 20.3 years (range, 16-26 years). Venous duplex ultrasound examination in 21 patients had a diagnostic sensitivity of 71%, and the mean interval between symptoms and definitive venographic diagnosis was 20.2 +/- 5.6 days (range, 1-120 days). Catheter-directed subclavian vein thrombolysis was performed in 26 (81%), with balloon angioplasty in 12 and stent placement in one. Paraclavicular thoracic outlet decompression was performed with circumferential external venolysis alone (56%) or direct axillary-subclavian vein reconstruction (44%), using saphenous vein panel graft bypass (n = 8), reversed saphenous vein graft bypass (n = 3), and saphenous vein patch angioplasty (n = 3). In 19 patients (59%), simultaneous creation of a temporary (12 weeks) adjunctive radiocephalic arteriovenous fistula was done. The mean hospital stay was 5.2 +/- 0.4 days (range, 2-11 days). Seven patients required secondary procedures. Anticoagulation was maintained for 12 weeks. All 32 patients resumed unrestricted use of the upper extremity, with a median interval of 3.5 months between operation and the return to participation in competitive athletics (range, 2-10 months). The overall duration of management from symptoms to full athletic activity was significantly correlated with the time interval from venographic diagnosis to operation (r = 0.820, P < .001) and was longer in patients with persistent symptoms (P < .05) or rethrombosis before referral (P < .01)., Conclusions: Successful outcomes were achieved for the management of effort thrombosis in a series of 32 competitive athletes using a multidisciplinary approach based on (1) early diagnostic venography, thrombolysis, and tertiary referral; (2) paraclavicular thoracic outlet decompression with external venolysis and frequent use of subclavian vein reconstruction; and (3) temporary postoperative anticoagulation, with or without an adjunctive arteriovenous fistula. Optimal outcomes for venous thoracic outlet syndrome depend on early recognition by treating physicians and prompt referral for comprehensive surgical management.

Objective: To determine the enhancement phase providing the highest contrast-to-noise ratio (CNR) between cholangiocarcinoma and liver or portal vein on dynamic and delayed gadolinium-enhanced magnetic resonance imaging (MRI)., Subjects and Methods: Precontrast, 3-phase dynamic postcontrast, and delayed postcontrast MRI of the liver was performed in 25 patients with cholangiocarcinoma and correlated with surgical findings, pathology, and other imaging studies. Contrast-to-noise ratios for tumor relative to adjacent liver and portal vein were calculated from signal intensities determined from regions of interest obtained for each phase of enhancement. A subjective assessment of the signal intensity of the periportal tissues relative to the portal vein was made for each set of delayed images., Results: A mass was visible in 24 of 25 patients. Tumor masses were hypointense in 92%, 67%, 75%, and 21%; isointense in 8%, 8%, 17%, and 12%; and hyperintense in 0%, 25%, 8%, and 67% of patients relative to liver on precontrast, arterial, portal venous, and delayed images, respectively. No single phase of gadolinium enhancement demonstrated consistently superior tumor-versus-liver CNR. Delayed imaging demonstrated the highest tumor-versus-liver CNR in 25% of patients and the lowest in 33%. The portal venous phase demonstrated the highest tumor-versus-portal vein CNR in 75% of patients. Delayed postcontrast images demonstrated the lowest tumor-versus-portal vein CNR in 38% of patients. Periportal tissues were isointense to portal vein in all but 1 patient on delayed images., Conclusion: No single phase of dynamic and delayed gadolinium-enhanced MRI demonstrates superior CNR between cholangiocarcinoma and normally enhancing liver, although the portal phase provides the best CNR between tumor and portal vein in most cases. Although delayed enhancement is typical of cholangiocarcinoma, delayed imaging does not necessarily offer superior contrast between tumor and liver parenchyma compared with other phases of enhancement. Differentiation between tumor and portal vein and periportal tissues may be difficult on delayed images.

Objective: Gadolinium is administered as a contrast agent in MRI procedures. Two gadolinium-based contrast agents, gadodiamide and gadoversetamide, interfere with colorimetric total serum calcium methods. The purpose of this prospective observational study was to examine the incidence of calcium interference after gadoversetamide procedures, associated clinical outcomes, and costs 20 months after implementation of quality assurance and physician education programs., Materials and Methods: Records of patients who received gadoversetamide from June 24, 2006, to October 7, 2006, were reviewed to determine if a routine calcium test had been performed after the injection. Calcium values were repeated with an alternate method that is less susceptible to gadoversetamide interference. If the difference was > or = 2.0 mg/dL or if the initial test value was < or = 7.0 mg/dL, patient charts were reviewed for any related treatment. Costs associated with this algorithm were tracked., Results: The initial calcium test was performed after gadoversetamide in 766 of 3,439 instances. The alternate test was performed in 633 of 766. One hundred twenty-five of 633 (20%) showed a difference in calcium values that was > or = 0.7 mg/dL, with 16 showing differences of > or = 1.6 mg/dL. Chart review for 56 instances revealed that calcium supplements were administered in 22 of 56 around the time of gadoversetamide injection. However, none appeared to be related to the spurious hypocalcemia. The total additional cost (reagent and technologist) for following this algorithm for just over 3 months was $6,807., Conclusion: Approximately 20% of patients receiving gadoversetamide exhibited spurious hypocalcemia. No patients were identified who received inappropriate calcium because of this interference. This may be attributable to the quality assurance and physician education programs.

The detection of vaginal lesions has increased with the expanding use of cross-sectional imaging. Magnetic resonance imaging (MRI) - with its high-contrast resolution and multiplanar capabilities - is often useful for characterizing vaginal masses. Vaginal masses can be classified as congenital, inflammatory, cystic (benign), and neoplastic (benign or malignant) in etiology. Recognition of the typical MR imaging features of such lesions is important because it often determines the treatment approach and may obviate surgery. Finally, vaginal MR imaging can be used to evaluate post-treatment changes related to previous surgery and radiation therapy. In this article, we will review pertinent vaginal anatomy, vaginal and pelvic MRI technique, and the MRI features of a variety of vaginal lesions with pathological correlation.

Neoplasms of the perivascular epithelioid cell (PEComas) represent a recently described heterogeneous group of mesenchymal tumors characterized by the presence of specific histological, immunohistochemical, and ultrastructural findings. The PEComas encompass a family of neoplasms that include angiomyolipomas, clear cell sugar tumors, and lymphangioleiomyomatosis. The PEComas demonstrate a wide spectrum of clinicobiological behavior and imaging findings. Perivascular epithelioid cell, as the name implies, is a unique cell that is characterized by perivascular distribution and epithelioid morphology. Perivascular epithelioid cell consistently shows immunoreactivity to melanocytic and smooth muscle markers including HMB-45 and actin. Abdominopelvic PEComas are found at a variety of somatic and visceral locations including kidney, liver, pancreas, gastrointestinal tract, genitourinary tract, peritoneum, and retroperitoneum. A subset of patients with abdominopelvic PEComas manifests tuberous sclerosis complex. In this paper, we review the histological spectrum and discuss the imaging findings of the PEComas that involve the abdomen and pelvis.

Recent advances in molecular genetics and immunocytochemistry have clarified the cell of origin in many renal disorders. Several renal disorders are thought to involve specific segments of the nephron. Renin-secreting tumours arise from juxtaglomerular cells. Clear cell and papillary renal cell carcinoma (RCC) recapitulate the epithelium of the proximal tubules. Oncocytoma and chromophobe RCC differentiate towards Type A and Type B intercalated cells of the cortical collecting duct, respectively. Medullary collecting ducts are the target sites for the development of autosomal recessive polycystic kidney disease, collecting duct carcinoma and medullary carcinoma. Renal papillae are susceptible to unique changes such as necrosis or papillitis. The purpose of our article is threefold: to illustrate the imaging findings of renal disorders that show segmental involvement of the nephron, to describe proximal and distal nephron disorders and to correlate imaging findings of some entities with histopathological features.

Various pathologies involving the gallbladder can manifest clinically, producing nonspecific clinical symptoms and making diagnosis difficult and challenging. Real-time sonography is the most widely used diagnostic study for the gallbladder and the primary screening examination of choice. With increasing use of magnetic resonance imaging (MRI) and MR cholangiopancreatography (MRCP), gallbladder pathology is frequently seen. Understanding the basic patterns of various disease manifestations and appearance on MRI is the key to making an accurate diagnosis. Given its inherent tissue contrast and contrast sensitivity, MRI in conjunction with MRCP can be a very valuable test in evaluating gallbladder pathology. Gallbladder pathology can be classified into congenital (such as absence), inflammatory (acute, hemorrhagic, and chronic cholecystitis), traumatic, benign (polyps) and malignant tumors (gallbladder carcinoma and lymphoma), and other disease processes can be seen in cholelithiasis, cholesterosis, thickened gallbladder wall, and Mirrizzi syndrome.

Primary retroperitoneal masses are a rare but diverse group of benign and malignant processes. Magnetic resonance (MR) imaging is playing an increasing role in evaluating retroperitoneal soft-tissue masses. Since the MR imaging features of most retroperitoneal soft-tissue masses are nonspecific, prediction of a specific histologic diagnosis remains a challenge for the radiologist. However, there are certain specific MR imaging appearances that are helpful. Dynamic enhancement patterns can reflect the vascularity of masses, differentiating benign from malignant soft-tissue masses. This article pictorially illustrates the MR imaging features of various common and uncommon retroperitoneal masses.

Objective: To evaluate the diagnostic yield of MRI performed for characterization of focal hepatic lesions that are interpreted as indeterminate on CT., Patients and Methods: In a retrospective investigation, 124 indeterminate focal hepatic lesions in 96 patients were identified on CT examinations over 5 years from 1997 to 2001. All patients had MRI performed for the liver within 6 weeks of their CT examination. CT and MR images were reviewed independently by two separate groups of two radiologists. The value of MRI in characterizing these lesions was assessed. Diagnoses were confirmed based on histology, characteristic imaging features, and clinical follow-up., Results: MRI definitely characterized 73 lesions (58%) that were indeterminate on CT. MRI was accurate in 72/73 of these lesions. MRI could not definitely characterize 51 lesions (42%). Ten lesions were not visualized on MRI, and follow-up imaging confirmed that no lesion was present in eight of these cases (pseudolesions)., Conclusion: MRI is valuable for the characterization of indeterminate focal hepatic lesions detected on CT.

Renal cell carcinoma (RCC) is a cause of significant morbidity and mortality, with an estimated 35,000 new cases and 12,480 deaths in the United States in 2003. Recent advances in imaging technology, pathology, urology, and oncology permit early diagnosis of RCC and facilitate optimal management. The 2004 World Health Organization classification for renal neoplasms recognizes several distinct histologic subtypes of RCC. These subtypes include clear cell RCC, papillary RCC, chromophobe RCC, hereditary cancer syndromes, multilocular cystic RCC, collecting duct carcinoma, medullary carcinoma, mucinous tubular and spindle cell carcinoma, neuroblastoma-associated RCC, Xp11.2 translocation-TFE3 carcinoma, and unclassified lesions. Different histologic subtypes of RCC have characteristic histomorphologic and biologic profiles. Clear cell RCC is the most common subtype and has a less favorable prognosis (stage for stage) than do papillary RCC and chromophobe RCC. Collecting duct carcinoma and renal medullary carcinoma are associated with aggressive clinical behavior and a poor prognosis., (RSNA, 2006)

Objective: It is important to recognize the imaging characteristics of peliosis hepatis because peliotic lesions may mimic several different types of focal hepatic lesions, Conclusion: We illustrate the spectrum of imaging findings of peliosis hepatis, including sonography, CT, MR, and angiography.

Magnetic resonance (MR) imaging has considerable potential in characterizing pancreatic masses. Certain features can be used by the radiologist to establish a definitive diagnosis for most pancreatic tumors including ductal adenocarcinoma, islet cell tumors, solid and papillary epithelial neoplasms, micro- and macrocystic adenoma, and metastases. Recognition of these tumors on imaging is important since it often changes the treatment approach and may obviate the need for surgery. Recent introduction of 3D gradient recalled echo (GRE) sequence such as volumetric interpolated breath hold examination (VIBE) has dramatically improved MR imaging by providing dynamic enhanced thin-slice images with fat saturation and high signal-to-noise ratio. In this article, special emphasis will be placed on the impact of 3D GRE sequence in the diagnosis of pancreatic neoplasms with pathologic correlation.

Objective: The objective of our study was to describe hybrid peripheral (HyPer) 3D contrast-enhanced MR angiography (CE-MRA) using sagittal acquisition with parallel imaging of the calf and foot station. The benefit of a dedicated sagittal 3D CE-MRA acquisition of the calf and foot was evaluated by assessing the degree of venous contamination and its diagnostic quality compared with standard bolus chase 3D CE-MRA alone., Materials and Methods: Fifty-three patients (99 legs) were scanned with a 1.5-T MR system equipped with a dedicated bilateral lower extremity phased-array coil. First, high-resolution 3D CE-MRA images of the calves and feet were obtained using two separate sagittal slabs with parallel imaging, with a resulting voxel size of 1.4 x 1.0 x 1.0 mm3. Second, standard bolus chase 3D CE-MRA was performed from the abdomen and pelvis station to the calf-foot station. Images were interpreted by two radiologists. The calf-foot arterial trees were divided into 12 segments. Each segment was characterized as diagnostic or nondiagnostic. The degree of venous contamination was assessed as interfering with the diagnosis or not. Paired Student's t test and Wilcoxon's signed rank test were used to test for statistically significant differences between the techniques., Results: For the left leg (n = 48), the mean number (+/- SD) of diagnosed arterial segments for HyPer 3D CE-MRA was 9.2 +/- 2.3 and for bolus chase 3D CE-MRA, 7.1 +/- 4.2 (p < or = 0.0004). For the right leg (n = 51), the corresponding values were 9.4 +/- 2.2 and 7.6 +/- 3.5 (p < or = 0.0005), respectively. For bolus chase 3D CE-MRA, venous contamination interfered with the diagnosis in 24 of 99 legs, whereas with HyPer 3D CE-MRA, there was no interference. Selective analysis of the dorsalis pedis arteries showed that the number of diagnostic vessels was 62 (62.6%) of 99 for HyPer 3D CE-MRA and 13 (13.1%) of 99 for bolus chase 3D CE-MRA., Conclusion: HyPer 3D CE-MRA is an alternative method for time-resolved high-resolution peripheral CE-MRA in evaluating the trifurcation and feet vessels with no venous contamination.

Primary sclerosing cholangitis is a progressive cholestatic disease of unknown etiology leading to cirrhosis and liver failure. Several imaging modalities have been used to study this disease, including ultrasonography, computed tomography and hepatobiliary scintigraphy, but accurate diagnosis was found to be best made with endoscopic retrograde cholangiopancreatography or direct cholangiography. However, these 2 methods are invasive and may produce serious complications. Magnetic resonance cholangiopancreatography is a noninvasive imaging technique that has become very useful for diagnosing primary sclerosing cholangitis. Contrast enhanced magnetic resonance imaging provides pertinent information of extraductal abnormalities in addition to biliary ductal changes.

Objective: Our objective was to detail peritoneal anatomy, techniques for optimizing peritoneal MRI, and the MRI characteristics of several disease processes that frequently involve the peritoneum., Conclusion: Homogeneous fat suppression and dynamic contrast-enhanced imaging, including delayed imaging, are critical technical factors for successful lesion detection and characterization on peritoneal MRI.

Magnetic resonance imaging (MRI) is playing an important role in the clinical evaluation of women presenting with urethral symptoms. Voiding cystourethrography, direct urethrography, and pelvic sonography provide limited information on abnormalities that are in continuity with the urethra. On the other hand, urethra and periurethral tissues can be noninvasively evaluated by high-resolution endocavitary MRI. Because of its multiplanar capability and high tissue contrast, endovaginal MRI is an extremely reliable diagnostic test in the evaluation of urethral abnormalities. In this article, the utility of endovaginal MRI in the detection and characterization of a wide spectrum of urethral pathologic conditions, such as congenital anomalies, diverticula, urethritis, and benign and malignant neoplasms, is discussed.

Three-dimensional (3D) imaging is playing an increasingly important role in modern diagnostic radiology. The recent improvements in magnetic resonance (MR) hardware, scanning protocols and 3D volumetric reconstruction software have facilitated great expansion of the role of 3D imaging for use in hepatobiliary surgery. In this review, we address the various 3D reconstruction techniques used in MRI and demonstrate the value of 3D imaging in preoperative evaluation of hepatobiliary diseases.

Prediction of risks and therapeutic outcome in nuclear medicine largely rely on calculation of the absorbed dose. Absorbed dose specification is complex due to the wide variety of radiations emitted, non-uniform activity distribution, biokinetics, etc. Conventional organ absorbed dose estimates assumed that radioactivity is distributed uniformly throughout the organ. However, there have been dramatic improvements in dosimetry models that reflect the substructure of organs as well as tissue elements within them. These models rely on improved nuclear medicine imaging capabilities that facilitate determination of activity within voxels that represent tissue elements of approximately 0.2-1 cm(3). However, even these improved approaches assume that all cells within the tissue element receive the same dose. The tissue element may be comprised of a variety of cells having different radiosensitivities and different incorporated radioactivity. Furthermore, the extent to which non-uniform distributions of radioactivity within a small tissue element impact the absorbed dose distribution is strongly dependent on the number, type, and energy of the radiations emitted by the radionuclide. It is also necessary to know whether the dose to a given cell arises from radioactive decays within itself (self-dose) or decays in surrounding cells (cross-dose). Cellular response to self-dose can be considerably different than its response to cross-dose from the same radiopharmaceutical. Bystander effects can also play a role in the response. Evidence shows that even under conditions of 'uniform' distribution of radioactivity, a combination of organ dosimetry, voxel dosimetry and dosimetry at the cellular and multicellular levels can be required to predict response.

Focal hepatic lesions constitute a daily challenge in the clinical setting. However, noninvasive methods can be useful in the detection and characterization of these lesions. The noninvasive diagnosis of liver lesions is usually achieved with contrast material-enhanced computed tomography and magnetic resonance (MR) imaging. Dynamic three-dimensional gradient-recalled-echo MR imaging provides dynamic contrast-enhanced thin-section images with fat saturation and a high signal-to-noise ratio and is excellent for the evaluation of various focal hepatic lesions. A comprehensive MR imaging examination in this setting includes T2-weighted and chemical shift T1-weighted imaging and demonstrates characteristic enhancement patterns that can be helpful in the diagnosis of most of these lesions. These enhancement patterns are seen during particular phases of contrast-enhanced imaging and include arterial phase enhancement, delayed phase enhancement, peripheral washout, ring enhancement, nodule-within-a-nodule enhancement, true central scar, pseudocentral scar, and pseudocapsule. Familiarity with these enhancement patterns can help in the identification of specific focal lesions of the liver., ((c) RSNA, 2005.)