Dynamic computed tomography in solitary pulmonary nodules

OBJECTIVE: To evaluate the utility of dynamic computed tomography (CT) imaging in the management of solitary pulmonary nodules. METHODS: We examined solitary pulmonary nodules in 45 patients. The nodules included in the study were solid, homogenous, and spherical or oval-shaped in precontrast images. Nodules that had calcification or fat density were excluded from the study. We were not able to obtain clinical or pathological diagnosis of the nodules in 23 patients, and we excluded these patients from statistical analysis. Patients were examined with 2-mm collimation and 1-mm reconstruction interval. Computed tomography examinations were done before and after injection of contrast material. Computed tomography scans of the nodule were obtained in the first, second, third, fourth, and fifth minutes after contrast injection. RESULTS: The malignancy prevalence was 40%. The mean enhancement of malignant nodules were significantly higher than the benign ones. Also, the peak attenuation value obtained after the administration of contrast material was 82.44 +/- 19.56 HU in malignant lesions and 54 +/- 23.10 HU in benign ones, with statistical significance (P = 0.006). Using enhancement values greater than 15 HU as a threshold for malignancy, the calculated sensitivity, specificity, positive and negative predictive values, and accuracy of the dynamic CT examination were 100%, 69.2%, 69.2%, 100%, and 81%, respectively. CONCLUSION: Dynamic CT imaging demonstrates significantly greater enhancement in malignant nodules than in benign ones. Lung nodule enhancement of 15 HU or less strongly indicates benignity.     

Solitary pulmonary nodules: dynamic enhanced multi-detector row CT study and comparison with vascular endothelial growth factor and microvessel density

PURPOSE: To evaluate enhancement dynamics of solitary pulmonary nodules at multi-detector row computed tomography (CT) and to correlate results with extent of tumor angiogenesis in pathologic specimens. MATERIALS AND METHODS: One hundred thirty-one patients with solitary pulmonary nodules underwent unenhanced thin-section CT, followed by dynamic helical CT (throughout the nodule for 30 mm along the z-axis [13 images] and at 20-second intervals for 3 minutes [130 images total]) after intravenous injection of 120 mL of contrast medium. Diagnosis of malignancy or benignancy was assigned in 109 patients, and follow-up imaging suggested benignancy in the remaining 22. CT findings were analyzed for peak attenuation, net enhancement, and enhancement dynamics. In 54 patients with surgical diagnoses, Pearson correlation coefficient was used to correlate enhancement pattern with extent of microvessel density and vascular endothelial growth factor (VEGF) staining. RESULTS: With 30 HU or more of net enhancement as a cutoff value in differentiation of malignant and benign nodules, sensitivity for malignant nodules was 99% (69 of 70 malignant nodules), specificity was 54% (33 of 61 benign nodules), positive predictive value was 71% (69 of 97 malignant readings), negative predictive value was 97% (33 of 34 benign readings), and accuracy was 78% (102 of 131 nodules). Peak attenuation was correlated positively with extent of microvessel density (r = 0.369, P =.006) and VEGF staining (r = 0.277, P =.042). Malignant nodules showed significantly higher VEGF expression (P =.009) than that of benign nodules. CONCLUSION: Dynamic enhancement with multi-detector row CT shows high sensitivity and negative predictive values for diagnosis of malignant nodules but low specificity because of highly enhancing benign nodules. Extent of enhancement reflects underlying nodule angiogenesis.     

Solitary pulmonary nodule: CT evaluation of enhancement with iodinated contrast material--a preliminary report.

The authors hypothesized that the degree of contrast material enhancement of a pulmonary nodule, measured with computed tomography (CT), may indicate the likelihood of malignancy. Fifty-two patients with uncalcified solitary pulmonary nodules (diameter, 6-30 mm) were studied. Five single serial thin-section CT scans were obtained at 1-minute intervals after injection of 100 mL of nonionic contrast material. Twenty-two patients were excluded because the diagnosis was not clearly established: The observation period was less than 2 years, or the examination was technically inadequate. Malignant nodules were identified in 23 of the 30 remaining patients, and benign nodules were identified in seven. Within the first 2 minutes after the injection, all the malignant nodules had enhanced by 20 HU or greater (only one benign nodule had that degree of enhancement). The authors conclude that the degree of contrast material enhancement of pulmonary nodules as measured with CT may indicate the likelihood of malignancy.     

Solitary pulmonary nodules: dynamic contrast-enhanced MR imaging--perfusion differences in malignant and benign lesions

PURPOSE: To determine whether dynamic contrast material-enhanced magnetic resonance (MR) imaging with use of kinetic and morphologic parameters reveals statistically significant differences between malignant and benign solitary pulmonary nodules. MATERIALS AND METHODS: Fifty-eight patients met the inclusion criteria of a solitary 5-40-mm pulmonary nodule without calcification or fat at computed tomography. Fifty-one patients were examined successfully; 46 received a histologic diagnosis, and five received a diagnosis by means of observation over 2 years. Dynamic MR images were acquired every 10 seconds for a total of 4 minutes. Diagnostic characteristics for differentiation were examined by using threshold values for maximum peak enhancement, slope of enhancement, and washout. Receiver operating characteristic curves were calculated to test the usefulness of these parameters. The diagnostic performance of a combination of curve profiles and morphologic contrast material distribution were tested by using a decision tree. RESULTS: Frequency of malignancy was 53% (27 of 51 nodules). Malignant nodules showed stronger enhancement with a higher maximum peak and a faster slope (P <.001). Significant washout (>0.1% increase in signal intensity per second) was found only in malignant lesions (14 of 27 lesions). Sensitivity, specificity, and accuracy were 96%, 88%, and 92%, respectively, for maximum peak; 96%, 75%, and 86% for slope; and 52%, 100%, and 75% for washout. When curve profiles and morphologic enhancement patterns were combined, sensitivity increased to 100%. CONCLUSION: Dynamic MR imaging delineates significant kinetic and morphologic differences in vascularity and perfusion between malignant and benign solitary pulmonary nodules. Washout seems to be highly specific for malignancy.     

Tissue characterization of solitary pulmonary nodule: comparative study between helical dynamic CT and integrated PET/CT.

Recent advances in the technology of helical multidetector CT allow precise evaluations of nodule hemodynamics. In addition, the efficacy of tissue characterization has improved, and now sensitivity and specificity of >90% are achieved. Moreover, the efficacy of PET for the tissue characterization of solitary pulmonary nodules (SPNs) has also become of importance. The purpose of this study was to compare the diagnostic accuracy of helical dynamic (HD) CT (HDCT) and integrated PET/CT for pulmonary nodule characterization. METHODS: One hundred nineteen patients with an SPN underwent both HDCT (unenhanced scans, followed by series of images at 30, 60, 90, 120 s and at 5 and 15 min after intravenous injection of contrast medium) and integrated PET/CT. On HDCT, a nodule was regarded as malignant with a net enhancement of > or =25 Hounsfield units (HU) and a washout of 5-31 HU. On integrated PET/CT, nodules were considered malignant with a > or =3.5 maximum standardized uptake value and an 18F-FDG uptake greater than that of mediastinal structures. The sensitivity, specificity, and accuracy of the 2 modalities for malignancy were compared using the McNemar test. RESULTS: There were 79 malignant and 40 benign nodules. The sensitivity, specificity, and accuracy for malignancy on HDCT were 81% (64/79 nodules), 93% (37/40), and 85% (101/119), respectively, whereas those on integrated PET/CT were 96% (76/79), 88% (35/40), and 93% (111/119), respectively (P = 0.008, 0.727, and 0.011, respectively). All malignant nodules were interpreted correctly on either HDCT or PET/CT. CONCLUSION: Integrated PET/CT is more sensitive and accurate than HDCT for the malignant nodule characterization; therefore, PET/CT may be performed as the first-line evaluation tool for SPN characterization. Because HDCT has high specificity and acceptable sensitivity and accuracy, it may be a reasonable alternative for nodule characterization when PET/CT is unavailable.     

动态增强CT扫描对孤立性肺结节的诊断价值

目的:探讨动态增强CT扫描对良、恶性孤立性肺结节(SPN)的诊断价值.方法:时40例SPN患者行同层动态CT增强扫描,分别在平扫及增强后30s、60s、120s和180s测量病灶的CT值,获得病灶的时间-密度曲线(TAC),并进行统计学分析.结果:小肺癌与肺炎性结节、结核瘤的平扫CT值无显著差异.增强扫描小肺癌与结核瘤的CT强化程度有显著差异,但炎性结节与小肺癌的CT强化程度无显著差异.小肺癌、炎性结节,结核瘤三种病变的TAC形态不同.结论:动态增强CT扫描能显示SPN的强化特征并有助于定性诊断,是鉴别SPN良、恶性的有效影像学方法.     

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.     

CT征象联合肿瘤标志物对孤立性肺结节良恶性的鉴别诊断分析

目的 探讨CT征象联合肿瘤标志物对孤立性肺结节良恶性的鉴别诊断价值.方法 选取70例孤立性肺结节患者,行高分辨率CT、肿瘤标志物检查及病理检查.以病理组织学检查结果分为恶性结节组39例,良性结节组31例,对比两组CT征象和肿瘤标志物水平差异,运用受试者工作特征曲线(ROC)分析CT联合肿瘤标志物检测鉴别孤立性肺结节良恶...     

双能CT对孤立性肺结节的诊断价值

目的:探讨双能CT对孤立性肺结节(SPN)的诊断价值.方法:采用双能CT(管电压为80和140kVp)对水模、体模、47例平扫CT无明显钙化的SPN(恶性31例,良性16例)进行扫描,测量其CT值变化,计算病灶内钙质含量,比较良恶性SPN的CT值变化及钙质含量.结果:良性SPN的CT值变化中位数为5HU,恶性SPN为4...     

Peripheral solitary pulmonary nodule: CT findings in patients with pulmonary emphysema

PURPOSE: To analyze retrospectively the computed tomographic (CT) features of peripheral noncalcified solitary pulmonary nodules in patients with and those without emphysema. MATERIALS AND METHODS: The authors' institutional review board required neither its approval nor patient informed consent for this retrospective study. The authors retrospectively reviewed 2-mm-thick CT images of 41 nodules (21 malignant, 20 benign) in 41 patients with emphysema (age range, 58-88 years; mean, 71.9 years) and 40 nodules (20 malignant, 20 benign) in 40 patients without emphysema (age range, 50-85 years; mean, 69.2 years). Two radiologists who were unaware of the diagnosis independently evaluated the shape and margin of the nodule, recorded the presence of ground-glass opacities and air bronchograms, and classified nodules into two diagnostic categories: malignant and benign. Final decisions were reached by consensus. For quantitative assessment of the nodules, the fractal dimensions of the nodule interfaces and circularity of the nodule shape were calculated with an image-processing program, and the percentage of the nodule surrounded by emphysema was obtained. Statistical comparisons were made with a chi(2) or Fisher exact test and the Mann-Whitney U test. RESULTS: In patients with emphysema, there were no significant differences in fractal dimension, circularity, or frequency of lobulation or spiculation between malignant and benign nodules. Of the 41 nodules in patients with emphysema, 26 (63%) were correctly diagnosed. Thirteen benign nodules (65%) were diagnosed as malignant in patients with emphysema. Of the 40 nodules in nonemphysematous lungs, 37 (93%) were correctly diagnosed. The mean percentage of emphysema around the nodule was greater for misdiagnosed nodules than for correctly diagnosed nodules (P = .003). CONCLUSION: Malignant and benign nodules associated with emphysema exhibited considerably more overlap in CT features than did nodules in nonemphysematous lungs.     

Development of a novel computer-aided diagnosis system for automatic discrimination of malignant from benign solitary pulmonary nodules on thin-section dynamic computed tomography

OBJECTIVES: As an application of the computer-aided diagnosis of solitary pulmonary nodules (SPNs), 3-dimensional contrast-enhanced (CE) dynamic helical computed tomography (HCT) was performed to evaluate temporal changes in the internal structure of nodules to differentiate between benign nodules (BNs) and malignant nodules (MNs). METHODS: There were 62 SPNs (35 MNs and 27 BNs) included in this study. Scanning (2-mm collimation) was performed before and 2 and 4 minutes after CE dynamic HCT. The CT data were sent to a computer, and the pixels inside the nodule were characterized in terms of 3 parameters (attenuation, shape index, and curvedness value). RESULTS: Based on the CT data at 4 (MN: 1.81-27.1, BN: -42.8 to -3.29) minutes after CE-dynamic HCT, a score of 0 or higher can be assumed to indicate an MN. CONCLUSIONS: Three-dimensional computer-aided diagnosis of the internal structure of SPNs using CE dynamic HCT was found to be effective for differentiating between BNs and MNs.     

Multi-detector row spiral CT pulmonary angiography: comparison with single-detector row spiral CT.

PURPOSE: To compare vascular conspicuity and ability to connect pulmonary arterial branches on pulmonary angiograms obtained with helical multi-detector row computed tomography (CT) with those on pulmonary angiograms obtained with helical single-detector row CT. MATERIALS AND METHODS: Of 93 consecutive patients suspected of having pulmonary embolism, 48 underwent scanning with multi-detector row CT and 45 with single-detector row CT; scans were obtained in 9 seconds and 28 seconds with 2.5-mm and 3.0-mm collimation, respectively. The lungs were divided into three zones: central, middle, and peripheral. Two independent observers used five-point grading scales. RESULTS: Conspicuity of pulmonary arteries in the central zone was ranked equal (median of 5), but in the middle and peripheral zones it was significantly higher at multi-detector row CT than at single-detector row CT (median 5 vs 4 and 4 vs 3, P < .001, respectively). In addition, multi-detector row CT improved the ability to connect peripheral arteries with their more centrally located pulmonary artery of origin in the peripheral but not the middle zone on transverse images and in both zones on multiplanar images. Viewing with a modified window setting (width, 1,000 HU; level, -100 HU) significantly increased pulmonary arterial conspicuity. Contrast material column in the pulmonary arteries was significantly more homogeneous at multi-detector row CT. CONCLUSION: Use of multi-detector row CT significantly improves pulmonary arterial visualization in the middle and peripheral lung zones.     

螺旋CT动态增强扫描对孤立性肺结节定性诊断的价值

目的:分析良恶性孤立性肺结节(SPN)的动态强化特点,探讨动态SCT增强扫描对SPN定性诊断的价值。方法:对50例SPN患者进行螺旋CT同层动态增强扫描,对比剂总量100ml,注射流率3ml/s,延迟15s开始扫描,至180s结束,测量结节中心增强前后的CT值,分析最大强化值及时间-密度曲线(TAC),全部病例经手术病理证实。结果:肺炎性结节及恶性结节均显著强化,肺炎性结节强化峰值的时间较肺癌结节延迟。恶性结节的TAC表现为陡峭的上升支后有一较长的平台期,炎性结节的TAC表现为上升支平缓,部分见降支。结核球等其它良性SPN无明显强化。结论:动态SCT增强扫描对SPN定性诊断有较高价值。SPN的强化峰值及TAC形态有助于良、恶性病变的鉴别诊断。     

Detection of pulmonary metastases with multi-detector row CT scans of 5-mm nominal section thickness: autopsy lung study

PURPOSE: To determine the effect of changing pitch and collimation on depiction of pulmonary metastases on scans of 5-mm section thickness obtained with multi-detector row computed tomography (CT) compared with those obtained with single-detector row CT. MATERIALS AND METHODS: In five autopsy lungs, 1,013 metastatic 0.5-30.0-mm nodules were detected at helical CT with 1-mm collimation and histopathologically diagnosed as metastases. Each nodule was numbered, and its localization was recorded as the standard for subsequent studies. Four types of scans of 5-mm section thickness were obtained with multi-detector row CT and four sets of helical pitch and table speed, respectively, as follows: set A, 3:1 and 7.5 mm per rotation; set B, 6:1 and 15 mm per rotation; set C, 6:1 and 30 mm per rotation; set D, conventional and 5-mm interval. Conventional helical CT scans (set E) were obtained with 5-mm collimation at single-detector row CT. Two independent observers evaluated the five sets of CT scans. RESULTS: Acquisition times for sets A-D, respectively, were 1.9, 3.8, 7.5, and 1.5 times faster than they were for set E. The mean numbers of detected nodules were 671 (66%) in set A, 661 (65%) in set B, 678 (67%) in set C, 654 (65%) in set D, and 656 (65%) in set E; there was no significant difference in the number of detected nodules among the five sets (P =.997, McNemar test and Bonferroni equation). CONCLUSION: Regardless of varying pitch or detector collimation, multi- and single-detector row CT scans obtained with 5-mm section thickness have almost the same ability to depict pulmonary metastases and are equivalent.     

Coronal multiplanar reconstruction view from whole lung thin-section CT by multidetector-row CT: determination of malignant or benign lesions and differential diagnosis in 68 cases of solitary pulmonary nodule

PURPOSE: The purpose of this study was to evaluate the usefulness of the coronal multiplanar reconstruction (MPR) view in comparison with transverse helical thin-section CT for both the determination of malignant or benign lesions and the differential diagnosis of solitary pulmonary nodules. MATERIALS AND METHODS: Sixty-eight cases of pathologically proved solitary pulmonary nodule less than 3 cm in diameter were enrolled in this study. For the routine study, transverse helical thin-section CT (1.25 mm collimation, FOV 20 cm) covering the areas with solitary pulmonary nodules as well as whole lung helical thin-section CT (2.5 mm collimation, 1.25 mm reconstruction interval, FOV 34.5 cm, pitch 6:1, high-spatial frequency algorithm) were scanned with a multidetector-row CT (MDCT) scanner. From the whole lung thin-section CT data, coronal MPR views (2.5 mm slice thickness) were reconstructed on a workstation. ROC analysis was used for an observer performance study, in which three observers indicated their confidence level for the determination of malignant or benign lesion for the nodules by means of transverse thin-section CT and coronal MPR. In addition, the observers recorded appropriate disease entities as the final diagnosis of each case. Accuracies of the final diagnosis based on the two sets of images were compared with McNemer' s test. RESULTS: In terms of the determination of malignant or benign lesion, there was no significant difference between the two sets of images (coronal MPR and transverse thin-section CT; mean Az=0.853 and 0.854, respectively). In addition, accuracy of the final diagnosis based on coronal MPR views (74%) was almost equal to that based on transverse thin-section CT (71%) (p=0.3). CONCLUSIONS: The diagnostic efficacy of the coronal MPR view is comparable to that of transverse thin-section CT for the evaluation of solitary pulmonary nodules.     

Usefulness of model-based iterative reconstruction in semi-automatic volumetry for ground-glass nodules at ultra-low-dose CT: a phantom study

This study aimed to investigate the effects of parameter presets of the forward projected model-based iterative reconstruction solution (FIRST) on the accuracy of pulmonary nodule volume measurement. A torso phantom with simulated nodules [diameter: 5, 8, 10, and 12 mm; computed tomography (CT) density: ? 630 HU] was scanned with a multi-detector CT at tube currents of 10 mA (ultra-low-dose: UL-dose) and 270 mA (standard-dose: Std-dose). Images were reconstructed with filtered back projection [FBP; standard (Std-FBP), ultra-low-dose (UL-FBP)], FIRST Lung (UL-Lung), and FIRST Body (UL-Body), and analyzed with a semi-automatic software. The error in the volume measurement was determined. The errors with UL-Lung and UL-Body were smaller than that with UL-FBP. The smallest error was 5.8% ± 0.3 for the 12-mm nodule with UL-Body (middle lung). Our results indicated that FIRST Body would be superior to FIRST Lung in terms of accuracy of nodule measurement with UL-dose CT.     

Solitary pulmonary nodules: morphological and metabolic characterisation by FDG-PET-MDCT

PURPOSE: This study was done to analyse the additional morphological and functional information provided by the integration of [18F]-2-fluoro-2-deoxy-D-glucose positron emission tomography ([18F]-FDG-PET) with contrast-enhanced multidetector computed tomography (MDCT) in the characterisation of indeterminate solitary pulmonary nodules (SPNs). MATERIALS AND METHODS: Fifty-six SPNs, previously classified as indeterminate, were evaluated using a Discovery ST16 PET/CT system (GE Medical Systems) with nonionic iodinated contrast material and [18F]-FDG as a positron emitter. Images were evaluated on a dedicated workstation. Semiquantitative parameters of [18F]-FDG uptake and morphological, volumetric and densitometric parameters before and after contrast administration were analysed. Results were correlated with the histological and follow-up findings. RESULTS: Twenty-six SPNs were malignant and 30 were benign. Malignant lesions at both PET/CT and histology had a mean diameter of 1.8+/-1.2 cm, a volume doubling time (DT) of 222 days, a mean standardized uptake value (SUV) of 4.7 versus 1.08 in benign lesions and a mean postcontrast enhancement of 44.8 HU as opposed to 4.8 HU in benign nodules. Malignant lesions had a significantly shorter doubling time and significantly greater postcontrast enhancement compared with benign nodules. Based on the SUV and using a cut-off value of >2.5, PET/CT had a sensitivity of 76.9%, specificity of 100%, diagnostic accuracy of 89.2%, positive predictive value (PPV) of 100% and negative predictive value (NPV) of 83.3%. Based on doubling time (cut off<400 days), it had a sensitivity of 76.9%, specificity of 93.3%, accuracy of 85.7%, PPV of 90.9% and NPV of 82.3%. Based on postcontrast enhancement (cut off>15 HU), it had a sensitivity of 92.3%, specificity of 100%, accuracy of 96.4%, PPV of 100% and NPV of 93.7%. CONCLUSION: PET/CT allows accurate analysis of anatomical/morphological and metabolic/functional correlations of SPN, providing useful data for identifying and locating the disease, for differentiating between malignant and benign nodules and for establishing the aggressiveness and degree of vascularity of pulmonary lesions. Therefore, partly in view of the considerable reduction in time and cost of the single examinations, we believe that PET/CT will gain an increasingly dominant role in the diagnostic and therapeutic approach to lung cancer, especially in the preclinical phase.     

孤立肺结节的增强CT诊断新进展

孤立肺结节(SPN)的增强CT诊断是近年来研究热点之一,检查方法分为动态和多期增强扫描两类,以SPN的强化程度、结节-主动脉强化值比(S/A)、时间-密度曲线类型、灌注值、强化模式、肿瘤血管征等作为诊断依据。以强化值<15HU、S/A<6%为界值,可区分出良性结节;时间-密度曲线类型有助于恶性与炎性结节的鉴别;肿瘤血管征可作为特异性诊断指征;包膜样强化或内壁规则的周围强化高度提示结核的诊断。     

空气支气管征在CT诊断外周型肺弧立结节中的价值

目的评价空气支气管征鉴别诊断外周型肺孤立结节(直径≤3em)的价值。方法作者回顾分析了经手术或/和纤支镜或/和肺穿刺活检病理证实的190例外周型肺结节的空气支气管征的薄层CT影像。结果100例肺癌CT显示空气支气管征52例(52％),其中腺癌71.9％(22/31)、鳞癌34.1％(14/41)、腺鳞癌4/5、小细胞癌7/14、低分化癌5/9。50例炎性假瘤CT显示空气支气管征29例(58％)。32例结核球、5例错构瘤及3例肺囊肿均无肺空气支气管征。结论空气支气管征可见于多种结节性肺病变,它似乎不是外周型小肺癌尤其腺癌的特征。也不能帮助鉴别良恶性肺结节。     

Thin-section CT features of intrapulmonary lymph nodes

PURPOSE: The objective of this study was to evaluate CT findings of pathologically proven intrapulmonary lymph nodes (IPLNs) and discuss the utility of thin-section CT and contrast-enhanced CT. METHOD: CT findings of 18 nodules in 14 patients with pathologically proven IPLNs were reviewed. CT scanning of the whole lung was performed contiguously with slice thickness of 10 mm. In addition, a helical scan with slice thickness of 2 mm was performed in nine patients, focusing on the nodule. Contrast-enhanced helical CT was performed in four patients, and the utility of thin section CT and contrast-enhanced CT was investigated. RESULTS: One patient had three nodules, 2 patients had two nodules, and the remaining 11 patients had a solitary nodule. All nodules were located below the level of the carina and within 15 mm of the pleura. In one case, conventional CT revealed the nodule 20 mm away from the pleura; however, the nodule attached to the major fissure was clearly revealed on thin-section CT. The size of the nodules was < or =15 mm, and the shape was round (n = 8), oval (n = 9), or lobulated (n = 1) with sharp border. One nodule demonstrated a spiculated border due to a surrounding pulmonary fibrosis on conventional CT; however, thin-section CT showed precisely a sharp border. The lobulated shape of one case histopathologically reflected a hilus of lymph node. On contrast-enhanced helical CT, all four nodules were enhanced and the degree enhancement was 36-85 HU (median 66.6 HU). CONCLUSION: In current times, IPLNs are not uncommon lesions. We should consider IPLN in the differential diagnosis of solitary or multiple pulmonary nodules in the peripheral field and below the level of the carina. Thin-section CT showed precisely the border or relation between IPLNs and the surrounding structure. It was difficult to distinguish between IPLNs and malignant nodules from the degree of enhancement on contrast-enhanced CT. On thin-section and contrast-enhanced CT, the findings of IPLNs are not necessarily specific. Therefore, strict observation on CT is necessary; in certain cases that are increasing in size, video-assisted thoracic surgery should be considered because of their location.