Pamela T. Johnson

Adrenal Mass Imaging with Multidetector CT: Pathologic Conditions, Pearls, and Pitfalls

The adrenal gland is involved by a range of neoplasms, including primary and metastatic malignant tumors; however, the most common tumor detected is the incidental benign adenoma. Although computed tomographic (CT) findings will not always yield a definitive diagnosis, attention to these findings provides a road map to guide image interpretation. Adenomas typically demonstrate rapid washout, which is defined as an absolute percentage washout (APW) of more than 60% and a relative percentage washout (RPW) of more than 40% on delayed images. Adrenocortical carcinoma typically has an RPW of less than 40%; however, large size and heterogeneity are more reliable indicators of the diagnosis than are washout values. Washout characteristics of pheochromocytoma are variable; in conjunction with high levels of dynamic enhancement, pheochromocytomas may mimic adenoma (ie, APW > 60%, RPW > 40%). Myelolipomas appear as well-defined masses with variable quantities of fat and soft tissue. After contrast material administration, metastases usually demonstrate slower washout on delayed images (APW < 60%, RPW < 40%) than do adenomas, although hypervascular metastases may enhance similarly to pheochromocytoma. Finally, a number of nonadrenal pathologic conditions have been reported to mimic adrenal masses at CT.

CT Dose Reduction Applications: Available Tools on the Latest Generation of CT Scanners

Increasing concerns about radiation dose have led CT manufacturers to further develop radiation dose reduction tools in the latest generation of CT scanners. These tools include automated tube current modulation, automated tube potential selection, and iterative reconstruction. This review details the principles underlying each of these 3 dose reduction utilities and their different permutations on each of the major vendors equipment. If available on the users equipment, all 3 of these tools should be used in conjunction to enable maximum radiation dose savings.

Multiphasic enhancement patterns of small renal masses (≤4 cm) on preoperative computed tomography: utility for distinguishing subtypes of renal cell carcinoma, angiomyolipoma, and oncocytoma.

OBJECTIVEnTo analyze the enhancement patterns of small renal masses (SRMs) during 4-phase computed tomography (CT) imaging to predict histology.nnnMETHODSnOne-hundred consecutive patients with SRMs and 4-phase preoperative CT imaging, who underwent extirpative surgery with a pathologic diagnosis of renal cell carcinoma (RCC), angiomyolipoma (AML), or oncocytoma, were identified from a single institution. An expert radiologist, blinded to histologic results, retrospectively recorded tumor size, RENAL (radius, exophytic/endophytic properties of the tumor, nearness of tumor deepest portion to the collecting system or sinus, anterior/posterior descriptor, and the location relative to polar lines) nephrometry score, tumor attenuation, and the renal cortex on all 4 acquisitions (precontrast, corticomedullary, nephrogenic, and delayed density).nnnRESULTSnPathologic diagnoses included 48 clear-cell RCCs (ccRCCs), 22 papillary RCCs, 10 chromophobe RCCs, 13 oncocytomas, and 7 AMLs. There was no significant difference in median tumor size (Pxa0= .8), nephrometry score (Pxa0= .98), or anatomic location (P >.2) among histologies. Significant differences were noted in peak enhancement (Pxa0<.001) and phase-specific enhancement (Pxa0<.007) by histology. Papillary RCCs demonstrated a distinct enhancement pattern, with a peak Hounsfield unit (HU) of 56, and greatest enhancement during the NG and delayed phases. The highest peak HU were demonstrated by ccRCC (117 HU) and oncocytoma (125 HU); ccRCC more often peaked in the corticomedullary phase, whereas oncocytoma peaked in the nephrogenic phase.nnnCONCLUSIONnIn a series of patients with SRMs undergoing 4-phase CT, tumor histologies demonstrated distinct enhancement patterns. Thus, preoperative 4-phase CT imaging may provide useful information regarding pathologic diagnosis in patients undergoing extirpative surgery.

The iPad as a mobile device for CT display and interpretation: diagnostic accuracy for identification of pulmonary embolism

Recent software developments enable interactive, real-time axial, 2D and 3D CT display on an iPad by cloud computing from a server for remote rendering. The purpose of this study was to compare radiologists’ interpretative performance on the iPad to interpretation on the conventional picture archive and communication system (PACS). Fifty de-identified contrast-enhanced CT exams performed for suspected pulmonary embolism were compiled as an educational tool to prepare our residents for night call. Two junior radiology attendings blindly interpreted the cases twice, one reader used the PACS first, and the other interpreted on the iPad first. After an interval of at least 2xa0weeks, the cases were reinterpreted in different order using the other display technique. Sensitivity, specificity, and accuracy for identification of pulmonary embolism were compared for each interpretation method. Pulmonary embolism was present in 25 patients, ranging from main pulmonary artery to subsegmental thrombi. Both readers interpreted 98 % of cases correctly regardless of display platform. There was no significant difference in sensitivity (98 vs 100 %, pu2009=u20091.0), specificity (98 vs 96 %, pu2009=u20091.0), or accuracy (98 vs 98 %, pu2009=u20091.0) for interpretation with the iPad vs the PACS, respectively. CT interpretation on an iPad enabled accurate identification of pulmonary embolism, equivalent to display on the PACS. This mobile device has the potential to expand radiologists’ availability for consultation and expedite emergency patient management.

Common Incidental Findings on MDCT: Survey of Radiologist Recommendations for Patient Management

PURPOSEnThe aim of this study was to evaluate for agreement with respect to how radiologists report incidental findings encountered on CT.nnnMETHODSnA multiple-choice survey was designed to query radiologists about how they handle 12 incidental findings on body CT, assuming the patient is a 45-year-old woman with no history of malignancy. Included were a 1-cm thyroid nodule, a 5-mm noncalcified lung nodule, coronary artery calcification, a 2-cm adrenal nodule, a 2-cm pancreatic cyst, a 1-cm enhancing liver lesion, a 2-cm high-density renal cyst, short-segment small bowel intussusception, a 1-cm splenic cyst, focal gallbladder wall calcification, and a 3-cm ovarian cyst in both a premenopausal woman and a postmenopausal woman. Choices ranged from do not report to advising interventional procedures tailored to the organ. Surveys were administered to body CT attending radiologists at 3 academic institutions.nnnRESULTSnTwenty-seven radiologists completed the survey. The mean experience level was 15.7 years after training. Seventy percent or greater agreement on interpretation was identified for only 6 findings: recommend ultrasound for a 1-cm thyroid nodule, recommend ultrasound for a 3-cm cyst in postmenopausal woman, follow Fleischner Society recommendations for a 5-mm lung nodule, describe only coronary calcification, and describe as likely benign both short-segment small bowel intussusception and a 1-cm splenic cyst.nnnCONCLUSIONSnAgreement is lacking, both across institutions and within departments, for the management of 6 commonly encountered incidental findings on body CT. Individual departments should develop internal guidelines to ensure consistent recommendations based on existing evidence.

IV Contrast Infusion for Coronary Artery CT Angiography: Literature Review and Results of a Nationwide Survey

OBJECTIVEnThe purpose of our study was to review investigations that evaluated contrast infusion using MDCT with submillimeter detector configuration for coronary artery CT angiography (CTA). Published data are supplemented with 2006 survey results from centers practicing 64-MDCT coronary artery angiography.nnnCONCLUSIONnLiterature and survey results suggest a consensus for the use of IV contrast volumes < 100 mL, infusion rate of 5 mL/s, and a saline chaser. A range of concentrations can be used to attain target coronary artery attenuation levels.

IV Contrast Selection for MDCT: Current Thoughts and Practice

OBJECTIVEnThe purpose of this article is to review studies evaluating how contrast concentration affects MDCT of the body and to report IV contrast infusion protocols from MDCT angiography and MDCT of abdominal tumors.nnnCONCLUSIONnHigher concentrations (350 mg I/mL or greater) may improve visualization of small abdominal arteries. However, preliminary data comparing 300 mg I/mL to higher concentrations for MDCT of hypervascular hepatocellular carcinoma and pancreatic cancer have shown that higher concentrations may not increase tumor conspicuity.

Intrapancreatic accessory spleen: CT appearance and differential diagnosis

Although autopsy studies report that the second most common site of the accessory spleen is in the tail of the pancreas, intrapancreatic accessory spleens (IPASs) are rarely recognized radiologically. With recent improvements in imaging techniques, IPASs are more commonly detected on imaging studies. IPAS can be mistaken for other type of mass-forming lesions in the tail of the pancreas, particularly an asymptomatic small neuroendocrine neoplasm. Rarely, an epidermoid cyst originating from IPAS may simulate other cystic pancreatic lesion. Accurate preoperative diagnosis would obviate unnecessary surgery. IPAS should be considered when a hypervascular mass is seen in the tail of the pancreas on CT. Typical location, similar attenuation of the lesion to the spleen on noncontrast, and postcontrast CT at different phases are helpful to make diagnosis of IPAS. In particular, characteristic heterogeneous contrast enhancement of IPAS on the arterial phase may be helpful for correct diagnosis. However, when it remains difficult to exclude the other diagnosis, 99mTc labeled heat-damaged red blood cell scintigraphy or superparamagnetic iron oxide-enhanced MRI can be used to confirm the diagnosis of IPAS.

64-MDCT Angiography of the Coronary Arteries: Nationwide Survey of Patient Preparation Practice

OBJECTIVEnThe purpose of this study was to evaluate the current practice of patient preparation for 64-MDCT angiography (CTA) of the coronary arteries.nnnMATERIALS AND METHODSnSites in the United States that perform 64-MDCT coronary angiography were surveyed by mail in 2006. Information requested included physician specialty; experience level; details about patient preparation, including the use, dose, route, and timing of premedication; and acceptable heart rate and rhythm. A total of 142 surveys were analyzed, with comparison of parameters across specialties (radiology, cardiology, or shared) and experience levels.nnnRESULTSnAll facets of the study (premedication, data acquisition, cardiac interpretation) are performed exclusively by radiologists in 49% of sites and by cardiologists in 14%. All sites administer beta-blockers. Target heart rate was reported as < or = 65 beats per minute (bpm) by 89% of responders. Despite most centers aiming for a heart rate of < or = 65 bpm, the maximum allowable heart rate is > 65 bpm in 80% of centers. Patients with arrhythmia are scanned in at least 25% of sites. Most sites (84%) administer nitroglycerin. Significant differences between specialties were noted for experience levels, timing and route of beta-blocker administration, and for target heart rate. The likelihood of scanning in the setting of arrhythmia and beta-blocker timing correlated with experience levels.nnnCONCLUSIONnThese 64-MDCT coronary artery data from 2006 reveal consensus for a range of patient preparation parameters. Use of beta-blockers and nitroglycerin is routine, and the target heart rate is usually < or = 65 bpm. However, differences were noted for beta-blocker protocols and acceptable heart rate and rhythm, and some differences in practice are associated with experience level and specialty.

How Not to Miss or Mischaracterize a Renal Cell Carcinoma: Protocols, Pearls, and Pitfalls

OBJECTIVEnMDCT protocol optimization for renal cell carcinoma requires attention to several data acquisition, reconstruction, and display parameters. Specifically, multiple acquisitions with varying coverage, careful timing of each contrast-enhanced phase, and use of 2D and 3D multiplanar displays are required. This article reviews these parameters, supplemented by experience-based pearls and pitfalls.nnnCONCLUSIONnProper data acquisition and utilization of postprocessing tools are essential to avoid missed diagnoses or misinterpretation when imaging renal cell carcinoma.