Bilal Tahir

Value of Diffusion-Weighted MRI for Assessing Liver Fibrosis and Cirrhosis

OBJECTIVE The objective of our study was to determine the usefulness of the apparent diffusion coefficient (ADC) of liver parenchyma for determining the severity of liver fibrosis. MATERIALS AND METHODS This study investigated 78 patients who underwent diffusion-weighted imaging (DWI) with 1.5-T MRI and pathologic staging of liver fibrosis based on biopsy. DWI was performed with b values of 50 and 400 s/mm(2). ADCs of liver were measured using 2.0- to 3.0-cm(2) regions of interest in the right and left lobes of the liver; the mean ADC value was used for analysis. Pathologic METAVIR scores for liver fibrosis stage were used as a reference standard. RESULTS The mean ADC values for fibrosis pathologically staged using the METAVIR classification system as F0 (n = 11), F1 (n = 16), F2 (n = 10), F3 (n = 14), and F4 (n = 27) were 125.9, 105.0, 104.5, 103.2, and 99.1 x 10(-5) s/mm(2), respectively. The correlation between the ADC values and the degree of liver fibrosis was moderate (Spearmans test, rho = -0.36). There was a significant difference in ADC values between patients with nonfibrotic liver (F0) and those with cirrhotic liver (F4) (p = 0.008). The best cutoff ADC value to distinguish between these groups was 118 x 10(-5) s/mm(2). However, ADC values were not useful for differentiating viral hepatitis patients with F2 fibrosis or higher from those with a lower degree of fibrosis (area under the receiver operating characteristic curve [AUC] = 0.66) or for differentiating low-stage fibrosis in all patients from high-stage fibrosis in all patients (AUC = 0.54). CONCLUSION The ADCs in cirrhotic livers are significantly lower than those in nonfibrotic livers. However, ADC values measured using the current generation of scanners are not reliable enough to replace liver biopsy for staging hepatic fibrosis.

The value of diffusion-weighted imaging in characterizing focal liver masses.

RATIONALE AND OBJECTIVES To determine if focal liver masses could be differentiated as benign or malignant on the basis of diffusion-weighted imaging (DWI). METHODS AND MATERIALS A total of 104 patients with focal liver masses were scanned using 1.5 T magnetic resonance imaging (MRI). DWI was performed with b values of 0, 50, and 400 s/mm(2). Of these, 76 patients had lesions larger than 2 cm diameter, radiologic or pathologic characterization of the lesion, and diagnostic quality DWI. The apparent diffusion coefficient (ADC) of the largest liver lesion was measured. The liver masses were diagnosed on histology or had characteristic computed tomography/MRI findings and follow up of more than 6 months. The analyzed lesions were hemangioma (n = 17), cysts (n = 5), hepatocellular cancer (HCC) (n = 41), adenoma (n = 3), focal nodular hyperplasia (FNH) (n = 6), and metastases (n = 4). RESULTS The mean (standard deviation) ADC values (10(-5) mm(2)/second) of hemangiomas, cysts, FNH, and HCC were 156.8 (54.1), 190.2 (43.0), 130.1 (81.9), and 107.6 (32.7). The ADC of cysts and hemangiomas were significantly higher than that of other lesions (P = .0003, t-test). There was no significant difference between ADC values of solid, benign liver lesions (FNH, adenoma) and malignant lesions (HCC, metastases) (P = .62). CONCLUSION Solid liver lesions have a lower ADC than cysts and hemangiomas. However, there is no significant difference in ADC between solid benign and malignant lesions. DWI appears to have only minimal additional value over currently used MRI sequences in characterizing liver masses.

Use of diffusion-weighted MRI to differentiate chronic pancreatitis from pancreatic cancer

OBJECTIVE The purpose of this study was to compare diffusion-weighted MRI (DWI) and conventional (non-DWI) MRI sequences in differentiating mass-forming chronic pancreatitis from pancreatic cancer. MATERIALS AND METHODS A retrospective cohort study included 36 patients who underwent pancreatic resection for pancreatic cancer (n = 13) and chronic pancreatitis (n = 23) after preoperative MRI with DWI. Two independent reviewers assessed the DW images for signal intensity and apparent diffusion coefficient (ADC) values. Four weeks later, they reviewed the other MR images for size of mass, double-duct sign, pancreatic duct cutoff, and perivascular soft-tissue cuffing. A score for conventional MRI was given with 1 meaning definitely benign and 5 meaning definitely malignant. Univariate and multivariate analyses and receiver operating characteristic (ROC) curve analysis were performed with surgical pathologic examination as the reference standard. RESULTS The only finding that differentiated the two groups was the presence of a well-defined mass, favoring the diagnosis of cancer (p = 0.02, p < 0.01). There was no significant difference between the two groups in signal intensity on DW images (p = 0.82, p = 0.85) or ADC (p = 0.51, p = 0.76). Double-duct sign, pancreatic duct cutoff, and perivascular soft-tissue cuffing were not useful in differentiating the two groups. The areas under the ROC curve were 0.873 and 0.878 for the conventional MRI scores, compared with 0.602 and 0.552 for ADC measurements (p = 0.02, p = 0.008). CONCLUSION The addition of DWI to conventional MRI does not facilitate differentiation of pancreatic cancer from chronic pancreatitis.

The usefulness of diffusion-weighted imaging in the characterization of liver lesions in patients with cirrhosis

AIM To evaluate if diffusion-weighted imaging (DWI) is useful in characterizing liver lesions in patients with cirrhosis. MATERIALS AND METHODS A retrospective review revealed 37 patients with cirrhosis who had 41 histologically proven hepatocellular carcinoma (HCC) lesions. Another 20 patents with cirrhosis had 29 solid nodules that remained stable for at least 12 months and were deemed to be benign hepatic nodules (BHN). Of the HCC lesions, 14 were well-differentiated (WD HCC), 20 were moderately differentiated, and seven were poorly differentiated histology. For all lesions, two reviewers analysed signal characteristics and made apparent diffusion coefficient value (ADC) measurements. RESULTS Visual analysis of DWI was useful in that no HCC was hypointense and no BHN was hyperintense to liver. Visual analysis of DWI was not useful in separating WD HCC from higher grades. There was substantial overlap in ADC values of the HCC and BHN. Among HCC lesions, ADC values of more than 0.99 × 10(-3) mm(2)/s had sensitivity and specificity of 85% and 86% for reviewer 1, and 63% and 64% for reviewer 2 in diagnosing WD HCC. CONCLUSIONS ADC measurements of BHN were higher than that of HCC, and the ADC values of WD HCC were higher than that of more aggressive grades of HCC. However, quantitative measurements may not help in determining the histological grade of individual cases of HCC.

The Value of Secretin-Enhanced MRCP in Patients With Recurrent Acute Pancreatitis

OBJECTIVE The purpose of this study is to assess the additional value of secretin-enhanced MRCP over conventional (non-secretin-enhanced) MRCP in diagnosing disease in patients with recurrent acute pancreatitis. MATERIALS AND METHODS A retrospective review of a radiology database found 72 patients with recurrent acute pancreatitis who had secretin-enhanced MRCP and ERCP correlation within 3 months of each other between January 2007 and December 2011. Of these patients, 54 had no history of pancreatic tumor or surgery and underwent MRI more than 3 months after an episode of acute pancreatitis. In addition, 57 age- and sex-matched control subjects with secretin-enhanced MRCP and ERCP correlation and without a diagnosis of recurrent acute pancreatitis or chronic pancreatitis were enrolled as the control group. All studies were anonymized, and secretin-enhanced MRCP images (image set A) were separated from conventional 2D and 3D MRCP and T2-weighted images (image set B). Image sets A and B for each patient were assigned different and randomized case numbers. Two blinded reviewers independently assessed both image sets for ductal abnormalities and group A image sets for exocrine response to secretin. RESULTS There were statistically significantly more patients with recurrent acute pancreatitis with reduced exocrine function compared with patients in the control group (32% vs 9%; p < 0.01) on secretin-enhanced images. Patients with recurrent acute pancreatitis were more likely to have side branch dilation (p = 0.02; odds ratio, 3.6), but not divisum, compared with the control group. Secretin-enhanced images were superior to non-secretin-enhanced images for detecting ductal abnormalities in patients with recurrent acute pancreatitis, with higher sensitivity (76% vs 56%; p = 0.01) and AUC values (0.983 vs 0.760; p < 0.01). CONCLUSION Up to one-third of patients with recurrent acute pancreatitis showed exocrine functional abnormalities. Secretin-enhanced MRCP had a significantly higher yield for ductal abnormalities than did conventional MRI and should be part of the MRCP protocol for investigation of patients with recurrent acute pancreatitis.

Streptococcal necrotizing myositis: a case report and clinical review.

BACKGROUND Streptococcal necrotizing myositis, also known as gangrenous myositis, is a very rare and severe soft tissue infection that predominately involves skeletal muscle and, eventually, superficial fascia and surrounding tissues. The presentation is often nonspecific until the rapidly progressing clinical course becomes apparent. A high morbidity and mortality rate has been reported in the small number of cases since 1900. Despite several attempts to better define the different entities causing necrotizing myositis, no single definitive causal relationship has been defined. OBJECTIVES A review of the literature is presented here to help clinicians distinguish those with necrotizing myositis from those with nonnecrotizing myositis when the clinician is at all confronted with the suspicion for such an infection. CASE REPORT The case presented is that of a 48-year-old woman who had streptococcal necrotizing myositis. She died roughly 72 h after admission. After the patients death, the clinical team sought consent for autopsy. Hospital staff made contact with family, and information was obtained from the family that the onset of the patients symptoms was allegedly temporally related to her acquisition of a new tattoo on the right back, where the tattoo process allegedly included injection of cremated ashes of a pet dog. CONCLUSION A high level of suspicion for necrotizing myositis must be maintained for a patient with unexplained severe muscle pain and soft tissue swelling accompanied by systemic inflammatory response syndrome.

Diffusion-weighted MRI of the transplanted liver

AIM To assess the value of diffusion-weighted imaging (DWI) in evaluating parenchymal disorders following orthotopic liver transplantation (OLT). MATERIALS AND METHODS This institutional review board-approved, retrospective study measured the hepatic apparent diffusion coefficients (ADC) in patients following OLT. Those with vascular complications or within 3 months of OLT were excluded. A single-shot echoplanar sequence with b values of 50, 400 (or 500), and 800 s/mm(2) was performed. Liver biopsy specimens [performed with a median of 17 days after magnetic resonance imaging (MRI)] were recorded for the presence and severity of parenchymal disorders, such as acute cellular rejection, and recurrence of fibrosis in all patients, and the recurrence of viral hepatitis in patients with hepatitis C. ADC values were measured blinded to histology in 41 patients (33 males) who had 56 MRI scans. RESULTS There was a significant difference in ADC values associated with a histological abnormality seen on core biopsy [n=43, mean (SD) ADC of 0.91 (0.15)×10(-3) mm(2)/s] and those associated with no histological abnormality [n=13, mean (SD) ADC of 1.11 (0.17)×10(-3) mm(2)/s; (p=0.003)]. ADC values did not predict any of the individual parenchymal disorders on logistic regression analysis. When the ADC value was <0.99×10(-3) mm(2)/s, there was a sensitivity and specificity of 85% and 72%, respectively, in predicting a parenchymal disorder (area under ROC curve=0.84; 95% CI 0.72 to 0.92). CONCLUSION ADC measurements may help in deciding which patients require core liver biopsy after OLT. However, ADC values are not likely to be reliable in differentiating between the various parenchymal disorders.

PACS and the Erosion of Professional Relationships

P icture archiving and communication systems (PACS) technology has enabled the physical separation of radiologists from many important members of the healthcare team, including technologists, radiology trainees, fellow radiologists, and ordering physicians, not to mention patients. The remarkable irony is that although PACS as a workflow tool has improved efficiency and allowed groups to grow, it has also degraded radiologists’ interpersonal relationships with many such colleagues (1). The erosion of these relationships threatens the valueadded model of radiology and may over time diminish the magnitude and quality of radiologists’ contributions to health care (2). In an effort to better understand both the nature of the toll that PACS is taking and the steps that radiologists might take to rectify the situation, we examine each of the major groups of caregivers with whom radiologists’ relationships have been disrupted.

Interferences in photodetachment of a triatomic negative ion

The photodetachment of a triatomic negative ion is studied and the detached-electron wave function is obtained as a superposition of coherent waves originating from each atom of the system. The photodetached electron flux is evaluated on a screen placed at a large distance from the system, which displays strong interferences. A simple analytical formula is also obtained for the total photodetachment cross section. The formula approaches one time the cross sections for the one-center and two-center systems in the high photon energy limits. Also it approaches three times the cross section for one-center system in the low photon energy limits.

When Quality Improvement Fails. A Case Study

N early all the published articles on quality improvement initiatives in radiology fall into one of two categories: articles outlining different approaches to quality improvement and articles describing successful quality improvement projects (1–3). Largely missing from the literature are examples of the trials and tribulations of quality improvement efforts, including accounts of how such efforts have failed. In this article, we briefly summarize some of the key features of a quality improvement program, describe a particular quality improvement effort in which we participated, and then discuss in greater detail how this quality improvement fell short and lessons to be learned going forward. Kruskal et al. (4) have identified key features of successful quality improvement programs. These include institutional leadership and support, just culture of safety and quality, an effective process for managing ‘‘customer’’ relations, a wellfunctioning quality management team, continuous engagement of all staff in the quality process, and the use of appropriate tools for measuring results.As this listmakes clear,manyof these factors are often not under the control of any radiologist or even any radiology department, at least when it comes to larger-scale projects such as hospital-wide initiatives, and this proved crucial in the case we are describing. We refer to this quality improvement project as the magnetic resonance imaging (MRI) Safety Initiative. It grew out of a convergence of two factors. First, beginning in the summer of 2013, MRI technologists at a large urban hospital had expressed concern about a number of ‘‘near misses’’ that had occurred in the MRI suite, including security staff approaching the MRI suite with their belts and holsters on, housekeeping staff rolling their cleaning carts toward the magnet, and patients being brought to the waiting room with various non–MRI-safe apparatuses in place, such as wound vacs. Second, both a radiology resident and an attending radiologist on