Biomedical subjects

E K Fishman

Publications and source records attributed to E K Fishman.

At least 613 records · Page 34Linked to original sources

PubMedDate not supplied

Recurrent pancreatic adenocarcinoma: spiral CT evaluation following the Whipple procedure.

Computed tomographic (CT) examination of patients who have undergone pancreaticoduodenectomy (Whipple procedure) for pancreatic adenocarcinoma is complex. The radiologist's assessment of the three surgically created anastomoses, as well as of subtle abnormalities that are the earliest signs of recurrent disease, is substantially aided by the volume acquisition capability of spiral CT and use of overlapping reconstruction intervals. Normal postoperative findings on spiral CT scans include ill-defined increased attenuation in the fat of the pancreatic bed and surrounding the superior mesenteric artery and pneumobilia. The most frequent sites of tumor recurrence are local disease in the pancreatic bed and metastases in the liver; concurrent local and liver disease may also be the initial manifestation of recurrent pancreatic adenocarcinoma. CA 19-9 is a tumor-associated antigen whose level is frequently elevated in patients with recurrent pancreatic cancer, and correlation of CT findings and the serum CA 19-9 level is helpful in differentiating between recurrent disease and postoperative changes. Correlation of CT appearances with clinical parameters, such as the type and position of surgically created anastomoses and knowledge of the radiation port in those patients receiving adjuvant radiation therapy, aids interpretation and helps one avoid false-positive diagnoses in the setting of complex anatomic and persistent postoperative changes inherent in this patient population.

Adenocarcinoma↗

PubMedDate not supplied

CT of renal inflammatory disease.

Although computed tomography (CT) is not routinely indicated in uncomplicated renal infection, it is of value in establishing the diagnosis in equivocal cases, in evaluating high-risk patients, and in determining the extent of disease. Unenhanced CT is useful in demonstrating gas, calculi, parenchymal calcifications, hemorrhage, and inflammatory masses. However, a contrast material-enhanced study is essential for complete evaluation of patients with renal inflammatory disease to demonstrate alterations in renal excretion of contrast material that occur as a result of the inflammatory process. In severe acute pyelonephritis, enhanced CT scans obtained during the cortical nephrographic phase typically demonstrate solitary or multifocal areas of hypoattenuation with loss of the corticomedullary interface. Delayed CT scans obtained during the excretory phase are frequently more helpful than early CT scans in defining the extent of the disease process, identifying complications such as renal abscess, and confirming the presence of urinary obstruction.

Abscess↗

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Developing a computer-assisted instruction program: a process overview for the radiologist.

Recent advances in computer technology have led to the creation and development of computer-assisted instruction (CAI) programs, which are rapidly assuming a prominent role in both medical and nonmedical education. The development process includes defining objectives, identifying the target audience, assembling the design team, selecting compatible hardware and software, optimizing image quality, designing a palette, structuring information, and evaluating the program through user feedback. Although the individual radiologist is unlikely to possess all the skills necessary for developing a CAI program, even a basic knowledge of the computer environment is sufficient to enable him or her to become integrally involved in the process. The radiologist as "content expert" can and should participate actively throughout the process to integrate medical content with CAI program design. Indirect involvement might include participation in creative brainstorming sessions; direct involvement might help ensure image quality. A comprehensive understanding of the development process will enable the radiologist to communicate effectively as an educator in the new medium of CAI.

Computer-Assisted Instruction↗

PubMedDate not supplied

Interactive three-dimensional volume rendering of spiral CT data: current applications in the thorax.

Spiral computed tomographic (CT) data sets coupled with a real-time volume-rendering technique allow creation of accurate three-dimensional (3D) images that can be used for a wide range of clinical applications. The image contrast of and relative pixel attenuations in the final image can be interactively modified by the user in real time by manipulating trapezoidal transfer functions. Although 3D images are not required for diagnosis, they aid both radiologists and referring clinicians by demonstrating anatomic relationships and the extent of disease, particularly for vessels oriented in the z axis. Three-dimensional imaging of the vasculature and airway structures has many advantages, including the potential to obviate invasive procedures such as angiography and bronchoscopy. Clinical applications of volume rendering of spiral CT data include cardiovascular imaging (aorta, pulmonary vasculature, and venous abnormalities), staging of thoracic neoplasms (mediastinal and pulmonary masses), tracheobronchial imaging, and imaging of chest wall disease.

Adult↗

PubMedDate not supplied

CT evaluation of small bowel neoplasms: spectrum of disease.

Neoplasms of the small bowel are rare lesions that account for less than 5% of all gastrointestinal tumors. Although the differential diagnosis for a small bowel tumor is extensive, various small bowel neoplasms have characteristic features at computed tomography (CT) that may aid in making a diagnosis. Small bowel adenocarcinoma may appear at CT as an annular lesion, a discrete nodular mass, or an ulcerative lesion. Non-Hodgkin lymphoma may appear as a segmental bulky mass that gradually merges into the normal bowel wall. Lymphoma is characteristically associated with marked luminal dilatation. Carcinoid tumor may appear as an ill-defined homogeneous mass that displaces bowel loops. Calcification and desmoplastic reaction in a mesenteric mass suggest the diagnosis of carcinoid tumor. Gastrointestinal stromal tumors (GISTs), both benign and malignant, may be submucosal, subserosal, or intraluminal. The CT appearance of a GIST may include a sharply defined mass with homogeneous attenuation, sometimes with calcification. Lipoma appears at CT as a well-circumscribed, intraluminal homogeneous mass with fat attenuation. Most malignant small bowel tumors are actually metastases that have spread intraperitoneally, hematogenously, or by local extension. Intraperitoneal seeding usually manifests at CT as multiple small nodular metastases along the small bowel serosa, mesentery, and omentum. In patients with Peutz-Jeghers syndrome, nonneoplastic lesions may mimic small bowel neoplasms.

Adenocarcinoma↗

PubMedDate not supplied

Spectrum of CT findings in nonmalignant disease of the adrenal gland.

Computed tomography (CT) plays a leading role in the evaluation of nonmalignant disease of the adrenal gland. CT is highly accurate in the localization of adrenal masses in patients with diseases associated with hyperfunctioning adrenal glands such as Cushing syndrome and Cushing disease, Conn syndrome, adrenal tumors leading to virilization or feminization, and pheochromocytomas. CT permits a specific diagnosis of acute or subacute adrenal hematoma and myelolipoma. Hematomas are round to oval and have increased attenuation (50-90 HU) that decreases on follow-up CT scans. Myelolipomas typically manifest as a well-defined suprarenal mass with an attenuation of-30 to -115 HU. Adrenal cysts are usually round to oval and manifest as a hypoattenuating mass with a smooth, thin wall. CT is useful in the evaluation of patients with Addison disease, particularly the subacute form secondary to tuberculosis or disseminated histoplasmosis. Findings typically include bilateral adrenal enlargement with a central necrotic area of hypoattenuation and peripheral enhancement. Thin-section unenhanced CT permits accurate measurement of attenuation and can be used to differentiate adrenal adenoma from metastasis in a cancer patient with an indeterminate mass: Attenuation of 10 HU or less usually indicates adenoma rather than cancer. If the mass is found incidentally at contrast material-enhanced CT, delayed scans obtained as early as 5-15 minutes after intravenous administration of contrast material appear to have comparable accuracy.

Addison Disease↗

PubMedDate not supplied

Role of CT angiography in the preoperative evaluation for laparoscopic nephrectomy.

Laparoscopic nephrectomy (LN) was recently introduced as a minimally invasive alternative to open nephrectomy in living related renal donation. Because of the limited field of view available with laparoscopic techniques, the role of preoperative radiologic evaluation in LN has expanded to include anatomic definition of the renal arteries, collecting system, renal parenchyma, and renal venous anatomy. Computed tomographic (CT) angiography has proved to be a minimally invasive alternative to conventional angiography in the preoperative evaluation of living related renal donors. CT angiography has been shown to have an accuracy comparable to that of conventional angiography in predicting renal arterial anatomy. In addition, CT angiography provides comprehensive definition of the renal vascular anatomy including the location, size, and length of the renal, adrenal, gonadal, and lumbar veins. Dual-phase spiral CT combined with three-dimensional CT angiography constitute a single, minimally invasive procedure that can provide a complete preoperative evaluation of potential living related renal donors prior to LN. Comprehensive anatomic depiction of the renal arterial and venous supplies aids in surgical planning and helps avoid potential complications.

Adult↗

PubMedDate not supplied

Nonneoplastic liver disease: evaluation with CT and MR imaging.

A wide range of nontumorous hepatic diseases may have an impact on liver function and serve as indications for computed tomographic (CT) or magnetic resonance (MR) imaging. New imaging techniques such as spiral CT and fast MR imaging aid in detecting and characterizing these disease processes and in assessing the extent of disease. Infectious liver disease (eg, hepatic abscess, echinococcal disease, fungal infection) typically has low attenuation at CT and high signal intensity at T2-weighted MR imaging. Cholangitis is characterized by ductal dilatation at both CT and MR imaging. In acute portal vein thrombosis, the thrombus has low attenuation at CT and is hyperintense relative to liver at MR imaging. Hepatic infarcts usually appear as well-circumscribed, peripheral, wedge-shaped areas of decreased attenuation at CT. The causes or complications of cirrhosis can be most readily identified with MR imaging. In patients with chronic radiation-induced hepatitis, CT shows the irradiated parenchyma as a region of increased attenuation, whereas T1- and T2-weighted MR imaging demonstrate geographic areas of low and high signal intensity, respectively. Hemachromatosis has homogeneously increased liver attenuation at CT and decreased signal intensity at gradient-echo MR imaging in particular. Familiarity with the CT and MR imaging features of the spectrum of nonneoplastic conditions of the liver is essential in making an accurate diagnosis.

Diagnosis, Differential↗

PubMedDate not supplied

Pancreatic disease in children and young adults: evaluation with CT.

In children with pancreatic disease, computed tomography (CT) has a primary role in the evaluation of pancreatitis, trauma, and malignancy. At CT, pancreatic abnormalities may manifest as pancreatic enlargement (tumor, acute pancreatitis), pancreatic atrophy (cystic fibrosis, chronic pancreatitis), cystic lesions (pseudocysts, congenital simple cysts, autosomal dominant polycystic kidney disease, von Hippel-Lindau disease, cystic fibrosis, cystic neoplasms), or fatty replacement (cystic fibrosis, Shwachman-Diamond syndrome, history of steroid therapy, Cushing syndrome, Johanson-Blizzard syndrome, obesity). CT is the best modality for evaluation of pancreatitis, allowing detection of pancreatic abnormalities as well as abnormal extrapancreatic fluid collections. In children who have undergone blunt abdominal trauma, CT has been shown to be the best initial imaging study, being more sensitive than ultrasound for detection of pancreatic injury. In neoplastic conditions, CT demonstrates the extent of disease, enables characterization of the tissue components of the tumor, and allows accurate posttreatment follow-up. Although the various diseases of the pancreas may have overlapping appearances at CT, the correct diagnosis can often be made on the basis of the CT findings in combination with the clinical history, laboratory data, and the patient's age.

Adolescent↗

PubMedDate not supplied

CT and MR imaging of benign hepatic and biliary tumors.

Benign hepatic and biliary tumors can present a difficult diagnostic challenge. Spiral computed tomography (CT) and magnetic resonance (MR) imaging are useful in the detection and characterization of these tumors. Imaging characteristics of lesions such as hepatic cyst, hemangioma, focal nodular hyperplasia (FNH), and hepatic adenoma are well known. Hepatic cysts demonstrate water attenuation at CT, are isointense relative to water at MR imaging, and do not enhance after intravenous administration of contrast material. Hemangiomas demonstrate characteristic nodular peripheral enhancement on early-phase images with subsequent fill-in centrally at both modalities. FNH classically demonstrates intense early enhancement with washout on delayed images. Although hepatic adenoma can also demonstrate intense early enhancement, it has a tendency to bleed and thus often appears more heterogeneous than FNH due to hemorrhage. Benign hepatic tumors that are less well described in the imaging literature include hepatic lipoma or angiomyolipoma, infantile hemangioendothelioma, and mesenchymal hamartoma. Hepatic lipoma has fat attenuation at CT, is isointense relative to fat at MR imaging, and does not enhance after intravenous administration of contrast material. Hepatic angiomyolipomas contain a variable amount of soft tissue in addition to fat and may therefore demonstrate enhancement at both modalities. The CT and MR imaging appearances of infantile hemangioma are similar to those of adult hemangioma. Infantile hemangioendothelioma occurs in infants under 6 months of age and is typically a larger lesion. Mesenchymal hamartoma also occurs in children, and its imaging appearance depends on the presence of stromal elements and the protein content of the cyst fluid. Familiarity with these imaging features can help distinguish particular disease entities.

Biliary Tract Neoplasms↗

PubMedDate not supplied

Three-dimensional volume rendering of spiral CT data: theory and method.

Three-dimensional (3D) medical images of computed tomographic (CT) data sets can be generated with a variety of computer algorithms. The three most commonly used techniques are shaded surface display, maximum intensity projection, and, more recently, 3D volume rendering. Implementation of 3D volume rendering involves volume data management, which relates to operations including acquisition, resampling, and editing of the data set; rendering parameters including window width and level, opacity, brightness, and percentage classification; and image display, which comprises techniques such as "fly-through" and "fly-around," multiple-view display, obscured structure and shading depth cues, and kinetic and stereo depth cues. An understanding of both the theory and method of 3D volume rendering is essential for accurate evaluation of the resulting images. Three-dimensional volume rendering is useful in a wide variety of applications but is just now being incorporated into commercially available software packages for medical imaging. Although further research is needed to determine the efficacy of 3D volume rendering in clinical applications, with wider availability and improved cost-to-performance ratios in computing, 3D volume rendering is likely to enjoy widespread acceptance in the medical community.

Algorithms↗

PubMedDate not supplied

Pseudomembranous colitis: spectrum of imaging findings with clinical and pathologic correlation.

Pseudomembranous colitis (PMC) is a potentially life-threatening acute infectious colitis caused by one or more toxins produced by an unopposed proliferation of Clostridium difficile bacteria. PMC is characterized by the presence of elevated, yellow-white plaques forming pseudomembranes on the colonic mucosa. These plaques can be visualized at both pathologic analysis and endoscopy. Plain radiography, contrast enema studies, and computed tomography (CT) are useful in the evaluation of PMC. Plain radiography of the abdomen can demonstrate polypoid mucosal thickening, "thumbprinting" (wide transverse bands associated with haustral fold thickening), or gaseous distention of the colon. A toxic megacolon with distention and occasionally pneumoperitoneum may be seen in the most severe cases of PMC involving perforation. At contrast enema studies, the primary finding in mild cases of PMC is small nodular filling defects representing the mucosal plaques. With more extensive colonic involvement, the plaques are larger and coalesce to form an irregular bowel wall margin. Mural thickening and wide haustral folds caused by intramural edema may also be seen. A contrast enema study is contraindicated in patients with severe PMC due to the danger of perforation. Common CT findings include wall thickening, low-attenuation mural thickening corresponding to mucosal and submucosal edema, the "accordion sign," the "target sign" ("double halo sign"), pericolonic stranding, and ascites. Familiarity with these imaging characteristics may allow early diagnosis and treatment and prevent progression to more serious pathologic conditions.

Barium Sulfate↗

PubMedDate not supplied

Imaging of nontraumatic hemorrhage of the adrenal gland.

Nontraumatic hemorrhage of the adrenal gland is uncommon. The causes of such hemorrhage can be classified into five categories: (a) stress, (b) hemorrhagic diathesis or coagulopathy, (c) neonatal stress, (d) underlying adrenal tumors, and (e) idiopathic disease. Computed tomography (CT), ultrasonography (US), and magnetic resonance (MR) imaging play an important role in diagnosis and management. CT is the modality of choice for evaluation of adrenal hemorrhage in a patient with a history of stress or a hemorrhagic diathesis or coagulopathy (anticoagulant therapy). CT may yield the first clue to the diagnosis of adrenal insufficiency secondary to bilateral massive adrenal hemorrhage; such insufficiency is rare but life threatening. US is the modality of choice for evaluation of neonatal hematoma, and MR imaging is helpful for further characterization. MR imaging is also useful in the diagnosis of coexistent renal vein thrombosis. When an adrenal abscess is suspected, percutaneous aspiration and drainage under imaging guidance should be performed. Hemorrhage into an adrenal cyst or tumor can cause acute onset of symptoms and signs in a patient without discernible risk factors for adrenal hemorrhage. A hemorrhagic adrenal tumor should be suspected when CT or MR imaging reveals a hemorrhagic adrenal mass of heterogeneous attenuation or signal intensity that demonstrates enhancement.

Adrenal Gland Diseases↗

PubMedDate not supplied

Volume-rendered three-dimensional spiral CT: musculoskeletal applications.

Spiral computed tomography (CT) is a powerful modality for evaluation of the musculoskeletal system, particularly when coupled with real-time, volume-rendering reconstruction techniques. Including volume-rendered spiral CT in routine musculoskeletal imaging protocols can change management in a significant number of cases. In cases of trauma, subtle fractures--particularly those oriented in the axial plane--are better seen on volume-rendered images. Complex injuries can be better demonstrated with volume-rendered images, and complicated spatial information about the relative positions of fracture fragments can be easily demonstrated to the orthopedic surgeons. The use of intravenously administered contrast material allows simultaneous evaluation of osseous and vascular structures within the affected area. Evaluation of suspected infectious or neoplastic disease is also aided by including volume-rendered imaging in the musculoskeletal spiral CT examination. The extent of disease can be thoroughly evaluated with volume-rendered images, and therapeutic planning--be it surgical or medical--is aided by the anatomic information available from volume-rendered images. Postoperative studies in patients with orthopedic hardware also benefit from volume-rendered imaging. Volume rendering eliminates most streak artifact and produces high-quality images on which the relationships among hardware, bones, and bone fragments are well demonstrated.

Abscess↗

PubMedDate not supplied

Renal lymphoma: CT patterns with emphasis on helical CT.

Renal lymphoma is most often seen in conjunction with multisystemic, disseminated lymphoma or as tumor recurrence. Renal lymphoma may also be seen in immunocompromised patients or, rarely, as primary disease. Computed tomography (CT) is the most sensitive, efficient, and comprehensive examination for evaluation of the kidneys in patients with suspected renal lymphoma. Helical CT in particular improves detection and characterization of lymphomatous renal involvement by optimizing contrast dynamics and data acquisition and is the current modality of choice for accurate staging of lymphoma. Typical CT patterns in renal lymphoma include single and multiple masses, invasion from contiguous retroperitoneal disease, perirenal disease, and diffuse renal infiltration. Atypical CT patterns may also be encountered and provide a diagnostic challenge. These include spontaneous hemorrhage, necrosis, heterogeneous attenuation, cystic transformation, and calcification. Solid renal masses including renal cell carcinoma and metastases are the most commonly encountered entities that mimic renal lymphoma at CT and require biopsy for definitive diagnosis. CT (particularly helical CT) is useful in the evaluation of patients with suspected renal lymphoma, and familiarity with the spectrum of findings in renal lymphoma is important for accurate diagnosis.

Biopsy↗

PubMedDate not supplied

Spiral CT of colon cancer: imaging features and role in management.

Colorectal cancer is a common malignancy that results in significant morbidity and mortality. Abdominal computed tomography (CT) is valuable in planning surgery for colon cancer because it can demonstrate regional extension of tumor as well as adenopathy and distant metastases. At CT, colorectal cancer typically appears as a discrete soft-tissue mass that narrows the colonic lumen. Colorectal cancer can also manifest as focal colonic wall thickening and luminal narrowing. Complications of primary colonic malignancies such as obstruction, perforation, and fistula can be readily visualized with CT. At CT, local extension of tumor appears as an extracolic mass or simply as thickening and infiltration of pericolic fat. Extracolic spread is also suggested by loss of fat planes between the colon and adjacent organs. The liver is the predominant organ to be involved with metastases from colorectal cancer. At CT, hepatic metastases usually appear as hypoattenuating masses, which are best visualized during the portal venous phase of liver enhancement. Other common sites of metastases from colon cancer include the lungs, adrenal glands, and bones. Use of CT is critical for identifying recurrences, evaluating anatomic relationships, documenting "normal" postoperative anatomy, and confirming the absence of new lesions during and after therapy.

Adipose Tissue↗

PubMedDate not supplied

CT evaluation of the colon: inflammatory disease.

Computed tomography (CT) is valuable for detection and characterization of many inflammatory conditions of the colon. At CT, a dilated, thickened appendix is suggestive of appendicitis. A 1-4-cm, oval, fatty pericolic lesion with surrounding mesenteric inflammation is diagnostic of epiploic appendagitis. The key to distinguishing diverticulitis from other inflammatory conditions of the colon is the presence of diverticula in the involved segment. In typhlitis, CT demonstrates cecal distention and circumferential thickening of the cecal wall, which may have low attenuation secondary to edema. In radiation colitis, the clinical history is the key to suggesting the diagnosis because the CT findings can be nonspecific. The location of the involved segment and the extent and appearance of wall thickening may help distinguish Crohn disease and ulcerative colitis. In ischemic colitis, CT typically demonstrates circumferential, symmetric wall thickening with fold enlargement. CT findings of graft-versus-host disease include small bowel and colonic wall thickening, which may result in luminal narrowing and separation of bowel loops. In infectious colitis, the site and thickness of colon affected may suggest a specific organism. The amount of wall thickening in pseudomembranous colitis is typically greater than in any other inflammatory disease of the colon except Crohn disease.

Adolescent↗

PubMedDate not supplied

Tailored helical CT evaluation of acute abdomen.

Helical computed tomography (CT) allows rapid, cost-effective evaluation of patients with acute abdominal pain. Tailoring the examination to the working clinical diagnosis by optimizing constituent factors (eg, timing of acquisition, contrast material used, means and rate of contrast material administration, collimation, pitch) can markedly improve diagnostic accuracy. Rapid (>/=3 mL/sec) intravenous injection of contrast material is required for optimal assessment of acute pancreatitis, ischemic bowel, aortic aneurysm, and aortic dissection. Narrow collimation and small reconstruction intervals can help detect calculi in the biliary system and genitourinary tract. Tailored helical CT in patients with acute pyelonephritis usually involves several acquisitions through the kidneys during various phases of renal enhancement. In patients with suspected renal infarction, CT protocol must include an acquisition during the corticomedullary phase. Helical CT with 5-mm collimation through the lower abdomen and pelvis is used to evaluate patients with suspected diverticulitis. Use of both oral and intravenous contrast material can help localize small bowel perforation and characterize related complications. Tailored helical CT for assessment of abdominal hemorrhage consists of initial unenhanced CT followed by optional contrast material-enhanced CT. Clear communication between the radiologist, the patient, and the referring physician is essential for narrowing the differential diagnosis into a working diagnosis prior to helical CT.

Abdomen, Acute↗