Doppler Ultrasound of the Renal Vasculature.

Ultrasound is the first-line imaging modality used in patients with suspected renovascular disease. Common indications include renovascular hypertension and unexplained renal dysfunction. We review the ultrasound imaging findings of various pathologies involving the renal vessels, including the renal arteries (atherosclerotic stenosis, fibromuscular dysplasia, dissection, arteriovenous fistula, and aneurysm) and veins (tumor and bland thrombus as well as vascular compression syndromes). The current role of renal artery stent placement for atherosclerotic stenosis is also discussed.

MR Imaging Biomarkers for the Prediction of Outcome after Radiofrequency Ablation of Hepatocellular Carcinoma: Qualitative and Quantitative Assessments of the Liver Imaging Reporting and Data System and Radiomic Features.

PURPOSE: To assess the Liver Imaging Reporting and Data System (LI-RADS) and radiomic features in pretreatment magnetic resonance (MR) imaging for predicting progression-free survival (PFS) in patients with nodular hepatocellular carcinoma (HCC) treated with radiofrequency (RF) ablation. MATERIAL AND METHODS: Sixty-five therapy-naïve patients with 85 nodular HCC tumors <5 cm in size were included in this Health Insurance Portability and Accountability Act-compliant, institutional review board-approved, retrospective study. All patients underwent RF ablation as first-line treatment and demonstrated complete response on the first follow-up imaging. Gadolinium-enhanced MR imaging biomarkers were analyzed for LI-RADS features by 2 board-certified radiologists or by analysis of nodular and perinodular radiomic features from 3-dimensional segmentations. A radiomic signature was calculated with the most informative features of a least absolute shrinkage and selection operator Cox regression model using leave-one-out cross-validation. The association between both LI-RADS features and radiomic signatures with PFS was assessed via the Kaplan-Meier analysis and a weighted log-rank test. RESULTS: The median PFS was 19 months (95% confidence interval, 16.1-19.4) for a follow-up period of 24 months. Multifocality (P = .033); the appearance of capsular continuity, compared with an absent or discontinuous capsule (P = .012); and a higher radiomic signature based on nodular and perinodular features (P = .030) were associated with poorer PFS in early-stage HCC. The observation size, presence of arterial hyperenhancement, nonperipheral washout, and appearance of an enhancing "capsule" were not associated with PFS (P > .05). CONCLUSIONS: Although multifocal HCC clearly indicates a more aggressive phenotype even in early-stage disease, the continuity of an enhancing capsule and a higher radiomic signature may add value as MR imaging biomarkers for poor PFS in HCC treated with RF ablation.

A pictorial review of non-traumatic adrenergic crisis.

Non-traumatic adrenal crisis is a rare but critical diagnosis to make in emergency settings due to grave consequences. Various pathologies can present as acute crisis, such as spectrum of endocrine imbalance, ranging from catecholamine excess in pheochromocytomas to acute adrenal insufficiency related to glandular dysfunction. Critical manifestations may be due to structural causes related to adrenal hemorrhage, especially when they are bilateral. Oncological complications such as vascular invasion, tumoral bleed, rupture, and hormonal dysfunction can occur. Due to non-specific clinical presentation, these conditions may come as a surprise on imaging performed for other reasons. Recognition of these imaging findings is critical for appropriate patient management. Although there are few articles discussing non-traumatic emergencies in literature, this review is inclusive of all possible etiologies, thus provides a holistic approach and insight into each situation. Specific imaging approach is needed to tailor the diagnosis. This article will also discuss about the advanced imaging techniques that will complement diagnosis.

Safety and Efficacy of Percutaneous Cholecystostomy for Emphysematous Cholecystitis.

OBJECTIVE: The objective of the study was to evaluate the safety and efficacy of percutaneous cholecystostomy (PC) in treating critically ill patients with emphysematous cholecystitis who were deemed poor surgical candidates. MATERIALS AND METHODS: The Institutional Review Board exemption was obtained for this retrospective study. Patients with emphysematous cholecystitis who were deemed to be poor operative candidates by the treating surgeon and underwent PC placement between May 2008 and April 2017 at a single institution were identified through a medical records search. Demographics, laboratory values, imaging data, procedural technique, complications, hospitalization course, clinical outcome, and survival data were obtained. RESULTS: Ten consecutive patients were included, with a mean age of 75.0 ± 12.2 years, including six men and four women. The most common comorbidity was diabetes (60%, 6/10) followed by hypertension (40%, 4/10). Intraluminal or intramural gas as well as gallbladder wall thickening were noted in all patients. Procedure technical success rate was 100%. There was a complete resolution of symptoms in 90% (9/10) of patients at a mean of 2.9 ± 1.4 days post-procedure. Thirty-day survival rate was 90% (9/10); one patient died on the 6th post- procedure day from sepsis. Two more deaths occurred within a year after PC from unrelated causes. About 50% (5/10) of patients underwent elective cholecystectomy at a median interval of 69 days post-procedure. In 40% (4/10) of patients, cholecystostomy was the definitive treatment, with tube removal at a median of 140 days post- procedure. CONCLUSION: PC appears to be a safe and generally effective alternative management option in patients with emphysematous cholecystitis that is considered very high risk for surgery.

Lung Nodule Detection via Deep Reinforcement Learning.

Lung cancer is the most common cause of cancer-related death globally. As a preventive measure, the United States Preventive Services Task Force (USPSTF) recommends annual screening of high risk individuals with low-dose computed tomography (CT). The resulting volume of CT scans from millions of people will pose a significant challenge for radiologists to interpret. To fill this gap, computer-aided detection (CAD) algorithms may prove to be the most promising solution. A crucial first step in the analysis of lung cancer screening results using CAD is the detection of pulmonary nodules, which may represent early-stage lung cancer. The objective of this work is to develop and validate a reinforcement learning model based on deep artificial neural networks for early detection of lung nodules in thoracic CT images. Inspired by the AlphaGo system, our deep learning algorithm takes a raw CT image as input and views it as a collection of states, and output a classification of whether a nodule is present or not. The dataset used to train our model is the LIDC/IDRI database hosted by the lung nodule analysis (LUNA) challenge. In total, there are 888 CT scans with annotations based on agreement from at least three out of four radiologists. As a result, there are 590 individuals having one or more nodules, and 298 having none. Our training results yielded an overall accuracy of 99.1% [sensitivity 99.2%, specificity 99.1%, positive predictive value (PPV) 99.1%, negative predictive value (NPV) 99.2%]. In our test, the results yielded an overall accuracy of 64.4% (sensitivity 58.9%, specificity 55.3%, PPV 54.2%, and NPV 60.0%). These early results show promise in solving the major issue of false positives in CT screening of lung nodules, and may help to save unnecessary follow-up tests and expenditures.

Radiation dose index of renal colic protocol CT studies in the United States: a report from the American College of Radiology National Radiology Data Registry.

PURPOSE: To determine radiation dose indexes for computed tomography (CT) performed with renal colic protocols in the United States, including frequency of reduced-dose technique usage and any institutional-level factors associated with high or low dose indexes. MATERIALS AND METHODS: The Dose Imaging Registry (DIR) collects deidentified CT data, including examination type and dose indexes, for CT performed at participating institutions; thus, the DIR portion of the study was exempt from institutional review board approval and was HIPAA compliant. CT dose indexes were examined at the institutional level for CT performed with a renal colic protocol at institutions that contributed at least 10 studies to the registry as of January 2013. Additionally, patients undergoing CT for renal colic at a single institution (with institutional review board approval and informed consent from prospective subjects and waiver of consent from retrospective subjects) were studied to examine individual renal colic CT dose index patterns and explore relationships between patient habitus, demographics, and dose indexes. Descriptive statistics were used to analyze dose indexes, and linear regression and Spearman correlations were used to examine relationships between dose indexes and institutional factors. RESULTS: There were 49 903 renal colic protocol CT examinations conducted at 93 institutions between May 2011 and January 2013. Mean age ± standard deviation was 49 years ± 18, and 53.9% of patients were female. Institutions contributed a median of 268 (interquartile range, 77-699) CT studies. Overall mean institutional dose-length product (DLP) was 746 mGy ⋅ cm (effective dose, 11.2 mSv), with a range of 307-1497 mGy ⋅ cm (effective dose, 4.6-22.5 mSv) for mean DLPs. Only 2% of studies were conducted with a DLP of 200 mGy ⋅ cm or lower (a "reduced dose") (effective dose, 3 mSv), and only 10% of institutions kept DLP at 400 mGy ⋅ cm (effective dose, 6 mSv) or less in at least 50% of patients. CONCLUSION: Reduced-dose renal protocol CT is used infrequently in the United States. Mean dose index is higher than reported previously, and institutional variation is substantial.

Imaging of tuberculosis of the abdominal viscera: beyond the intestines.

There is an increasing incidence of both intra- and extra-thoracic manifestations of tuberculosis, in part due to the AIDS epidemic. Isolated tubercular involvement of the solid abdominal viscera is relatively unusual. Cross-sectional imaging with ultrasound, multidetector computed tomography (CT), and magnetic resonance imaging (MRI) plays an important role in the diagnosis and post treatment follow-up of tuberculosis. Specific imaging features of tuberculosis are frequently related to caseous necrosis, which is the hallmark of this disease. However, depending on the type of solid organ involvement, tubercular lesions can mimic a variety of neoplastic and nonneoplastic conditions. Often, cross-sectional imaging alone is insufficient in reaching a conclusive diagnosis, and image-guided tissue sampling is needed. In this article, we review the pathology and cross-sectional imaging features of tubercular involvement of solid abdominopelvic organs with a special emphasis on appropriate differential diagnoses.

MDCT of abdominopelvic oncologic emergencies.

Acute complications arising in abdominopelvic malignancies represent a unique subset of patients presenting to the emergency room. The acute presentation can be due to complications occurring in the tumor itself or visceral or vascular structures harboring the tumor. Multidetector computed tomography (MDCT) is the investigation of choice in the workup of these patients and enables appropriate and timely management. Management of the complication depends primarily on the extent of the underlying malignancy and the involvement of other viscera. The purpose of this article is to depict the imaging features of these complications on MDCT.

Non-invasive diagnosis of abdomino-pelvic masses: role of multimodality imaging.

Recent advances in radiology have greatly increased the ability to make highly accurate diagnosis. Biopsy of many commonly seen lesions is no longer performed as the radiological findings are pathognomonic. This gives rise to the concept of 'virtual biopsy', a term coined on the lines of other imaging techniques such as virtual colonoscopy. Virtual biopsy is not a new imaging technique but a new concept which refers to the use of existing imaging modalities to evaluate the morphological features of tumors and arriving at a non-invasive diagnosis with a high degree of confidence obviating the need for true biopsy. Elements of virtual biopsy have already been incorporated into some evidence-based guidelines, and it is expected that with further technological advancements, an increasing number of tumors may be diagnosed and managed accordingly. A wider acceptance of virtual biopsy could further reduce the need for invasive biopsies and its attendant costs and risks. In this review article, we use index cases to further emphasize this concept.

Abdominal hemangiomas: a pictorial review of unusual, atypical, and rare types.

Hemangiomas are a radiologist's dream lesions because they allow a confident diagnosis most of the time. However, within the abdomen, hemangiomas may occur in such atypical locations and can have such unusual features that they cause significant diagnostic dilemma and may end up being excised surgically. The literature is replete with isolated case reports of atypical hemangiomas in the abdominal cavity, and, to our knowledge, so far, there is no comprehensive review. We present, in this article, a pictorial review of a gamut of uncommon hemangiomas and hemangiomatosis syndromes. Knowledge of these rare types can help in limiting diagnostic errors and increase the confidence of radiologists, thus avoiding unnecessary surgeries.

Small-bowel obstruction after laparoscopic Roux-en-Y gastric bypass surgery.

PURPOSE: The purpose of this study was to review the etiology and computed tomography (CT) findings of small-bowel obstruction (SBO) in patients who have undergone bariatric laparoscopic Roux-en-Y gastric bypass (LGBP) surgery. MATERIALS AND METHODS: Prospectively entered data from a surgical database of 835 consecutive patients who underwent antecolic-antegastric LGBP for morbid obesity from June 1999 to April 2005 in a single institution were retrospectively reviewed. A total of 42 cases of bowel obstruction were observed in 41 patients. Surgical proof was available in 38 cases, and 4 cases had characteristic imaging features and/or clinical follow-up. Seventeen CT scans were reviewed to determine cause and level of obstruction, and this was correlated with surgical findings and clinical follow-up. RESULTS: Internal hernia was the most common (13 cases) and also the most frequently missed etiology of SBO on CT scans, with the diagnosis being made prospectively in only 2 of 6 cases, in which CT was done. Adhesions, ventral hernia, postoperative ileus, and jejunojejunal (JJ) anastomotic strictures, in that order, were the other commonly observed etiologies for SBO, with 11, 7, 5, and 4 cases, respectively. Some causes of SBO post-LGBP (JJ anastomotic stricture and postoperative ileus) developed relatively early, whereas others (internal hernia) tended to develop later or had a bimodal distribution (adhesions and ventral hernia). Fifteen (36%) of 42 cases had SBO at or near the level of jejunojejunostomy site; causes included internal hernia (5 cases), adhesions/kinking of small bowel (5 cases), JJ anastomotic stricture (4 cases), and JJ intussusception (1 case). CONCLUSION: The time interval between LGBP and development of SBO might provide a useful clinical clue to its etiology. The JJ level is an important location for SBO post-LGBP because of a variety of causes, and special attention must be paid to this site at imaging of post-LGBP patients.

Hemoperitoneum from ruptured cyst in a hyperstimulated ovary: a sonographic mimic of ovarian hyperstimulation syndrome.

We report a case of a ruptured cyst in a hyperstimulated ovary that was initially misinterpreted as ovarian hyperstimulation syndrome (OHSS). A 22-year-old woman who was on oral clomiphene citrate for primary infertility presented with pain in the lower abdomen, hypotension, and tachycardia. Sonographic examination revealed multiple cysts in both ovaries and free fluid in the abdomen, and the initial diagnosis was OHSS. However, sonographically guided aspiration of free fluid revealed a hemoperitoneum, and the patient underwent emergent surgery. At laparotomy, an actively bleeding ruptured cyst in a hyperstimulated ovary was found to be the cause of the hemoperitoneum. Radiologists must be familiar with the imaging features of this condition to avoid misdiagnosing it as OHSS, because this could potentially delay urgently required surgery.

Radiofrequency ablation of liver metastases from breast cancer: results in 14 patients.

PURPOSE: To evaluate the results of radiofrequency ablation in treating hepatic metastases from breast cancer. MATERIALS AND METHODS: Fourteen breast cancer patients with 16 hepatic metastases measuring 1.1 to 4.0 cm in the longest axis (mean, 1.9 cm) were prospectively studied. All patients had previously received chemotherapy. Radiofrequency ablation was done using 17-G, internally cooled electrodes under ultrasound guidance. A single index tumor was treated in 12 patients, and two tumors each were treated in two patients. Follow-up was done using serial computed tomography for a duration ranging from 6 to 45 months (mean, 18 months; median, 16 months). RESULTS: All patients were treated in a single session. No major complications occurred. Minor complications or side effects (asymptomatic pleural effusion, perihepatic fluid collection) were observed in three patients. Complete necrosis, defined as an absence of detectable disease on computed tomography at 6 months follow-up was achieved in 14 (88%) of 16 index tumors. Treatment failure due to the development of new metastases was observed in seven (50%) of 14 patients. Five (36%) patients died in the first 12 months after radiofrequency ablation due to the development of new hepatic and extrahepatic metastases. At the time of writing, nine (64%) of 14 patients are alive, of whom four patients (29%) are disease-free and three patients (21%) are progression-free. CONCLUSIONS: A high overall treatment failure rate (50%) was observed due to the development of new metastases on follow-up. Despite this, radiofrequency ablation appears to be a safe and effective adjunct to systemic chemotherapy for the loco-regional treatment of liver metastases from breast cancer.

Mesenteric gastrointestinal stromal tumour presenting as intracranial space occupying lesion.

BACKGROUND: Gastrointestinal stromal tumours (GIST) usually present with non-specific gastrointestinal symptoms such as abdominal mass, pain, anorexia and bowel obstruction. METHODS: We report a case of a 42 year old male who presented with a solitary intracranial space occupying lesion which was established as a metastasis from a mesenteric tumour. RESULTS: The patient was initially treated as a metastatic sarcoma, but a lack of response to chemotherapy prompted testing for CD117 which returned positive. A diagnosis of mesenteric GIST presenting as solitary brain metastasis was made, and the patient was treated with imatinib. CONCLUSION: We recommend that all sarcomas with either an intraabdominal or unknown origin be routinely tested for CD117 to rule out GIST.