Selenium-based digital radiography versus high-resolution storage phosphor radiography in the detection of solitary pulmonary nodules without calcification: receiver operating characteristic curve analysis

OBJECTIVE: The purpose of this study was to compare selenium-based digital radiography with high-resolution storage phosphor radiography for the detection of solitary pulmonary nodules without calcification. MATERIALS AND METHODS: One hundred twenty-four patients underwent selenium-based digital radiography, high-resolution storage phosphor radiography, and chest CT for evaluation of pulmonary nodules. Thirty-one patients with pulmonary nodules smaller than 3 cm in diameter and 40 patients with normal lungs were selected for receiver operating characteristic curve analysis. Five board-certified radiologists who were unaware of the CT results independently reviewed each of the hard copies of selenium-based digital radiography and storage phosphor radiography, identified pulmonary nodules, and graded their confidence for the presence of each nodule. For each radiologist, we calculated the areas under the receiver operating characteristic curve (AUC) for selenium-based digital radiography and storage phosphor radiography. RESULTS: The average performance of selenium-based digital radiography (AUC = 0.72) was higher than that of high-resolution storage phosphor radiography (AUC = 0.64), which is statistically significant (p <0.05). CONCLUSION: Our results indicate that selenium-based digital radiography is superior to high-resolution storage phosphor radiography for detecting solitary pulmonary nodules without calcification.     

Calcification in pulmonary nodules: detection with dual-energy digital radiography

The authors undertook a clinical study to determine the accuracy of dual-energy digital radiography in revealing nodule calcification because calcification in a pulmonary nodule almost excludes the possibility of malignancy. Over a 6-month period, 61 patients with pulmonary nodules (less than or equal to 3 cm) or masses (greater than 3 cm) were examined on a prototype scanned projection unit using a dual-energy detector. In 49 of 61 patients, nodules were noncalcified, and in 12, they were calcified. In 57 patients, the benignancy or malignancy of nodules was established beyond reasonable doubt by pathologic confirmation in 38 and by strong inference in 19 (four patients with noncalcified solitary pulmonary nodules either refused further investigation or surgery or their follow-up was too short to permit exclusion of malignancy). Dual-energy radiography was found to be highly accurate in assessing the presence or absence of calcification in pulmonary nodules and thus in determining their benignancy or possible malignancy.     

Simulated pulmonary nodules: detection with dual-energy digital versus conventional radiography

Performance of a prototype dual-energy digital chest radiography unit in detecting calcified and noncalcified simulated pulmonary nodules was compared with that of a highly optimized, conventional system. Nodules ranging in size (0.5, 1.0, and 1.6 cm), in number (five to 11), and in calcium content (0-25 mg) were superimposed over the lungs of a frozen, unembalmed, human chest phantom. For each technique, six observers examined 50 posteroanterior projections with different randomized nodule locations. Detection consisted of locating and assigning a level of confidence to each perceived nodular opacity. The resulting plots of the true-positive fraction versus the mean number of false-positive calls per projection indicate that for both calcified and noncalcified nodules, the digital unit performed significantly better (P less than .01).     

Detection of pulmonary nodules by computed tomography.

In 11 of 23 patients, computed tomography of the chest detected pulmonary nodules that were not detected by conventional chest radiography or whole lung tomography. CT is recommended for patients suspected of having pulmonary metastasis and those with a solitary pulmonary nodule.     

Current evaluation of the solitary pulmonary nodule

The solitary pulmonary nodule is one of the most common radiologic findings. The best approach to its management remains controversial. In this article, the role of computed tomography in the evaluation of the solitary pulmonary nodule is reviewed. The potential contributions of digital radiography and magnetic resonance imaging of the chest to the evaluation of the pulmonary nodule are also discussed.     

Quantitative computed tomography evaluation of benign solitary pulmonary nodules

A retrospective evaluation of stable solitary pulmonary nodules was completed in 14 patients using a GE 8800 CT scanner and the Computerized Imaging Reference Systems, Inc., computed tomography chest phantom. Patients with a stable nodule for at least 24 months and no evidence of calcification within the nodule by plain radiography were selected for the study. Using the phantom, a quantitative assessment of nodule density was done in each patient. Of 14 nodules, five were categorized as benign. Linear conventional tomography was performed on these five patients, and only one had evidence of benign calcifications. All patients lived in an area endemic for Coccidioides immitis and six of 14 had culture, serologic, or skin test evidence of previous infection with C. immitis. Two of these six patients had nodules that were characterized as benign using the computed tomography chest phantom. This study indicates that the computed tomography chest phantom is useful in identifying benign nodules in patients living in an area endemic for C. immitis pulmonary infections.     

Computed tomography of the solitary pulmonary nodule

The value of computed tomography (CT) using thin-slice technique in the differentiation between benign and malignant pulmonary nodules was evaluated both experimentally and clinically. Experiments using a standard reference phantom and simulation nodules showed that CT number varies according to the size of the nodule and the difference of CT unit. A standard CT number above which a nodule should be considered as calcified and benign was first calculated for various sizes of nodules and then was applied to clinical cases. Motion artifact which can give falsely high CT numbers was also created and its characteristic appearance was identified. Clinically 101 cases of solitary pulmonary nodules whose diagnoses were confirmed either histologically or on follow-up were studied. There were 40 benign nodules, 53 primary lung cancers, and 8 metastatic lung tumors. There was no case of malignancy in which calcification was diagnosed to be present on CT. On the other hand, 14 of 40 benign nodules (35.0%) was diagnosed to contain calcium and therefore benign on CT. As for the margin of the nodule described on CT, a moderate to marked irregularity was predominantly seen in primary lung cancers, while most benign nodules and metastatic lung tumors had smooth margins. If CT criteria for benignancy are limited to the nodule both with calcification and smooth margin, 13 of 40 cases (32.5%) would be correctly diagnosed. CT is considered to be useful in distinguishing between benign and malignant solitary pulmonary nodules as far as herein described technique is observed.     

Development of a digital image database for chest radiographs with and without a lung nodule: receiver operating characteristic analysis of radiologists' detection of pulmonary nodules

OBJECTIVE: We developed a digital image database (www.macnet.or.jp/jsrt2/cdrom_nodules.html ) of 247 chest radiographs with and without a lung nodule. The aim of this study was to investigate the characteristics of image databases for potential use in various digital image research projects. Radiologists' detection of solitary pulmonary nodules included in the database was evaluated using a receiver operating characteristic (ROC) analysis. MATERIALS AND METHODS: One hundred and fifty-four conventional chest radiographs with a lung nodule and 93 radiographs without a nodule were selected from 14 medical centers and were digitized by a laser digitizer with a 2048 x 2048 matrix size (0.175-mm pixels) and a 12-bit gray scale. Lung nodule images were classified into five groups according to the degrees of subtlety shown. The observations of 20 participating radiologists were subjected to ROC analysis for detecting solitary pulmonary nodules. Experimental results (areas under the curve, Az) obtained from observer studies were used for characterization of five groups of lung nodules with different degrees of subtlety. RESULTS: ROC analysis showed that the database included a wide range of various nodules yielding Az values from 0.574 to 0.991 for the five categories of cases for different degrees of subtlety. CONCLUSION: This database can be useful for many purposes, including research, education, quality assurance, and other demonstrations.     

Clinical results of CsI-detector-based dual-exposure dual energy in chest radiography

The aim of this study was to compare the sensitivity and specificity of digital chest radiography alone with digital chest radiography combined with dual-energy chest radiography in the detection of small non-calcified pulmonary nodules. Standard and dual-energy radiographs were obtained with a flat-panel digital chest system. Four radiologists reviewed digital posteroanterior chest radiographs in random order either alone or in conjunction with dual-energy soft tissue and bone images. Twenty patients with a total of 59 pulmonary nodules (median 0.5 cm, range 0.3 – 2.5 cm) confirmed by computed tomography (HU 100) were included. A level of confidence for each diagnosis was documented using a rating scale of 1–5. Brunner and Langer's test was performed for statistical analysis. Subgroup analysis was performed for nodules greater than 1 cm, 1–0.5 cm, and <0.5 cm. For posteroanterior chest radiography, sensitivity was 33%, positive predictive value 83%, specificity 81%, and negative predictive value 30%. Review in conjunction with dual-energy images resulted in a sensitivity of 42%, positive predictive value 88%, specificity 85%, and negative predictive value 34%. The increase of nodule detection overall as well as for different size categories was significant (p<0.05). The increase of the confidence level rating was also significant (p<0.001). Dual energy added to standard posteroanterior chest radiography significantly improves the sensitivity, specificity, and confidence in detection of small non-calcified pulmonary nodules.     

Effect of greyscale liquid crystal displays of different resolutions on observer performance during detection of small solitary pulmonary nodules

Objective The aim of this study was to evaluate the effect of monochrome liquid crystal displays (LCDs) with different resolutions on observer performance during detection of small solitary pulmonary nodules. Methods Chest images of digital radiography were selected online from the hospital's picture archiving and communication system. Of the 164 images selected, small solitary non-calcified pulmonary nodules were present in 63 images and absent in 101 images. Observer performance was assessed among 3 extremely experienced, 3 very experienced and 3 moderately experienced radiologists, who independently interpreted these images on 2, 3 and 5 megapixel greyscale LCDs. A five-point confidence level rating scale was used to represent the presence of nodules: definite absence, probable absence, indetermination, probable presence and definite presence. The observers were requested to rank each image on the given display according to the presence of the pulmonary nodule. Observer performance was analysed in terms of receiver operating characteristics (ROCs). Results The areas under the ROC curves which represented the observer performance for the 2, 3 and 5 megapixel LCDs were found to be 0.705, 0.722 and 0.764, respectively, for the extremely experienced radiologists; 0.687, 0.712 and 0.721, respectively, for the very experienced radiologists; and 0.689, 0.696 and 0.711, respectively, for the moderately experienced radiologists. These differences were not statistically significant. Conclusion The observer performances for detection of small solitary non-calcified pulmonary nodules by radiologists with varying degrees of experience were comparable between the 2, 3 and 5 megapixel monochrome LCDs.     

Computed tomography of solitary pulmonary nodules: experience with scanning times longer than breath-holding

Thirty-one patients with solitary pulmonary nodules--18 benign and 13 malignant--proven by either tissue diagnosis or prolonged follow-up were evaluated by computed tomography (CT). A device (ACTA scanner 0100) with scanning times greater than breath-holding was used with full understanding of its related limitations. A retrospective study of the CT features of these nodules led us to establish several criteria for benign nodules. CT evidence of calcium is felt to be the most important feature of benignancy. In the absence of calcium, irregular nodule margins, perinodular fibrosis, satellite nodules, and pleural thickening opposite a peripherally situated nodule are helpful to suggest its benign nature.     

Solitary pulmonary nodules: Part I. Morphologic evaluation for differentiation of benign and malignant lesions.

The solitary pulmonary nodule is a common radiologic abnormality that is often detected incidentally. Although most solitary pulmonary nodules have benign causes, many represent stage I lung cancers and must be distinguished from benign nodules in an expeditious and cost-effective manner. Evaluation of specific morphologic features of a solitary pulmonary nodule with conventional imaging techniques can help differentiate benign from malignant nodules and obviate further costly assessment. Small size and smooth, well-defined margins are suggestive of but not diagnostic for benignity. Lobulated contour as well as an irregular or spiculated margin with distortion of adjacent vessels are typically associated with malignancy. There is considerable overlap in the internal characteristics (eg, attenuation, cavitation, wall thickness) of benign and malignant nodules. The presence of intranodular fat is a reliable indicator of a hamartoma. The presence and pattern of calcification can also help differentiate benign from malignant nodules. Computed tomography (CT) (particularly thin-section CT) is 10-20 times more sensitive than standard radiography and allows objective, quantitative assessment of calcification. Initial evaluation often results in nonspecific findings, in which case nodules are classified as indeterminate and require further evaluation to exclude malignancy. Growth rate assessment, Bayesian analysis, contrast material-enhanced CT, positron emission tomography, and transthoracic needle aspiration biopsy can be useful in this regard.     

相同分辨力不同品牌影像诊断显示器对孤立性肺结节识读的影响

目的：通过不同品牌间相同分辨力的影像诊断显示器对胸部数字化X线摄影（DR）肺结节检出准确率的比较,评价品牌之间显示器的诊断效能。方法：从图像存储与传输系统（PACS）数据库中搜寻本院2005年3月～2008年12月胸部DR中发现或可疑有肺结节者行CT检查,CT发现单发、直径≤30mm的结节,列为阳性组;而CT证实无结节者列入阴性组。5位医师分别应用三种品牌显示器用5分法：肯定有、可能有、不确定、可能无、肯定无,独立判断结节有无。利用识读结果绘制ROC曲线,并比较曲线下面积及各品牌显示器之间的诊断效能。结果：5位影像诊断医师在3个品牌显示器中对1～10mm组孤立性肺结节识读的总平均值分别为Az（A）=0.877±0.053,Az（B）=0.895±0.050,Az（C）=0.887±0.051,对10～30mm组孤立性肺结节识读的总平均值分别为Az（A）=0.891±0.045,Az（B）=0.901±0.044,Az（C）=0.892±0.045。所使用的三种显示器中,由于分辨力相同,3百万象素（3MP）,从ROC曲线中可以看出,曲线下的面积Az虽然是有差别的,但都接近于0.9,说明3MP的液晶显示器（LCD）在孤立性肺结节的诊断效能是比较高的,其中品牌B的面积最大。经过统计学检验,P值有所不同。结论：3MP显示器在肺结节识读影像上差异具有统计学意义,但总的诊断效能无明显差异。     

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.     

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.     

数字化断层融合技术对肺结节筛查应用的初步研究

目的：探讨数字化断层融合技术对肺结节的检出价值.方法：选取48例肺结节患者,先后分别行DR、断层融合（DTS）及CT检查.将CT检查结果作为判断肺结节的标准,另选择两位有3年以上工作经验的放射科医师,在已知每例患者CT所显示的结节位置后,分别观察胸片和数字断层融合图像上对相应部位结节的显示率,对结果进行x2检验.将结节依据直径大小分为3组（3～5 cm,5～10 cm和10～20 cm）后,对组与组之间的观察结果进行比较.结果：48例患者共发现结节59个,DR和DTS发现结节的敏感度分别为47.46%（28/59）和88.14%（52/59）,x2检验示差异有显著性意义（P〈0.01）,结节直径为5～10 mm组DTS较DR检出结节的敏感度最高.59个结节中,CT显示磨玻璃密度结节16个,其中,DTS可显示14个（14/16）,DR显示2个（2/16）,DTS较DR显示率明显高.结论：数字化断层融合较传统DR可显著提高肺结节的检出率,对磨玻璃密度结节的检出率较高.     

ROC Analysis of Detection of Metastatic Pulmonary Nodules on Digital Chest Radiographs with Temporal Subtraction

RATIONALE AND OBJECTIVES: The authors' purpose was to evaluate the effect of temporal subtraction on digital chest radiographs in the detection of metastatic pulmonary nodules. MATERIALS AND METHODS: The study included 21 cases with metastatic pulmonary nodule and 21 cases without metastatic nodule. Eleven radiologists, including eight residents and three certified radiologists, provided their confidence levels for the presence or absence of pulmonary nodules without and with temporal subtraction. Their performances without and with temporal subtraction were evaluated by means of receiver operating characteristic analysis with both independent and sequential tests. RESULTS: For the independent test, the radiologists' Az (area under the receiver operating characteristic curve) values were 0.871 without and 0.954 with temporal subtraction, compared with 0.882 and 0.955, respectively, for the sequential test. Diagnosis accuracy was significantly improved with the use of temporal subtraction. There was no significant difference in Az values between the independent and sequential tests. CONCLUSION: Temporal subtraction is useful in the detection of metastatic pulmonary nodules, and this technique augments the value of digital chest radiography.     

CT densitometry of pulmonary nodules in a frozen human thorax

The influence of (1) calcium concentration, (2) exposure technique, (3) reconstruction algorithm, (4) nodule size, and (5) nodule location on the CT attenuation values (CT density) of pulmonary nodules was examined in a frozen human thorax. Nodules with calcium concentrations of 0-310 mg/ml and diameters of either 0.95 or 1.59 cm were inserted into a frozen, unembalmed human thorax. The nodules were placed either at the lung apex or 4 cm below the tracheal carina. Each nodule was scanned on a GE CT 9800 scanner; five different exposure techniques were used. The slice thickness was uniformly 1.5 mm. As expected, increasing the kilovoltage caused a significant decrease in CT nodule density in all nodules with calcium concentrations greater than 80 mg/ml. The inverse relationship between kilovoltage and nodule density was exaggerated with increasing calcium concentration. A high-resolution (bone) algorithm gave a significantly higher CT number than did a smoothed (standard) algorithm, regardless of nodule size and location, but this difference could be attributed almost entirely to the edge-enhancement effect of the bone algorithm. The CT density of the larger nodules was significantly higher than that of the smaller nodules at calcium concentrations greater than 65 mg/ml for both standard and bone algorithms. Densities were significantly higher in the mid lung than in the apex with a standard algorithm, but this was not the case with a bone algorithm. The GE CT 9800 scanner had a linear response between CT density and increasing calcium concentration within the confines of a human thorax. A high-resolution (bone) reconstruction algorithm has higher spatial resolution but does show an edge-enhancing effect not found with the smoothed algorithm. Two major variables in CT densitometry for pulmonary nodules are the kilo electron voltage of the X-ray beam and the reconstruction algorithm used; these two parameters should be standardized, with a high kilovoltage and high-resolution algorithm favored on the GE CT 9800 scanner.     

Solitary pulmonary metastases in high-risk melanoma patients: a prospective comparison of conventional and computed tomography

A prospective comparison of chest radiography, conventional tomography, and computed tomography (CT) in the detection or confirmation of solitary pulmonary nodules was made in 42 patients with high propensity for pulmonary metastases due to advanced local (Clark level IV or V) or regional malignant melanoma. Unequivocal nodules were revealed by chest radiography in 11 patients, conventional tomography in 16, and computed tomography in 20 patients. Both plain films and tomography in three of these 20 were normal, but follow-up verified pulmonary metastases. Computed tomography detected more pulmonary nodules than conventional tomography in 11 patients in addition to identifying lesions in extrapulmonary sites. Therefore, chest CT is recommended before institution of immunotherapy or surgical removal of a solitary pulmonary melanoma metastasis. Once chemotherapy had been instituted for bulky regional or cutaneous involvement, however, the findings of either conventional or computed tomography were comparable in this study.     

数字化体层融合在肺结节探查中的初步应用

目的 探讨数字化体层融合在肺结节探查中的应用价值.方法 30例疑有肺内结节的患者,均先后行胸部X线平片、体层融合和CT检查.将上述影像资料传至后处理工作站,由2名具有3年以上胸部影像诊断经验的医师分别进行双盲法阅片,观察每例患者肺部结节的数量,每个肺结节的部位、大小.然后,2名阅片者再共同阅片,使单独阅片不一致的结果得到统一.以CT结果作为标准,分别计算胸部X线平片和体层融合探查肺结节的敏感性.采用配对四格表资料的X~2检验比较两者的差异性.结果 30例患者,胸部X线平片检查9例阴性,21例阳性,共发现肺结节40个.体层融合检查4例阴性,26例阳性,共发现肺结节89个.CT检查3例阴性,27例阳性,共发现肺结节102个.以CT作为标准对照,胸部X线平片探查肺结节的敏感性为27.4%(28/102),体层融合的敏感性为87.2%(89/102),差异有统计学意义(X~2=4.35,P<0.05).结论 数字化体层融合可显著提高肺结节探查的敏感性,可以作为胸部X线平片良好和必要的补充.