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Objective: To evaluate the significance of oesophageal dilatation on high-resolution CT (HRCT) chest in patients with systemic sclerosis., Methods: We retrospectively retrieved the database of patients with systemic sclerosis seen at our hospital between January 2008 and January 2009. A total of 50 patients (46 women and four men) who had HRCT chest, pulmonary function testing and echocardiography within 1 month were included in the study. Peak pulmonary artery (PA) pressures and pulmonary function testing were charted. The HRCT chest was interpreted by a chest radiologist. Oesophageal dilatation was defined as a luminal coronal diameter of ≥9 mm in infra-aortic oesophagus. Extent of ground glass, reticulation and honeycombing was objectively scored., Results: Statistical analysis using independent t-test showed that diffusion capacity of carbon monoxide was significantly lower (P = 0.042) and peak PA pressures were significantly higher (P = 0.045) in patients with oesophageal dilatation (n = 29) as compared with those without oesophageal dilatation (n = 21). The two cohorts had no significant difference in their total lung capacity and HRCT determined extent of interstitial lung disease., Conclusion: Patients with oesophageal dilatation on HRCT chest had significantly lower diffusion capacity of carbon monoxide and higher peak PA pressures, which suggest that these patients tend to have more severe pulmonary vascular disease., (© 2011 The Authors. Journal of Medical Imaging and Radiation Oncology © 2011 The Royal Australian and New Zealand College of Radiologists.)

Objective: The purpose of this study was to compare the subjective image quality, image noise, and radiation dose of chest CT images reconstructed with a 30% blend of iterative reconstruction and 70% conventional filtered back projection (FBP) with those of images generated with 100% FBP., Subjects and Methods: Clinically indicated chest CT examinations of 292 consecutively registered patients were prospectively alternately assigned to two scanners on which different reconstruction techniques were used: adaptive statistical iterative reconstruction (ASIR) blended with FBP and 100% FBP. Both acquisitions were performed with dose modulation (noise index, 25 for ASIR and 21 for FBP). Patient demographics and habitus were recorded. Two radiologists blinded to the reconstruction algorithm independently scored subjective image quality on a 3-point Likert scale and measured image noise and radiation dose., Results: Compared with FBP images, ASIR images had significantly lower subjective image quality (p = 0.01), less image noise (p = 0.02), and less radiation dose (p < 0.0001). The CT dose index of the ASIR cohort (11.3 ± 51) was significantly lower than that of the 100% FBP cohort (15.4 ± 6.3) (p < 0.0001). Interobserver agreement on subjective image quality was excellent for both ASIR and FBP (Cronbach α, 0.92, p < 0.0001; Cronbach α, 0.85, p < 0.0001)., Conclusion: In clinically indicated chest CT examinations, ASIR images had better image quality and less image noise at a lower radiation dose than images acquired with a conventional FBP reconstruction algorithm.

Objective: To compare the detection rate of pulmonary abnormalities between conventional high-resolution computed tomography (HRCT) and high-resolution multidetector computed tomography (MDCT) in lung transplant recipients and to correlate a composite computed tomography (CT) score with bronchiolitis obliterans syndrome (BOS) stage., Methods: Twenty-four lung transplant recipients (12 single/12 double lung transplants, 13 males/11 females, mean age: 53 y, range: 28 to 71) underwent contiguous 16-slice high-resolution MDCT of the lungs at maximal inspiration and maximal expiration. Eight reformatted image sets were reconstructed: (i) contiguous 1-mm slice MDCT image set in the transverse, sagittal, and coronal image planes at maximal inspiration; (ii) contiguous 1-mm slice MDCT image set in the transverse, sagittal, and coronal image planes at maximal expiration; (iii) conventional HRCT image set of 1-mm slices every 10 mm at maximal inspiration; and (iv) conventional expiratory HRCT of 1-mm slices at 3 selected levels at maximal expiration. Individual pulmonary abnormalities were added to give a composite CT score. Individual abnormalities and the composite CT score were correlated with BOS stage, as based on functional testing of airflow obstruction, for each of the 8 image sets., Results: Transverse, sagittal, and coronal MDCT correlated significantly with BOS stage (R=0.46, 0.49, 0.52, respectively), whereas conventional HRCT did not. Multiple regression analysis demonstrated that transverse MDCT was the only independent predictor of BOS stage (R=0.33, P<0.01). Interobserver agreement for composite CT scores for HRCT, transverse, sagittal, and coronal MDCT were R2=0.89, 0.87, 0.83 and 0.80, respectively. Interobserver agreement for individual abnormalities was better with MDCT than with conventional HRCT., Conclusions: In lung transplant recipients, high-resolution MDCT detects significantly more pulmonary abnormalities and has better interobserver agreement than conventional HRCT and is an independent predictor of BOS stage.

The introduction of helical single-detector row computed tomography (CT) and, more recently, multi-detector row CT has greatly increased the clinical indications for CT. Correspondingly, CT examinations now account for greater than one-half of the radiation dose due to medical procedures in the population of North America. The level of CT radiation dose, especially in the pediatric population, is of concern to radiologists, medical physicists, government regulators, and the media. This review addresses this problem with particular reference to radiation dose in chest CT. Specifically it outlines the topics of measurement units used to quantify radiation exposure, factors affecting CT scanner dose efficiency, scanner settings that determine the administered radiation dose, and radiation dose reduction in chest CT. A table of reference dose values is provided. Given the wide variation documented in chest CT radiation exposure, the authors suggest that reference standards be promoted to minimize excessive CT radiation exposure. In addition, further research into the complex relationship between radiation exposure, image quality, and diagnostic accuracy should be encouraged in order to establish the minimum radiation dose necessary to provide adequate diagnostic information for standard clinical questions.

Purpose: To prospectively compare the accuracy of ultrasonography (US) with that of supine chest radiography in the detection of traumatic pneumothoraces, with computed tomography (CT) as the reference standard., Materials and Methods: Thoracic US, supine chest radiography, and CT were performed to assess for pneumothorax in 27 patients who sustained blunt thoracic trauma. US and radiographic findings were compared with CT findings, the reference standard, for pneumothorax detection. For the purpose of this study, the sonographers were blinded to the radiographic and CT findings., Results: Eleven of 27 patients had pneumothorax at CT. All 11 of these pneumothoraces were detected at US, and four were seen at supine chest radiography. In the one false-positive US case, the patient was shown to have substantial bullous emphysema at CT. Sensitivity and negative predictive value of US were 100% (11 of 11 and 15 of 15 patients, respectively), specificity was 94% (15 of 16 patients), and positive predictive value was 92% (11 of 12 patients). Chest radiography had 36% (four of 11 patients) sensitivity, 100% (16 of 16 patients) specificity, a 100% (four of four patients) positive predictive value, and a 70% (16 of 23 patients) negative predictive value., Conclusion: In this study, US was more sensitive than supine chest radiography and as sensitive as CT in the detection of traumatic pneumothoraces.

Purpose: To validate a technique of computer-simulated dose reduction for conventional chest computed tomography (CT)., Materials and Methods: In 27 patients, CT scans were obtained at 200, 100, and 40 mAs at two levels. The raw data from the 200-mAs scan were modified on a computer workstation to simulate the increased noise present on 100- and 40-mAs scans. Real and simulated 100- and 40-mAs images were independently assessed in random order for overall image quality and radiologic findings by four subspecialty-trained chest radiologists who were blinded to the technique. The four observers were given paired real and simulated images. They were asked to identify the real image and note any difference in diagnostic quality., Results: No difference was seen in overall image quality or radiologic findings between real and simulated images (P > .05). In the paired comparison, 433 of 864 (50.1%) real images were correctly identified., Conclusion: Computer modification of 200-mAs raw scan data to simulate 100- and 40-mAs noise levels produces reconstructed images indistinguishable from real 100- and 40-mAs scans. This technique provides realistic reduced-dose images without patient radiation exposure and with identical image registration and motion artifact.

Objective: We wanted to determine minimal tube current (mAs) required for consistently good image quality on conventional 10-mm collimation chest CT and effect of tube current reduction on detection of mediastinal and lung abnormalities. Tube current reduction is desirable to reduce patient radiation dose., Subjects and Methods: Prospectively, 30 consecutive patients (mean weight, 68 kg; range, 34-93 kg) older than 45 undergoing conventional chest CT with standard technique (120 kVp, 400 mAs) had four additional sections imaged at reduced tube current (200, 140, 80, 20 mAs) at two levels (tracheal carina and left atrium). CT scans were evaluated in random order by two independent observers who were blinded to technical factors used. Subjective image quality was graded on a five-point scale from non-diagnostic to excellent. Visualization of mediastinal adenopathy (n = 18), pleural plaques (n = 17), effusions (n = 28), lung parenchymal nodules (n = 37), and emphysema (n = 15) were assessed. The 400 mAs scan was considered the reference standard., Results: When compared with the reference technique (400 mAs), the first and second (200 mAs and 140 mAs) reduction levels showed no significant difference (p > .05) in subjective image quality. A significant difference (p < .001) was seen at the third and fourth (80 mAs and 20 mAs) reduction levels. However, no significant difference (p > .05) was seen in detection of mediastinal or lung parenchymal abnormalities with different tube currents., Conclusion: A twofold reduction in tube current (400-140 mAs) and resultant radiation dose did not cause a significant change in subjective image quality or in detection of mediastinal or lung abnormalities with conventional chest CT. One hundred forty milliampere-seconds is the minimal tube current required to provide good image quality in patients of average weight.

Objective: The purpose of this study was to compare the skin radiation dose to the chest produced by high-resolution CT (HRCT) with the radiation dose produced by conventional CT. Previous studies have reported that radiation doses with HRCT are equal to or higher than those with conventional CT. These results, however, were based on the assumption that in HRCT, contiguous sections were scanned without the intersection gaps of 10 or 20 mm that are used clinically., Subjects and Methods: We used radiotherapy verification film to measure the skin radiation dose in 56 patients who had chest CT scans. Twenty-two had 1.5-mm collimation HRCT scans at 10-mm intervals, 15 had 1.5-mm collimation HRCT scans at 20-mm intervals, and 19 had 10-mm collimation conventional CT scans at 10-mm intervals. Scan parameters were identical in all cases: 120 kVp, 200 mA, 2 sec. Step wedges were used to generate calibration films with identical beam quality on the CT scanner, and exposure was measured with an ionization chamber. Calibration films and patients' radiotherapy verification films were digitized, and the radiation dose was calculated., Results: Mean skin radiation dose was 4.4 (standard error [SE], 0.2) mGy for 1.5-mm HRCT scans at 10-mm intervals, 2.1 (SE, 0.1) mGy at 20-mm intervals, and 36.3 (SE, 0.9) mGy for conventional 10-mm scans at 10-mm intervals., Conclusion: HRCT scanning at 10- and 20-mm intervals produced 12% and 6%, respectively, of the radiation dose associated with conventional CT. This is considerably less radiation than suggested in earlier studies. Combining HRCT scans at 20-mm intervals with low-dose scan (20 mA, 2-sec scans) would result in an average skin dose comparable with the dose administered with chest radiography.