Errors in radiology


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Errors in radiology

  1. 1. L. Romano, A. Pinto (eds.), Errors in Radiology, © Springer-Verlag Italia 2012 19Errors in the Diagnosis of Lung NeoplasmsLuigia Romano, Antonio Pinto, and Carlo Muzj3L. Romano ( )Department of Diagnostic Radiological Imaging, “A. Cardarelli” Hospital,Naples, Italy3.1 IntroductionImaging diagnosis of lung cancer frequently occurs in the context of screen-ing. In other cases, nodules may be detected on a routine CT scan or chestradiograph in asymptomatic patients. These tumors, which tend to be smallerat diagnosis, are referred to as central or peripheral as they have not spreadbeyond their local confines. While the features of the lesions’ borders can besuggestive of malignancy, they are not diagnostic. However, the presence ofspiculation is thought to indicate a higher likelihood of malignancy [1] where-as clearly defined edges [2] may indicate an inflammatory process. Cavitation,frequently an indication of long-standing or advanced lung cancer, is mostcommonly seen in squamous cell lung cancer [3].The diagnosis of a subtle lung cancer at chest radiography remains a for-midable challenge. Several investigators [4-8] have described the substantialpitfalls of interpretation created by overlapping structures and by the smallsize and low conspicuity typical of many lesions. Notwithstanding the diffi-culty in making the diagnosis, missed lung cancer is the second-leading causeof malpractice claims against radiologists [9].Chest images contain a range of perceptual ambiguities that contribute to asignificant error rate in diagnosis [10]. Indeed, is not unusual to retrospective-ly discover significant radiological abnormalities in patients who are later diag-nosed with lung cancer [8]. The term missed cancer can refer to a lesion thatwas detected but misinterpreted by the radiologist [6]. The failure to detect alung cancer, under any conditions, would be considered as negligence.
  2. 2. 3.2 Misdiagnosis of Lung Cancer on Chest RadiographThe chest radiograph is a two-dimensional projection of a complex array ofthree-dimensional structures. Each of these structures, i.e., the pulmonary ves-sels, bones, and parts of the mediastinum, may project over the lung and there-by partly or totally obscure pulmonary lesions at chest radiography. Some lungnodules are small or inconspicuous because of ill-defined margination or lowopacity. Consequently, a radiologist may fail to detect the lesion or may dis-count it as a benign structure.Most overlooked lung neoplasms on chest radiographs are solitary pul-monary nodules. Missed cancer usually has a substantial upper lobe predilec-tion [4, 11]. This predominance probably reflects the tendency of bron-chogenic carcinoma to involve the upper lobes more frequently than otherregions [4]. The perihilar regions are less common sites of overlooked lungcancer. Radiologist-missed lung cancers on chest radiographs have beenreported to share the following characteristics: (a) most missed nodular can-cers are visually subtle, but they are not always very small (median diameter,16–20 mm); (b) missed cancers are located predominantly in the upper lobes;(c) superposing structures and distracting lesions are frequently present; and(d) image quality is commonly poor [4, 5, 9, 11]. The findings in the radiolo-gist-missed cancer series that served as the basis for those conclusions weresimilar to those reported in previous studies [5, 7], although image quality wasgenerally high.The role of the lateral chest radiograph in the detection of lung cancer hasbeen discussed for over 30 years [12, 13]. In the series by Shah et al. [7], onlythe lateral chest radiograph revealed the lung neoplasm retrospectively in twopatients (5%) and the cancer was better seen on the lateral radiograph than onthe frontal projection in one other patient (2%) in the same series. Theseresults are comparable to those of other series, in which the detection rate forlung cancer on the lateral radiograph vs. the frontal chest radiograph was2–4% [14, 15].Lung cancer nodules are frequently missed on chest radiographs by radiolo-gists in clinical practice, with reported error rates of 20–90% [14, 16] (Fig. 3.1).Even in observer performance studies, in which the participating radiologistsare aware that many lung cancers are included, up to 40% of previously missedcancers remain undetected [17]. In one classic study [14] of lung cancerdetected during the Mayo Lung Screening Project, 45 (90%) of 50 peripheraland 12 (75%) of 16 central lung lesions were visible in retrospect on filmsobtained 4 months prior to the radiograph on which the diagnosis was estab-lished (Fig. 3.2a, b). In several clinical series of missed lung cancer, in whichthe numbers of patients ranged from 27 to 40, the median diameter of suchlesions was fairly large (> 1.5 cm) [4-7]. Missed tumors were attributed tomultiple factors, including failure of perceptual analysis by the radiologist,lack of comparison with previous radiographs, inadequate awareness of clini-cal information, and deficiencies in film quality [6, 7].20 L.Romano et al.
  3. 3. 3.3 Source of Errors in Chest Film InterpretationThere are many sources of error in the radiographic diagnosis of lung cancer:image quality, lesion detection, lesion recognition, and communication of theradiological findings to the referring physician [18]. Lesion size is an impor-tant factor influencing detectability on chest radiographs; according to somereports, only 50% of 1-cm lesions are detected [19]. Lesion shape may alsoinfluence detectability, as sharply marginated lesions are found more easilythan spiculated or poorly defined cancers.In addition, technical features play an important role in the failure to diag-nose lung cancer [19]. On chest radiography, film contrast, density, and kVP3 Errors in the Diagnosis of Lung Neoplasms 21Fig.3.2 a Coronal reformatting CT image shows an irregular rounded nodule with a poorly definedborder, localized at the right upper pulmonary lobe (white arrow). Biopsy revealed a poorly dif-ferentiated cancer. b A lung nodule was visible (white arrow) retrospectively on the X-ray film ob-tained 4 months previouslya bFig.3.1 Missed cancer of themiddle pulmonary right field:a subtle low-density small nodule(white arrow) is partially hiddenby the superposing ribs
  4. 4. all influence lesion detection [9]. Manning et al. [20] reported that the major-ity of errors related to lung cancer missed on the posteroanterior chest radi-ograph were failures of decision rather than of detection, supporting the ideathat the complexity of the visual information in chest imaging makes it diffi-cult for observers to discriminate between normal anatomic structures andnodular pathological features, even when such features have been made visu-ally obvious by the imaging process.A missed diagnosis of a lung neoplasm can also be due to observer error.In the study of Kundel et al. [21] three types of observer error were described:scanning error (failure of the radiologist to fixate on the area of the lesion),recognition error, and decision-making error, which in the authors’ series wasthe most common [21]. A decision-making error is due to the incorrect inter-pretation of a malignant lesion as a normal structure after detection. Anotherform of observer error that may contribute to lesions being overlooked (includ-ing lung cancer) is the satisfaction of search (SOS) error [10], in which anabnormality is missed because another abnormality has been detected and fur-ther image interpretation subsequently discontinued. Sources of error in inter-pretation include the patient’s clinical history, the presence or absence of pre-vious studies, the index of suspicion, the presence of an abnormality, the read-ing room environment, and the level of interpreter vigilance.In case of evidence of a suspected lung neoplasm on chest plain film, it isimportant that the radiologist suggests the next appropriate imaging procedure(Fig. 3.3a, b). Indeed, the failure to do so is another cause of malpracticeclaims against radiologists. These recommendations or suggestions for addi-tional radiologic procedures must be appropriate and add meaningful informa-tion to clarify, confirm, or rule out the initial impression. The American22 L.Romano et al.Fig.3.3 a A chest X-ray film shows a poorly marginated opacity (white arrow) of the right lung inan asymptomatic smoker. b The axial CT image shows the irregular infiltrating edge of the nod-ule (white arrow) with distortion of the adjacent small vesselsa b
  5. 5. College of Radiology “Practice Guideline for Communication of DiagnosticImaging Findings” [22] states that “follow-up or additional diagnostic studiesto clarify or confirm the impression should be suggested when appropriate.”3.4 Errors in the Diagnosis of Lung Cancer on ChestComputed TomographyThe number of lung cancers missed at CT, as cited in the literature, has beenlimited probably because it is difficult to identify the missed cases among themany routine CT examinations performed in most medical centers [23, 24].Gurney [23] reported that nine lung cancers missed at CT were identified froma monthly tumor registry that was maintained for about 10 years; five of thesetumors were peripheral lung cancers < 3 mm in diameter, which was consid-ered as the threshold size for detectability. White et al. [24] reported 14 lungcancers overlooked at CT from about 37,500 chest CT scans at more than threeinstitutions; the most common characteristic among these cases was an endo-bronchial location.A more recent study of seven lung cancers missed at low-dose CT wasreported on by Kakinuma et al. [25], based on 5,418 lung cancer CT screeningstudies performed over a period of more than 3 years. In the study by Li et al.[26], 83 primary lung cancers were found during an annual low-dose CTscreening program and confirmed histopathologically at either surgery orbiopsy. Of these lung cancers, 32 were missed on 39 CT scans: on 23 scansowing to detection errors and on 16 scans owing to interpretation errors(Fig. 3.4a-d). In their interpretation error cases, 88% of the missed cancers, orthe features of these tumors, mimicked benign lesions and/or were associatedwith underlying lung disease. Missed cancers with linear, triangular, and irreg-ular patterns, similar to the patterns of benign lesions, were common findings,and the underlying lung diseases were due to other abnormalities, such asresidual tuberculosis (including pleural thickening) or residual or new inflam-matory lesions, emphysema, or lung fibrosis [26].Due to improvements in CT imaging technology, the detection of small pul-monary nodules has improved. The ability to detect small nodules is of para-mount importance in finding early-stage lung cancer. However, nodules < 1 cmin diameter often pose a dilemma, for both clinicians and patients, as they maybe difficult to biopsy and can easily be confused with normal anatomic struc-tures within the lung.3.5 ConclusionsLung cancer is the most frequently occurring cancer in the world; in the USAit is the second most commonly diagnosed cancer. Accurate imaging-basedstaging can have a significant impact on appropriate treatment and surgical3 Errors in the Diagnosis of Lung Neoplasms 23
  6. 6. options. The failure to detect, identify, or describe an abnormality that on aplain chest radiograph is subsequently shown to be lung cancer has potential-ly very serious consequences in medical malpractice litigation.Multiple strategies have been recommended to reduce the rate of missedlung cancer. These include scrupulous comparison of the current radiographicstudy with the results of previous examinations, avoidance of distracting find-ings leading to SOS errors, and the double reading of images. Each of theseapproaches has drawbacks related to workflow and the limitations of humanperception. Computer-aided detection (CAD) systems are increasingly beingintroduced as a “second reader” to assist in the evaluation of images of com-plex anatomic structure, and they can mark many visually subtle lung cancersthat may be missed by radiologists. Although false-positive detections arenumerous and potentially distracting, the majority of them are clearly due tosuperposing anatomic structures. Accordingly, the reduction of false-positivesshould be a priority in the development of CAD programs.24 L.Romano et al.Fig.3.4 a Admission radiograph from a young male with chest pain, hemoptysis, and breathless-ness: the right pulmonary artery is enlarged. b Axial CT scan obtained during the arterial phaseshows a typical filling defect of the right pulmonary artery (white arrow) due to a thromboembolism.c,dAfter 2 weeks of anticoagulant therapy, the axial CT scan obtained during the portal phase demon-strates contrast enhancement of the embolus (white arrow): the filling defect of the right pulmonaryartery is due to hilar cancerc da b
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  8. 8. 26. Li F, Sone S, Abe H et al (2002) Lung cancers missed at low-dose helical CT screening in ageneral population: comparison of clinical, histopathologic, and imaging findings. Radiology225:673-68326 L.Romano et al.