Comparison of Transaxial Source Images and 3-Plane, Thin-Slab Maximal Intensity Projection Images for the Diagnosis of Coronary Artery Stenosis with Using ECG-Gated Cardiac CT

OBJECTIVE: We wanted to compare the transaxial source images with the optimized three plane, thin-slab maximum intensity projection (MIP) images from electrocardiographic (ECG)-gated cardiac CT for their ability to detect hemodynamically significant stenosis (HSS), and we did this by means of performing a receiver operating characteristic (ROC) analysis. MATERIALS AND METHODS: Twenty-eight patients with a heart rate less than 66 beats per minute and who were undergoing both retrospective ECG-gated cardiac CT and conventional coronary angiography were included in this study. The contrast-enhanced CT scans were obtained with a collimation of 16x0.75-mm and a rotation time of 420 msec. The transaxial images were reconstructed at the mid-diastolic phase with a 1-mm slice thickness and a 0.5-mm increment. Using the transaxial images, the slab MIP images were created with a 4-mm thickness and a 2-mm increment, and they covered the entire heart in the horizontal long axis (4 chamber view), in the vertical long axis (2 chamber view) and in the short axis. The transaxial images and MIP images were independently evaluated for their ability to detect HSS. Conventional coronary angiograms of the same study group served as the standard of reference. Four radiologists were requested to rank each image with using a five-point scale (1 = definitely negative, 2 = probably negative, 3 = indeterminate, 4 = probably positive, and 5 = definitely positive) for the presence of HSS; the data were then interpreted using ROC analysis. RESULTS: There was no statistical difference in the area under the ROC curve between transaxial images and MIP images for the detection of HSS (0.8375 and 0.8708, respectively; p > 0.05). The mean reading time for the transaxial source images and the MIP images was 116 and 126.5 minutes, respectively. CONCLUSION: The diagnostic performance of the MIP images for detecting HSS of the coronary arteries is acceptable and this technique's ability to detect HSS is comparable to that of the transaxial source images.

Performance of Computer-aided Detection in False-Negative Screening Mammograms of Breast Cancers

PURPOSE: To analyze retrospectively the abnormalities visible on the false-negative screening mammograms of patients with breast cancer and to determine the performance of computer-aided detection (CAD) in the detection of cancers. MATERIALS AND METHODS: Of 108 consecutive cases of breast cancer diagnosed over a period of 6 years, of which previous screening mammograms were available, 32 retrospectively visible abnormalities (at which locations cancer later developed) were found in the previous mammograms, and which were originally reported as negative. These 32 patients ranged in age from 38 to 72 years (mean 52 years). We analyzed their previous mammographic findings, and assessed the ability of CAD to mark cancers in previous mammograms, according to the clinical presentation, the type of abnormalities and the mammographic parenchymal density. RESULTS: In these 32 previous mammograms of breast cancers (20 asymptomatic, 12 symptomatic), the retrospectively visible abnormalities were identified as densities in 22, calcifications in 8, and densities with calcifications in 2. CAD marked abnormalities in 20 (63%) of the 32 cancers with false-negative screening mammograms; 14 (70%) of the 20 subsequent screening-detected cancers, 5 (50%) of the 10 interval cancers, and 1 (50%) of the 2 cancers palpable after the screening interval. CAD marked 12 (50%) of the 24 densities and 9 (90%) of the 10 calcifications. CAD marked abnormalities in 7 (50%) of the 14 predominantly fatty breasts, and 13 (72%) of the 18 dense breasts. CONCLUSION: CAD-assisted diagnosis could potentially decrease the number of false-negative mammograms caused by the failure to recognize the cancer in the screening program, although its usefulness in the prevention of interval cancers appears to be limited.

Liquid-Crystal Display Monitors and Cathode-Ray Tube Monitors: A Comparison of Observer Performance in the Detection of Small Solitary Pulmonary Nodules

OBJECTIVE: To compare observer performance using liquid-crystal display (LCD) and cathode-ray tube (CRT) monitors in the interpretation of soft-copy chest radiographs for the detection of small solitary pulmonary nodules. MATERIALS AND METHODS: By reviewing our Medical Center's radiologic information system, the eight radiologists participating in this study (three board-certified and five resident) retrospectively collected 40 chest radiographs showing a solitary noncalcified pulmonary nodule approximately 1 cm in diameter, and 40 normal chest radiographs. All were obtained using a storage-phosphor system, and CT scans of the same patients served as the gold standard for the presence of a pulmonary nodule. Digital images were displayed on both high-resolution LCD and CRT monitors. The readers were requested to rank each image using a five point scale (1 = definitely negative, 3 = equivocal or indeterminate, 5 = definitely positive), and the data were interpreted using receiver operating characteristic (ROC) analysis. RESULTS: The mean area under the ROC curve was 0.8901+/-0.0259 for the LCD session, and 0.8716+/-0.0266 for the CRT session (p > 0.05). The reading time for the LCD session was not significantly different from that for the CRT session (37.12 and 41.46 minutes, respectively; p = 0.889). CONCLUSION: For detecting small solitary pulmonary nodules, an LCD monitor and a CRT monitor are comparable.

The Diagnosis of Small Solitary Pulmonary Nodule: Comparison of Standard and Inverse Digital Images on a High-Resolution Monitor using ROC Analysis

PURPOSE: To study the impact of inversion of soft-copy chest radiographs on the detection of small solitary pulmonary nodules using a high-resolution monitor. MATERIALS AND METHODS: The study group consisted of 80 patients who had undergone posterior chest radiography; 40 had a solitary noncalcified pulmonary nodule approximately 1 cm in diameter, and 40 were control subjects. Standard and inverse digital images using the inversion tool on a PACS system were displayed on high-resolution monitors (2048x2560x8 bit). Ten radiologists were requested to rank each image using a five-point scale (1=definitely negative, 3=equivocal or indeterminate, 5=definite nodule), and the data were interpreted using receiver operating characteristic (ROC) analysis. RESULTS: The area under the ROC curve for pooled data of standard image sets was significantly larger than that of inverse image sets (0.8893 and 0.8095, respectively; p0.05). CONCLUSION: For detecting small solitary pulmonary nodules, inverse digital images were significantly inferior to standard digital images.

High-Resolution PACS Work station: Diagnostic Performance and Comparison with Laser-Printed CR Films in Chest Diseases

OBJECTIVES: To compare the diagnostic performance of a high-resolution picture archiving and communications system (PACS) workstation directly interfaced with computed radiography(CR) with laser-printed CR films in chest diseases. MATERIALS AND METHODS: Chest radiographs with (n=91) and without (n=25) abnormalities were included. Atotal of 100 abnormalities from 91 radiographs consisted of irregular lines, pneumothoraces, nodules and consolidations (25 of each). Laser-printed hard copies with dynamic range compression (DRC) were produced. InPACS, soft copies of 1760 X 2140 X 10 bits CR images were displayed on 1536 X 2048 with 8 bit gray-scale monitors.The performance of four observers was compared between laser-printed hard copies and CR images displayed on a workstation according to receiver operating characteristic analysis. RESULTS: Overall, no significant difference sin observer performance were observed between laser-printed hard copies and CR images displayed on a workstation(p=.2454). Even though statistically not significant, the former was slightly superior to the latter for lesions of irregular lines, pneumothoraces, and consolidations, whereas for nodules, the latter was slightly better than the former. CONCLUSION: The diagnostic performance of a high-resolution PACS workstation in chest radiographs is acceptable and comparable to CR hard copies printed with DRC processing mode.