The effect of varying high pass filter parameters on the detectability of isolated pulmonary nodules in digitized chest images

The effect of image processing of digital radiographic data on lesion detectability in clinical images has not been systematically studied. In this experiment, we evaluated a low frequency suppression filter program applied to CT digital radiographic localization images (General Electric Scoutview). Three different filter parameters affecting edge enhancement and local image contrast were applied to a set of digital chest images. A standard observer detection experiment comparing the variously filtered digital images and standard chest radiographs in the detection of lung nodules (11 peripheral lung fields, one superimposed on aortic arch) was performed. Standard chest radiography was more sensitive than the digital chest images, although some improvement was noted with increase in local image contrast and edge enhancement. Both image formats were equally specific. Image processing would be better evaluated using a digital imaging system with better performance parameters.     

Differentiation of benign from malignant pulmonary nodules with digitized chest radiographs

To assess whether it is possible to distinguish benign from malignant solitary pulmonary nodules with digital techniques, a retrospective study of 68 patients with proved solitary nodules was performed. The conventional chest radiograph for each patient was digitized to 2,048 X 2,048 X 12 bits, and changes in the optical density within the nodule were analyzed. A number (the corrected gradient number) was then generated that reflected this variation. Striking differences were noted between 26 malignant nodules and 21 calcified granulomas. The technique was then applied to 21 benign nodules that had initially required thoracotomy or further study for diagnosis. In nine of these 21 patients (43%), the corrected gradient number allowed correct classification as a benign lesion.     

Subtle pulmonary nodules: detection and identification with storage phosphor radiographs and conventional chest films

To determine the value of digital storage-phosphor radiography (SR) on the detection and identification of subtle lung nodules, postero-anterior (PA) and lateral (LAT) film-screen (FR) chest radiographs were compared with isodose SR images of 45 patients with metastatic malignancies. The SR postprocessing was done with a particular mode previously optimized for routine chest radiography. Pulmonary metastases were found in 34 patients and were proved or excluded by CT (n = 28) or longterm follow-up FR (n = 17). Chest images were divided into four regions for evaluation of image quality, number of lung nodules per region and marked pulmonary structures by receiver-operating characteristics (ROC) analysis (45 patients; 125 nodules; 2810 observations; five readers). Of the nodules selected for an ROC study 82 % were 0.5–1.0 cm in diameter. Overall image quality was rated better for FR concerning lung fields (PA) and mediastinum/hilum (LAT). More lung-field nodules were detected on FR than on SR chest images (P < 0.05). Use of FR was superior to SR in the general identification of nodules (PA chest), especially concerning intermediate (P < 0.01) and subtle abnormalities (P < 0.05), whereas there was no significant difference for LAT chest images. Our results show, that currently FR still has advantages over SR in the detection and identification of subtle lung nodules in routine clinical radiography. Correspondence to: R. Scheck     

Pneumothorax and other lung diseases: effect of altered resolution and edge enhancement on diagnosis with digitized radiographs

Prior studies have shown that pneumothorax is one of the more difficult entities to diagnose with digitized radiography. This study was designed to test whether increasing resolution from 1.25 to 2.5 line pairs per millimeter (lp/mm) and image processing (edge enhancement from unsharp masking) would increase accuracy and confidence in the diagnosis of pneumothorax, as well as normal cases and other forms of lung disease. Conventional radiographs were digitized with use of a laser reader and then reformatted as film hard copy. Eleven observers read 35 cases reformatted in three different ways (1.25 lp/mm, 2.5 lp/mm, 1.25 lp/mm unsharp mask). The images with finer resolution (2.5 lp/mm) and unsharp mask images were superior to those with coarser resolution (1.25 lp/mm) for the diagnosis of pneumothorax. There was no difference in diagnostic accuracy for normal patients. For abnormalities other than pneumothorax, the unsharp mask images were significantly worse. Confidence in the diagnosis of pneumothorax and other abnormalities was highest with the finest resolution (2.5 lp/mm).     

Effect of kilovoltage on detectability of pulmonary nodules in a chest phantom.

A partial chest phantom was constructed to examine the effect of kilovoltage on the detectability of pulmonary nodules. Four different energies were studied: 100, 150, 200, and 300 kVp. Nodule detectability improved with increasing energies up to 200 kVp, but improvement was relatively small and was accompanied by an almost equal rise in the number of false positive readings. Patient exposures were least at 200 kVp. There seems to be no advantage in a 300 kVp technique, since nodule detectability decreased and patient exposures increased at this energy.     

The effect of varying spectral resolution on the quality of high spectral and spatial resolution magnetic resonance images of the breast

PURPOSE: To evaluate the effect of varying spectral resolution on image quality of high spectral and spatial resolution (HiSS) images. MATERIALS AND METHODS: Eight women with suspicious breast lesions and six healthy volunteers were scanned using echo-planar spectroscopic imaging (EPSI) at 1.5 Tesla with 0.75- to 1-mm in-plane resolution and 2.3- to 2.6-Hz spectral resolution. Time domain data were truncated to obtain proton spectra in each voxel with varying (2.6-83.3 Hz) resolution. Images with intensity proportional to water signal peak heights were synthesized. Changes in water signal line shape following contrast injection were analyzed. RESULTS: Fat suppression is optimized at approximately 10-Hz spectral resolution and is significantly improved by removal of wings of the fat resonance. This was accomplished by subtracting a Lorentzian fit to the fat resonance from the proton spectrum. The water resonance is often inhomogeneously broadened, and very high spectral resolution is necessary to resolve individual components. High spectral resolution is required for optimal contrast in anatomic features with very high T(2)* (e.g., within a lesion) and for detection of often subtle effects of contrast agents on water signal line shape. CONCLUSION: Despite a trade-off between the spectral resolution and signal-to-noise ratio, it is beneficial to acquire data at the highest spectral resolution currently attainable at 1.5 Tesla.     

Comparative studies on physical characteristics and clinical efficacy of conventional and digitized chest radiographs

Comparative studies were performed between digitized and conventional radiographs of the chest in terms of their physical characteristics and diagnostic efficacy. The purpose of these studies is to confirm the diagnostic capability of digitized image whether it can use for primary diagnosis in routine works. The results of two studies show good correlation each other. It is strongly suggested that the conventional chest radiographs should be digitized with 100 microns pixel in 12 bit density resolution.     

Neural network based detection of pulmonary nodules on chest radiographs

PURPOSE: We investigated the capabilities of an artificial neural network-based Computer-Aided Diagnosis (CAD) system in improving early detection of pulmonary nodules on chest radiographs. MATERIAL AND METHODS: We used a data-set of 145 digitized chest films. Two different radiologists read the radiographs to detect the sites of possible nodules. The system uses two neural networks trained on a training-set of 100 radiographs selected from the data-set. The first network is used to focus attention on the sites of potential nodules while the second calculates the likeliness of nodule presence in ROIs. The clinical test was performed on 45 more radiographs from the training-set, but different from those in the data-set, which were positive for both benign and malignant nodules. These latter plain films showed 65 nodular lesions which differed by shape and acquisition technique. RESULTS: Sensitivity was 89% in all radiographs while specificity, evaluated by ROI, and accuracy, were 98%. CONCLUSIONS: There are potential limitations in nodule detection on plain radiographs. Some of them are operator-dependent, such as nonsystematic investigation, lesion underestimation, and poor reading, and some are technique-dependent, such as X-ray beam/tube, low voltage, patient positioning, focus-film distance and development process. CADs may contribute to improving detection of pulmonary nodules because the false-negative rate is decreased and sensitivity consequently increased. The high sensitivity and specificity rates of neural networks encourage further trials on wider data-sets to help the radiologist in the early detection of pulmonary nodules.     

Effect of radiation dose level on the detectability of pulmonary nodules in chest tomosynthesis

Objective

To investigate the detectability of pulmonary nodules in chest tomosynthesis at reduced radiation dose levels.

Methods

Eighty-six patients were included in the study and were examined with tomosynthesis and computed tomography (CT). Artificial noise was added to simulate that the tomosynthesis images were acquired at dose levels corresponding to 12, 32, and 70 % of the default setting effective dose (0.12 mSv). Three observers (with >20, >20 and three years of experience) read the tomosynthesis cases for presence of nodules in a free-response receiver operating characteristics (FROC) study. CT served as reference. Differences between dose levels were calculated using the jack-knife alternative FROC (JAFROC) figure of merit (FOM).

Results

The JAFROC FOM was 0.45, 0.54, 0.55, and 0.54 for the 12, 32, 70, and 100 % dose levels, respectively. The differences in FOM between the 12 % dose level and the 32, 70, and 100 % dose levels were 0.087 (p?=?0.006), 0.099 (p?=?0.003), and 0.093 (p?=?0.004), respectively. Between higher dose levels, no significant differences were found.

Conclusions

A substantial reduction from the default setting dose in chest tomosynthesis may be possible. In the present study, no statistically significant difference in detectability of pulmonary nodules was found when reducing the radiation dose to 32 %.

Key Points

? A substantial radiation dose reduction in chest tomosynthesis may be possible. ? Pulmonary nodule detectability remained unchanged at 32 % of the effective dose. ? Tomosynthesis might be performed at the dose of a lateral chest radiograph.     

Gray-scale inversion radiographic display for the detection of pulmonary nodules on chest radiographs

The purpose of this study was to investigate gray-scale inversion in nodule detection on chest radiography. Simulated nodules were superimposed randomly onto normal chest radiographs. Six radiologists interpreted 144 chest radiographs during three reading sessions: traditional presentation, inverted gray-scale, and a choice session allowing use of traditional and gray-scale inverted views. Sensitivity and specificity were used to assess accuracy based on presence or absence of a nodule. Gray-scale inversion and choice display sessions resulted in significantly higher nodule detection specificity and decreased sensitivity compared to traditional display. Gray-scale inversion may decrease false-positive nodule findings during chest X-ray interpretation.     

The effect of periapical rarefying osteitis on cortical and cancellous bone. A study comparing conventional radiographs with computed tomography.

OBJECTIVE: To determine whether erosion of the cortical plate is necessary for successful radiographic identification of periapical rarefying osteitis. METHODS: Forty-two periapical osteitic lesions were diagnosed from periapical radiographs of 26 patients who were subsequently examined by cross-sectional computed tomography (CT). The relation of the lesions to the buccal and lingual cortical plates was determined and their size measured. RESULTS: The 42 lesions varied in size from 2 - 10 mm. Thirty one (74%) lesions diagnosed on the periapical radiographs were limited on CT to the cancellous bone with no erosion of the cortical plates. The 11 lesions with cortical erosion were randomly located throughout the jaws. Erosion was due to either the eccentric buccal or lingual location of the tooth apex, large size (>6 mm) of the lesion or narrowness of the jaw. CONCLUSIONS: Periapical lesions can be diagnosed from periapical radiographs while they are limited to the cancellous bone and before they have eroded the cortices.     

良性的术后胆道狭窄球囊扩张术的30年经验：长期结果

目的 确定经皮球囊扩张术对良性术后胆道狭窄的有效性。材料和方法 这项遵从HIPAA的回顾性研究经机构委员会批准,免除知情同意书。从1977年4月1日—2007年4月1日．85例良性胆道狭窄病人行经皮胆道球囊扩张术（PBBD）。在随访的75例病人中（男31例,女44例;平均年龄56岁：平均随访时间为8a）,84处胆道狭窄的112次治疗中总共行205次PBBD操作。     

孤立性肺结节CT与HRCT表现的对照评价

目的：评价CT与HRCT在检出和显示弧立性肺结节微细表现的价值。方法：35例中，36个孤立性结节经普通CT检查后对兴趣区行HRCT扫描。比较常规CT与HRCT显示结节的大小、位置、轮廓边缘、胸膜相邻关系的差异。结果：HRCT能充分显示孤立性肺结节内的细微结构：①结节内钙化；②脂肪成份；③密度变化；④空洞；⑤肿瘤样坏死。6例炎块中4例钙化，3例结核瘤中3例钙化，1例错构瘤中既有钙化又含脂肪成份。21例恶性结节中点状钙化2例，空洞6例，密度不均坏死10例。4个转移瘤中无以上表现。结论：HRCT在显示弧立性肺结节内部结构、形态等方面优于常规CT、是区分良恶性弧立性肺结节的有效方法。     

Evaluation of usefulness of color digital summation radiography for solitary pulmonary nodules on chest radiographs

Purpose The aim of this study was to evaluate the usefulness of novel color digital summation radiography (CDSR) for detecting solitary pulmonary nodules on chest radiographs by observers with different levels of experience. Materials and methods A total of 30 healthy controls and 30 patients with newly detected solitary pulmonary nodules were evaluated. Six radiologists and five residents evaluated three image sets: set A, current and prior radiographs only; set B, set A with temporal subtraction images; and set C, set A with CDSR. The observers were asked to rate each image set using a continuous rating scale. In addition, the reading time required for each set was recorded. Results The radiologists showed no significant differences in the mean A_z value between set A, set B, and set C. However, the residents showed significant differences between set A and set B and between set A and set C. In addition, for set B and set C, the mean reading time per case of all readers was significantly shorter than that for set A. Conclusion The detection capability of observers with little experience is comparable to that of experienced observers when reading radiographs with temporal subtraction images or with CDSR. The usefulness of CDSR is comparable to that of temporal subtraction.     

Improved detection of pulmonary nodules on energy-subtracted chest radiographs with a commercial computer-aided diagnosis software: comparison with human observers

Objective  

To retrospectively analyze the performance of a commercial computer-aided diagnosis (CAD) software in the detection of pulmonary nodules in original and energy-subtracted (ES) chest radiographs.     

Comparison of radiologist and CAD performance in the detection of CT-confirmed subtle pulmonary nodules on digital chest radiographs

OBJECTIVES: Detection of subtle pulmonary nodules on digital radiography is a challenging task for radiologists. The aim of this study was to evaluate the performance of a newly approved computer aided detection (CAD) system. MATERIALS AND METHODS: The sensitivity of 3 radiologists and of a CAD system for the detection of pulmonary nodules from 5 to 15 mm in size on digital chest radiography of 117 patients was compared. The reference standard was established by consensus reading of computed tomography scans by 2 experienced radiologists. Computed tomography scans and chest radiographs were performed within 4 weeks. Sixty-six pulmonary nodules from 42 patients, with a mean nodule diameter of 7.5 mm (standard deviation: 2.2 mm), were included in the statistical analysis. Seventy-five of the 117 patients did not have nodules from 5 to 15 mm of size. RESULTS: Two hundred and eighty-eight false-positive detections of the CAD system were found with an average of 2.5 false-positives per image. Sensitivity of the CAD system was 39.4% (95% confidence interval: 11.8%), when compared with 18.2% to 30.3% (95% confidence interval 9.3% to 11.1%) of the 3 radiologists. Substantial agreement for nodule detection ([kappa]N: 0.64-0.73) was found among the 3 radiologists, whereas only moderate agreement was found between the radiologists and the CAD performance ([kappa]N: 0.45-0.52). CONCLUSIONS: The CAD system's diagnostic sensitivity in detecting pulmonary nodules of 5 to 15 mm of size was superior to the 1 of radiologists. The CAD system may be used for assisting the radiologist in the detection of lung nodules on digital chest radiographs.     

双能量减影与常规胸片诊断肺内孤立性结节的临床对比

我们对40例经CT证实肺内确实存在孤立性结节患者行常规胸片和胸部DES检查,依此来探讨DES与常规胸片在显示肺内孤立性结节方面的优势和价值。1资料与方法搜集2004年5~12月经CT检查证实肺内有孤立性结节的患者40例,男24例,女16例;年龄32~70岁,平均49岁。所有患者均在CT检查3 d内进行常规胸片及DES检查,使用GE RevolutionXR/d型DR摄影系统。常规X线成像条件是110~120 kV,DES的2次曝光间隔为0·2 s,条件分别为120~140 kV和60~70 kV。焦点到平板探测器的距离为180 cm,投照体位均为后前位,深吸气屏(+)(-)2416346合计40 40χ2=6·270 P…