Influence of rib structure on detection of subtle lung nodules

PURPOSE: To access the influence of anatomic noise on the detectability of subtle lung nodules depicted on chest radiographs. MATERIAL AND METHODS: From normal chest radiography images, 132 square regions were extracted, of which the centers were on the upper margin of a rib, the inside of a rib, the lower margin of a rib, and the central region between two adjoining ribs. Simulated nodules were digitally superimposed at the centers of these extracted square images. Twelve radiologists viewed 50 soft-copy images consisting of these 792 processed images, including the noise-added images. The observer's confidence level for the square images containing single nodules was used as an index of observer performance. RESULTS: Results indicated statistically reliable effects of the relationship between rib structures and nodule positions on the detection performance (P < 0.001). The nodule detectability on the images with a center located between two adjoining ribs was significantly the best, whereas it was significantly the worst on the noise-added images with a center located between two adjoining ribs. CONCLUSION: The rib structures overlying a subtle lung nodule on chest X-ray images have a detrimental effect on nodule detection performance as anatomic noise, regardless of the nodule location on ribs.     

Influence of availability of clinical history on detection of early stroke using unenhanced CT and diffusion-weighted MR imaging

OBJECTIVE: The radiologic diagnosis of stroke requires accurate detection and appropriate interpretation of relevant imaging findings; both detection and interpretation may be influenced by knowledge of the patient's presentation. In our study, we evaluated the effect of the availability of clinical history on the sensitivity for stroke detection using unenhanced CT and diffusion-weighted MR imaging. MATERIALS AND METHODS: The records of 733 consecutive patients with a clinically based admission diagnosis of early stroke were reviewed. Among the criteria for inclusion in our study were the availability of an unenhanced CT scan (561 cases) or diffusion-weighted MR imaging examination (409 cases) obtained at admission and a discharge diagnosis indicating whether a patient had actually had a stroke. The radiology requisition forms, available at the time of image interpretation, were classified as either indicating or not indicating a clinical suspicion of early stroke. Sensitivity, specificity, and accuracy of stroke detection were computed, stratified by the presence or absence of an available history indicating suspicion of stroke. Results were compared using the Fisher's exact two-tailed test. RESULTS: Unenhanced CT sensitivity was 52% (specificity, 95%) for the suspicion-of-stroke group and 38% (specificity, 89%) for the no-suspicion-of-stroke group (p = 0.008). Diffusion-weighted MR imaging sensitivity was 95% (specificity, 94%) for the suspicion-of-stroke group and 94% (specificity, 98%) for the no-suspicion-of-stroke group (p = 0.822). CONCLUSION: Availability of a clinical history indicating that early stroke is suspected significantly improves the sensitivity for detecting strokes on unenhanced CT without reducing specificity. In contradistinction, the availability of such a history did not significantly improve the sensitivity for detecting stroke using diffusion-weighted MR imaging. Whenever possible, relevant clinical history should be made available to physicians interpreting emergency CT scans of the head.     

Impact of clinical history on fracture detection with radiography

The effect of knowledge of localizing symptoms and signs in the detection of fractures was studied. Forty radiographs of the extremities were examined twice by seven radiologists; the sessions were separated by 4 months. In 26 cases, a subtle fracture was present; 14 cases were normal. In half of the cases at each session, the precise location of pain, tenderness, or swelling was provided. The observer was asked to determine if the case was normal or abnormal (provide the exact location of the fracture) and to indicate the degree of confidence in the diagnosis. Responses were converted to a numeric scale for analysis. Analysis of receiver operator characteristic parameters indicates that clues regarding location of trauma facilitate detection of fractures. The improvement is based largely on an increased true-positive rate without an increased false-positive rate, regardless of the decision criteria of the radiologist (overall willingness to "overread" or "underread"). This has direct clinical applicability and reinforces the plea of radiologists for precise clinical information.     

临床病史在CT平扫诊断早期大脑中动脉梗死中的价值:ROC分析

目的 :用受试者操作特性 (ROC)分析方法评价临床病史在CT平扫诊断早期大脑中动脉 (MCA)供血区梗死中的价值。方法 :回顾性分析证实的有或无早期MCA梗死 ( <12h)病例各 3 5例 ,3名医师在有或无病史情况下分别进行诊断 ,采用Windows 95版Rockit软件进行分析。结果 :无病史结果与有病史结果相比 ,诊断敏感性和准确率分别从 77%、67%增至 88%、88%,有病史结果ROC曲线下面积明显大于无病史时的面积 (P <0 .0 5 )。结论 :在CT平扫诊断早期MCA梗死中了解病史能提高诊断准确率     

Coincidence of developmental venous anomalies and other brain lesions: a clinical study

In a retrospective study of 72 patients with developmental venous anomalies (DVA) diagnosed by MRI and/or angiography, 33 associated lesions were found in 32 patients (44%). Study of the clinical files allowed classification of the patient population into three groups. In group 1 (11 patients: 34%) the symptoms were attributed with certainty to the associated lesions (1 brain infarction, 2 multiple sclerosis patients, 1 case of meningitis, and 7 patients with tumors). In group 2 (9 patients: 28%) the symptoms were probably caused by the associated lesion and not by the associated DVA (1 contusion, 1 Sturge-Weber angiomatosis, and 7 hemorrhagic DVA). In group 3 (12 patients: 38%) the symptoms were nonspecific (10 cavernous angiomas, 1 varix with sinus pericranii, and 1 ectasia of the middle cerebral artery. These findings sustain the theory that DVA is a congenital anomaly of the venous drainage of the brain, without pathological significance, and must be considered as an incidental finding. Correspondence to: G. Wilms     

Influence of display quality on radiologists' performance in the detection of lung nodules on radiographs

The purpose of this study was to evaluate the influence of display quality on radiologists' performance in the detection of lung nodules. Display systems with various technical properties were considered based on their general availability in a radiology department. Their quality was assessed by physical tests. Multireader-multicase receiver operating characteristic (ROC) analysis was used to evaluate observer performance. The area under the curve (Az) was used as a metric for detectability of simulated lung nodules with diameters of 5 mm and 10 mm, and peak contrast values ranging from 0.1 (subtle) to 0.4 (evident) that were digitally superimposed on normal chest radiographs. Three experienced radiologists interpreted a batch of 60 radiographs on five different display systems; four monitors (two liquid crystal display (LCD) and two cathode ray tube (CRT) monitors) and one printed hardcopy. The physical tests showed superior performance of the two LCD monitors. ROC analysis resulted in the following Az scores: LCD-5MP Az = 0.78, hardcopy Az = 0.77, LCDc-2MP Az = 0.75, CRT-5MP Az = 0.72 and CRTc-1MP Az = 0.71. Difference in Az scores between the LCD-5MP monitor and both the CRT-5MP (p = 0.04) and CRTc-1MP (p = 0.01) monitors was significant. The primary class CRT-5MP monitor that showed reduced observer performance failed to comply with physical acceptance requirements. Luminance response was particularly observed to be insufficient. The results indicate that a quality assurance program has the potential to detect non-optimised display systems that could otherwise result in reduced observer performance.     

Benign regenerative nodules in Budd-Chiari syndrome and other vascular disorders of the liver: radiologic-pathologic and clinical correlation.

Large regenerative nodules are benign liver lesions that are frequently seen in Budd-Chiari syndrome and less commonly in other vascular disorders of the liver or systemic conditions such as autoimmune disease, myeloproliferative disorders, and lymphoproliferative disorders. They are usually multiple, with a typical diameter of 0.5-4 cm. At pathologic analysis, large regenerative nodules are well-circumscribed, round lesions that may distort the contour of the liver. Only a minority of these nodules are detected at cross-sectional imaging. At multiphasic helical computed tomography, large regenerative nodules are markedly and homogeneously hyperattenuating on arterial dominant phase images and remain slightly hyperattenuating on portal venous phase images. Large regenerative nodules are bright on T1-weighted magnetic resonance images and show the same enhancement characteristics after intravenous bolus administration of gadolinium contrast material. They are predominantly isointense or hypointense relative to the liver on T2-weighted images. There is no evidence that large regenerative nodules degenerate into malignancy. If these nodules are misdiagnosed as multifocal hepatocellular carcinoma, patients might be denied transplantation or offered inappropriately aggressive therapy such as transcatheter arterial chemoembolization. Understanding the clinical setting and imaging appearance of large regenerative nodules can help avoid misdiagnosis as other hypervascular masses.     

多层螺旋CT胸部低剂量扫描发现肺结节的临床研究

目的 研究降低电流对发现肺结节，尤其是直径≤5mm结节的影响，并观察低剂量CT在胸部初步应用的影像效果。方法 对6例病理证实为肺内多发结节的尸检离体肺脏制成充气固定的肺标本，分别行多层螺旋CT的常规剂量(130mA)和低剂量CT(50、30、10mA)扫描。对40例体检者和60例转移瘤近期复查的患者行低剂量CT(30mA)扫描。记录直径≤5mm的结节的数目并判断影像有无伪影。根据诊断的把握度将结节分为肯定是结节、不能确定和肯定不是结节。对40例体检者及60例转移瘤仅评价影像的伪影情况。结果 肺标本研究中，低剂量各组(50、30、10mA)的Kappa值为0．515、0．242、0．154。经U检验，低剂量50mA组与常规剂量组结节的发现一致性较好。50、30、10mA组的敏感度分别为88．0％、78．4％、75．0％，阳性预测值分别为98％、94％、93％，准确度分别为85％、73％、69％。标本影像仅在10mA组中21幅(70％，21／31)图像的椎体旁的肺区见到细小条状伪影。100例病人的影像中仅在3例的肺尖可见到能影响小结节发现的条状伪影。结论 低剂量CT有望提高肺癌的早期发现。低剂量50mA组对直径≤5mm的结节能可靠发现。研究显示30mA可得到满意的影像质量。有条件者应开展低剂量CT筛查肺癌。     

Grey-scale inversion improves detection of lung nodules

Objective

The current study aims to establish whether detection of solitary pulmonary nodules can be improved by inverting the grey scale of posteroanterior (PA) chests.

Methods

30 PA chest images were presented on 2 occasions to 16 senior radiologists on either primary or secondary class displays in the standard or inverted mode. 15 images within each group contained a single nodule positioned in a range of anatomical sites. A receiver operating characteristic (ROC) methodology was used to explore differences between the presentation modes.

Results

Improved ROC scores were evident with inverted (Az 0.77) compared with standard (Az 0.73) (p=0.02) images; however, this difference was seen only with the primary displays. The benefits seen are most likely owing to increased nodule luminance with the inverted images, particularly when using primary displays.

Conclusion

This study demonstrates that the inverted image can offer advantages in lung nodule detection over the standard presentation mode when images are viewed on high-specification viewing systems. The study has demonstrated that there is an improvement in the detectability of lung nodules on an inverted image with a primary display monitor that is not evident with secondary displays. This is likely to be the result of increased nodule luminance on primary displays when images are presented in the inverted mode.In radiology there is an increasing use of digital display technology, which has had an enormous impact on medical image presentation [1-3]. This is no longer limited to CT or MRI, but is equally relevant to projectional radiography in which digital images are acquired using computed radiography, direct and indirect digital radiography and scanning technologies [3].In digital imaging systems raw image data are normally processed using look-up tables and other algorithms so that, when the image is first presented, it requires minimum reader time or effort to change contrast or brightness details. Nonetheless, further image processing techniques are often applied by the observer with the aim of increasing the diagnostic value of an image [4,5], and one such feature, which is available with almost all image workstations, is inversion of the grey scale of an image. Even though inversion algorithms have been available for as long as digital images, the diagnostic advantages of the inverted mode over the standard mode remain unclear.Previous work examining the efficacy of image inversion has focused on either dental or chest radiology. The dental research demonstrated higher levels of accuracy when measuring endodontic wires inserted into extracted pre-molars for the inverted compared with the standard mode [6]; no differences in periodontal bone loss measurements between inverted and unprocessed images [7]; and low diagnostic agreement between standard and inverted panoramic images for the detection of mental foramen and mandibular canal [8]. The chest studies showed that inversion mode is commonly used by intensive care unit clinicians to view the end point of line and tube placements but was inconclusive regarding detection sensitivity [9]; no advantage in inversion mode for nodule detection of pulmonary nodules, but the effect of familiarity with standard image and observer experience needs to be accounted for [10]; and better detection in the inverted mode than in the standard mode using film–screen systems assessed by residents-in-training [11]. Although these previous studies suggest that inverting the images may offer certain advantages in specific situations, further studies involving expert thoracic radiologists and a better understanding of the mechanisms for potential improvement with inversion are required.The current study focused on inversion of chest images and used a receiver operating characteristic (ROC) methodology to investigate the detectability of a solitary pulmonary nodule. Two classes of monitor displays were considered and images were assessed by expert chest radiologists.     

Automatic detection of pulmonary nodules at spiral CT: clinical application of a computer-aided diagnosis system

The aim of this study was to evaluate a computer-aided diagnosis (CAD) workstation with automatic detection of pulmonary nodules at low-dose spiral CT in a clinical setting for early detection of lung cancer. Eighty-eight consecutive spiral-CT examinations were reported by two radiologists in consensus. All examinations were reviewed using a CAD workstation with a self-developed algorithm for automatic detection of pulmonary nodules. The algorithm is designed to detect nodules with diameters of at least 5 mm. A total of 153 nodules were detected with at least one modality (radiologists in consensus, CAD, 85 nodules with diameter < 5 mm, 68 with diameter > or = 5 mm). The results of automatic nodule detection were compared to nodules detected with any modality as gold standard. Computer-aided diagnosis correctly identified 26 of 59 (38%) nodules with diameters > or = 5 mm detected by visual assessment by the radiologists; of these, CAD detected 44% (24 of 54) nodules without pleural contact. In addition, 12 nodules > or = 5 mm were detected which were not mentioned in the radiologist's report but represented real nodules. Sensitivity for detection of nodules > or = 5 mm was 85% (58 of 68) for radiologists and 38% (26 of 68) for CAD. There were 5.8+/-3.6 false-positive results of CAD per CT study. Computer-aided diagnosis improves detection of pulmonary nodules at spiral CT and is a valuable second opinion in a clinical setting for lung cancer screening despite of its still limited sensitivity.     

Computer-aided detection and automated CT volumetry of pulmonary nodules

With use of multislice computed tomography (MSCT), small pulmonary nodules are being detected in vast numbers, constituting the majority of all noncalcified lung nodules. Although the prevalence of lung cancers among such lesions in lung cancer screening populations is low, their isolation may contribute to increased patient survival. Computer-aided diagnosis (CAD) has emerged as a diverse set of diagnostic tools to handle the large number of images in MSCT datasets and most importantly, includes automated detection and volumetry of pulmonary nodules. Current CAD systems can significantly enhance experienced radiologists’ performance and outweigh human limitations in identifying small lesions and manually measuring their diameters, augment observer consistency in the interpretation of such examinations and may thus help to detect significantly higher rates of early malignomas and give more precise estimates on chemotherapy response than can radiologists alone. In this review, we give an overview of current CAD in lung nodule detection and volumetry and discuss their relative merits and limitations.     

Haemorrhage in intracerebral arteriovenous malformations: detection with MRI and comparison with clinical history

Fifty-one patients with 59 angiographically proven cerebral arteriovenous malformations (AVMs) were examinded by high-field MRI to detect blood breakdown products. Results were correlated with the history of intracranial bleeding. Evidence of previous episodes of haemorrhage was seen in 10 of 12 patients (83.3%) with verified bleeding, in 4 of 9 patients (44.4%) with symptoms which could suggest bleeding and in 6 of 30 patients (20%) with negative histories. Because of the known rebleeding rate and the increased risk of associated complications, identification of the subgroup who had had haemorrhage and should therefore be considered for surgery may be beneficial. MRI can make a contribution to management by demonstrating prior haemorrhage in patients with an inadequate clinical history.     

Impact of clinical history on radiographic detection of fractures: a comparison of radiologists and orthopedists

Are the methods used by radiologists in interpreting imaging studies different from those of attending physicians? We evaluated the influence that knowledge of localizing clinical signs has on the accuracy of fracture detection by orthopedic surgeons and compared the results with those of an identical study of radiologists performed earlier. The orthopedists studied had the same degree of experience as the radiologists. Forty radiographs of the extremities were examined twice by seven orthopedic surgeons. In 26 cases, a subtle fracture was present; 14 cases were normal. During one interpretation of the radiographs of each case, the precise location of pain, tenderness, or swelling was provided; during the other, this information was withheld. Analysis of receiver-operating-characteristic parameters indicates that the clues regarding location of trauma facilitate detection of fractures by orthopedists (an 11% improvement in Az, the area under the ROC curve, F[1,12] = 49.67, p less than .001). This finding is similar to the results of the earlier study with radiologists (a 6% improvement in Az, F[1,12] = 14.77, p less than .005). Statistical comparison of the two experiments showed that orthopedists depend on this information much more than do radiologists, demonstrated by a statistically significant prompting-by-specialty interaction (F[1,12] = 5.13, p less than .05). Localization clues improve ability of orthopedic surgeons to detect fractures in the trauma patient even more than they improve the ability of radiologists. The accuracy of the radiologist will suffer less than that of the orthopedist when localization clues are unavailable. Nonetheless, the findings show that localizing clues are important to both orthopedists and radiologists when searching for fractures.     

Pulmonary nodules: detection, assessment, and CAD

OBJECTIVE: The imaging of pulmonary nodules is an evolving and dynamic field. In this review, we discuss the detection and multitechnique characterization of pulmonary nodules, emphasizing the impact of technological advances on both noninvasive and invasive evaluation and surveillance. The potential contribution of MRI, evolving imaging-guided techniques, and computer applications are also discussed. CONCLUSION: Advances in MDCT and PET and the potential contribution of fast-imaging MRI sequences and computer applications should continue to improve our evaluation of the solitary pulmonary nodule.     

CT时间减影技术在肺结节检测中的应用

目的 探讨CT时间减影技术在检测肺结节中的应用价值.方法 回顾性分析80例CT图像(每例均有过去和当前的CT图像)和相应的CT减影图像,其中30例有肺结节(共75个结节)作为研究组,50例无肺结节作为对照组.2名高年资与2名低年资放射科医师分别首先分析普通CT图像,然后再同时分析普通图像与CT减影图像.阅读时诊断是否存在较前次增大、实性成分增多或者新发的结节并对诊断的肯定度进行评分.观察的结果采用受试者工作特征(ROC)曲线进行分析.结果 4名放射科医师使用CT减影图像前后的平均ROC曲线下面积(AUC)分别为0.860和0.925,两者有统计学差异(P<0.01).使用CT减影图像后,肺结节检出率由77.3%(58/75)提高到89.3%(67/75).结论 CT时间减影技术可以显著提高放射科医师的肺结节检出率,尤其是对靠近肺门的亚实性小结节,而且低年资医师受益更多.     

Cost-effectiveness of stereoscopic radiographs in detection of lung nodules

Detection of lung nodules was assessed using a series of radiographs which were either normal or showed only one nodule. Stereoscopic pairs were obtained in 26 cases (10 positive and 16 normal). A "singles" series comprising one radiograph from each pair was presented to each observer on three occasions. The pairs were later presented side by side and finally were viewed stereoscopically. The results indicate that a second shifted radiograph improves detection of lung nodules enough to be cost-effective. The shifted radiographs do not need to be viewed stereoscopically.