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OBJECTIVE. Patient-specific organ and effective dose provides essential information for CT protocol optimization. However, such information is not readily available in the scan records. The purpose of this study was to develop a method to obtain accurate examination- and patient-specific organ and effective dose estimates by use of available scan data and patient body size information for a large cohort of patients. MATERIALS AND METHODS. The data were randomly collected for 1200 patients who underwent CT in a 2-year period. Physical characteristics of the patients and CT technique were processed as inputs for the dose estimator. Organ and effective doses were estimated by use of the inputs and computational human phantoms matched to patients on the basis of sex and effective diameter. Size-based ratios were applied to correct for patient-phantom body size differences. RESULTS. Patients received a mean of 59.9 mGy to the lens of the eye per brain scan, 10.1 mGy to the thyroid per chest scan, 17.5 mGy to the liver per abdomen and pelvis scan, and 19.0 mGy to the liver per body scan. A factor of 2 difference in dose estimates was observed between patients of various habitus. CONCLUSION. Examination- and patient-specific organ and effective doses were estimated for 1200 adult oncology patients undergoing CT. The dose conversion factors calculated facilitate rapid organ and effective dose estimation in clinics. Compared with nonspecific dose estimation methods, patient dose estimations with data specific to the patient and examination can differ by a factor of 2.

OBJECTIVE. The standard of care for the diagnosis and follow-up of urolithiasis is unenhanced CT. The hypothesis of this study was that that by using image fusion of subsequent ultrasound (US) with the initial unenhanced CT, ureteral stones can be precisely localized. CONCLUSION. Of the 25 stones founds on unenhanced CT studies, 22 (88%) were confidently identified using US–unenhanced CT fusion within 72 hours after the initial CT scan was obtained. US–unenhanced CT fusion might obviate the need for repeated CT scans for monitoring urolithiasis.

The purpose of this study was to conduct longitudinal analyses of radiation dose data from adult patients undergoing clinically indicated, repeat identical thoracoabdominal CT examinations.Radiation dose data were electronically collected from 2851 subjects undergoing 12,635 repeat identical CT scans (mean number of scans per patient, 4.8; range, 2-33) in one health system. Included CT protocols were chest-abdomen-pelvis with contrast administration (n = 4621 CT studies of 1064 patients), abdomen-pelvis with contrast administration (n = 876 CT studies of 261 patients), renal stone (n = 1053 CT studies of 380 patients), and chest (n = 6085 CT studies of 1146 patients) without contrast administration. A radiation-tracking software infrastructure was adopted to extract data from DICOM headers in PACS. Size-specific dose estimate (SSDE) was calculated.A trend was observed toward global reduction in SSDE values with all protocols investigated (chest-abdomen-pelvis slope, -1.78; abdomen-pelvis slope, -0.82; renal stone slope, -0.83; chest slope, -0.47; p0.001 for all comparisons). The intraindividual analyses of radiation dose distribution showed widespread variability in SSDE values across the four protocols investigated (chest-abdomen-pelvis mean coefficient of variance, 14.02 mGy; abdomen-pelvis mean coefficient of variance, 10.26 mGy; renal stone mean coefficient of variance, 34.18 mGy; chest mean coefficient of variance, 6.74 mGy).Although there is a trend toward global reduction in radiation doses, this study showed widespread variability in the radiation dose that each patient undergoing identical repeat thoracoabdominal CT protocols absorbs. These data may provide a foundation for the future development of best-practice guidelines for patient-specific radiation dose monitoring.

Pelvic binders may hinder radiologic assessment of pelvic instability after trauma, and avulsive injuries can potentially unmask instability in this setting. We compare the performance of MDCT for the detection of pelvic disruptions in patients with binders to a matched cohort without binders, and we assess the utility of avulsive injuries as signs of pelvic instability.MDCT examinations of 56 patients with binders were compared with MDCT examinations of 54 patients without binders. Tile grading by an experienced orthopedic surgeon was used as the reference standard (A, stable; B, rotationally unstable; C, rotationally and vertically unstable). Two radiologists performed blinded reviews of CT studies in two reading sessions (sessions 1 and 2). In session 1, Tile grade was predicted on the basis of established signs of instability, including pubic symphysis and sacroiliac (SI) joint widening. In session 2, readers could change the Tile grade when avulsive injuries were seen. Diagnostic performance for predicting rotational instability and vertical instability was assessed.In the binder group, AUCs under the ROC curves for rotational instability increased from fair (0.73-0.77) to good (0.82-0.89) when avulsive signs were considered. In the control group, AUCs were good in both sessions. AUCs for vertical instability were fair with binders in both sessions. Agreement with the reference standard increased from fair (0.30-0.32) to moderate (0.46-0.54) when avulsive signs were considered in the binder group but were in the moderate range for both sessions in the control group. Combined evaluation for inferolateral sacral fractures, ischial spine fractures, and rectus abdominis avulsions resulted in optimal discrimination of rotational instability.Evaluation for avulsive signs improves MDCT sensitivity for the detection of rotational instability but not vertical instability in patients with binders.

Planning imaging performed during CT-guided procedures may occasionally contain important incidental findings. The purpose of this study was to identify and characterize by clinical relevance the extraspinal findings detected on planning imaging for CT-guided lumbar transforaminal epidural steroid injections (TFESIs).Four radiologists retrospectively evaluated the planning scout views and CT studies for 488 consecutive CT-guided lumbar TFESIs performed in 400 patients over a 1-year period. Incidental extraspinal findings were identified and used to characterize patients by the need for follow-up using the CT Colonography Reporting and Data System (C-RADS), a classification scheme originally developed to characterize incidental findings on CT colonography. Patients with C-RADS E4 findings have potentially important findings that should be communicated to the referring physician; patients with C-RADS E3 findings have findings that are likely unimportant, but workup may be indicated. All previously unknown C-RADS E3 and E4 findings discovered in the course of this research were reported to referring physicians for appropriate patient follow-up.Ten of 400 (2.5%) patients were classified as C-RADS E4; the most common C-RADS E4 finding was vascular aneurysm or stenosis (4/400, 1.0%). Thirteen of 400 (3.3%) patients were classified as C-RADS E3; the most common C-RADS E3 finding was hepatomegaly (4/400, 1.0%). Of 22 patients with C-RADS E3 and E4 findings unknown to clinicians, the finding for only one (4.5%) was communicated to clinicians at the time of the procedure.Clinically important incidental extraspinal findings were identified in 5.8% of patients on the planning imaging performed for CT-guided lumbar TFESIs. Communication of clinically important findings was poor (4.5%).

We sought to evaluate specific CT criteria for the diagnosis of usual interstitial pneumonitis (UIP) in the absence of honeycombing. These criteria included peripheral reticulation and lobular distortion; some upper lobe involvement, but a lower zone predominance; a heterogeneous appearance with areas of normal lung, minimal reticulation, and substantial distortion alternating throughout the study and often on an individual image; a nonsegmental distribution; and traction bronchiectasis.We searched reports of CT studies performed between January 1, 2009, and January 1, 2012, to identify patients for whom UIP was a likely or probable diagnosis and reviewed the CT study for each case (n = 106). There were 38 patients who met all CT criteria and who also had a clinical diagnosis of idiopathic UIP (also known as idiopathic pulmonary fibrosis [IPF]) and follow-up of at least 6 months, as determined from the electronic medical record. We reviewed prior and subsequent CT examinations in this cohort.The median age of our patients was 80 years, and the duration of clinical follow-up was 6-104 months (mean, 38 months; median, 37 months). For all patients, a pulmonary medicine physician made a working diagnosis of IPF. Fifteen patients died from pulmonary complications, and 16 of the surviving patients had clinical or functional progression of disease. There were no instances in which the initial diagnosis was revised or reversed.Strict application of specific CT criteria may allow a specific diagnosis of UIP in the proper clinical setting in the absence of honeycombing.

OBJECTIVE. This article discusses the clinical challenge of low-radiation-dose examinations, the commonly used approaches for dose optimization, and their effect on image quality. We emphasize practical aspects of the different iterative reconstruction techniques, along with their benefits, pitfalls, and clinical implementation. CONCLUSION. The widespread use of CT has raised concerns about potential radiation risks, motivating diverse strategies to reduce the radiation dose associated with CT. CT manufacturers have developed alternative reconstruction algorithms intended to improve image quality on dose-optimized CT studies, mainly through noise and artifact reduction. Iterative reconstruction techniques take unique approaches to noise reduction and provide distinct strength levels or settings.

OBJECTIVE. The purpose of this article is to evaluate the hypothesis that Alvarado scores of 3 or lower identify adult patients who are unlikely to benefit from CT after appendiceal ultrasound fails to show the appendix and is otherwise normal. MATERIALS AND METHODS. We identified 119 consecutive adults for whom the appendix was not seen on otherwise normal appendiceal sonography performed as the first imaging study for suspected appendicitis, who subsequently underwent CT within 48 hours, and whose data permitted retrospective calculation of admission Alvarado scores. Specific benefits of CT were defined as diagnoses of appendicitis or significant alternative findings, and specific benefits were compared between patients with Alvarado scores of 3 or less and 4 or higher. Significant alternative findings on CT were findings other than appendicitis that were treated with medical or surgical therapy during the admission or that were to be addressed during follow-up care. Diagnostic reference standards were discharge diagnoses, pathologic examinations, and clinical follow-up. RESULTS. No patients (0.0%, 0/49) with Alvarado scores 3 or lower had appendicitis, compared with 17.1% (12/70) of patients with Alvarado scores 4 or higher (p = 0.001), and CT showed neither appendicitis nor significant alternative findings in 85.7% (42/49) versus 58.6% (41/70) of these patients, respectively (p = 0.002). The rates of perforated appendicitis, as well as significant alternative CT findings, did not differ significantly. CONCLUSION. Adults with Alvarado scores 3 or lower who have nonvisualized appendixes and otherwise normal appendiceal sonography are at very low risk for appendicitis or significant alternative findings and therefore are not likely to benefit from CT.

OBJECTIVE. The purpose of this article is to review the utility of CT in diagnosing bladder malignancies, CT protocol options that may improve the conspicuity of bladder tumors, suggestive imaging features, and potential mimics. CONCLUSION. Although evaluation of the bladder has traditionally been considered purely the realm of cystoscopy, many bladder tumors can be identified with CT. However, diagnosis requires optimization of CT technique and close attention to a number of potentially subtle findings.

The purpose of this study was to determine MDCT dose variability due to technologist variability in performing CT studies.Fifty consecutive adult patients who underwent two portal venous phase CT examinations of the abdomen and pelvis on the same 64-MDCT scanner between January and December 2011 were retrospectively identified. Tube voltage (kVp), tube current (mA), use of automated tube current modulation (ATCM), dose-length product (DLP), volume CT dose index (CTDIvol), table height, whether the localizer image was obtained using the posteroanterior or the anteroposterior technique, arm position, and number of overscanned slices were recorded.For a given patient, the total examination DLP difference comparing the two MDCT studies ranged from 0.1% to 238.0%. For the same patient, total examination DLP was always higher when the localizer image was obtained with the posteroanterior compared with the anteroposterior technique. When table position was closer to the x-ray source, patients appeared magnified in the posteroanterior localizer image (8-29%; average, 14%) and higher tube currents were selected with ATCM. Localizer technique, table height, arm position, number of overscanned slices, and technologist were all significant predictors of dose.Patient off-centering closer to the x-ray source resulted in patient magnification in the posteroanterior localizer image, leading to higher tube currents with ATCM and increased DLP. Differences in technologist, arm position, and overscanning also resulted in dose variability.

The purpose of this study was to characterize the normal pediatric appendix and the variables that affect its diameter.Imaging and medical records, including CT studies, from 420 unique patients with normal appendixes were reviewed by two pediatric radiologists. Appendiceal diameter was measured on the axial images, and appendiceal content and the presence of enlarged lymph nodes were recorded.The mean appendiceal diameter was 5.6 ± 1.4 and 5.7 ± 1.5 mm for reviewer 1 and reviewer 2, respectively, with 34% and 39% of appendixes measuring larger than 6 mm. Appendiceal diameter was normally distributed across the population and was significantly associated with patient age (p0.0001). Diameter increased by 0.4 mm/y until 6-7 years of age, after which, it remained stable. The quantity of pericecal fat (p = 0.03 and p0.0001) and type of appendiceal content (p = 0.0002 and p0.0001), respectively, were multivariate predictors of diameter. Lymphoid stimulation was a multivariate predictor of diameter for only one reviewer (p = 0.0008). Patient sex and the month or season of imaging were not predictors of diameter.Uniform diameter cutoffs for appendiceal diameter should not be applied across the pediatric population because the appendix grows during childhood. Additionally, this study calls into question a 6-mm diameter cutoff for appendicitis. Normal pediatric appendixes measure up to 8.7 mm, with up to 39% measuring more than 6 mm in diameter. Nonpathologic factors, including pericecal fat, appendiceal content, and presence of lymphoid stimulation, influence appendiceal diameter in healthy children.

OBJECTIVE. CT is the primary imaging modality used after aortic root repair. Distinction of normal findings from postoperative complications is imperative and requires optimization of acquisition parameters and interpretation with advanced postprocessing tools. CONCLUSION. After aortic root surgery, findings can be categorized as complications within the aorta, complications outside the aorta, and benign postoperative changes. Distinction of normal findings from postoperative complications requires proper CT technique and an understanding of CT findings that require intervention.

The purpose of this study is to describe a new practice model (overnight subspecialty radiology coverage) and to determine its impact on CT utilization rates in academic and community emergency departments.Overnight subspecialty (neuroradiology and abdominal imaging) attending coverage was instituted at the University of Pittsburgh Medical Center in 2008. Previously, preliminary interpretations of CT studies performed at four academic emergency departments were provided by radiology residents. Interpretations were provided to five community emergency departments by either a senior resident or a contracted teleradiology service. Rotating shifts of neuroradiologists and abdominal imagers have since provided contemporaneous final reports for emergency department CT studies from 5:00 pm to 7:00 am. We compared total CT volume, emergency department visits, and CT "intensity" (CT volume / emergency department visits) within academic and community hospitals 12 months before and after institution of overnight coverage. We also compared on-call (5:00 pm to 7:00 am) and daytime CT intensity in academic and community emergency departments during these time periods.Academic emergency department visits increased 7% and community emergency department visits decreased 3% during the study period. Total academic emergency department CT volume increased 8%, and community emergency department CT volume increased 9%. Daytime community emergency department CT volume remained constant, but on-call CT volume increased 16%. Academic emergency department CT intensity remained constant at 0.57, whereas community emergency department CT intensity increased from 0.40 to 0.45 (12.5%).Institution of overnight subspecialty emergency department coverage resulted in a disproportionate increase in CT utilization in community emergency departments. We hypothesize that community emergency departments lacking in-house clinical subspecialists may be more apt to use subspecialist radiology interpretations for patient management. Overnight subspecialty coverage increases CT utilization in the community emergency department, but the appropriateness and clinical impact is uncertain and in need of exploration.

The objective of our study was to retrospectively determine the accuracy of CT for differentiating intrarenal transitional cell carcinoma (TCC) from centrally located renal cell carcinoma (RCC) and to define the most discriminating diagnostic CT features.CT studies of 98 pathologically proven central renal tumors (64 centrally located RCCs and 34 intrarenal TCCs) seen over 5 years at three university hospitals were reviewed by five specialty-trained radiologists who were blinded to the final diagnosis. Multiple CT features and global impression were graded on a 4-point score. The sensitivity and specificity of each feature and of global assessment were calculated and compared using receiver operating characteristic (ROC) analysis. Interobserver agreement (kappa values) was also calculated for each parameter.All five readers recognized intrarenal TCCs with a high diagnostic accuracy (sensitivity, 90%; specificity, 90%; area under ROC curve [AUC], 0.80-0.95 for global assessment) with moderate-to-excellent interobserver agreement (κ = 0.72-1). Six CT features were most diagnostically specific for identifying intrarenal TCCs: tumor centered within the collecting system; focal filling defect in the pelvicalyceal system; preserved renal shape; absence of cystic or necrotic change; homogeneous tumor enhancement; and tumor extension toward the ureteropelvic junction (sensitivity, 68-82%; specificity, 79-89%; AUC, 0.75-0.84). There was moderate-to-good agreement among the readers over all these features (κ = 0.44-0.69).Intrarenal TCC can be recognized with a high accuracy on CT; global impression showed the best diagnostic performance. A solid, homogeneously enhancing mass that is centered on the collecting system and extends toward the ureteropelvic junction combined with a focal pelvicalyceal filling defect and preserved renal outline is more likely to be an intrarenal TCC than a centrally located RCC.

The purpose of our study was to evaluate the association of hepatic hemangiomatosis with giant cavernous hemangioma (GCH) and describe the imaging appearances and clinical relevance.Forty-one patients who had undergone CT or MRI with reported GCH (8 cm) between 1997 and 2009 were identified retrospectively. Three readers interpreted 27 MRI studies, 36 CT studies, and 16 ultrasound studies of these patients. Prevalence, extent, and imaging appearance of coexistent hemangiomatosis in the surrounding liver parenchyma were evaluated.Forty-two GCHs were identified in 41 patients and hemangiomatosis was present in 18 of 41 patients (44%) with GCH. Twelve patients had a diffuse pattern of hemangiomatosis (67%), and six patients showed a nodular pattern consisting of multiple coalescent nodules measuring5 mm (33%). There was no association between the size of the GCH and presence and extent of hemangiomatosis. The common hepatic artery was enlarged (5 mm) in 14 patients with GCH, of whom 12 had associated hemangiomatosis. There was a statistically significant association between the size of the hepatic artery and presence of hemangiomatosis (p0.001).Hemangiomatosis is not rare in the liver parenchyma adjacent to a GCH. The presence and extent of hemangiomatosis must be specifically communicated to referring physicians. Surgical candidates have to be carefully selected to avoid complications, such as excessive blood loss and diminished risk of postoperative liver decompensation from apparent overestimation of functional residual volume due to oversight of involved liver areas by hemangiomatosis.

The purpose of this study was to determine whether specific findings determined to be critical and standard of care by expert witnesses in a legal case are identifiable by radiologists blinded to clinical outcome and litigation.Images from six CT studies were sent to radiologists for interpretation. Two studies were performed for screening after major trauma, one of the cases being the subject of a settled legal action; three were randomly selected from studies performed in the evaluation of emergency department patients; and one was the control. The cases were selected to simulate a typical emergency department caseload. In the medicolegal case, four plaintiff expert witness radiologists had identified three findings in the CT study that were not described by the radiologist of record (primary reader). One of these findings was considered critical and was the basis for the legal case.Thirty-one radiologists participated in the study. The three findings made by the expert witnesses-T3 and T10 vertebral body fractures and 1-mm symmetric widening of the facet joints at T10-were made by none, 19 (61.3%), and none of the 31 radiologists in this study.Thirty-one radiologists who had no knowledge of the clinical outcome or litigation did not confirm the expert witness interpretation. This finding prompts questions about the current method of determining standard of care in legal cases, that is, use of paid medical expert witnesses. Our findings suggest that use of radiologists blinded to clinical outcome may be a more objective method of evaluating legal cases.

We prospectively evaluated the usefulness of MDCT using a curved planar reformation technique for the noninvasive assessment of the causes of biliary stent occlusion in patients with malignant biliary obstruction.Between December 2004 and January 2009, 173 patients with unresectable malignant biliary obstruction underwent biliary stent insertion. Among them, 26 patients with suspected biliary stent occlusion underwent 29 sessions of ERCP within 2 weeks after MDCT was performed. Curved planar reformation images were obtained along the pathway of the biliary stent. We interpreted tissue growth or stent clogging by comparing attenuation values inside the biliary stent between the unenhanced and contrast-enhanced phases of CT. The cause of biliary stent occlusion was confirmed by using ERCP.The differences in attenuation value inside the biliary stent between the contrast-enhanced and unenhanced phases of CT in the tissue growth group was 27.7 +/- 21.7 HU (SD) and 4.2 +/- 10.6 HU in the stent-clogging group (p = 0.002). The sensitivity and specificity of MDCT for the diagnosis of tissue growth were 86.7% and 85.7%, respectively. The overall accuracy of curved planar reformation images of MDCT for diagnosing the causes of stent occlusion was 86.2%.Curved planar reformation MDCT is a useful noninvasive technique that is relatively accurate for diagnosing the cause of biliary stent occlusion and is helpful for planning the therapeutic management of such patients.

AJR:194, April 2010 This article suggests 10 steps that radiologists and radiologic technologists, with the assistance of their medical physicist, can take to obtain good quality CT images while properly managing radiation dose for children undergoing CT. The first six steps ideally should be completed before performing any CT on a pediatric patient. The final four steps address the unique consideration that should be given for each scanned patient.

Protocols for PET/CT are not yet standardized. In particular, image quality, utilization, and reporting of the findings of the CT component of PET/CT can vary widely, making it complicated for physicians to request the appropriate information. In an effort to address this problem, we describe a set of four PET/CT protocols that satisfy a broad range of clinical needs among oncology patients. Current technology allows acquisition of diagnostic-quality CT scans as part of PET/CT examinations, and referring physicians are given the option of requesting formal interpretation of the CT findings. In this case, the PET and CT images are interpreted by the corresponding specialists, and equivocal or discordant findings are adjudicated through joint review of the PET/CT images.The menu of PET/CT imaging protocols has gained wide acceptance by our referring physicians and have been used successfully in more than 6,000 PET/CT studies. Newer PET/CT protocols will be developed as technology advances. Continued collaboration among oncologists, CT specialists, and nuclear medicine specialists is essential for deriving the maximum clinical benefit from combined PET/CT. Standardization of imaging protocols will become increasingly important as multiple-institution trials are developed for evaluation of present and future applications of PET/CT.

Chance-type fractures are subtle unstable injuries that are often associated with intraabdominal injuries. CT-based observations made during routine interpretations revealed involvement of a burst component to this fracture pattern and a clue on the transaxial images to its presence. The purpose of this review was to determine how often these features occurred in a retrospective study of a large sample because these findings influence diagnosis and management.A retrospective review of all patients identified from the University of Maryland Shock Trauma Center trauma registry and IDXRad system diagnosed with flexion-distraction injuries of the thoracolumbar spine over an 8-year period was performed. Three trauma radiologists assessed the admission spinal radiographs, CT studies with multiplanar images, and available MRI examinations. Imaging findings were confirmed by consensus. Abdominopelvic CT studies and surgical reports were reviewed for evidence and type of intraabdominal injury. A literature review of previous similar series was performed.Fifty-three patients were identified for inclusion in the study. Associated intraabdominal injury occurred in 40% and most commonly involved the bowel and mesentery. A close examination of the fracture patterns on CT revealed that a burst-type fracture with posterior cortex buckling or retropulsion was a common finding (48%). Also, serial transaxial CT images often (76%) showed a gradual loss of definition of the pedicles that we refer to as the "dissolving pedicle" sign. The study showed that the horizontally oriented fracture planes through the posterior elements can often be recognized radiographically, but these fractures can be very subtle.Intraabdominal injuries occurred in 40% of flexion-distraction thoracolumbar fractures in our study cohort, which is slightly lower than previously reported. About half of the patients with this injury displayed a burst-type component that could have a significant influence on surgical management. The dissolving pedicle sign can assist in recognition of this often subtle injury on transaxial CT.

Our objective was to prospectively compare colonic distention and patient comfort at screening CT colonography (CTC) with patient-controlled room air (RA) insufflation versus automated carbon dioxide (CO2) delivery.Two hundred eight adults undergoing CTC were randomized to RA or CO2 (104 per method). Colonic distention was prospectively assessed by segment using a 4-point scale (1 = optimal, 2 = adequate, 3 = inadequate, 4 = collapsed). Adequacy of combined supine/prone segmental evaluation was also recorded. Patients provided discomfort ratings on a 0-10 scale (0-1 = none/insignificant, 2-3 = minimal, 4-6 = intermediate, 7-10 = significant) before, during, and after the procedure.No significant differences in segmental distention were observed in the prone position between techniques. In the supine position, CO2 resulted in significantly greater distention in the sigmoid, descending, and transverse segments (p0.01). After combined supine/prone assessment, two/104 (1.9%) and three/104 (2.9%) patients were judged to have an inadequately evaluated segment on RA and CO2, respectively (four sigmoid, one transverse). Mean discomfort scores for RA and CO2 were 3.97 and 5.08 during the examination (p0.01); 0.91 and 0.42 immediately after (p0.01); 0.51 and 0.25 15 min later (p0.05); and 0.15 and 0.04 2 hours later (p0.01), respectively. During active distention, 19 (18.3%) and 33 (31.7%) patients reported significant transient discomfort with RA and CO2, respectively (p0.05). Beyond 15 min, only two (1.9%) patients with RA and no patients with CO2 had a discomfort level higher than 3.Although patient-controlled RA insufflation and automated CO2 delivery each resulted in negligible postprocedure discomfort and reliable colonic distention, CO2 was better for both categories.

In this study we analyzed the impact of multislice CT technology on scanner productivity in a tertiary care medical center.We compared the productivity of two diagnostic CT scanners during the periods January 1 to August 31, 1999 (when both scanners had single-slice CT capability) and January 1 to August 31, 2000 (when one of these scanners was replaced with a multislice CT scanner). The scanners were used primarily for outpatients during the day shift and for inpatients during the evening shift; the demand for CT services was stable. For this analysis, we queried the hospital's radiology information system and identified the number of CT examinations performed during the two analysis periods. We also determined the examination mix, including proportion of enhanced and unenhanced examinations and the anatomic region examined, to ensure comparable patient populations. Statistical analysis was performed.The number of CT studies performed on the two scanners increased by 1772 (13.1%) from 13,548 (before multislice CT) to 15,320 (when multislice CT was available). The number of examinations enhanced with contrast media increased from 52% to 65%. Between 9:00 A.M. and 5:00 P.M., the number of CT examinations was similar on the single-slice scanners in the two periods (p0.05). However, in the period when multislice CT was available, the number of studies performed on the multislice scanner (5919) was 51.9% higher than those performed using the single-slice scanner (3896) (p0.0006).Using a multislice CT scanner leads to an increase in CT productivity, even though multislice studies are performed using more complicated protocols than are used on a single-slice CT scanner.

The purpose of our study was to establish the most suitable algorithm to compare coronary artery calcium measurements performed with electron beam CT and multirow detector CT for the assessment of coronary artery disease.Coronary artery screening was performed in 100 patients with both electron beam and multirow detector CT. The images were transferred to a dedicated workstation for determination of the calcium score, volume, mass, density, and number of lesions. In addition to the traditional threshold of 130 H, the score of multirow detector CT studies was reevaluated at a threshold of 90 H. Fifty-nine of the patients underwent conventional coronary catheterization. Receiver operating characteristic curve analysis of the different scoring algorithms for detection of significant coronary artery stenosis was performed.The correlation between electron beam CT and multirow detector CT was high for every quantification algorithm. Determination of the score and the number of lesions with multirow detector CT revealed a systematic error of the measurement compared with electron beam CT. The areas under the curve in the receiver operating characteristic curve analyses for electron beam and multirow detector CT were similar for the score, volume, and mass, whereas they were lower for the density. No significant difference was found for the areas under the curve between scores using a 130-H and those using a 90-H threshold.Volume and mass indexes are superior to the traditional score, density, and number of lesions for comparing the results of electron beam and multirow detector CT and for determining significant coronary artery disease.

The characteristic findings of pulmonary involvement in polymyositis (PM) or dermatomyositis (DM) and the change in findings before and after treatment were evaluated with sequential high-resolution CT studies.CT images of pulmonary involvement in 19 patients with PM or DM were reviewed. During a period of 2-61 months, 17 of these patients underwent sequential CT before and after treatment with corticosteroids, immunosuppressants, or both.Findings of the initial CT studies included pleural irregularities and prominent interlobular septa (n = 19), ground-glass attenuation (n = 19), patchy consolidation (n = 19), parenchymal bands (n = 15), irregular peribronchovascular thickening (n = 15), and subpleural lines (n = 7). Honeycombing was not detected on any CT images. These findings were more remarkable in the lower portion and the subpleural area of the lungs. In 16 of the 17 patients who underwent sequential CT conditions such as patchy consolidation, parenchymal bands, and irregular peribronchovascular thickening improved, becoming pleural irregularities and prominent interlobular septa, ground-glass attenuation, and subpleural lines on follow-up CT scans.Consolidation with patchy and subpleural distribution, parenchymal bands, and irregular peribronchovascular thickening were characteristic and reversible CT findings in patients with PM or DM.

The purpose of our study was to evaluate the usefulness of diagnostic joint injections in patients with foot and ankle pain when the radiologist attempts to identify the source of pain. This study also correlated the results of injection with outcome after arthrodesis.We retrospectively reviewed the records of 22 patients who had a foot or ankle joint injected to identify a source of pain and who later underwent arthrodesis of the painful joint. All patients had long-term foot and ankle symptoms of variable causes. Twenty-four joints were assessed: 13 subtalar, five talonavicular, four ankle, one calcaneocuboid, and one metatarsocuneiform. All patients had plain radiographs, 11 had CT studies, and five had bone scans. Contrast material was used to assess adequate positioning of the needle inside the joint before injection. All joints were injected under fluoroscopic control. Steroid was added in eight joints. After injection, patients were assessed for relief of symptoms. Patients subsequently underwent arthrodesis on the basis of the results of the injection.In 20 patients (22 joints), long-term follow-up showed that injections allowed us to correctly identify the source of pain and successfully guide arthrodesis. Of these 20 patients, 17 had significant pain relief after injection and fusion, whereas three patients had mild or no response. With one of these patients, we injected other joints and changed surgical plans. One of the two remaining patients had more pain relief after injection than after arthrodesis. The other patient had no relief after injection, but subsequent fusion because of persistent pain was successful. We found imaging studies to be less useful than diagnostic injections when we were attempting to identify the source of pain.Intraarticular injection of anesthetic in painful foot and ankle joints helped us confirm the source of pain in 20 of 22 patients, which in turn led to successful arthrodesis and good outcomes for these patients.

The purpose of this study was to determine if the selective use of low-osmolality contrast material for excretory urography and CT is safe and if it saves money.At the University Medical Center in Tucson, a questionnaire was developed to identify high-risk patients who would benefit from the use of a low-osmolality contrast agent. High-risk patients were defined as those with a history of a reaction to contrast material, severe allergies, asthma, severe cardiac disease, multiple myeloma, sickle cell disease, polycythemia, pheochromocytoma, or renal impairment. Beginning in March 1993, the questionnaire was given to all adult outpatients scheduled for daytime excretory urography and routine CT studies of the head and body. Only patients identified as high risk were given a low-osmolality (non-ionic) contrast agent. All other patients received high-osmolality (ionic) contrast material. The contrast agent chosen for a patient was determined by the person administering the questionnaire, usually a radiologic technologist.From March 1993 through December 1993, 1114 adult daytime outpatient excretory urographic and contrast-enhanced CT studies were examined at our institution. In 235 (21%) of the studies, a low-osmolality agent was used and in 879 (79%) studies, a high-osmolality agent was used. This represented a reduction in the use of low-osmolality agents from more than 90% of patients to 21%, an annual cost reduction from $288,000 to $60,480. We observed no untoward reactions to contrast material that could be specifically attributed to the increased use of high-osmolality agents.Selective use of low-osmolality contrast agents during excretory urography and CT can provide substantial cost savings and is not associated with a significant risk of major complications.

The usefulness of CT in diagnosing, staging, and establishing the prognosis in cutaneous T-cell lymphoma was assessed. CT abnormalities indicative of the disease, diffuse peripheral adenopathy and skin lesions, as well as less specific signs of generalized lymphoma, were correlated with clinical findings.The study group comprised 33 patients from a total of 87 with pathologically proved cutaneous T-cell lymphoma who were seen at the University of Pittsburgh Medical Center between 1986 and 1991 and who had CT scans. All patients had body CT imaging with contiguous axial sections no thicker than 10 mm of the chest, abdomen, and pelvis; other CT studies were performed as clinically indicated. Because of the cutaneous nature of this lymphoma, collimation included the skin surface.In 10 of the 33 patients, all of whom had stage II or higher disease, abnormalities indicative of cutaneous T-cell lymphoma were seen on CT scans. All 10 had multiple areas of focal skin thickening or plaques several centimeters or more in diameter and 5 mm or greater in thickness affecting the dermal tissues while leaving the subcutaneous fat intact. Extension of individual lesions below the dermis was associated with the development of squamous cell cancers in two patients, both of whom had previous topical therapy. Seven of the 10 also had an unusual pattern of lymphadenopathy: the mediastinum or paraaortic regions were spared while enlarged peripheral nodes were seen in both the axillary and inguinal areas. Skin abnormalities were seen on CT scans of all patients with lymphadenopathy.CT findings in cutaneous T-cell lymphoma are related to the pathophysiology of the disease: cutaneous plaques and diffuse peripheral adenopathy that spare the mediastinal and paraaortic lymph nodes. Although the skin lesions can be easily evaluated clinically, secondary malignant neoplasms arising in treated skin lesions can be found with CT by their extension into the subcutaneous fat.

The preoperative detection of peritoneal metastases from gynecologic malignancies is difficult; in particular, CT often fails to detect peritoneal implants. This study was designed to determine if the administration of intraperitoneal iodinated contrast media would increase the CT detection of such peritoneal metastases. Prospectively, both standard and intraperitoneal contrast-enhanced CT studies of the abdomen and pelvis were performed in 16 patients with suspected gynecologic tumors. All patients then underwent operative staging, with the location and number of metastases documented. The intraperitoneal enhanced CT studies were more sensitive in the detection of peritoneal metastases than standard CT examinations. Whereas routine CT detected peritoneal metastases in seven (64%) of 11 patients with surgically proved implants, the intraperitoneal enhanced CT studies detected peritoneal metastases in all 11 patients. Depending on the specific intraperitoneal compartments involved, the sensitivity of intraperitoneal enhanced CT in the detection of peritoneal metastases was two- to fourfold greater than that of standard CT examinations. Our results suggest that intraperitoneal enhanced CT is superior to standard CT in the detection of peritoneal metastases.

The role of CT in determining the need for angiography in patients with possible thoracic vascular injury resulting from blunt trauma is controversial. During a 24-month period, we prospectively evaluated the results of CT to screen 90 patients with a history of decelerating thoracic trauma for evidence of mediastinal hemorrhage or great vessel abnormality. All patients either had equivocally abnormal mediastinal contours on chest radiographs (64%) or had technically suboptimal chest radiographs owing to body habitus or restriction to the supine projection (36%). Patients with unequivocal signs of mediastinal hemorrhage on chest radiographs underwent immediate arteriography without prior CT. Thoracic CT was interpreted as normal in 63 (77%) patients and no further imaging was performed. Five patients had technically suboptimal CT studies, and CT scans were interpreted as equivocal in six. These 11 patients had normal arteriograms. Sixteen CT scans (18%) demonstrated evidence of mediastinal hemorrhage and/or great vessel contour abnormality. Four (27%) of 15 patients who underwent arteriography had injury to the great vessels. One patient refused to undergo angiography. In 11 patients with CT evidence of mediastinal hemorrhage, major vascular injury was not seen on arteriography. These results suggest a valuable role for CT in determining the need for arteriography to detect potential great vessel injury in patients with blunt decelerating thoracic trauma and equivocally abnormal mediastinal contours on chest radiographs.

Radiologic detection of bone lesions from malignant melanoma is reported to be uncommon or infrequent. To ascertain the characteristics and frequency of detection of melanoma metastases to the axial skeleton by CT, we retrospectively reviewed 464 body CT studies of 125 consecutive melanoma patients for presence, appearance, and site of skeletal metastases. Results were correlated with patient's age, sex, clinical course, and both the Clark and Breslow classifications of the primary lesion. Of 98 patients with metastatic disease evident on their CT studies, 17 (17%) had bony metastases; two (12%) of these 17 patients had skeletal lesions as the only CT evidence of metastatic disease. Metastatic bony lesions were predominantly osteolytic, slightly expansile, and commonly located in the spine. Associated soft-tissue masses were frequent, but periosteal reaction and identifiable tumor matrix were not seen. Skeletal metastases were found only in those patients with thick or intermediate primary melanoma (Breslow) classified as Clark level III or greater, and the CT demonstration of osseous metastases was a poor prognostic sign. The data suggest that CT detection of skeletal melanoma metastases is not uncommon. When CT is performed to evaluate for metastatic melanoma, the axial skeleton should be carefully examined, especially in those patients with more advanced primary lesions.

The CT findings in 14 patients who underwent hepatic or renal embolizations are presented. In 11 patients who had postinfarction CT studies, linear, branching air collections were noted within the embolized tumor. In two patients the amount of air increased on later CT studies. This configuration of air suggested an abscess, but in no case was an abscess encountered. This air was located distal to the high density embolization material in four cases. In four cases the infarcted organ appeared denser due to "trapped contrast." The seven embolized livers did not change in size on follow-up examinations, while three renal tumors demonstrated variable size changes after embolization.

The inferior pulmonary ligament, a double layer of pleura that tethers the lower lobe of the lung to the mediastinum, is rarely appreciated on plain radiographs but may be involved in pathologic processes. A linear structure on axial computed tomographic (CT) images of the lung bases corresponds to the inferior pulmonary ligament on cadaver sections. Review of 100 CT studies identified at least one inferior pulmonary ligament in 42%. Its presence and configuration did not correlate with patient age or gender. The anatomy and CT appearance of the ligament are discussed.

Changes in the size and density of intracerebral hematomas were investigated by analyzing the sequential CT studies of 40 patients. Intracerebral hematomas decrease in density by an average of 0.7 EMI units per day. The dense portion of the hematoma decreases in size by an average of 0.65 mm per day. Mass effect does not decrease in proportion to the decrease in size of the dense portion of the hematoma but is delayed. The only instances of increasing mass effect occurred in patients undergoing surgical evacuation of the hematoma and in those who sustained trauma. Posthematoma residua include decreased parenchymal density, focal atrophy, and ventricular enlargement.

Skeletal muscle hemangiomas are uncommon tumors of young adults. More than 90% are misdiagnosed preoperatively. Plain-film examinations, bone scans, CT studies, and angiography may not always be specific for this tumor. Seven MR examinations were performed in five young adult patients with pathologically proved skeletal muscle hemangiomas. All five hemangiomas showed high signal intensity on both T1- and T2-weighted images. The signal intensity in these tumors was less than that of subcutaneous fat on relatively T1-weighted images and greater than that of fat on relatively T2-weighted images. Four tumors had a serpiginous pattern. Four patients had focal muscle atrophy. Three patients had all three findings (high signal intensity on both T1- and T2-weighted images, serpiginous pattern, and associated focal muscle atrophy) while the other two patients had at least two of the three findings. These three patients did not undergo angiography or needle biopsies before surgery because the MR findings were highly suggestive of hemangioma. Our experience with this small series of patients suggests that skeletal muscle hemangiomas have a consistent appearance on MR. MR may be able to contribute significantly to the preoperative diagnosis of this tumor and may also supply valuable information about the extent of the lesion.

The members of the Society of Body Computed Tomography were surveyed to determine the most frequently used method of administering contrast material in CT studies of the liver. The respondents represented CT departments performing liver examinations in 22 institutions. No department relied solely on noncontrast scans. In 12 (54%) of 22 institutions, only contrast-enhanced scans were performed. The preferred dose for enhancement was 150 ml of 60% contrast material. Eight (36%) of the 22 respondents obtained images during the administration of a bolus of contrast material, whereas nine (41%) obtained images during the administration of a sustained drip infusion given after a loading bolus. Follow-up in 1987 revealed that two departments had switched to obtaining images during the administration of a bolus. The availability of CT power injectors and refinements in the rapid-scanning capabilities of CT scanners have increased the popularity of obtaining images of the liver during the administration of a bolus of contrast material. Despite this, in many departments, contrast material is still administered via drip infusion in CT studies of the liver.

Making a clinical diagnosis of infection in prosthetic vascular grafts is difficult but when undiagnosed, this condition has a high mortality rate. Using Indium-111-labeled white-blood cells, 30 scans were performed in 21 patients suspected of having a prosthetic graft infection. The diagnosis of infected graft was confirmed by surgery in all cases, and lack of infection was established by resolution of symptoms with conservative therapy. Twenty-four hour scans of autologous Indium-111 leukocytes were obtained, and correlative CT studies were done in 11 cases. There were 13 infected grafts at surgery (purulent material present), and scans were positive in all (100% sensitivity); of 17 scans, there were 15 true negatives and two false positives (88% specificity). Using the criteria of gas or fluid around the graft, the sensitivity of CT was only 37% in a small subset of these patients. One-half of the cases in which infection was suspected clinically had no infection and had negative scans. Various types of grafts and graft materials were used, and there was no correlation with presence or absence of infection on the basis of the type of graft. Extragraft infection sites were found in five patients. In conclusion, use of Indium-111 leukocytes has been found to be an accurate and valuable diagnostic method for evaluation of suspected prosthetic vascular graft infection, and to have higher diagnostic accuracy than CT.

A prospective study using sonography and computed tomography (CT) was performed on 102 patients consecutively identified as having acute pancreatitis to see which method provided the most information. Each examination was graded for visualization of the pancreas, extent of disease, and the detection of complications. CT was found to be of significantly greater value than sonography due to the high percentage (38%) of nondiagnostic studies with the latter method. Of the 102 patients, 70% had abnormal CT studies, including 18% with extrapancreatic phlegmons, 10% with pseudocysts, 5% with acute hemorrhage, and 3% with pancreatic abscesses.

Transmission CT studies of 40 patients with intracerebral hematomas were used for an analysis of the perihematoma region. Nineteen of these patients had radionuclide studies. In the brain adjacent to an intracerebral hematoma, the patterns of pertechnetate uptake on scintillation scans and contrast enhancement on transmission CT resemble those observed in cerebral infarctions. The healing of the perihematoma region proceeds similarly to that of infarcts. The brain about the hematoma is ischemic tissue which behaves much like cerebral infarction not related to hematomas.

A review of the lateral radiographs and CT studies of 114 patients with burst fractures, 46 patients with combined injuries in whom bursting was a major component, and 82 patients with simple anterior compression fractures was performed to evaluate the integrity of the posterior vertebral body margin. This structure normally produces a single or bifid vertical line on the lateral radiograph. Disruption, displacement, or rotation of this line was found in all 114 patients with "pure" burst fractures. These abnormalities were also present in 36 of the 46 patients with combined burst injuries. In all patients with simple compression fracture, flexion, distraction or dislocation, and extension injuries, the line was normal. CT studies showed these abnormalities to be the result of retropulsion of one or more bone fragments from the posterior margin of the vertebral body. Disruptive abnormalities of the posterior vertebral body line are reliable plain-film signs that a burst fracture has occurred and that compromise of the vertebral canal and subarachnoid space is present.

A 3-year longitudinal study was conducted with 50 Alzheimer's disease patients and 45 elderly control subjects. All study participants received an extensive evaluation that included brain CT at baseline and follow-up. Quantitation of ventricular size, using both linear and volume methods, revealed highly significant cross-sectional and longitudinal differences between the Alzheimer patients and control subjects. Specifically, the annual rate of change in ventricular volume was approximately 9% in the Alzheimer patients and approximately 2% in the controls. The presence of age-related white matter lesions had no effect on the clinical course of the patients or on the changes in ventricular size. Among the Alzheimer patients, the rate of clinical decline was strongly related to the rate of change in ventricular size. Baseline ventricular measurements were of no value in predicting the subsequent rate of clinical deterioration or ventricular enlargement. The results suggest that changes in ventricular size closely reflect the clinical changes in Alzheimer patients.

A detailed analysis of the coronal anatomic and CT appearances of the orbital apex is presented. In cadavers, coronal CT 9800 scans of the orbital apex and precisely corresponding cryomicrotomic sections were obtained. The CT appearance of the optic nerve, anulus of Zinn, and cranial nerves III-VI at the superior orbital fissure and orbital apex were determined. These anatomic structures were also demonstrated in clinical CT studies. Practical applications of the anatomic landmarks in evaluating orbital apex tumors are illustrated.

Previous reports describing the use of ultrafast CT have emphasized its value in evaluating the heart, chest, and airway. We describe our experience using this technology on children with blunt abdominal trauma. We retrospectively reviewed 54 consecutive ultrafast CT studies and 30 consecutive conventional dynamic CT studies performed on children after blunt abdominal trauma. Thirty percent of the scans showed abnormalities. CT or pathologic follow-up was available for all abnormal cases. We compared scans made with these two techniques for diagnostic accuracy, amount of visible motion on each slice, and contrast enhancement seen on each study. A protocol of 0.4-sec images and 2 ml/kg IV contrast material administered before scanning was used for the ultrafast CT scans. A standard protocol of 2-sec scanning and 3 ml/kg IV contrast material was used for conventional CT studies. There was no difference in diagnostic accuracy between the two techniques. There was significantly less visible motion (p less than .0001) and significantly better contrast enhancement (p less than .0001) seen on the ultrafast CT studies. Two of 54 ultrafast scans had images with sufficient motion to require repeated scanning, compared with 13 of 30 conventional CT studies. In addition, ultrafast scans required less sedation, decreased radiation dose, and improved accessibility of the patient to support personnel. Ultrafast CT is a valuable technique for abdominal imaging, offering equal diagnostic accuracy with improved image quality and important benefits to the patient.