Diagnostic efficacy of handheld devices for emergency radiologic consultation.

OBJECTIVE: Orthopedic injury and intracranial hemorrhage are commonly encountered in emergency radiology, and accurate and timely diagnosis is important. The purpose of this study was to determine whether the diagnostic accuracy of handheld computing devices is comparable to that of monitors that might be used in emergency teleconsultation. SUBJECTS AND METHODS: Two handheld devices, a Dell Axim personal digital assistant (PDA) and an Apple iPod Touch device, were studied. The diagnostic efficacy of each device was tested against that of secondary-class monitors (primary class being clinical workstation display) for each of two image types-posteroanterior wrist radiographs and slices from CT of the brain-yielding four separate observer performance studies. Participants read a bank of 30 wrist or brain images searching for a specific abnormality (distal radial fracture, fresh intracranial bleed) and rated their confidence in their decisions. A total of 168 readings by examining radiologists of the American Board of Radiology were gathered, and the results were subjected to receiver operating characteristics analysis. RESULTS: In the PDA brain CT study, the scores of PDA readings were significantly higher than those of monitor readings for all observers (p < or = 0.01) and for radiologists who were not neuroradiology specialists (p < or = 0.05). No statistically significant differences between handheld device and monitor findings were found for the PDA wrist images or in the iPod Touch device studies, although some comparisons approached significance. CONCLUSION: Handheld devices show promise in the field of emergency teleconsultation for detection of basic orthopedic injuries and intracranial hemorrhage. Further investigation is warranted.

Ambient lighting: effect of illumination on soft-copy viewing of radiographs of the wrist.

OBJECTIVE: The aim of the work was to establish optimum ambient light conditions for viewing radiologic images of the wrist on liquid crystal display monitors. MATERIALS AND METHODS: Five ambient light levels were investigated: 480, 100, 40, 25, and 7 lux. Seventy-nine experienced radiologists were asked to examine 30 posteroanterior wrist images and decide whether a fracture was present. All images were displayed on liquid crystal display monitors. Receiver operating characteristic analysis was performed, and the numbers of false-positive and false-negative findings were recorded. RESULTS: For all the radiologists, greater area under the receiver operating characteristic curve and lower numbers of false-positive and false-negative findings were recorded at 40 and 25 lux compared with 480 and 100 lux. At 7 lux, the results were generally similar to those at 480 and 100 lux. The experience and knowledge of radiologists specializing in imaging of musculoskeletal trauma appeared to compensate in part for inappropriate lighting levels. CONCLUSION: Typical office lighting and current recommendations on ambient lighting can reduce diagnostic efficacy compared with lower levels of ambient lighting. If, however, no light other than that of the monitor is used, results are similar to those with excessive levels of lighting. Careful control of ambient lighting is therefore required to ensure that diagnostic accuracy is maximized, particularly for clinicians not expert in interpreting posteroanterior wrist images.

The impact of greyscale inversion for nodule detection in an anthropomorphic chest phantom: a free-response observer study.

OBJECTIVE:: The aim of this work was to assess the impact of greyscale inversion on nodule detection on posteroanterior chest X-ray images. Previous work has attempted this, with no consensus opinion formed. We assessed the value of "fast-flicking" between standard and inverted display modes for nodule detection. METHODS:: Six consultant radiologists (with 5-32 years' reporting experience) completed an observer task under the free-response paradigm. An anthropomorphic chest phantom was loaded with 50 different configurations of simulated nodules (1-4 nodules per case) measuring 5, 8, 10 and 12 mm in spherical diameter; each configuration represented a single case. In addition, 25 cases contained no nodules. Images were displayed in three modes: (i) standard, (ii) inverted and (iii) fast-flicking between standard and inverted display modes. Each observer completed the study in a different order of display (i, ii, iii) using a calibrated 5-megapixel monitor. Nodules were localized with mouse clicks and ratings assigned using a 1-10 discrete slider-bar confidence scale. Rjafroc (Pittsburgh, PA) was used for data analysis; differences in nodule detection performance were considered significant at 0.05. RESULTS:: The observer-averaged weighted jackknife alternative free-response receiver-operating characteristic figures of merit were 0.715 (standard), 0.684 (inverted) and 0.717 (fast-flicking). Random-reader fixed-case analysis revealed no statistically significant difference between any treatment pair [F(2,8) = 1.22; p = 0.345]. CONCLUSION:: No statistically significant difference in nodule detection was found for the three display conditions. ADVANCES IN KNOWLEDGE:: We have investigated the impact of fast-flicking between standard and inverted display modes for the detection of nodules. We found no benefit.

A free-response evaluation determining value in the computed tomography attenuation correction image for revealing pulmonary incidental findings: a phantom study.

RATIONALE AND OBJECTIVES: The purpose of this study was to compare lesion-detection performance when interpreting computed tomography (CT) images that are acquired for attenuation correction when performing single photon emission computed tomography/computed tomography (SPECT/CT) myocardial perfusion studies. In the United Kingdom, there is a requirement that these images be interpreted; thus, it is necessary to understand observer performance on these images. MATERIALS AND METHODS: An anthropomorphic chest phantom with inserted spherical lesions of different sizes and contrasts was scanned on five different SPECT/CT systems using site-specific CT protocols for SPECT/CT myocardial perfusion imaging. Twenty-one observers (0-4 years of CT experience) searched 26 image slices (17 abnormal, containing 1-3 lesions, and 9 normal, containing no lesions) for each CT acquisition. The observers marked and rated perceived lesions under the free-response paradigm. Four analyses were conducted using jackknife alternative free-response receiver operating characteristic (JAFROC) analysis: (1) 20-pixel acceptance radius (AR) with all 21 readers, abbreviated to 20/ALL analysis, (2) 40-pixel AR with 21 readers (40/ALL), (3) 20-pixel AR with 14 readers experienced in CT (20/EXP), and (4) 20-pixel AR with 7 readers with no CT experience (20/NOT). The significance level of the test was set so as to conservatively control the overall probability of a type I error to <0.05. RESULTS: The mean JAFROC figure of merit (FOM) for the five CT acquisitions for the 20/ALL study were 0.602, 0.639, 0.372, 0.475, and 0.719 with a significant difference in lesion-detection performance evident between all individual treatment pairs (P < .0001) with the exception of the 1-2 pairing, which was not significant (these differed only in milliamp seconds). System 5, which had the highest performance, had the smallest slice thickness and the largest matrix size. For the other analyses, the system orderings remained unchanged, and the significance of FOM difference findings remained identical to those for 20/ALL, with one exception: for 20/EXP analysis the 1-2 difference became significant with the higher milliamp seconds superior. Improved detection performance was associated with a smaller slice thickness, increased matrix size, and, to a lesser extent, increased tube charge. CONCLUSIONS: Protocol variations for CT-based attenuation correction (AC) in SPECT/CT imaging have a measurable impact on lesion-detection performance. The results imply that z-axis resolution and matrix size had the greatest impact on lesion detection, with a weaker but detectable dependence on the product of milliamp and seconds.

The value of observer performance studies in dose optimization: a focus on free-response receiver operating characteristic methods.

Receiver operating characteristic (ROC) analysis has been successfully used in radiology to help determine the combined success of system and observer. There is great value in these methods for assessing new and existing techniques to see if diagnostic accuracy can be improved. Within all aspects of radiology there should be compliance with the as-low-as-reasonably-achievable principle, which requires optimization of the diagnostic suitability of the image. Physical measures of image quality have long been used in the assessment of system performance, but these alone are not sufficient to assess diagnostic capability. It is imperative that the observer be included in any assessment of diagnostic performance. The free-response ROC paradigm has been developed as a statistically powerful advancement of traditional ROC analysis that allows a precise interpretation of complex images by adding location information to the level of observer confidence. The following review of free-response ROC methodology will explain how observer performance methods can be valuable in image optimization, including examples of how these have already been successful in hybrid imaging.

Viewing another person's eye movements improves identification of pulmonary nodules in chest x-ray inspection.

Double reading of chest x-rays is often used to ensure that fewer abnormalities are missed, but very little is known about how the search behavior of others affects observer performance. A series of experiments investigated whether radiographers benefit from knowing where another person looked for pulmonary nodules, and whether the expertise of the model providing the search behavior was a contributing factor. Experiment 1 compared the diagnostic performance of novice and experienced radiographers examining chest x-rays and found that both groups performed better when shown the search behavior of either a novice radiographer or an expert radiologist. Experiment 2 established that benefits in performance only arose when the eye movements shown were related to the search for nodules; however, only the novices' diagnostic performance consistently improved when shown the expert's search behavior. Experiment 3 reexamined the contribution of task, image, and the expertise of the model underlying this benefit. Consistent with Experiment 1, novice radiographers were better at identifying nodules when shown either a naïve's search behavior or an expert radiologist's search behavior, but they demonstrated no improvement when shown a naïve model not searching for nodules. Our results suggest that although the benefits of this form of attentional guidance may be short-lived, novices can scaffold their decisions based on the search behavior of others.