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The use of 18F-fluorodeoxyglucose (FDG) positron emission tomography combined with computed tomography (PET/CT) is well established in the evaluation of alimentary tract malignancies. This review of the literature and demonstration of correlative images focuses on the current role of PET/CT in the diagnosis (including pathologic/clinical staging) and post-therapy follow-up of esophageal, gastric, and colorectal cancers. PET/CT provides utility in the management of esophageal cancer, including detection of distant disease prior to resection. In gastric cancer, PET/CT is useful in detecting solid organ metastases and in characterizing responders vs. non-responders after neoadjuvant chemotherapy, the latter of which have poorer overall survival. In patients with GIST tumors, PET/CT also determines response to imatinib therapy with greater expedience as compared to CECT. For colorectal cancer, PET/CT has proven helpful in detecting hepatic and other distant metastases, treatment response, and differentiating post-radiation changes from tumor recurrence. Our review also highlights several pitfalls in PET/CT interpretation of alimentary tract lesions.

Coronary artery disease is a leading cause of death worldwide. There has been a myriad of advancements in the field of cardiovascular imaging to aid in diagnosis, treatment, and prevention of coronary artery disease. The application of artificial intelligence in medicine, particularly in cardiovascular medicine has erupted in the past decade. This article serves to highlight the highest yield articles within cardiovascular imaging with an emphasis on coronary CT angiography methods for % stenosis evaluation and atherosclerosis quantification for the general cardiologist. The paper finally discusses the evolving paradigm of implementation of artificial intelligence in real world practice.

Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved. BACKGROUND: Atherosclerosis evaluation by coronary computed tomography angiography (CCTA) is promising for coronary artery disease (CAD) risk stratification, but time consuming and requires high expertise. Artificial Intelligence (AI) applied to CCTA for comprehensive CAD assessment may overcome these limitations. We hypothesized AI aided analysis allows for rapid, accurate evaluation of vessel morphology and stenosis. METHODS: This was a multi-site study of 232 patients undergoing CCTA. Studies were analyzed by FDA-cleared software service that performs AI-driven coronary artery segmentation and labeling, lumen and vessel wall determination, plaque quantification and characterization with comparison to ground truth of consensus by three L3 readers. CCTAs were analyzed for: % maximal diameter stenosis, plaque volume and composition, presence of high-risk plaque and Coronary Artery Disease Reporting & Data System (CAD-RADS) category. RESULTS: AI performance was excellent for accuracy, sensitivity, specificity, positive predictive value and negative predictive value as follows: >70% stenosis: 99.7%, 90.9%, 99.8%, 93.3%, 99.9%, respectively; >50% stenosis: 94.8%, 80.0%, 97.0, 80.0%, 97.0%, respectively. Bland-Altman plots depict agreement between expert reader and AI determined maximal diameter stenosis for per-vessel (mean difference -0.8%; 95% CI 13.8% to -15.3%) and per-patient (mean difference -2.3%; 95% CI 15.8% to -20.4%). L3 and AI agreed within one CAD-RADS category in 228/232 (98.3%) exams per-patient and 923/924 (99.9%) vessels on a per-vessel basis. There was a wide range of atherosclerosis in the coronary artery territories assessed by AI when stratified by CAD-RADS distribution. CONCLUSIONS: AI-aided approach to CCTA interpretation determines coronary stenosis and CAD-RADS category in close agreement with consensus of L3 expert readers. There was a wide range of atherosclerosis identified through AI. proof published

The purpose of this study is to compare dose-length product (DLP)-based calculation of effective dose (EDDose data were obtained from 50 consecutive unenhanced head CT examinations, unenhanced chest CT examinations, and unenhanced and contrast-enhanced abdominopelvic CT examinations performed using 16- and 64-MDCT scanners, as well as from 50 pulmonary CT angiography (CTA) examinations performed using a 64-MDCT scanner and 31 pulmonary CTA examinations performed using a 16-MDCT scanner. The EDEDED

As use of imaging in the evaluation of pregnant and lactating patients continues to increase, misperceptions of radiation and safety risks have proliferated, which has led to often unwarranted concerns among patients and clinicians. When radiologic examinations are appropriately used, the benefits derived from the information gained usually outweigh the risks. This review describes appropriateness and safety issues, estimated doses for imaging examinations that use iodizing radiation (ie, radiography, computed tomography, nuclear scintigraphy, and fluoroscopically guided interventional radiology), radiation risks to the mother and conceptus during various stages of pregnancy, and use of iodinated or gadolinium-based contrast agents and radiotracers in pregnant and lactating women. Maternal radiation risk must be weighed with the potential consequences of missing a life-threatening diagnosis such as pulmonary embolus. Fetal risks (ie, spontaneous abortion, teratogenesis, or carcinogenesis) vary with gestational age and imaging modality and should be considered in the context of the potential benefit of medically necessary diagnostic imaging. When feasible and medically indicated, modalities that do not use ionizing radiation (eg, magnetic resonance imaging) are preferred in pregnant and lactating patients. Radiologists should strive to minimize risks of radiation to the mother and fetus, counsel patients effectively, and promote a realistic understanding of risks related to imaging during pregnancy and lactation.

Introduction: Cardiac computed tomography (CT) has emerged as a diagnostic technique beyond the evaluation of outpatient stable chest pain; however, as quality in imaging has only recently been defined by the American Heart Association, understanding the changing utilization of CT use may inform application of these standards. This study aims to characterize changes in cardiac CT utilization and for chest pain, assess the impact on downstream invasive testing over a 3 year time period. Methods: 439 consecutive patients from July 2013 through June 2016 who had cardiac CT performed at an urban academic medical center were evaluated. Patient demographics and cardiac CT indications were reviewed from electronic medical records and archived cardiac CT reports. Cardiac CT indication categories included calcium scoring, outpatient chest pain, inpatient chest pain, electrophysiology applications, transcatheter aortic valve replacement (TAVR) and other. For patients who had cardiac CT for outpatient or inpatient chest pain, all records were reviewed to assess for further invasive cardiac catheterization. The studies were divided into three academic years. Results: The average age of patients undergoing cardiac CT was 60 ± 14 years, 64% were male and 55% were white. Overall, there was a 34% increase in the utilization of Cardiac CT across the study period. There was a significant rise in CT for inpatient chest pain from 2% (2/123) to 14% (26/187; p=0.0002) from year one to year three of the study period. In addition there was a significant rise in CT for TAVR planning from 7% (8/123) in year one to 14% (26/187; p=0.04) in year three. The proportion of patients undergoing evaluation for outpatient chest pain and calcium scoring was relatively unchanged from year one to year three. There was a decrease in cardiac CT for electrophysiology applications from 33% (41/123) to 15% (28/187) from year one to year three (p=0.0001). Among patients who had cardiac CT for either inpatient or outpatient chest pain, 23% (29/123) patients had previous equivocal stress testing. Only 3 of these pts required further cardiac catheterization potentially preventing 90% (26/29)of patients from undergoing invasive cardiac catheterization. Conclusion: Cardiac CT utilization is rising for inpatient chest pain and for TAVR planning. For 90% of the patients undergoing evaluation for chest pain, and 90% of patients with equivocal stress testing, cardiac CT potentially prevented need for further downstream invasive testing. This hypothesis-generating data has potential implications that may inform application of quality standards for TAVR and chest pain imaging. Further research is needed to disseminate the effect of cardiac CT on patient outcomes in this cohort.

All women, during their lifetime, are at risk of developing some form of gynecologic malignancy. The role of FDG-PET/CT has become more established in the management of gynecologic malignancies in the last decade. In this article, we will review the role of FDG-PET/CT in endometrial, cervical, ovarian, and vaginal cancer, by highlighting its strengths and limitations. While the role in initial or pre-operative staging for FDG-PET/CT is controversial, it allows noninvasive detection of equivocal or distant metastases, may alter stage and prognosis, and can guide or help eliminate unnecessary interventions that may not be beneficial. FDG-PET/CT is a useful adjunct to traditional staging with MR and CT.

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 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.

Purpose: The clinical significance of newly identified left atrial anatomic abnormalities (LAAA)— accessory appendages, diverticula, septal pouches—by multidetector CT (MDCT) remains unclear. Similar anatomical outpouchings, i.e., the left atrial appendage, have been associated with cardioembolisms and arrhythmia. To test the hypothesis that LAAA are also associated with increased risk of these events, we performed a retrospective analysis to examine the association of LAAA in patients undergoing CT with embolic events and arrhythmia. Methods: 242 patients (mean age 56 SD 12 years, 41% female) were selected who had CT coronary angiography performed with 64-row MDCT between 2007 and 2012 if complete clinical history records were available. CT images were independently reviewed for the presence of LAAA. Association of cerebrovascular accident (CVA) or transient ischemic attack (TIA), atrial fibrillation, and palpitations to LAAA was calculated using odds ratios (OR) with 95% confidence interval (CI) and Fisher’s exact test. Results: After adjusting for age, sex, hypertension, dyslipidemia and diabetes via multiple logistic regression, patients with accessory appendages are more likely to have reported palpitations (OR: 1.80; CI: 1.03 - 3.16). Patients with diverticula and septal pouches are significantly older than those without these abnormalities (p = 0.01 and p = 0.02, respectively). Septal pouches are associated with diabetes (OR: 2.29; 95%CI: 1.15 - 4.54). Conclusions: Accessory left atrial appendages are associated with palpitations. Patients with septal pouches and diverticula are significantly older than those patients without these anatomic abnormalities, suggesting age dependency of these findings. None of these anatomic abnormalities were associated with thromboembolic events after adjustment for potentially confounding comorbidities.

Many previous studies have shown that nonradiologist physicians who can refer advanced MRI and CT examinations to themselves or within their practices use these modalities at a much higher rate than those who refer their examinations to unaffiliated radiology facilities. This led Maryland to pass a unique self-referral law in 1993 to directly address self-referred advanced imaging. The authors discuss the politics and economics of self-referral and provide a comprehensive review of the creation, progression, and impact of this landmark law.

Cardiac CT with body and vascular imaging (CCT) is essential in transcatheter aortic valve replacement (TAVR) planning for patients with severe aortic stenosis (AS). Clinical and prognostic implications of significant non-cardiac findings (NCF) are not well defined. This study is aimed to evaluate

This study aimed to determine the incidence of non-traumatic acute aortic injury (AAI) extending from the chest into the abdomen or pelvis in emergency department (ED) patients with acute aortic syndrome (AAS), to estimate the effective dose of the abdominopelvic portion of these CT exams, and to compare the number needed to screen (NNS) with the collective population radiation dose of imaging those stations. All patients (n = 238) presenting to the ED with AAS between March 2014 and June 2015 who were imaged per CT AAI protocol (noncontrast and contrast-enhanced CT angiography of the chest, abdomen, and pelvis) were retrospectively identified in this IRB-approved HIPAA-compliant study. The Stanford classification for positive cases of AAI was further subclassified based on chest, abdominal, or pelvic involvement. The dose length product (DLP) of each exam was used to estimate the dose of the abdominal and pelvic stations and the collective effective dose for the population. There were five cases of aortic dissection (AD) and two of intramural hematoma (IMH), with an AAI incidence of 2.9/100. Three cases of AAI were confined to the chest. Two cases of AAI were confined to the chest and abdomen, and two cases involved the chest, abdomen, and pelvis. There was only one case of AAI involving the ascending aorta that extended into the abdomen or pelvis. The number needed to screen to identify (a) AAI extending from the chest into the abdomen or pelvis was 59.5 and (b) Stanford A AAI extending into the abdomen or pelvis was 238. The estimated mean effective dose for the abdominopelvic stations were unenhanced abdomen 2.3 mSv, unenhanced pelvis 3.3 mSv, abdominal CTA 2.5 mSv, and pelvic CTA 3.6 mSv. The collective effective doses to the abdomen and pelvis with unenhanced CT and CTA in 59.5 patients and 238 patients were 761.6 and 3046.4 mSv, respectively. While the estimated mean effective dose for imaging of the abdominopelvic stations are low, the collective effective dose should also be considered. It may be beneficial to modify or omit routine unenhanced CT and/or CTA of the abdomen/pelvis in this patient population in the absence of abdominal symptoms, and image the abdomen and pelvis in positive thoracic cases only.

Background: Cardiac output can be estimated during retrospectively gated CT coronary angiography by anatomically determining left ventricular volumes; prospective triggering to minimize radiation precludes this methodology. We propose an alternative method for cardiac output estimation based on preclinical models suggesting that cardiac output may be inversely related to contrast washout from the aortic root during timing bolus scanning, as measured by peak aortic root contrast attenuation. Methods: 34 patients had CT coronary angiography timing bolus performed with 20 ml iodixanol at 5.5 ml/s followed by 20 ml normal saline at 5.5 ml/s through an 18-Ga antecubital catheter. Peak aortic root contrast attenuation was correlated to cardiac output calculated by echocardiography using heart rate stroke volume from biplane Simpson’s method.Results: Mean age was 58 ± 13 years; body surface area, 2.0 ± 0.5 m2. 53% were women. Stroke volume, cardiac output and cardiac index were 67 ± 19 ml, 4.5 ± 1.6 L/min, and 2.2 ± 0.7 L/min/m2, respectively. Peak aortic root contrast attenuation was 207 ± 46 HU and correlated to cardiac output and cardiac index with r = –0.64, p Conclusion: This novel method for cardiac output estimation by CTCA appears feasible. The CT physiologic parameters using the timing test-bolus data moderately correlated with echocardiographic assessment of cardiac output. The calculation of cardiac output adds important hemodynamic data to anatomic information provided by CTCA, and further development of this method may preserve assessment of left ventricular performance in prospective triggering.

Purpose The aim of this study was to assess the distribution of CT dose index (CTDI) values reported by sites undergoing ACR CT accreditation between 2002 and 2004. Methods Weighted CTDI (CTDI w ) values were measured and reported by sites applying for ACR CT accreditation, and the percentage of scanners with values above the 2002 ACR diagnostic reference levels (DRLs) was determined. Acquisition parameters for a site's adult head, adult abdominal, and pediatric abdominal examinations were used to calculate volume CTDI (CTDI vol ), and the average and standard deviation were calculated by year. Histogram analysis was performed to determine 75th and 90th percentiles of CTDI vol . Results Between September 2002 and December 2004, 829 scanners underwent the accreditation process. Volume CTDI values (average ± SD) for 2002, 2003, 2004, and 2002 to 2004, respectively, were 66.7 ± 23.5, 58.5 ± 17.5, 55.8 ± 15.7, and 59.1 ± 18.6 mGy for adult head examinations; 18.7 ± 8.0, 19.2 ± 8.6, 17.0 ± 7.6, and 18.4 ± 8.3 for adult abdominal examinations; and 17.2 ± 9.7, 15.9 ± 8.6, 14.0 ± 7.0, and 15.5 ± 8.4 for pediatric abdominal examinations. For 2004 data, 23.8%, 2.3%, and 6.9% of sites reported doses above the 2002 CTDI w reference levels, compared with 49.6%, 4.7%, and 15% for 2002 data for adult head, adult abdominal, and pediatric abdominal examinations, respectively. Seventy-fifth percentiles of CTDI vol were 76.8 mGy (adult head, 2002 only), 22.2 mGy (adult abdominal), and 20.0 mGy (pediatric abdominal). Conclusions From 2002 to 2004, average CTDI vol values decreased by 10.9, 1.7, and 3.2 mGy for adult head, adult abdominal, and pediatric abdominal examinations. Effective January 1, 2008, the ACR program implemented United States-specific diagnostic reference levels of 75, 25, and 20 mGy, respectively, for the CTDI vol of routine adult head, adult abdominal, and pediatric abdominal CT scans.

Purpose The aim of this study was to determine, for 3 basic clinical examinations, whether blinded, experienced CT radiologists participating in the ACR's CT Accreditation Program could use scan parameters such as tube current–time product (mAs), tube voltage (kVp), and pitch to predict scanner output settings, expressed as weighted CT dose index (CTDIw) and volume CT dose index (CTDIvol), exceeding CTDIw diagnostic reference levels (DRLs) set by the ACR in 2002 and CTDIvol DRLs adopted by the ACR in 2008. Methods CT sites with 829 scanners submitted examinations to the ACR between 2002 and 2004, yielding 518 eligible examinations for analysis (138 adult head CT scans, 333 adult abdominal CT scans, and 47 pediatric abdominal CT scans). The sites' measured CTDIw values for each type of examination were compared with the ACR's CTDIw DRLs in effect from 2002 to 2004 and compared with comments regarding excessively high mAs or kVp made by radiologist clinical reviewers to determine if excessively high-dose index measurements could be predicted. The same analysis was repeated using CTDIvol DRLs adopted by the ACR in 2008 and compared with excessively high mAs or kVp and excessively low-pitch comments. Results Excessively high mAs or kVp comments yielded sensitivity of only 21.2% in predicting examinations above the CTDIw DRLs, with specificity of 87.6%. Using the 2008 CTDIvol DRLs, the corresponding sensitivity was 13.1% and specificity was 86.2%. Significance was not achieved for use of clinical parameters in predicting either the CTDIw or CTDIvol. Conclusion Experienced CT radiologists cannot reliably use scan parameters to predict examinations that exceed CTDIw or CTDIvol DRLs.

Background Computed tomography coronary angiography (CTCA) provides an accurate noninvasive alternative to the invasive assessment of coronary artery disease. However, a specific limitation of CTCA is inability to assess hemodynamic data. Objective We hypothesized that CTCA-derived measurements of contrast within the superior vena cava (SVC) and inferior vena cava (IVC) would correlate to echocardiographic estimations of right atrial and right ventricular pressures. Methods Medical records of all patients who underwent both echocardiography and CTCA in our center were reviewed (n = 32). Standard CTCA was performed with a 64-detector CT using test-bolus method for image acquisition timing and iso-osmolar contrast injection through upper extremity vein. The length of the column of contrast reflux into the inferior vena cava (IVC) was correlated to echocardiographically determine tricuspid regurgitation jet velocity (TRV). SVC area change with contrast injection at the level of the bifurcation of the pulmonary artery was also correlated with IVC sniff response by echocardiogram. Results The reflux column length was interpretable in 27 of 32 patients with a mean length of 10.1 ± 1.1 mm, and a significant bivariate correlation was observed between reflux column length and the tricuspid regurgitant jet velocity ( r = 0.84; P r of 0.57 ( P = .04). Conclusion Quantification of IVC and SVC contrast characteristics during CTCA provides a feasible and potentially accurate method of estimating right atrial and ventricular pressure.

Computed tomography (CT) plays an important role in the evaluation of patients presenting to the emergency department with a suspected spontaneous gastrointestinal tract (GIT) perforation. Prospective identification of the site of perforation helps the emergency department physician plan the appropriate treatment in a potentially unstable patient. The purpose of this pictorial essay is to review the CT approach a radiologist should take when evaluating the patient with suspected perforation in the emergent setting. A series of patients presenting to the emergency department with surgically proven GIT perforations were retrospectively reviewed, and key images were obtained. For the purposes of this review, the anatomy of the abdominal cavity in relation to sites of GIT perforation will be discussed. CT findings of perforation will be described, including free intraperitoneal/extraperitoneal air, bowel wall discontinuity, and localized inflammatory changes. The use of a bone window setting to increase the free air conspicuity will be emphasized. The mimics of pneumoperitoneum will be demonstrated, including pneumothorax, pneumomediastinum, and venous air. Using a systematic approach, CT can precisely determine the presence and site of a gastrointestinal perforation in a majority of patients. This greatly assists the surgeon in planning the correct surgical approach.

Computed tomography (CT) is an effective, readily available diagnostic imaging tool for evaluation of the emergency room (ER) patients with the clinical suspicion of perianal abscess and/or infected fistulous tract (anorectal sepsis). These patients usually present with perineal pain, fever, and leukocytosis. The diagnosis can be easy if the fistulous tract or abscess is visible on inspection of the perianal skin. If the tract or abscess is deep, then the clinical diagnosis can be difficult. Also, the presence of complex tracts or supralevator extension of the infection cannot be judged by external examination alone. Magnetic resonance imaging (MRI) is the best imaging test to accurately detect fistulous tracts, especially when they are complex (Omally et al. in AJR 199:W43–W53, 2012). However, in the acute setting in the ER, this imaging modality is not always immediately available. Endorectal ultrasound has also been used to identify perianal abscesses, but this modality requires hands-on expertise and can have difficulty localizing the offending fistulous tract. It may also require the use of a rectal probe, which the patient may not be able to tolerate. Contrast-enhanced CT is a very useful tool to diagnose anorectal sepsis; however, this has not received much attention in the recent literature (Yousem et al. in Radiology 167(2):331–334, 1988) aside from a paper describing CT imaging following fistulography (Liang et al. in Clin Imaging 37(6):1069–1076, 2013). An infected fistula is indicated by a fluid-/air-filled soft tissue tract surrounded by inflammation. A well-defined round to oval-shaped fluid/air collection is indicative of an abscess. The purpose of this article is to demonstrate the usefulness of contrast-enhanced CT in the diagnosis of acute anorectal sepsis in the ER setting. We will discuss the CT appearance of infected fistulous tracts and abscesses and how CT imaging can guide the ER physician in the clinical management of these patients.

Solitary fibrous tumor (SFT) is a rare neoplasm that, in addition to its classic presentation as a pleural-based mass, can also be encountered in unusual sites. The main difficulty in making the diagnosis of SFTs results from the unfamiliarity with its diverse clinical and pathologic features. This series of SFTs, some with unusual clinicopathologic presentation, included nine women and two men, ranging in age from 28 years to 74 years (five in pleura, one in lung parenchyma, one in breast, and four in mediastinum). The tumors were locally excised in eight cases and were resected along with portions of lung parenchyma in three. A panel of immunohistochemical stains was used to characterize these tumors. They were all vimentin-positive and, with the exception of one case, CD34-positive. Tumors were negative with antibodies directed against cytokeratin, factor VIII-related antigen, S-100 protein, muscle-specific actin, and smooth-muscle actin. Various diagnoses were initially rendered for these clinically and pathologically diverse lesions by the examining pathologists. Awareness of the various gross and microscopic patterns of these tumors, the possibility of occurring in unusual sites, and the use of immunohistochemical stains, particularly CD34, should eliminate most of the difficulties in arriving at a correct diagnosis. One patient died of metastatic breast cancer; all other patients were alive and well with a median follow-up of 17 months.

We studied which set of CT parameters and modeling parameters yielded accurate measurements of three graded artificial renal artery stenoses.An acrylic phantom resembling the abdominal aorta and renal arteries was constructed. Stenotic segments had diameters of 1.8, 3.2, and 4.8 mm; nonstenotic segment diameter was 6.3 mm. Helical scans were done using 1 and 3 mm collimation at pitches of 1, 1.5, and 2. 3D renderings were produced and measured. Multifactorial and regression tree analysis were used to determine the accuracy of the 3D renderings. Mean squared error (MSE) was used to compare true diameter with measured diameter.Collimation of 1 mm produced an MSE of 0.55 versus an MSE of 1.35 for 3 mm collimation. Stenosis grade was the next most important parameter in the 1 mm subgroup and viewing direction in the 3 mm collimation subgroup. In the 1 mm subgroup, high and mid grade stenoses had an MSE of 0.52 versus low grade stenosis that had an MSE of 0.61. Pitch was a fourth-order effect.Collimation of 1 mm combined with a pitch ratio as high as 2:1 is superior to 3 mm collimation. Shaded surface modeling was the single best choice for rendering 3D data. Stenosis grade interacted strongly with user-controllable parameters.

A new computed tomography (CT) technology, helical (spiral) CT, allows the entire neck to be imaged in only 30 seconds. Although multiplanar and three-dimensional (3-D) imaging could be performed with conventional CT, the volumetric acquisition provided by helical (spiral) CT allows significantly improved quality and easier reconstruction for more applications. These 3-D models show an airway appearance similar to that obtained with laryngography. Independent review of the 3-D images in 12 patients with lesions by two radiologists and one otolaryngologist was performed to assess 1) image quality, 2) ability to judge lesion extent, and 3) assistance in understanding the lesion compared to that provided by routine axial scans. Rating scores of 1 to 5 were assigned, with 5 representing the best quality or greatest value. The results showed that both groups scored image quality equally: 4.7. Lesion extent for the radiologists was 2.6, while the otolaryngologist's ranking was 3.7 (p < .01). In assisting understanding of lesions versus axial scans, radiologists ranked 3-D images 2.1, while the otolaryngologist ranked them 3.1 (p < .01). In summary, 3-D models provide a complementary imaging technique in understanding upper airway disease.

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[Figure][1] [![Graphic][3] ][3][![Graphic][4] ][4] A 65-year-old woman with history of trigeminal neuralgia presented with left facial tic douloureux soon followed by substernal chest pain. Electrocardiogram demonstrated T-wave inversions in leads I and aVL, and an initial

We evaluated seven patients undergoing gallstone lithotripsy for evidence of hepatic or renal trauma after each of 10 lithotripsy treatments. Postlithotripsy magnetic resonance imaging (MRI) and sonography showed no evidence of hepatic or renal injury as compared with baseline studies. Four treatments resulted in sonographic evidence of gaseous hepatic microbubbles (analogous to "the bends") due to cavitation effects of the shockwaves. Three of these four treatments produced serum glutamicoxaloacetic transaminase and -pyruvic transaminase elevation. One patient had microscopic hematuria. Minimal tissue damage results from gallstone lithotripsy. MRI and ultrasound, performed after lithotripsy, appear to be less sensitive than transaminasemia in detecting this low-grade injury.

Georgetown University Hospital has been operating an image management and communications system (IMACS or PACS) for three-and-a-half years. This work was initially funded under the Army Medical Research and Development Command Digital Imaging Network Systems (DINS) project. The system was taken from a research system supporting only radiology tasks to one extended to clinical use, and has been used in clinical work for two-and-a-half years. This paper will summarize our PACS clinical experience and will describe the operational features implemented and those still necessary.

After Wilhelm Conrad Roentgen's discovery of the X-ray in 1895, it was initially thought that gallstones could not be visualized. Surgeons relied solely on the clinical examination to detect biliary disease. Today, no evaluation of the gallbladder would be complete without the performance of an imaging study. Radiology has gone through several eras in the imaging of gallstones. The plain film era, 1895-1924, was characterized by techniques that improved soft-tissue detail, allowing better detection of radiopaque stones. The contrast media era, 1924-1960, was initiated by the invention of IV cholecystography. In 1925, oral cholecystography was developed. During the era of expanding technology, 1960-1979, percutaneous transhepatic cholangiography, scintigraphy, and sonography came into use. The therapeutic era began in the 1980s.

The benefits of diagnostic imaging are immense and have revolutionized the practice of medicine. The increased sophistication and clinical efficacy of imaging have resulted in its dramatic growth over the past quarter century. Although data derived from the atomic bomb survivors in Japan and other events suggest that the expanding use of imaging modalities using ionizing radiation may eventually result in an increased incidence of cancer in the exposed population, this problem can likely be minimized by preventing the inappropriate use of such imaging and by optimizing studies that are performed to obtain the best image quality with the lowest radiation dose. The ACR, which has been an advocate for radiation safety since its inception in 1924, convened the ACR Blue Ribbon Panel on Radiation Dose in Medicine to address these issues. This white paper details a proposed action plan for the college derived from the deliberations of that panel.

Duodenal diverticulitis is a rare complication of duodenal diverticulosis. It is often clinically misdiagnosed because it has no pathognomonic signs or symptoms and its CT findings may mimic other intraabdominal processes. We describe two patients with duodenal diverticulitis who presented with abdominal pain, nausea, and leukocytosis. At the time of initial presentation, only one of the two patients was diagnosed correctly. In the first case, which was initially misdiagnosed as acute pancreatitis, the correct diagnosis was evident only after the disease process had become more quiescent and a follow-up CT scan using orally and i.v.-administered contrast agents was performed. In the second case, the coronal reformatted images confirmed the diagnosis suggested by the axial images.Duodenal diverticulitis can be a difficult CT diagnosis to make; however, maintaining it in the differential diagnosis of duodenal and pancreatic inflammatory processes and masses as well as defining the anatomy with nonaxial imaging including coronal images may be helpful in confirming the diagnosis.

The ACR CT accreditation program, begun in 2002, requires the submission of approximately 20 images, several completed data sheets and printouts of three Excel worksheets. The procedure manual is very detailed, yet participants unfamiliar with the program or having minimal CT experience have needed to redo aspects of their submission, or in some cases do not receive accreditation, due to mistakes made by the physicist. This review of the phantom portion of the ACR CT accreditation program supplements the ACR provided instructions with additional photos of phantom setup, region-of-interest (ROI), and image placement on the film sheets, and examples of completed portions of actual (but anonymous) submissions. Common mistakes, as well as uncommon but interesting images, are shown and explanations are given as to what could have been done to avoid the problem. Additionally, a review of CT dose measurement techniques and calculations will enable the physicist to better assist sites where typical exam doses are above the ACR reference values.

Rapid, dynamic computed tomography (CT) is essential in scanning the body in order to maintain adequate contrast enhancement during the entire examination. In the case of the liver, this is most critical in order to complete scanning prior to the equilibrium phase when lesions are less conspicuous or may be missed entirely. This technical note describes the application of "cluster scanning" to conventional scanning in order to optimize body CT by decreasing the total exam time.

We have examined the changing demographics of adult intussusception and implicate human immunodeficiency virus (HIV)- and acquired immune deficiency syndrome (AIDS)-associated gastrointestinal pathology as risk factors for intussusception in young adults. The clinical index of suspicion for intussusception should be raised for an HIV-positive young adult with intermittent crampy abdominal pain. Over a 10-year period, eight cases of adult intussusception were diagnosed at our institution, and we reviewed the diagnostic computed tomography (CT) scans and records of these patients to correlate them with radiological studies, clinical history, surgical findings, laboratory studies, pathologic analysis, and outcome. Three of the eight patients with adult intussusception had AIDS, all diagnosed by CT scans. Their average age was 41 years, whereas average age of the non-HIV-associated patients was 63. These findings suggest that HIV- and AIDS-associated gastrointestinal pathology provide lead points for intussusception and are significant risk factors for intussusception in young adults. We reviewed the five previously reported cases of AIDS and intussusception and conclude that intussusception should be a diagnostic consideration in an HIV-positive young adult with abdominal complaints. It is clear that AIDS-associated intussusception is a real clinical problem and that CT is an effective method of diagnosing it.

A survey of the Society of Computed Body Tomography/Magnetic Resonance (SCBT/MR) was performed to assess current techniques in liver CT scanning. The study was designed as an update to a study performed in 1987. The survey was distributed to 67 members of the SCBT/MR at 35 institutions. Twenty-six institutions responded. As in 1987, none relied solely on noncontrast scans. In 1987, only 54% (12/22) of institutions performed contrast-enhanced scans as their primary technique compared with 73% (19/26) in 1993. Ionic contrast was used exclusively in the earlier study, whereas in the present study 58% used nonionic contrast in the majority of cases and 38% used nonionic contrast routinely. In 1987, 41% performed scans with a power injector compared with 85% in the present study. Enhanced scans were performed during the contrast bolus in 36% of institutions in 1987 compared with 76% in this study. No institution relied on noncontrast scans alone. In the previous study the delay between injection and scanning was variable (0–60 s), whereas in the present study 83% specified a delay of 21–45s. Significant refinements in CT technique, wider use of power injectors, utilization of nonionic contrast, and a more critical approach to optimize liver imaging have created a significant impact on the practice of liver CT.

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.

Purpose: The purpose of this study was to evaluate the utility of helical computed tomography (CT) in the preoperative assessment of abdominal aortic aneurysms (AAA) and to compare its accuracy with aortography and operative findings. Methods: Thirty-two patients with suspected AAA were evaluated by helical CT with either 5 mm collimation (slice thickness) or a combination of 3 mm collimation through the renal and mesenteric arteries and 7 mm collimation through the remainder of the AAA. Three-dimensional reconstructions were performed with use of three different techniques, and results were compared with aortography and surgery. Results: Twenty-five patients were found to have an aneurysm, and 19 subsequently underwent surgery. Standard angiography was also performed in 13. The location, size, and extent of the aneurysm, as well as the wall calcification and intraaneurysmal thrombus, were well depicted with helical CT. The visceral aortic branches, including the detection of renal artery stenosis and accessory renal arteries, were consistently seen with the 3 mm/7 mm collimation protocol and three-dimensional reconstruction. Conclusion: Helical CT with three-dimensional display of the aorta and its branches combines the advantages of conventional CT imaging and aortography. This technique appears to provide comprehensive preoperative evaluation of AAA. (J Vasc Surg 1994;20: 367-76.)