Single-energy non-contrast hepatic steatosis criteria applied to virtual non-contrast images: is it still highly specific and positively predictive?

AIM: To determine the sensitivity, specificity, and predictive values of single-energy non-contrast hepatic steatosis criteria on dual-energy virtual non-contrast (VNC) images. MATERIALS AND METHODS: Forty-eight computed tomography (CT) examinations, which included single-energy non-contrast (TNC) and contrast-enhanced dual-energy CT angiography (CTA) of the abdomen, were enrolled. VNC images were reconstructed from the CTA. Region of interest (ROI) attenuations were measured in the right and left hepatic lobes, spleen, and aorta on TNC and VNC images. The right and left hepatic lobes were treated as separate samples. Steatosis was diagnosed based on TNC liver attenuation of ≤40 HU or liver attenuation index (LAI) of ≤-10 HU, which are extremely specific and predictive for moderate to severe steatosis. The sensitivity, specificity, and predictive values of VNC images for steatosis were calculated. VNC-TNC deviations were correlated with aortic enhancement and patient water equivalent diameter (PWED). RESULTS: Thirty-two liver ROIs met steatosis criteria based on TNC attenuation; VNC attenuation had sensitivity, specificity, and a positive predictive value of 66.7%, 100%, and 100%, respectively. Twenty-one liver ROIs met steatosis criteria based on TNC LAI. VNC LAI had sensitivity, specificity, and positive predictive values of 61.9%, 90.7%, and 65%, respectively. Hepatic and splenic VNC-TNC deviations did not correlate with one another (R2=0.08), aortic enhancement (R2<0.06) or PWED (R2 <0.09). CONCLUSIONS: Non-contrast hepatic attenuation criteria is extremely specific and positively predictive for moderate to severe steatosis on VNC reconstructions from the arterial phase. Hepatic attenuation performs better than LAI criteria. VNC deviations are independent of aortic enhancement and PWED.

Renal mass imaging: the internist's role.

The busy internist will encounter numerous renal masses when ordering nonurologic imaging. Concise and quick delineation of cystic from solid masses is necessary. Cystic masses constitute the majority of these masses and once their nature is diagnosed, they require no further work-up or referral. Often, a single imaging technique is unable to confidently establish the cystic nature of a renal mass. Proper selection of an additional imaging modality will often be successful in establishing the cystic characteristics of a benign mass. Referral to a urologist is not necessary in this setting, since the internist can coordinate the imaging evaluation with proper radiologic consultation. Alternatively, when a mass is determined to be solid, urologic consultation and surgical evaluation are necessary. Minimization of the imaging sequence and hospitalization are critical in the diagnostic-related group era. Aimless wandering in the quagmire of imaging techniques is very expensive and nonproductive. Proper selection of one or two imaging tools and occasionally needle puncture should produce clarification of the cystic or solid nature of renal mass. On the basis of our experience, we have designed an imaging algorithm that provides a simple and concise approach to the diagnosis of a renal mass. It differs in design from that previously suggested by us and others because of decreased emphasis on nuclear medicine and greater emphasis on computed tomography. The more pivotal position assumed by computed tomography is based on improved scanner design and several large series attesting to the accuracy and cost-effectiveness of this imaging technique. It behooves internists to appreciate the role of various imaging tools in evaluating a renal mass. With radiologic consultation, internists should strive to confidently establish the cystic nature of a renal mass and to refer to a urologist solid masses or those whose nature remains persistently equivocal.

The value of bowel preparation in Ga-67 citrate scanning: concise communication.

In order to assess the value of bowel preparation in Ga-67 citrate scanning, we retrospectively analyzed 156 randomly selected 72-hr Ga-67 scans and compared the extent of bowel activity in two groups of patients: those receiving a vigorous 3-day bowel preparation and those receiving no preparation. The populations were studied with regard to age, sex, and bowel preparation. A three-way analysis of variance (prep X sex X age) revealed no influence of these parameters on the degree of colonic gallium activity. We conclude that bowel preparation as used at our institution did not seem to reduce colonic gallium content significantly (p greater than 0.10).

Tc-99m HIDA cholescintigraphy: the distended photon-deficient gallbladder.

Four patients with distended, photon-deficient gallbladders are presented. Markedly delayed apearance of Tc-99m HIDA in a distended gallbladder may represent chronic cholecystitis, partial obstruction of the common bile duct, or physiologic gallbladder distention. Obtaining delayed images is important in this group of patients to avoid premature diagnosis of cystic-duct obstruction. If the distended gallbladder fails to visualize within 24 hr, hydrops with cystic-duct obstruction is suggested.

Tc-99m HIDA scintigraphy in segmental biliary obstruction.

Segmental biliary obstruction as a result of primary or secondary hepatic malignancy has been reported with increasing frequency. For two representative patients, the clinical and Tc-99m HIDA scintigraphic findings in segmental biliary obstruction are described. The presence of photon-deficient dilated bile ducts in one segment of the biliary tree is highly suggestive of localized biliary obstruction and should be considered in the patient with suspected or proven hepatic malignancy despite the absence of jaundice.

Improved detection of small cavernous hemangiomas of the liver with high-resolution three-headed SPECT.

The purpose of this study was to review our experience with 99mTc-red blood cell scintigraphy for diagnosis of cavernous hemangiomas of the liver using a new three-headed, high-resolution dedicated SPECT system. Of 19 patients referred with a total of 38 lesions seen on CT, US, or MRI, 14 patients had 24 lesions that were hemangioma-positive with SPECT (all true-positives). Six of these 14 patients also had 9 hemangioma-negative lesions; all were less than or equal to 1.3 cm in size and false-negative. The remaining five patients had hemangioma-negative lesions only (1 false-negative, 4 true-negatives). Two hemangiomas were seen by SPECT that were not detected by CT, US, or MR. The sensitivity for hemangiomas greater than or equal to 1.4 cm. was 100% (20/20). The sensitivity was 33% for lesions 0.9-1.3 cm, and 20% for lesions less than or equal to 0.8 cm. The smallest hemangioma detected was 0.5 cm. These results show a definite improvement in sensitivity with high-resolution triple-headed SPECT over previously reported results using single-headed SPECT. High-resolution SPECT has improved our ability to detect small cavernous hemangiomas of the liver.

Computed tomography appearance of a right cervical aortic arch.

The clinical diagnosis of cervical aortic arch rests on the detection of a pulsatile mass in the supraclavicular fossa. Unfortunately, clinical differentiation of a cervical arch from an aneurysm of the great vessels can be difficult. Dynamic computed tomography (CT) can aid in this differentiation and avert the need for angiography.

Computed tomographic cholangiography in a canine model of biliary obstruction.

The CT scanner was used to generate the time-density relationship for hepatic parenchyma following Iodipamide (Cholografin, E.R. Squibb Co., New York, N.Y.) infusion. The curves which resulted from the normal, acutely obstructed, and chronically obstructed biliary system are shown. The peak enhancement of parenchyma is seen to be blunted in acute obstruction prior to anatomic evidence of dilated ducts. This finding may be of value in the early diagnosis of obstructive jaundice.

Enhanced pancreatic CT imaging utilizing a geometric magnification technique.

Computed tomography (CT) using a geometric magnification technique was found to improve spatial resolution in phantom studies when compared with conventional third-generation geometry images. The clinical feasibility of using geometric magnification, small focal spot size, and dynamic contrast enhancement was studied in 143 patients referred to CT for clinically suspected pancreatic disease. This population included 46 patients with a normal pancreas and 36 patients subsequently proven to have primary pancreatic carcinoma. Using this new technique in conjunction with dynamic contrast enhancement resulted in high quality pancreatic images. Despite the limitations in tube current associated with a small focal spot size and low total heat capacity of the system, clinical imaging was not adversely affected. Use of the geometric magnification technique is recommended in departments where it is technically feasible.

Quantitative ultrasonic detection of parenchymal structural change in diffuse renal disease.

OBJECTIVE: The authors determined whether quantitative ultrasound could be useful in the evaluation of diffuse renal disease. METHODS: Digitized radiofrequency ultrasound data were acquired from the kidneys of patients with biopsy-proven diffuse renal disease and transplant rejection (37 patients plus 18 normal volunteers). The results of the quantitative analysis were compared with histology results to determine if microscopic renal structure could be correlated with quantitative features such as scatterer size and scatterer spacing. The results also were analyzed using receiver operating characteristic analysis to determine if diffuse disease could be detected reliably using quantitative methods. RESULTS: The three most useful features in the native kidneys were mean scatterer spacing (MSS), sigma's, and average scatterer size (D). Using these features, it was possible to detect diffuse renal disease causing a decrease in renal function with an area under the ROC curve (Az) of 0.93. The feature D corresponded closely to histologically measured average glomerular diameters. For normals, D = 216 microns and glomerular diameter = 211 microns. No histologic correlate was found for scatterer spacing. In transplants, MSS and integrated backscatter were most useful for detecting rejection (Az = 0.87), and D in rejection was similar to the values for normal kidney and normally functioning transplants. CONCLUSIONS: The D value corresponds to glomerular diameter, and glomerular enlargement can be detected readily using quantitative ultrasound. Combinations of two to four quantitative features can detect diffuse renal disease and transplant rejection reliably.

Oat cell carcinoma metastatic to ureter.

A rare and perhaps unique case of oat cell carcinoma metastatic to the ureter is presented.

Rhabdomyolysis: need for high index of suspicion.

Rhabdomyolysis, both traumatic and nontraumatic, may be defined as a triad of skeletal muscle injury, pigmented urine, and acute renal failure. Nontraumatic rhabdomyolysis may be more of a subtle diagnosis and requires a high index of suspicion. Pertinent findings in the history as well as clinical evidence of muscle injury with a marked elevation of creatinine kinase will suggest the diagnosis. A disproportionate elevation of serum creatinine to blood urea nitrogen may also occur. Treatment consists of adequate hydration to help prevent oliguric or anuric renal failure without additional calcium or bicarbonate supplementation in most cases. Radiologic studies involving intravenous contrast media as well as urologic instrumentation should be avoided in the acute setting. With early diagnosis and prompt treatment the prognosis for recovery is excellent.

Magnetic resonance. Principles and applications.

Magnetic resonance is a unique, noninvasive imaging modality which allows direct, multiplanar imaging and the possibility of obtaining biochemical information in vivo. Presently, MR appears most applicable to the evaluation of central nervous system abnormalities. The high sensitivity of MR in the evaluation of intracranial pathology suggests that it may eventually replace CT for many suspected diseases, if future investigations are able to improve its specificity. As previously noted, MR may be more diagnostic than other radiologic studies in the evaluation of suspected Chiari malformation, syringomyelia, congenital abnormalities, tumors of the spinal axis, and disc space infection. In the chest, MR appears to be more accurate than CT in the determination of the extent of mediastinal tumor, but at present cannot replace CT because of the lack of experience in imaging parenchymal nodules and benign diseases. MR of the breast is promising, but the size of the lesion may prove to be a limiting factor with magnetic field strengths commonly being utilized. There are inherent difficulties in the evaluation of cardiac disease with MR, but it offers a noninvasive method of investigating congenital heart disease and may provide valuable information in suspected myocardial ischemia and altered cardiac function. MR provides a new method of evaluating the vascular system, both in terms of providing anatomic information on large and medium-sized vessels and flow analysis. In the abdomen, MR appears to be most sensitive in the evaluation of suspected hepatic masses, but as with the brain, greater specificity will be needed to replace CT. At the present time, MR offers no distinct advantage over conventional imaging modalities in the evaluation of pancreatic disease, it maybe more accurate than CT in the staging of renal cell carcinoma. Larger studies are needed to determine the role of MR in the investigation of retroperitoneal adenopathy and adrenal abnormalities. In the pelvis, MR offers the hope of earlier diagnosis of prostatic carcinoma and may replace CT for staging of prostatic carcinoma and transitional cell carcinoma of the bladder. Limited MR experience with benign disease of the female pelvis suggests that it is currently more accurately evaluated with ultrasound. MR appears to be highly sensitive and specific for the diagnosis of avascular necrosis and may provide an early clue in suspected osteomyelitis. Finally, in vivo MR spectroscopy may provide unique metabolic information that was unobtainable prior to the advent of magnetic resonance, if this proves to be technically feasible.

Noninvasive imaging of the gastrointestinal tract.

Numerous radiographic and scintigraphic imaging modalities are now available for evaluating the gastrointestinal system. With a well-formulated plan based on patient history, physical examination, and laboratory values, together with knowledge of patient preparation techniques and consultation, an efficient customized approach to gastrointestinal disease can be accomplished.

Imaging of the liver, biliary tract, and pancreas.

The interaction between the various noninvasive and invasive imaging modalities used to evaluate the liver, biliary tract, and pancreas is demonstrated in this article. By understanding this interaction and correlating noninvasive studies, the clinician will avoid diagnostic redundancy and the need for invasive testing may be reduced.

Imaging of urinary tract disease. Current approaches.

Current modalities and techniques used in imaging of the urinary tract offer prompt and accurate diagnoses as well as treatment in some cases. Careful planning and judgement in the choice of the imaging sequence is important in avoiding redundant or ill-advised tests. Individual tailoring will be necessary in some patients. It is hoped that with the rational use of the diagnostic tools now available and with the continued improvement in MRI technology, safe and accurate diagnoses will be expected in practically all patients with diseases of the urinary tract.

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.

Pancreatic imaging.

In this article, the pancreas is evaluated with regard to the controversies surrounding this organ from a clinical standpoint, and an approach to imaging modalities is examined. The roles of computed tomography, ultrasound, endoscopic retrograde cholangiopancreatography, and magnetic resonance imaging are put into proper perspective.

Imaging approach to the suspected renal mass.

The authors present their algorithmic approach to the detection, characterization, and staging of renal masses. Based on classification of urographic findings, the patient may be triaged to the appropriate cross-sectional or invasive imaging modality that will result in the most cost-effective management.

Hepatic imaging: current status.

The radiologist needs to be aware of the varied appearance of hepatic mass lesions and be prepared to recommend the most cost-effective imaging approach. In this article, the authors discuss their hepatic imaging experience, common pitfalls, and current recommendations.