Detection of CT-proved pulmonary nodules: comparison of selenium-based digital and conventional screen-film chest radiographs.

PURPOSE: To compare hard-copy digital chest radiographs obtained with a selenium-based system with wide-latitude asymmetric screen-film radiographs for detection of pulmonary nodules. MATERIALS AND METHODS: Fifty patients undergoing thoracic computed tomography (CT) for suspected pulmonary nodules were recruited to undergo both digital and screen-film posteroanterior (PA) and lateral chest radiography. Three chest radiologists blinded to the CT results independently reviewed each digital and screen-film radiograph, identified each nodule, and graded their confidence for its presence. RESULTS: Seventy-eight pulmonary nodules (mean diameter, 1.5 cm; range, 0.5-3.5 cm; 62 soft tissue, 16 calcified) were identified with CT in 34 patients, while 16 patients had clear lungs. The mean sensitivity for the detection of all nodules by all readers (PA and lateral) was 66% (95% Cl, 54%, 76%) for digital radiographs and 64% (95% Cl, 52%, 74%) for screen-film radiographs. Differences between the two techniques were not statistically significant (P > .05, Student t test). There was no difference in mean false-positive-true-positive ratios (PA, 0.35; lateral, 0.53) or positive predictive values (PA, 74%; lateral, 65%), and no significant difference (P > .05) was seen in mean reader confidence rating. CONCLUSION: In detecting pulmonary nodules, radiologists perform comparably with selenium-based digital and wide-latitude asymmetric screen-film radiographs.

Lung volume reduction surgery: comparison of preoperative radiologic features and clinical outcome.

PURPOSE: To examine the relationship between preoperative radiologic findings and clinical outcome after lung volume reduction surgery. MATERIALS AND METHODS: In 50 consecutive patients, preoperative chest radiographs and computed tomographic (CT) scans were scored by four radiologists for features related to the severity and distribution of emphysema and compared with clinical improvement in forced expiratory volume in 1 second (FEV1), arterial partial pressure of oxygen, and exercise tolerance 6 months after surgery. RESULTS: In the 47 surviving patients, follow-up data showed greater postoperative improvement in function in patients with a global pattern of predominantly upper-lobe emphysema (P < .05) and in patients with a more heterogeneous distribution of emphysema, compressed lung, and a larger percentage of normal and mildly emphysematous lung (P < .05 for improvement in FEV1). Radiographic scores for individual features were more strongly correlated with outcome than CT scores. The combination of upper-lobe severity and percentage of normal and mildly emphysematous lung at CT were the strongest predictors of improvement in FEV1 (r2 = .49). The three patients who died were older (P = .05) and had more severe, diffuse emphysema compared with other patients. CONCLUSION: Imaging studies may help predict the degree of improvement and therefore should be considered an integral part of an objective patient selection process. Radiography alone may be adequate for initial screening.

Hepatic spiral CT: reduction of dose of intravenous contrast material.

PURPOSE: To assess the potential for reduction of contrast material dose in hepatic spiral computed tomography (CT). MATERIALS AND METHODS: Four hundred eighty-seven outpatients were randomized prospectively into nine biphasic and eight uniphasic injection protocols: 75, 100, or 125 mL of 240, 300, or 350 mg of iodine per milliliter of iohexol (18-44 grams of iodine). Protocols were compared according to the maximum hepatic enhancement (MAX) and the contrast enhancement index (CEI). RESULTS: Uniphasic injection was superior to biphasic injection for all protocols. No statistically significant difference in contrast enhancement was present for 38-44 grams of iodine with the uniphasic technique. Adequate enhancement thresholds (MAX > 50 HU, CEI at 30 HU > 300 HU x sec) were exceeded in more than 70% of heavy patients ( > 183 lb [83 kg]) with uniphasic injection of 38 g. For thin patients ( < 183 lb [83 kg]), uniphasic injection of 26 g produced adequate enhancement. CONCLUSION: Contrast material dose may be reduced by up to 40% in thin patients undergoing hepatic spiral CT after uniphasic injection of contrast material; this may result in substantial cost savings.

Dynamic incremental CT: effect of volume and concentration of contrast material and patient weight on hepatic enhancement.

PURPOSE: To develop an individualized approach to the intravenous administration of contrast material for hepatic computed tomography (CT). MATERIALS AND METHODS: Two hundred patients were randomized into eight protocols. Each group received different volumes and concentrations of contrast material. For each protocol, maximum hepatic enhancement (MHE) was calculated, with an adjustment for iodine dose and patient weight. The contrast enhancement index (CEI) and optimum scanning interval were calculated for hepatic enhancement thresholds of 10-60 HU. RESULTS: The MHE calculated as a function of patient weight was 96 HU +/- 19 per gram of iodine per kilogram of body weight. CEIs obtained with a contrast material concentration of 240 mg of iodine per milliliter were inferior to those obtained with a concentration of 320 or 350 mg I/mL. At low enhancement thresholds, the volume of contrast material had a more important effect than the concentration on CEI and optimum scanning interval; at high thresholds, concentration had a more important effect. CONCLUSION: For a patient of known weight, one can calculate the iodine dose needed to provide a desired level of hepatic enhancement. Use of a contrast material with a concentration of 240 mg L/mL is not recommended for dynamic incremental hepatic CT, except in small patients (eg, those weighing less than 73 kg).

Aortic dissection: effect of prospective chest radiographic diagnosis on delay to definitive diagnosis.

PURPOSE: To determine the effect of the interpretation of plain chest radiographs on the time to definitive diagnosis of aortic dissection. MATERIALS AND METHODS: The authors evaluated chest radiographs from 75 patients in whom chest radiography was performed before aortic dissection was diagnosed. The radiographs and available comparison images were retrospectively reviewed to identify cases in which aortic dissection should have been suggested before the diagnosis was made. RESULTS: Radiographic reports suggested that only 19 patients (25%) had an aortic dissection or thoracic aortic aneurysm or needed additional imaging of the aorta. No statistically significant correlation existed between interpretation of the chest radiographs and delay to diagnosis, type of dissection, availability of previously obtained images, or presence of characteristic clinical symptoms. Retrospective analysis showed that the chest radiographs of 36 patients (48%) contained sufficient findings to suggest the diagnosis. In five patients, failure to prospectively suggest dissection was associated with a delay to diagnosis of more than 24 hours. CONCLUSION: Although prospective interpretation of the chest radiograph shortened the delay to definitive diagnosis for only a limited number of patients, retrospective analysis suggests that the delay can be shortened for additional patients.

Chest radiography in patients with early stage prostatic carcinoma. Effect on treatment planning and cost analysis.

STUDY OBJECTIVE: An evaluation of the impact of routine preoperative chest radiographs was retrospectively undertaken in a pilot group of 292 patients with prostatic carcinoma who were part of a prospective study of prostate specific antigen screening for prostate carcinoma. DESIGN: Retrospective. SETTING: Hospital-based outpatients. PATIENTS AND PARTICIPANTS: A cost-effectiveness model was used to assess the value of routine chest radiography in this patient population. Chest radiography findings were categorized into four groups based on follow-up and impact. MEASUREMENTS AND RESULTS: Forty-three patients (15 percent) had a total of 45 positive findings on their chest radiographs. No patient had intrathoracic metastases from prostatic carcinoma. Only two patients (both with unsuspected second neoplasms) had findings that impacted on their treatment and one avoided retropubic radical prostatectomy. Total cost was $2,000 (based on Medicare reimbursement), or $14,000 (based on physician and hospital charges). CONCLUSION: Although benefit is small in terms of number of patients affected, clinical impact, in the two patients with significant findings, was great. Although cost-effectiveness cannot be confirmed on the basis of this series, further evaluation of its utility for this application should be undertaken.

Abnormalities of the diaphragm and adjacent structures: findings on multiplanar spiral CT scans.

Abnormalities of the diaphragm and surrounding tissues have been notoriously difficult to image with conventional axial CT. During the past 10 years, the multiplanar imaging capabilities of MR have been used to clarify the organ of origin of masses near the diaphragm. Spiral CT now offers a similar capability. With spiral CT, the peri-diaphragmatic region can be scanned in a single breath-hold, minimizing motion artifacts and virtually eliminating respiratory mis-registration. Axial images of closely spaced, overlapping sections are reconstructed retrospectively from the volumetric spiral CT projection data set. From these images, one can generate high-detail multiplanar reformations through the diaphragm and adjacent abnormalities. As the CT attenuation values inherent to the chest and abdomen cover a wide range, three-dimensional reformations are not expected to depict this anatomy better than two-dimensional reformations can. This is because three-dimensional images generally render structures at the extremes of CT attenuation, or within a narrow window of CT attenuation values. This pictorial essay illustrates the importance of two-dimensional sagittal and coronal reformations of spiral CT scans in evaluating the peri-diaphragmatic area. With these reformations, peri-diaphragmatic abnormalities seen on axial images are localized to the lung, pleura, pericardium, cardiophrenic space, or intraabdominal viscera.

New techniques in chest radiography.

Advances in film-screen radiography (e.g., InSight) and beam equalization radiography (e.g., AMBER) have improved the quality of standard chest radiographs. Despite the improved visibility of the mediastinum and retrocardiac and retrodiaphragmatic lung with AMBER, it is debatable whether this advantage outweighs its disadvantages, especially the increased cost of the unit and decreased reliability. The benefits of storage phosphor systems have largely been in the area of bedside radiography, where consistent image quality over a wide range of exposures and image processing compensate for the lower spatial resolution. More routine application of this technology to standard chest radiography is likely, especially as image processing techniques improve and digital units become more cost effective. Storage phosphor digital imaging may be the most appropriate technique for entry of images into a picture archiving and communication system in which images stored in image management systems can be displayed on high-resolution monitors in local or distant sites. Such systems have the potential of improving patient care by providing more rapid access to radiographic images, especially if the image is accompanied by an immediate report. Because of the significant expense of a picture archiving and communication system, their introduction is likely to be gradual, via networks in specific areas such as between intensive care units and radiology departments.

Dynamic contrast-enhanced CT of the liver: comparison of contrast medium injection rates and uniphasic and biphasic injection protocols.

To determine the effect of contrast medium injection rate and biphasic versus uniphasic bolus on hepatic parenchymal enhancement at computed tomography (CT), 105 patients were randomized into four protocols. Hepatic and aortic enhancement curves were measured for each protocol. The optimal scanning interval (the duration between onset of a desired hepatic enhancement threshold and decline of enhancement below the threshold or onset of the equilibrium phase) and contrast enhancement index (CEI) (area under the hepatic enhancement curve above a desired threshold during the nonequilibrium phase) were the primary determinants of merit. Measurements were performed at hepatic enhancement thresholds between 10 and 60 HU. At most thresholds of hepatic enhancement, optimal scanning intervals were significantly longer and CEIs were significantly higher for the biphasic protocols than for the uniphasic protocols (P < .03). A biphasic injection with a high initial flow rate produces high peak contrast enhancement but delayed onset of equilibrium and thus provides a longer optimal scanning interval.

Omental flap in lung transplantation.

Some surgeons performing lung transplantation will wrap the bronchial anastomosis with omentum in an attempt to improve healing. The authors retrospectively reviewed the chest radiographs and computed tomographic (CT) scans of 31 patients who underwent lung transplantation with bronchial omentopexy to determine the CT appearance of the intrathoracic omentum and the frequency and type of chest radiographic manifestations created by the omental flap. The omental flap was seen at CT in all patients, was predominantly of fatlike attenuation, and contained linear areas of increased attenuation representing omental vessels. In 16 patients (52%), a total of 29 chest radiographic findings that corresponded to the omental flap were seen. There was no statistically significant correlation between the type of operative procedure and the presence of a chest radiographic correlate for the omentum. The results showed that the omental flap is a potential diagnostic pitfall on post-lung transplantation chest radiographs; when there is confusion, however, the omentum can be identified with CT because of its attenuation value and characteristic course.

Spiral CT: decreased spatial resolution in vivo due to broadening of section-sensitivity profile.

Comparable conventional and spiral computed tomographic (CT) scanning protocols for transaxial (n = 30) and multiplanar reformation (MPR) (n = 15) imaging were performed to image the adrenal gland and the upper pole of the right kidney in the same patient, without use of intravenously administered contrast media. The sharpness of soft-tissue-fat interfaces oriented in the transverse (xy) and longitudinal (z) directions was measured as the maximum and full width at half maximum (FWHM) of the edge attenuation profile first derivative. Edge sharpness was qualitatively assessed by three blinded reviewers, who used a four-point scale. In vivo transaxial CT studies showed that the conventional scans produced slightly sharper edges than the spiral scans (mean difference of spiral and conventional FWHM = 0.30 mm [P < .05] [in z direction] and 0.21 mm [P < .05] [in xy direction]). In vivo MPR studies showed that interfaces in the xy plane were significantly less sharp with spiral scanning, whereas interfaces in the z direction were equivalent for conventional and spiral scanning (mean difference of spiral and conventional FWHM = 0.03 mm [P > .05] [in z direction] and 1.19 mm [P < .05] [in xy direction]). Significant respiratory misregistration was present on seven of 15 (47%) conventional MPR scans and on no spiral MPR scans.

Pulmonary nodular opacities after transbronchial biopsy in patients with lung transplants.

Focal nodular opacities were seen on 26 of 74 (35%) postbiopsy radiographs obtained in 39 patients who underwent lung transplantation. The subsequent clinical course and diagnostic evaluation suggested that the opacities were due to focal hemorrhage at the biopsy sites. This finding was evident on only three of 40 (8%) postbiopsy radiographs obtained in 40 control patients who underwent transbronchial biopsy for diffuse interstitial lung disease. The differential diagnosis of new pulmonary nodular opacities in lung transplantation patients should include focal postbiopsy hematomas, because of their relatively frequent occurrence in this clinical situation.

Anatomy of the major fissure: evaluation with standard and thin-section CT.

The major fissures of the right and left lungs were studied with standard computed tomography (CT) (10-mm-thick sections) and thin-section CT (2-mm-thick sections) in 50 patients. On standard CT scans, the major fissures were seen in 90%-100% of cases at each of three selected levels. They usually appeared as hypoattenuating bands and less often as lines or hyperattenuating bands. Although in most cases the major fissure was seen as a line on thin-section CT scans, this appearance was more common in the upper portion of the left major fissure than in the upper portion of the right major fissure. A "double-fissure sign" was most frequently seen at the base of the left lung; however, the sign was also seen at higher levels, with approximately equal frequency in the right and left lungs. An incomplete major fissure was noted in the right lung in 32 cases (64%) and in the left lung in 26 cases (52%). The upper and middle portions of the left major fissure were less frequently incomplete than were the comparable portions of the right major fissure. Thin-section CT provided better delineation of the major interlobar fissures than did standard CT.

Motion artifact simulating aortic dissection on CT.

We recently imaged two patients clinically suspected of having aortic dissection whose contrast-enhanced CT examinations, obtained on a new scanner with a 1-sec scanning time, showed findings suggesting an ascending aortic dissection. The subsequent clinical course and evaluation implied that the CT findings were predominantly artifactual. We identified identical artifacts in 18% of 50 consecutive contrast-enhanced CT examinations performed for a variety of indications on the same scanner. The double-lumen artifact, simulating an intimal flap, occurs in the proximal ascending aorta and is limited to one or two contiguous transaxial images. The artifact was not detected on two other CT units. We believe the artifact arises from motion of the aortic wall and the surrounding pericardial recesses during image acquisition.

Artifacts in computed radiography.

Storage-phosphor digital radiographic systems are becoming widely used in a variety of diagnostic procedures. The equipment is reliable and produces images of consistently high quality. However, the images may contain artifacts directly related to the digital techniques used, to the phosphor imaging plate, or to radiography in general. This article illustrates many of the artifacts encountered that are specific to computed radiography, some of which can simulate pathologic lesions. Their causes and remedies are discussed briefly.

High-attenuation mediastinal masses on unenhanced CT.

On unenhanced CT scans, a variety of mediastinal masses contain areas with attenuation values higher than the attenuation value of the chest wall musculature. The increased attenuation may be diffuse or focal and may be a result of calcium deposition, high iodine content, or areas of acute hemorrhage. This report illustrates the gamut of high-attenuation mediastinal masses seen on unenhanced CT. Masses that are of high attenuation only on IV contrast-enhanced images (e.g., aberrant vessels) are not included.