Faculty Bibliography

PURPOSE: To assess for change in the 1990s in the failure of detection at chest radiography of potentially resectable non-small cell lung cancer (NSCLC) lesions compared with experience in the previous decade. MATERIALS AND METHODS: From 1993 to 2001, an observational cohort was identified that consisted of 40 instances of NSCLC evident retrospectively at chest radiography but undetected by a radiologist at a time when the cancer was potentially resectable for cure. Sizes and locations of the tumors were assessed. Pearson chi(2) testing was performed to compare the sex distribution of lung cancer in the present series with population data for the sex distribution of lung cancer in the United States during the present study. RESULTS: Twenty-five (62%) undetected NSCLCs were in men and 15 (38%) were in women, yielding a ratio not significantly different from that for the sex distribution of NSCLC according to national data (chi(2) = 0.22, P =.64). Median patient age was 62 years (range, 37-87 years). Median diameter of the missed cancers was 1.9 cm. Missed cancers were most commonly located in the upper lobes (right, 45%; left, 28%; total, 72%), especially in the apical and posterior segments/subsegments (60% of all the missed cancers). A clavicle obscured 22% of the missed cancers. Eighty-five percent of the missed cancers were in peripheral locations. CONCLUSION: Potentially resectable NSCLC lesions missed at chest radiography were characterized by predominantly peripheral (85%) and upper lobe (72%) locations and by apical and posterior segmental/subsegmental locations in an upper lobe (60%). Distribution by sex of the missed cancers was comparable to national data for NSCLC. The missed cancers had a median diameter of 1.9 cm

PURPOSE: To determine the frequency, clinical characteristics, and radiologic findings of bronchogenic carcinoma in patients surviving more than 1 month after lung transplantation. MATERIALS AND METHODS: The study population was composed of 2,168 consecutive patients at seven lung transplantation centers who survived longer than 1 month after lung transplantation. Medical records, chest radiographs, and computed tomographic (CT) scans obtained at the time of diagnosis and prior images when available were reviewed for various items of information and imaging features. RESULTS: Twenty-four (1%) of the 2,168 patients, all with single-lung transplants, developed cancer in the native lung. Eighteen patients had emphysema, and six had pulmonary fibrosis. The frequencies of cancer in patients with emphysema and fibrosis were 2% (18 of 859 patients) and 4% (six of 147 patients), respectively. Twelve (50%) of their 24 cancers were detected at chest radiography. Fourteen (58%) patients had clinical symptoms. Twenty-one (88%) of the 24 patients had one (n = 11) or more (n = 10) nodules, and nine (38%) had one (n = 8) or more (n = 1) masses visible on CT scans. Nodules and masses were visible on 12 (50%) and seven (29%) of 24 chest radiographs, respectively. Eleven (48%) of 23 cancers for which prior chest radiographs were available were seen retrospectively on prior chest radiographs. CONCLUSION: Bronchogenic carcinoma develops in the native lung of transplant recipients with emphysema and pulmonary fibrosis with frequencies of 2% and 4%, respectively. The carcinomas most commonly manifest as a pulmonary nodule or mass on chest radiographs, with more nodules seen on CT scans

OBJECTIVE: In patients undergoing a combined CT angiographic and CT venographic protocol, the accuracy of helical CT venography for the detection of deep venous thrombosis was compared with that of lower extremity sonography. MATERIALS AND METHODS: Patients who had undergone a combined CT angiographic and CT venographic protocol and sonography of the lower extremities within 1 week were identified. The final reports were evaluated for the presence or absence of deep venous thrombosis. Statistical measures for the identification of deep venous thrombosis with helical CT venography were calculated. In each true-positive case, the location of the thrombus identified with both techniques was compared. All false-positive and false-negative cases were reviewed to identify the reasons for the discrepancies. RESULTS: Seventy-four patients were included. There were eight patients (11%) with true-positive findings, 61 patients (82%) with true-negative findings, four patients (5%) with false-positive findings, and one patient (1%) with a false-negative finding. When comparing helical CT venography with sonography for the detection of lower extremity deep venous thrombosis, the sensitivity measured 89%; specificity, 94%; positive predictive value, 67%; negative predictive value, 98%; and accuracy, 93%. Of the eight true-positive cases, five had sites of thrombus that were in agreement on both CT venography and sonography. Of the five discordant cases, four were false-positives and one was a false-negative. Possible explanations for all discrepancies were identified. CONCLUSION: Compared with sonography, CT venography had a 93% accuracy in identifying deep venous thrombosis. However, the positive predictive value of only 67% for CT venography suggests that sonography should be used to confirm the presence of isolated deep venous thrombosis before anticoagulation is initiated. In addition, interpretation of CT venography should be performed with knowledge of certain pitfalls.

PURPOSE: To compare single- versus four-channel helical computed tomographic (CT) aortography. MATERIALS AND METHODS: Forty-eight patients with aortic aneurysm or dissection underwent four- and one-channel CT angiography. Scan pairs covered the thoracic inlet to the diaphragm (n = 10) and supraceliac abdominal aorta (n = 19) or thoracic inlet (n = 19) to the femoral arterial bifurcations. For four-channel CT, nominal section thickness and pitch were 2.5 mm and 6.0, respectively, and for one-channel CT, 3.0 mm and 2.0 to the infrarenal aorta and 5.0 mm and 2.0 to the femoral arteries. Effective section thickness, scanning duration, scanning coverage, dose of iodinated contrast material, and mean aortoiliac attenuation were compared. Data were summarized as speed (coverage/duration), scanning efficiency (speed/section thickness), and contrast efficiency (mean aortic attenuation/dose of contrast material). RESULTS: At four- versus one-channel CT, CT angiography was 2.6 times faster, scanning efficiency was 4.1 times greater, contrast efficiency was 2.5 times greater, dose of contrast material was reduced (mean, 57%; 97 vs 232 mL) without a significant change in aortic enhancement, and sections were thinner (mean, 40%; 3.2 vs 5.3 mm) despite a 59% shorter scanning duration (22 vs 56 seconds). CONCLUSION: Substantially reduced doses of contrast medium, shorter scanning durations, and narrower effective sections result with four- versus one-channel CT aortography. No advantages of one-channel CT aortography were demonstrated

Since its clinical introduction in 1991, volumetric computed tomography scanning using spiral or helical scanners has resulted in a revolution for diagnostic imaging. In addition to new applications for computed tomography, such as computed tomographic angiography and the assessment of patients with renal colic, many routine applications such as the detection of lung and liver lesions have substantially improved. Helical computed tomographic technology has improved over the past eight years with faster gantry rotation, more powerful X-ray tubes, and improved interpolation algorithms, but the greatest advance has been the recent introduction of multi detector-row computed tomography scanners. These scanners provide similar scan quality at a speed gain of 3-6 times greater than single detector-row computed tomography scanners. This has a profound impact on the performance of computed tomography angiography, resulting in greater anatomic coverage, lower iodinated contrast doses, and higher spatial resolution scans than single detector-row systems

Proper positioning and assessment of abnormalities and complications of the above-mentioned devices have a significant impact on the management of critically ill patients in the intensive care unit (ICU). The timely assessment of new or rapidly evolving findings is critical. Optimal radiographic technique, availability of images to the clinicians, and rapid reporting by the radiologist all serve to maximize the efficacy of bedside chest radiography in the ICU. Sometimes, changes in cardiopulmonary status may only be appreciated on chest radiographs (CXRs). Complications from ventilatory assistance, such as barotrauma, occur frequently and must be detected promptly. The position of monitoring devices, an important component of critical care management, is best checked radiographically. Indications for CXRs and the recommended frequency for repeat follow-up CXRs are based on the existing literature and the consensus of an expert panel formed by the American College of Radiology.

In summary, the chest radiograph has only moderate accuracy in visualizing opacification caused by cardiopulmonary abnormalities and may be quite nonspecific as to etiology, whereas it has high diagnostic accuracy for detecting malpositioning of tubes and lines. While focal parenchymal abnormalities are usually visualized on chest radiographs, identification of concomitant abnormalities when ARDS or PE already exist is more difficult. Atelectasis, aspiration, pneumonia, pulmonary hemorrhage, pulmonary thromboembolism, atypical cardiogenic edema, asymmetric ARDS, and neoplasms may be indistinguishable. Repeat chest radiographs and different views may be helpful, as the progression and time course of various etiologies can be quite different. On the other hand, Winer-Muram et al found that review of prior radiographs and clinical data did not improve the diagnostic accuracy for either ARDS or pneumonia. Pleural effusions may even be difficult to distinguish from parenchymal processes, particularly when the patient is in the supine position. Additional views with the patient in a different position--semi-erect, decubitus, or cross-table lateral--may be of assistance. In most cases, pneumothorax is readily detected. Additional studies such as the decubitus view occasionally may be necessary for further evaluation when there is uncertainty about the findings. Subcutaneous air is readily visualized radiographically. Pneumomediastinum and interstitial pulmonary emphysema may be more difficult to see. It is well known that CT allows visualization of much smaller abnormal air collections than radiography. Despite this lack of sensitivity and specificity of chest films, studies have shown that up to 65% of daily films in the ICU reveal significant and/or unsuspected abnormalities that may change the patient's diagnosis or management. Based on these results, the consensus opinion of the ACR Expert Panel found that daily chest radiographs are indicated on patients with acute cardiopulmonary problems and those receiving mechanical ventilation. Patients who require cardiac monitoring but are otherwise stable require only an initial admission film. Additional radiographs are indicated only when a new device is placed or when there is a specific question regarding cardiopulmonary status. It is also noteworthy that despite the chest film being the most commonly ordered radiologic examination for inpatients, there are no comprehensive studies evaluating its cost-effectiveness. Although several studies have done a very limited cost accounting of the potential savings by eliminating routine films in the evaluation of specific subsets of patients, overall impact on patient outcome has not been investigated. Thus, a true assessment of cost-effectiveness has yet to be determined.