Diagnosis of acute appendicitis: comparison of 5- and 10-mm CT sections in the same patient.

PURPOSE: To compare 5- and 10-mm computed tomographic (CT) sections in the same patient to diagnose acute appendicitis. MATERIALS AND METHODS: During an 11-month period, 100 consecutive patients clinically suspected to have acute appendicitis underwent abdominal and pelvic CT. Helical, 10-mm-collimated sections from the diaphragm to the pubic symphysis and 5-mm-collimated sections through the lower part of the abdomen and upper part of the pelvis were obtained. The 10- and 5-mm sections from each patient were separated into two groups and were interpreted independently by two abdominal imaging attending physicians who were blinded to the final results. The interpretations were correlated with the histopathologic or final clinical diagnoses. RESULTS: Data analysis from blinded reader interpretations of the 5- and 10-mm sections, respectively, revealed sensitivities of 99% and 82% (P <.001), specificities of 98% and 95% (P =.426), and accuracies of 99% and 89% (P <.001). Among the 48 cases of acute appendicitis, abnormal appendices were identified in 94% (n = 45) and 69% (n = 33) (P <.05) on 5- and 10-mm-collimated sections, respectively. Right-lower-quadrant inflammatory changes were identified in 98% (n = 47) and 71% (n = 34) (P <.05) on 5- and 10-mm-collimated sections, respectively. Normal appendices were identified in 75% (n = 39) and 52% (n = 27) of the 52 negative cases on 5- and 10-mm sections (P =.025), respectively. CONCLUSION: Use of thin-section CT significantly improves the diagnosis of acute appendicitis.

Helical (spiral) computed tomography. Implications for imaging of the abdomen.

Dramatic refinements in CT technology are resulting in improved evaluation of the liver, pancreas, and gastrointestinal tract. Further clinical trials are necessary to compare the relative merits of CT versus MR imaging and endoscopic ultrasonography in a wide variety of gastrointestinal diseases.

Helical CT: practical considerations and potential pitfalls.

Helical (spiral) computed tomography (CT) is having a dramatic impact on body imaging. Unlike conventional CT, helical CT provides continued volumetric acquisition as the patient moves through the gantry. Advantages of helical CT include dramatically shortened examination times, improved visibility of vascular structures, better enhancement of parenchymal organs, the capability for retrospective imaging and three-dimensional (3D) vascular studies, and potential reduction in use of contrast material. However, helical CT requires one to be more cognizant of the relationship between contrast material administration and scanning, since the optimal temporal window for detection of disease can be missed. Factors unique to helical technology can produce artifacts, which one must be aware of when interpreting helically generated scans. Many of these artifacts relate to accentuation of vascular or parenchymal enhancement. Others occur during production of high-quality 3D images. Additional artifacts are sure to be identified with increased experience with helical CT.

Abdominal aortic aneurysms: evaluation with variable-collimation helical CT and overlapping reconstruction.

PURPOSE: To determine the value of variable collimation and overlapping reconstruction in helical computed tomography (CT) to evaluate abdominal aortic aneurysm. MATERIALS AND METHODS: Twenty-three patients (15 men and eight women, aged 59-85 years) underwent helical CT scanning, nine with fixed 5-mm collimation and 14 with 3- and 7-mm collimation combined. The ability to visualize main and accessory renal arteries, detect stenoses, and determine aneurysm extent were evaluated. RESULTS: Extent of aneurysm was accurately determined in 17 of 23 cases without overlapping sections; failure to detect ancillary findings such as accessory arteries or stenosis occurred in nine of these cases. With overlapping sections, determination of aneurysm extent improved to 19 of 23 cases and ancillary errors were reduced to four. Five errors occurred with fixed collimation and three errors with variable collimation. CONCLUSION: Overlapping, variable-collimation helical CT allows for a more complete evaluation of abdominal aortic aneurysms than does nonoverlapping, fixed-collimation CT.

Acute diseases of the gallbladder and biliary ducts.

Approximately 10% to 15% of adults have gallstones, resulting in more than 600,000 cholecystectomies being performed annually in the United States. It is not surprising, therefore, that biliary disease is a major consideration in the patient with acute abdominal pain. Although there is no substitute for skillful physical diagnosis, the radiologist is often the central player in the evaluation of biliary disease. This article focuses on three specific areas of importance to the radiologist: (1) the diagnostic approach to acute biliary disease, (2) imaging of specific clinical entities, and (3) the relationship between imaging findings and the use of new therapeutic modalities.

Three-dimensional models of the abdominal vasculature based on helical CT: usefulness in patients with pancreatic neoplasms.

Three-dimensional (3D) rendering of helical (spiral) CT data is used increasingly to show abnormalities of the vascular system [1]. Abdominal applications have focused mainly on the arterial system, but the portal venous system also can be depicted effectively with this technique. In patients with pancreaticobiliary neoplasms, axial display of helical CT images generally allows accurate staging of the lesion [2, 3]. Many surgeons, however, continue to request arteriography to specifically look for evidence of vascular encasement that would preclude surgery or vascular anomalies that would alter the surgical approach [4, 5]. The purpose of this essay is to illustrate the value of 3D rendering of CT data in providing useful information for surgical planning and showing the extent of vascular involvement by tumor.

Routine helical CT of the abdomen: image quality considerations.

PURPOSE: Both helical and nonhelical abdominal computed tomographic (CT) scans were obtained to compare image quality, study the effect of patient size and collimation, and compare the frequency of visualization of normal abdominal structures. MATERIALS AND METHODS: The study group consisted of 60 consecutive patients with clinically suspected metastatic malignancy. RESULTS: Both helical and nonhelical image quality was excellent, with equal mean image quality scores of 4.1 on a 5-point scale. In patients weighing more than 175 lb (79 kg), both helical and nonhelical image quality degraded equally when 5-mm collimation was used; 10-mm collimation resulted in excellent image quality, regardless of patient size. Small in-plane structures (eg, renal arteries, renal veins, pancreatic duct) were seen best on helical scans. With the addition of retrospectively reconstructed overlapping images, improvement in visualization of these structures was statistically significant. CONCLUSION: Helical CT scanning should be the preferred means of acquiring routine abdominal CT images.

Helical (spiral) CT of the abdomen.

Since its clinical introduction in the mid 1970s, techniques for CT have undergone many changes that have dramatically altered how CT scans are obtained. Helical (spiral) CT allows for faster acquisition of truly volumetric CT data than is possible with conventional scanners. Routine helical CT of the abdomen is now possible because of three major technical refinements: the development of the slip-ring gantry, improved detector efficiency, and greater tube cooling capability. This article reviews the technical principles that govern helical CT, the potential advantages and disadvantages of this technique, and initial clinical experience with helical CT of the abdomen.