Helical computed tomography for abdominal imaging.

Significant technologic advances have taken place in computed tomography (CT). Current-generation conventional CT scanners are able to image a slice of tissue in as little as 2 to 3 seconds and can acquire several consecutive images. Although it is a substantial improvement from the CT of 5 years ago, there remain practical limits to the utility of conventional CT imaging within the abdomen. Recently, a new type of CT gantry design ("slip-ring") and faster computers have contributed to the development of a new generation of CT scanners, the "helical" or "spiral" CT scanners.

Proximal fetal cerebral ventricle: description of US technique and initial results.

PURPOSE: To establish adequacy and ease of visualization of the proximal ventricle, normal range of measurements of the proximal ventricle, and distance of the proximal choroid plexus from the lateral ventricular wall. MATERIALS AND METHODS: With use of an angled technique, ultrasound (US) evaluation of the proximal fetal ventricle was attempted in 439 fetuses during routine obstetric US examination. Ease of examination, additional time required, mean measurements, and standard deviation (SD) were calculated. RESULTS: Visualization and measurement of the proximal ventricle were performed without difficulty in 77% of cases and with difficulty in 19%, and were impossible in 4%. Average additional time required was 4.2 minutes. The upper limit of normal for the midportion of the proximal ventricle was 8 mm (mean + 2.5 SD). In no normal pregnancy was the proximal ventricle separated from the choroid plexus by greater than 3 mm. CONCLUSION: Visualization and measurement of the proximal fetal cerebral ventricle can be performed during routine obstetric US examination in little additional time and can be used to detect abnormalities that might otherwise be overlooked because of fetal position.

Local staging of pancreatic cancer: criteria for unresectability of major vessels as revealed by pancreatic-phase, thin-section helical CT.

OBJECTIVE: This study was conducted to determine the criteria for unresectability of major peripancreatic vessels in patients with pancreatic carcinoma as revealed by optimally enhanced, pancreatic-phase thin-section helical CT. SUBJECTS AND METHODS: Twenty-five patients with pancreatic adenocarcinoma who underwent local dissection during curative or palliative surgery also underwent preoperative pancreatic-phase thin-section helical CT (40- to 70-sec delay, 2.5- to 3-mm collimation). Tumor involvement of the portal and superior mesenteric veins and the celiac, hepatic, and superior mesenteric arteries was prospectively graded on a 0-4 scale based on circumferential contiguity of tumor to vessel. Subsequent surgical results were then correlated with the CT grades. RESULTS: At surgery, definitive evaluation was possible for 80 vessels. Forty-eight of 48 vessels graded 0 and three of three vessels graded 1 were resectable. Four of seven vessels graded 2, seven of eight vessels graded 3, and 14 of 14 vessels graded 4 were unresectable. A threshold of between grades 2 and 3, which corresponded to tumor involvement of one-half circumference of the vessel, yielded the lowest number of false-negatives and an acceptable number of false-positives for unresectability. Such a threshold would have yielded a sensitivity of 84%, a specificity of 98%, a positive predictive value of 95%, and a negative predictive value of 93% for unresectability of the vessels studied. CONCLUSION: A grading system for tumor involvement of the major vessels in patients with pancreatic adenocarcinoma can be based on the degree of circumferential contiguity of tumor to vessel. Involvement of vessel to tumor that exceeds one-half circumference of the vessel is highly specific for unresectable tumor.

Pain: a poor parameter of evaluation in dentistry.

In summary, we must be aware of the limitations of our instruments for determining success. A diagnosis is achieved by developing a composite picture through a keen gathering of all factors leading to the disease. Pain must surely be considered in patient management and patient-dentist rapport, but to allow our judgment to be swayed by pain alone is no more rational than to hinge our diagnosis upon a single other test. It is of paramount importance that we realize that, pulpally, periodontally, and periapically, there is no correlation between amount of destruction and reported presence or absence of pain. Pain is a poor parameter of evaluation.

Hepatic lesion characterization in cirrhosis: significance of arterial hypervascularity on dual-phase helical CT.

OBJECTIVE: Our goal was to evaluate the diagnostic significance of the presence and pattern of arterial hypervascularity in lesions detected on dual-phase helical CT in cirrhotic patients. MATERIALS AND METHODS: Fifty-eight lesions greater than 1 cm in size were prospectively identified in 26 patients with end-stage liver disease who had undergone dual-phase helical CT for preoperative liver transplantation evaluation. All 26 patients had diagnoses proven by histologic evaluation or by clinical criteria. All arterial phase scans were retrospectively reviewed and lesions were categorized for the presence and pattern of arterial hypervascularity. Radiologic findings were correlated with histopathologic data. RESULTS: Thirty-seven of the 58 lesions had hypervascular components on arterial phase scans. All 37 of these lesions were found to represent hepatocellular carcinoma (HCC) (positive predictive value, 100%). Of the 21 remaining hypovascular lesions, 17 were HCC and four were benign (positive predictive value, 81%). Of the nine patients in whom all lesions were hypovascular, six had HCC (positive predictive value, 66%). The value of the presence of arterial hypervascularity for diagnosing HCC was statistically significant (p < .05). However, the presence or absence of arterial hypervascularity and the specific enhancement pattern revealed by helical CT did not correlate with histologic grading. CONCLUSION: The presence of hypervascularity in hepatic masses found in cirrhotic patients is highly predictive of malignancy.

Two-phase helical CT for pancreatic tumors: pancreatic versus hepatic phase enhancement of tumor, pancreas, and vascular structures.

PURPOSE: To quantitatively evaluate and validate a two-phase helical computed tomographic (CT) protocol for evaluation of pancreatic tumors. MATERIALS AND METHODS: Twenty-seven patients with pathologically proved pancreatic adenocarcinomas prospectively underwent two-phase CT examination with helical acquisition during the pancreatic phase (40-70 seconds after infusion of intravenous contrast material at 3 mL/sec) and the hepatic phase (70-100 seconds after infusion). Mean CT attenuation values of tumor, bordering pancreas, and all major peripancreatic vessels were obtained for both time intervals. RESULTS: Mean tumor-pancreas contrast was significantly greater during the pancreatic phase (67 HU +/- 19) than the hepatic phase (39 HU +/- 16) (P < .001) This was the result of both greater enhancement of normal pancreas and lower tumor enhancement during the pancreatic phase. Opacification of all vascular structures, including the portal vein, was also greater during the pancreatic phase (P < .001). CONCLUSION: Two-phase helical CT with pancreatic phase acquisition provides statistically significantly better pancreatic, arterial, and portal venous enhancement than that of hepatic phase imaging, with improved tumor-pancreas contrast.

Percutaneous nephrostomy: placement under CT and fluoroscopy guidance.

OBJECTIVE: The purpose of this paper is to present our experience with CT- and fluoroscopy-guided percutaneous nephrostomy tube (PNT) placement and to describe the technique of placement with patients in the supine-oblique position. MATERIALS AND METHODS: A CT scanner was coupled with a ceiling-mounted C-arm for fluoroscopy at the CT table, PNT was done with CT localization and fluoroscopic control. We attempted 148 placements in 129 patients, with most patients in the supine or the supine-oblique position. RESULTS: Successful PNT placement was achieved in 144 (97%) of 148 kidneys. In the native kidney group, 101 (81%) of 124 PNTs were placed with the patients in the supine-oblique position. We experienced no major complications, three (2%) minor complications, and two (1%) catheter dislodgments. CONCLUSION: CT-fluoroscopy control allows routine PNT placement with patients in the supine or the supine-oblique position and is associated with the lowest complication rate to our knowledge.

Helical CT angiography for examination of living renal donors.

OBJECTIVE: This prospective study was intended to determine if helical CT arteriography plus conventional radiography is sufficiently accurate to replace and less costly than excretory urography and conventional renal arteriography, the techniques currently used to examine living renal donors. SUBJECTS AND METHODS: Patients underwent CT arteriography with a helical CT scanner. Conventional radiographs were obtained during the pyelographic phase to evaluate the urothelium. Findings on CT arteriograms were compared with findings on conventional arteriograms and at surgery. RESULTS: Of 57 patients who underwent CT arteriography, 46 also underwent conventional arteriography and 40 underwent surgery. For those 46 patients, we found agreement between results of CT arteriography and conventional arteriography in 89% of kidneys. For those 40 patients, we found agreement between results of CT arteriography and findings at surgery in 90% of kidneys and agreement between results of conventional arteriography and findings at surgery in 87% of kidneys. Of the 57 patients, six (11%) had findings on CT angiograms that precluded further consideration for donation. CONCLUSION: Eight to ten percent of renal arteries are not seen on renal arteriograms when compared with findings at surgery. Our results indicate that CT arteriography is as accurate as conventional arteriography at revealing the number of vessels that perfuse and drain the kidneys and can replace conventional arteriography. Use of CT angiography plus conventional radiography instead of excretory urography and conventional arteriography can result in a 35-50% reduction in cost of the imaging studies in potential renal donors.