Lewis K. Shin

Ultrasonography of abnormal neck lymph nodes.

Ultrasonography is a useful imaging modality for assessing cervical lymphadenopathy in patients with head and neck carcinomas. Features of cervical lymph nodes using gray-scale and color and power Doppler ultrasonography can help to distinguish normal and reactive lymph nodes from potentially metastatic lymph nodes. The distinguishing features that separate abnormal from normal cervical lymph nodes include peripheral vascularity, shape, overall lymph node echogenicity, absence of hilus, presence of nodal microcalcifications, and cystic changes. Often, a combination of these features is needed to assign a cervical lymph node as being abnormal.

Intraoperative ultrasound of the pancreas.

Abstract Intraoperative ultrasound provides spatial resolution of the pancreas superior to computed tomography, magnetic resonance imaging, and transabdominal sonography. This pictorial essay will review common benign and malignant pancreatic processes including the following: pancreatic ductal adenocarcinoma, pancreatitis, endocrine tumors, mucinous cystic neoplasm, intraductal papillary mucinous neoplasm, serous cystadenoma, and solid pseudopapillary tumor. The use of intraoperative ultrasound in specific surgical situations will be discussed, which include the following: (1) identification of insulinoma(s) which are not detectable preoperatively, (2) identification of the pancreatic duct to determine dissection planes for chronic pancreatitis surgery (eg, Puestow procedure) and for tumor resection, and (3) staging purposes for malignant disease.

Non-emergency small bowel obstruction: assessment of CT findings that predict need for surgery

ObjectiveTo identify CT findings predictive of surgical management in non-emergency small bowel obstruction (SBO).MethodsContrast-enhanced abdominal CT of 129 patients with non-emergency SBO were evaluated for small bowel luminal diameter, wall thickness, presence of the small bowel faeces sign (intraluminal particulate matter in a dilated small bowel) and length, transition point, submucosal oedema, mesenteric stranding, ascites and degree of obstruction (low grade partial, high grade partial and complete obstruction). Medical records were reviewed for age, gender, management and history of abdominal surgery, abdominal malignancy, or SBO. Statistical analyses were performed with Stata Release 9.2.ResultsDegree of obstruction was the only predictor of need for surgery. Whereas 18.0% of patients with low-grade partial obstruction (n = 50) underwent surgery, 32.5% of patients with high-grade partial obstruction (n = 77) and 100% of patients with complete obstruction (n = 2) required surgery (P = 0.004). The small bowel faeces sign was inversely predictive of surgery (P = 0.018).ConclusionIn non-emergency SBO patients with contrast-enhanced CT imaging, grade of obstruction predicts surgery, while the small bowel faeces sign inversely predicts need for surgery.

Complicated cholecystitis: the complementary roles of sonography and computed tomography.

Acute cholecystitis is a common cause of abdominal pain in the Western world. Unless treated promptly, patients with acute cholecystitis may develop complications such as gangrenous, perforated, or emphysematous cholecystitis. Because of the increased morbidity and mortality of complicated cholecystitis, early diagnosis and treatment are essential for optimal patient care. Nevertheless, complicated cholecystitis may pose significant challenges with cross-sectional imaging, including sonography and computed tomography (CT). Interpreting radiologists should be familiar with the spectrum of sonographic findings seen with complicated cholecystitis and as well as understand the complementary role of CT. Worrisome imaging findings for complicated cholecystitis include intraluminal findings (sloughed mucosa, hemorrhage, abnormal gas), gallbladder wall abnormalities (striations, asymmetric wall thickening, abnormal gas, loss of sonoreflectivity and contrast enhancement), and pericholecystic changes (echogenic fat, pericholecystic fluid, abscess formation). Finally, diagnosis of complicated cholecystitis by sonography and CT can guide alternative treatments including minimally invasive percutaneous and endoscopic options.

Hypermetabolism on F-18 FDG PET of multiple pulmonary nodules resulting from bronchiolitis obliterans organizing pneumonia

Abstract:There have been multiple reports of benign thoracic conditions demonstrating hypermetabolism on F-18 FDG PET scans, including granulomatous infection, benign tumors, and autoimmune diseases, but bronchiolitis obliterans organizing pneumonia (BOOP) is not a well-known cause of such hypermeta

In vivo deformation of the human abdominal aorta and common iliac arteries with hip and knee flexion: implications for the design of stent-grafts.

Purpose: To quantify in vivo deformations of the abdominal aorta and common iliac arteries (CIAs) caused by musculoskeletal motion. Methods: Seven healthy subjects (age 34±11 years, range 24–50) were imaged in the supine and fetal positions (hip flexion angle 134.0°±9.7°) using contrast-enhanced magnetic resonance angiography. Longitudinal strain, twisting, and curvature change of the infrarenal aorta and CIAs were computed. The angle between the left and right CIAs and translation of the arteries were also computed. Results: Maximal hip flexion induced shortening (5.2%±4.6%), twisting (0.45±0.27 °/mm), and curvature changes (0.015±0.007 mm−1) of the CIAs. The angle between the CIAs increased by 17.6°±8.6°. The iliac arteries moved predominantly in the superior direction relative to the aortic bifurcation, which would induce compression and bending, thus increasing curvature and angle between the CIAs. The abdominal aorta also exhibited shortening (2.9%±2.1%) and twisting (0.07±0.05 °/mm) deformation associated with the hip flexion. Conclusion: Although this study was limited to a few healthy young adults, musculoskeletal motion, specifically hip flexion, caused significant in vivo morphological changes (shortening, twisting, and bending) of the arteries. Predominant superior translation of the CIAs was observed, which suggests that preclinical testing of cyclic superior-inferior translational motion may aid in predicting stent-graft fractures. In turn, stent-graft design could be improved, decreasing overall stent-graft–related complications.

Pathologic continuum of acute appendicitis: sonographic findings and clinical management implications.

Appendicitis is one of the most common causes of the acute abdomen often requiring emergent surgery. Delayed diagnosis leads to the progression of uncomplicated appendicitis to complicated (gangrenous, perforated) appendicitis, often changing clinical management. Computed tomography and ultrasound are imaging modalities of choice to preoperatively diagnose appendicitis. Recent concerns of radiation exposure and cost have renewed interest in using ultrasound as an initial, diagnostic study. A sonographic pictorial and histopathologic review of the continuum of appendicitis is presented. A comprehensive sonographic examination of the appendix should investigate the size (maximal diameter), the echogenic submucosal layer integrity, the mural color Doppler signature, the presence of a fecalith, and the periappendiceal changes. Features of an uncomplicated appendicitis include size greater than 6 to 7 mm, hyperemia on color Doppler, mural thickening, and an intact echogenic submucosal layer. Gangrenous appendicitis is characterized by loss of the echogenic submucosal layer with absent color Doppler flow. Loculated pericecal fluid, prominent pericecal fat, and circumferential loss of the submucosal layer are suggestive of perforation. Sonographic staging can triage management of appendicitis by directing urgent laparoscopic appendectomy for uncomplicated appendicitis, open appendectomy for complicated appendicitis, and conservative management (antibiotics with percutaneous drainage) for perforated appendicitis with abscess formation.

Ultrasonographic Evaluation of Malignant and Normal Cervical Lymph Nodes

Head and neck malignancies, including squamous cell carcinoma, lymphoma, and thyroid cancer, are a major cause of morbidity and mortality worldwide and frequently present with cervical lymphadenopathy. Distinguishing normal from malignant lymph nodes is critical for accurate staging, prognosis, and determination of optimal therapeutic options. Gray-scale, power, and color Doppler ultrasonography offers an inexpensive yet effective method in identifying abnormal cervical lymph nodes. Sonographic nodal features that should be assessed include size, shape, echotexture (including microcalcifications and cystic changes), presence of an echogenic hilus, and vascularity. Although no single sonographic feature can accurately distinguish malignant from normal nodes, a combination of these characteristics can help to make this determination.

Sonographic evaluation of cervical lymph nodes in papillary thyroid cancer.

Sonography is the modality of choice for imaging cervical lymph nodes in patients with papillary thyroid cancer, both before surgery and for postoperative surveillance. Sonography is also an invaluable tool to guide fine-needle aspiration of abnormal nodes. Microcalcifications, cystic changes, abnormal morphology, and disordered vascularity are features of metastatic nodal involvement with papillary thyroid carcinoma and should be sought during surveillance scans as well as in targeting for fine-needle aspiration.

Model-based iterative reconstruction compared to adaptive statistical iterative reconstruction and filtered back-projection in CT of the kidneys and the adjacent retroperitoneum.

RATIONALE AND OBJECTIVES To prospectively evaluate the perceived image quality of model-based iterative reconstruction (MBIR) compared to adaptive statistical iterative reconstruction (ASIR) and filtered back-projection (FBP) in computed tomography (CT) of the kidneys and retroperitoneum. MATERIALS AND METHODS With investigational review board and Health Insurance Portability and Accountability Act compliance, 17 adults underwent 31 contrast-enhanced CT acquisitions at constant tube potential and current (range 30-300 mA). Each was reconstructed with MBIR, ASIR (50%), and FBP. Four reviewers scored each reconstructions perceived image quality overall and the perceived image quality of seven imaging features that were selected by the authors as being relevant to imaging in the region and pertinent to the evaluation of high-quality diagnostic CT. RESULTS MBIR perceived image quality scored superior to ASIR and FBP both overall (P < .001) and for observations of the retroperitoneal fascia (99.2%), corticomedullary differentiation (94.4%), renal hilar structures (96.8%), focal renal lesions (92.5%), and mitigation of streak artifact (100.0%; all, P < .001). MBIR achieved diagnostic overall perceived image quality with approximately half the radiation dose required by ASIR and FBP. The noise curve of MBIR was significantly lower and flatter (P < .001). CONCLUSIONS Compared to ASIR and FBP, MBIR provides superior perceived image quality, both overall and for several specific imaging features, across a broad range of tube current levels, and requires approximately half the radiation dose to achieve diagnostic overall perceived image quality. Accordingly, MBIR should enable CT scanning with improved perceived image quality and/or reduced radiation exposure.