Single-source dual-energy spectral multidetector CT of pancreatic adenocarcinoma: optimization of energy level viewing significantly increases lesion contrast.

AIM: To evaluate lesion contrast in pancreatic adenocarcinoma patients using spectral multidetector computed tomography (MDCT) analysis. MATERIALS AND METHODS: The present institutional review board-approved, Health Insurance Portability and Accountability Act of 1996 (HIPAA)-compliant retrospective study evaluated 64 consecutive adults with pancreatic adenocarcinoma examined using a standardized, multiphasic protocol on a single-source, dual-energy MDCT system. Pancreatic phase images (35 s) were acquired in dual-energy mode; unenhanced and portal venous phases used standard MDCT. Lesion contrast was evaluated on an independent workstation using dual-energy analysis software, comparing tumour to non-tumoural pancreas attenuation (HU) differences and tumour diameter at three energy levels: 70 keV; individual subject-optimized viewing energy level (based on the maximum contrast-to-noise ratio, CNR); and 45 keV. The image noise was measured for the same three energies. Differences in lesion contrast, diameter, and noise between the different energy levels were analysed using analysis of variance (ANOVA). Quantitative differences in contrast gain between 70 keV and CNR-optimized viewing energies, and between CNR-optimized and 45 keV were compared using the paired t-test. RESULTS: Thirty-four women and 30 men (mean age 68 years) had a mean tumour diameter of 3.6 cm. The median optimized energy level was 50 keV (range 40-77). The mean ± SD lesion contrast values (non-tumoural pancreas - tumour attenuation) were: 57 ± 29, 115 ± 70, and 146 ± 74 HU (p = 0.0005); the lengths of the tumours were: 3.6, 3.3, and 3.1 cm, respectively (p = 0.026); and the contrast to noise ratios were: 24 ± 7, 39 ± 12, and 59 ± 17 (p = 0.0005) for 70 keV, the optimized energy level, and 45 keV, respectively. For individuals, the mean ± SD contrast gain from 70 keV to the optimized energy level was 59 ± 45 HU; and the mean ± SD contrast gain from the optimized energy level to 45 keV was 31 ± 25 HU (p = 0.007). CONCLUSION: Significantly increased pancreatic lesion contrast was noted at lower viewing energies using spectral MDCT. Individual patient CNR-optimized energy level images have the potential to improve lesion conspicuity.

Double-blind comparison of Hexabrix and Renografin-76 in computed tomography.

In a double-blind randomized assignment of Renografin-76 or Hexabrix, 65 patients were evaluated to determine the safety and efficacy of Hexabrix, and to assess subtle differences and their implications in image quality. Dosage was adjusted for patient weight, and up to 150-ml of Hexabrix or Renografin-76 were injected over a 2-minute period during which rapid sequence CT was performed. Less heat and discomfort were noted with Hexabrix. No difference was evidenced in the side effects of emesis or hives, and no real difference in renal dysfunction was noted from a clinical standpoint. Image quality was generally equivalent, with possibly better renal concentration achieved with Hexabrix.

Comparison of contrast media injection rates and volumes for hepatic dynamic incremented computed tomography.

Contrast injection techniques now in use for hepatic dynamic incremented computed tomography (DICT) were designed for scanners using slower scan acquisition rates than the currently available 6 to 12 scans/minute. Of 53 patients examined, (1) 19 received a conventional 2-minute injection of 150 or 120 mL of 60% contrast material selected by patient weight; (2) 19 received the same doses within 1 minute; and (3) 15 received 20% lower doses within 1 minute. The faster injection groups 2 and 3 reached peak enhancement sooner (57 and 60 seconds vs. 97 seconds) with similar or higher peak hepatic enhancement (73 and 64 HU vs. 58 HU) and equivalent hepatic enhancement (52 and 48 HU vs. 54 HU) after 150 seconds. Because detecting neoplastic liver lesions often depends on enhancement, 1-minute injections of high doses of contrast material with rapid scan rates may be superior to 2-minute injections. When cost or dose-related toxicity are important, 1-minute injections of 20% lower contrast doses may be considered.

Ultrasound evaluation of pelvic infections.

Sonography is used infrequently for diagnosing acute pelvic inflammatory disease because the physical examination is highly sensitive, because the sonogram lacks specificity, and because the patient is often scheduled for surgery or laparoscopy or treated medically based on clinical findings, obviating the need for diagnostic studies. Sonography is usually reserved for identifying, localizing, and following pelvic abscesses complicating pelvic inflammatory disease. The sonogram is valuable in identifying the location of intrauterine devices because of the increased incidence of inflammatory pelvic disease in these patients. Postoperative and posttraumatic abscesses and abscesses of gastrointestinal origin may require the concomitant use of computed tomography and radionuclide studies, with ultrasonography performing a complementary function. The ultrasound examination may be valuable both in improving diagnostic confidence and providing guidance for aspiration. Because of the limited spectrum of appearances of numerous pelvic diseases, the most accurate diagnoses are obtained when the sonogram is interpreted in light of the detailed clinical information.

Duplex assessment of the portal venous system.

The clinical applications of duplex ultrasound and color Doppler imaging in the evaluation of the portal venous system and hepatic vasculature are quite diverse and widespread. These include identification of portal vein thrombosis, portal venous hypertension, and hepatic veno-occlusive disease as well as a role in the preoperative and postoperative treatment of patients who are candidates for portosystemic shunts or for liver allografts. As technological improvements continue, the current applications will almost certainly be refined, with resultant improvements in sensitivity, specificities, and accuracy rates.

Duplex assessment of the splanchnic vasculature.

The role of duplex ultrasound and color Doppler imaging in the evaluation of patients with suspected splanchnic vasculature obstructive disease and chronic mesenteric ischemia is not clearly defined. In this report the examination technique, as well as normal and abnormal findings, is discussed. Limitations are also described.

Duplex evaluation of native renal vessels and renal allografts.

Duplex ultrasound and color duplex imaging are useful in evaluating the renal vasculature. Investigation of native renal vessels includes the diagnosis of renal artery stenosis and occlusion and renal vein thrombosis. The sonographic examination of renal allografts may detect vascular complications and peritransplant fluid collections, both of which may impair allograft function. In order to perform and interpret renal vascular sonography, knowledge of pertinent vascular anatomy and proper duplex technique is essential. Renal arterial and venous examination with gray-scale, Doppler, and color duplex imaging is reviewed, comparing their performance with other methods of assessing renal vessels when appropriate.

Slip-ring and conventional dynamic hepatic CT: contrast material and timing considerations.

The major conclusions and recommendations of this review of contrast material use are summarized as follows: 1. Our recommendations for routine administration of contrast material are summarized in the Table. 2. Patient factors, such as weight, and liver and cardiovascular disorders may be taken into account when the above recommendations are modified. 3. Unenhanced scanning should be performed selectively. It is unnecessary for routine examinations performed with modern scanners and good contrast material injection techniques. 4. Although conclusive evidence is lacking regarding efficacy, reduced doses of contrast material may be given to patients with an elevated serum creatinine level. A full dose of low-osmolar contrast material may be given to functionally anephric patients if otherwise medically appropriate. 5. Differences in enhancement patterns produced by low-osmolar contrast agents and by high-osmolar contrast agents are small. Choice of contrast material should be based on other factors. 6. The dose of low-osmolar contrast material may be lower than the dose of high-osmolar contrast material so the examination cost may be reduced. 7. Low-osmolar contrast material is not satisfactory to use with delayed iodine scanning. 8. With use of slip-ring scanners and either helical or incremented scanning and recommended techniques, scanning should begin by the end of the injection of contrast material for biphasic techniques and within about 5-15 seconds after the end of injection for monophasic techniques. 9. Section thicknesses no greater than 8 mm should be used for helical or nonhelical scanning. 10. With helical scanning, a 1:1 pitch is preferred with a thickness of 5-8 mm. Overlapping sections may be used selectively to help identify and characterize small lesions. 11. Multiple-pass scanning is helpful to identify hepatocellular carcinoma in cirrhotic livers. This technique may also prove helpful in other conditions. As with any new technology, considerable advantages have come with new challenges, which can be overcome by knowing underlying principles and by attending to detail. Although we have learned much over the past 15 years about proper performance of abdominal CT examinations, we have much yet to learn about the effects of such examinations on the improved health of our patients and on the economic costs to society of providing this form of health care. Opinions on techniques have converged recently, as summarized herein. Therefore, we hope that some centers will now redirect their CT research toward the profoundly difficult, timely, and important issues of examination appropriateness, the value of quality improvement programs, clinical outcomes, and cost-effectiveness.

Focal areas of decreased echogenicity in the liver at the porta hepatis.

Twelve patients are described in whom solitary focal hypoechoic areas in the liver were observed adjacent to the gallbladder and portal vein. These areas were all homogeneously hypoechoic relative to adjacent liver, had variable shapes but well-defined borders, and were less than 4 cm in diameter. These apparent pseudolesions were incidental findings in patients who had no evidence of significant liver disease, metastatic malignancy, or subsequent evidence of developing liver masses. In one patient, a second sonogram done 21 months after one such area was identified showed no change. In another patient, a computed tomogram done to clarify the finding was normal. Solitary hypoechoic areas in the liver at the porta hepatis fitting the above criteria should be interpreted cautiously. When there is no clinical suspicion of focal liver disease, these areas may be dismissed as insignificant or may be followed. If focal liver disease is suspected, the liver should be assessed by an additional method of examination.

The year 2000 threat: preparing radiology for nine realms of risk.

The year 2000 computer problem arises from a long-standing and often-duplicated computer programming error. Affected programs use only two digits to represent years, which may lead to a variety of computer malfunctions and data errors related to crossing from 1999 (99) to 2000 (00), at which point computers may interpret 00 as 1900 or other incorrect dates. Radiology and medicine may be seriously affected by this problem as it relates to the function of its equipment; business functions such as scheduling, billing and purchasing; the reliability of infrastructure such as power and telecommunications; the availability of supplies; and many other issues. It is crucial that radiologists, as practitioners of one of the most computer-oriented medical specialties, help lead the effort to ensure continuity of operations as the year 2000 boundary approaches and passes. This article provides suggestions for a structured approach, as well as tools and checklists, to guide project leaders attempting to identify and remediate year 2000-associated problems within radiology facilities.

Screening for diffuse and focal liver disease: the case for hepatic computed tomography.

I believe that CT should usually be the first choice for examining patients with suspected liver disease. Precontrast scans may suffice when results are clearly abnormal, but when contrast is given it should be in a high dose, bolus injection with rapid sequential scanning and table incrementation. This opinion is based upon: (1) the greater sensitivity and specificity of contrast enhanced CT compared to sonography and radionuclide scanning in focal liver lesions; (2) the ability of CT to detect diffuse liver abnormalities; (3) the greater ease in standardizing the CT examination and interpretation; (4) the ability of CT to predict accurately the histology of many focal and diffuse liver diseases; and (5) the superiority of CT in accurately detecting and characterizing extrahepatic abnormalities. The advantages of CT are somewhat mitigated by its limited availability, and relatively greater risk and cost, but these factors are often overcome by facilitating diagnosis and management by more accurate initial evaluation. Sonography may be done first when fast CT scanners are not available, when intravenous contrast cannot be administered satisfactorily, when other problems arise with technique, for patients requiring sonography for other reasons, or when delays for scheduling CT scans are too long. Radionuclide liver-spleen scanning should play a very limited role in the early evaluation of liver disease, being reserved for occasionally clarifying the presence of diffuse liver disease, or for patients difficult to study either by CT or sonography.

Cine display of numerous static ultrasound images: a step toward automation of ultrasound studies.

Ultrasound images were assembled and viewed in a motion picture format to facilitate the laborious task of reviewing numerous sonograms. Sequential, closely spaced images from an automated water bath ultrasound scanner were recorded both on a video disc recorder capable of high speed playback and on a film strip using a 35-mm half frame camera. A conventional 35-mm cine viewer was used to evaluate the film strip. Advantages of the motion picture format are (a) many images can be reviewed easily and rapidly, (b) objects that extend through several images are easily perceived and an impression of the third dimension is obtained, (c) the chances of diagnostic errors due to wide spacing or selective recording of images are lessened, and (d) fuller advantage can be taken of the scanner's capacity for automatic operation. Disadvantages of the technique are (a) respiratory motion must be minimized, and (b) the method is useful only in conjunction with water bath scanners.

A radiology department intranet: development and applications.

An intranet is a "private Internet" that uses the protocols of the World Wide Web to share information resources within a company or with the company's business partners and clients. The hardware requirements for an intranet begin with a dedicated Web server permanently connected to the departmental network. The heart of a Web server is the hypertext transfer protocol (HTTP) service, which receives a page request from a client's browser and transmits the page back to the client. Although knowledge of hypertext markup language (HTML) is not essential for authoring a Web page, a working familiarity with HTML is useful, as is knowledge of programming and database management. Security can be ensured by using scripts to write information in hidden fields or by means of "cookies." Interfacing databases and database management systems with the Web server and conforming the user interface to HTML syntax can be achieved by means of the common gateway interface (CGI), Active Server Pages (ASP), or other methods. An intranet in a radiology department could include the following types of content: on-call schedules, work schedules and a calendar, a personnel directory, resident resources, memorandums and discussion groups, software for a radiology information system, and databases.

Pulsed Doppler duplex sonography and CT of portal vein thrombosis.

Five patients with partial or complete portal vein thrombosis were examined by both computed tomography (CT) and pulsed Doppler duplex scanning. Duplex scanning correctly identified portal vein thrombosis in all five. Duplex sonography may be the preferred technique to detect and follow portal vein thrombosis because of lower cost, lack of need for intravenous contrast material, and easier availability for multiple follow-up examinations.

Decreased splenic enhancement on CT in traumatized hypotensive patients.

Three patients with transient episodes of hypotension following blunt abdominal trauma incurred in motor vehicle accidents were examined by computed tomography within 6 hours of injury. The examinations were done using a contrast material injection technique that ordinarily leads to greater splenic than hepatic attenuation. None of the patients had splenic injury evident on autopsy, surgery, or clinical follow-up study (one case each), nor did they have other characteristic features of splenic infarction. However, in each case the spleen was less enhanced than the liver, leading to an erroneous impression in one patient that the splenic artery had been disrupted. Physiologic studies have shown that splenic perfusion decreases with sympathetic stimulation; this may have been the cause of the diminished enhancement. Decreased splenic enhancement should be interpreted cautiously in traumatized hypotensive patients.

Duplex Doppler examination of the liver and portal venous system.

Duplex Doppler scanning has many applications in the evaluation of the liver and the portal venous system. It can be a useful adjunct to real-time sonographic identification of normal and variant anatomy, and lesion detection in the liver and porta hepatis. It is able to document both portal venous thrombosis and portal venous hypertension. It plays an important role in the pre- and postoperative assessment of patients undergoing portosystemic shunts or liver transplants. It allows the observation and measurement of portal venous systemic physiologic responses. In addition to the above applications, duplex Doppler scanning's future potential, including full-field color Doppler imaging, is discussed.

Acute hemorrhage into the gallbladder diagnosed by computed tomography and ultrasonography.

Hemorrhage into the gallbladder occurs rarely and may result from gangrenous cholecystitis, cystic artery aneurysm, or varicose veins in the gallbladder wall. A definitive diagnosis of intraluminal gallbladder hemorrhage is possible with computed tomography.

Radiologic follow-up of vena cava filter devices.

A total of 66 vena cava filters was implanted to prevent pulmonary emboli: 33 Mobin-Uddin umbrellas and 33 Kim-Ray-Greenfield devices. Radiologic examinations were available in 59 patients, 37 having one or more follow-up studies. Most of the Mobin-Uddin umbrellas became thrombosed. Although most Kim-Ray-Greenfield devices remained patent, some migrated, and several penetrated the cava wall; this latter finding can be diagnosed on plain films. Neither of these devices is fully safe nor effective in preventing pulmonary emboli; further improvements are needed.

Cervical Castleman disease: CT study with angiographic correlation.

The computed tomographic (CT) appearance, angiographic appearance, and clinical features of a patient with cervical Castleman disease, an uncommon disease of benign lymph node hyperplasia, are reported. CT scans showed a densely enhancing cervical mass. On external carotid angiography, the mass was seen as hypervascular with a capillary blush. Differential diagnosis included carotid body chemodectoma, vagal neuroma, tumor of the salivary gland, tuberculous adenitis and other granulomatous diseases, inflammatory lymph nodes, metastatic disease, and lymphoma.

Evaluation of canine renal transplants with pulsed Doppler duplex sonography.

Preliminary studies of human renal transplants suggested that pulsed Doppler sonography may complement other studies of renal transplant dysfunction. To further evaluate the Doppler technique, 11 dogs who received renal transplants were examined a total of 50 times. No antirejection chemotherapy was used, and following rejection the kidneys were removed and examined histologically. The canine transplants underwent accelerated acute or hyperacute rejection. A pulsed Doppler index (PDI) was derived to quantitate patterns of renal blood flow and peripheral vascular resistance. Arterial Doppler signals were obtained from renal transplant branch vessels in vivo and the PDI consistently fell as rejection occurred. No arterial signals were obtained from one kidney which was subsequently proven to have arterial thrombosis. Pulsed Doppler analysis provides new information about renal transplant blood flow patterns and may demonstrate evidence of rejection and renal arterial occlusion.