CT of the solitary pulmonary nodule

Computed tomography (CT) with thin sections (2-5 mm) was used to assess tissue density in 91 apparently noncalcified pulmonary nodules in 88 patients. The study included 45 primary lung malignancies and 13 metastases proven by subsequent lung biopsy or thoracotomy. There were 33 benign lesions of which 13 were biopsy proven. The other 20 nodules were presumed benign on the basis of serial radiography showing no growth. A representative CT number based on the 32 most dense voxels was calculated for each lesion. For the primary malignancies, the mean representative CT number was 92 H, with a standard deviation of 18 H. The highest representative CT number for any malignant lesion was 147 H. Of the 33 benign lesions, 20 had a representative CT number of 164 H or greater. It is presumed that nodules with representative CT numbers of 164 H are benign, and that diffuse calcification likely accounts for the higher CT number of some benign lesions. CT has proven to be more objective and more sensitive than standard tomography in assessing the density of pulmonary nodules.     

Comparison of computed and conventional whole lung tomography in detecting pulmonary nodules: a prospective radiologic-pathologic study.

Whole lung computed tomography (CT) was performed on 25 patients with clinical diagnoses including osteogenic sarcoma. Ewing's sarcoma, rhabdomyosarcoma, fibrosarcoma, and melanoma in whom conventional tomography had revealed from one to four parenchymal nodules in one lung deemed resectable for either staging or treatment purposes. Thoracotomy was performed within 3 weeks after conventional and computed whole lung tomography. All palpable nodules were resected, measured at the time of surgery, mapped by anatomic segment, and submitted for individual histologic evaluation. CT defined more nodules than conventional tomography in 48% of cases. The additional nodules were usually pleural or subpleural and 3--6 mn in diameter. CT identified 78% of all resected nodules greater than 3 mm in diameter, compared to 59% using conventional tomography. CT was also of value in detecting bilateral nodules earlier than conventional tomography and in documenting small nodule growth on successive examination. However, 60% of the additional nodules defined by CT and resected proved to be benign granulomas and pleural-based nodes at thoracotomy.     

18F-FDG PET/CT对不同大小孤立性肺结节的诊断价值

目的 评价18F-脱氧葡萄糖(FDG) PET/CT对不同大小范围孤立性肺结节(SPN)良恶性鉴别诊断的价值.方法 从全国拥有PET/CT的10家医院筛选出已经获得病理学检查结果的SPN病例,收集诊断CT、PET/CT和病理检查结果以及标准摄取值(SUV)、结节大小等资料.诊断CT、PET/CT结果为肺癌、肺癌可能性大、肺癌可能者为阳性;结果为良性病变、良性可能性大、良性可能者为阴性;难以确定阳性和阴性者为不确定.采用SPSS 10.0软件对资料进行分析.结果 120个(120例)SPN中良性结节28个,恶性结节92个.直径或(长径+短径)/2≤1.0cm的结节17个,恶性病变9个;1.1～2.0cm 57个,恶性病变占75.44%;2.1～3.0cm 46个,恶性病变占86.96%.28个良性结节SUV最大值(SUVmax)的平均值为4.5±4.9, SUV平均值(SUVmean)的平均值为2.9±3.6;92个恶性结节SUVmax平均值为6.7±4.2, SUVmean平均值为4.9±3.6;良性结节的SUV显著低于恶性结节的SUV.无论良性还是恶性结节,随着结节的增大,SUV升高.诊断CT对结节良恶性鉴别的灵敏度为78.26%,特异性3/8,准确性72.22%; PET/CT灵敏度为94.51%,特异性64.00%,准确性87.93%.结论 18F-FDG PET/CT在SPN鉴别诊断中具有较高的灵敏度、特异性和准确性,优于诊断CT;结节大小是判断SPN良恶性的重要指标,直径或(长径+短径)/2＞2.0cm的结节,恶性可能性约为87%; SUV可以作为鉴别诊断的依据,但鉴于良性结节SUVmean的平均值为2.9±3.6,界值2.5仅供参考,尤其是对于≤1.0cm的结节.     

Solitary pulmonary nodule: characterization with combined wash-in and washout features at dynamic multi-detector row CT

PURPOSE: To prospectively assess the accuracy of combined wash-in and washout characteristics at dynamic contrast material-enhanced multi-detector row computed tomography (CT) in distinguishing benign from malignant solitary pulmonary nodules. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. The study included 107 patients (62 men, 45 women; mean age, 55 years; range, 22-81 years) with a solitary pulmonary nodule. After unenhanced CT (2.5-mm collimation) scans were obtained, dynamic CT was performed by using a helical technique (series of images obtained throughout the nodule, with 2.5-mm collimation, at 30, 60, 90, and 120 seconds and 4, 5, 9, 12, and 15 minutes) after intravenous injection of contrast medium (120 mL). Tissue diagnosis was made in 70 nodules, and follow-up images showed benignancy in the remaining 37 (no change in size, n = 32; decrease in size, n = 5). CT findings were analyzed in terms of wash-in and washout of contrast medium. Sensitivity, specificity, and accuracy for malignant nodules were calculated by considering both the wash-in and washout characteristics at dynamic CT. RESULTS: There were 49 malignant and 58 benign nodules. When diagnostic criteria for malignancy of both wash-in of 25 HU or greater and washout of 5-31 HU were applied, sensitivity, specificity, and accuracy for malignancy were 94% (46 of 49 nodules), 90% (52 of 58 nodules), and 92% (98 of 107 nodules), respectively. Of 58 benign nodules, 27 showed less than 25 HU wash-in, 14 showed persistent contrast enhancement without washout and with wash-in of 25 HU or greater, and 11 showed washout greater than 31 HU and wash-in of 25 HU or greater. CONCLUSION: Evaluation of solitary pulmonary nodules by analyzing combined wash-in and washout characteristics at dynamic contrast-enhanced multi-detector row CT showed 92% accuracy for distinguishing benign nodules from malignant nodules.     

CT evaluation of solitary pulmonary nodules: value of 185-H reference phantom

The pulmonary nodule CT reference phantom is widely used in the evaluation of nodules 2 cm or less in diameter. It is used to detect benign patterns of calcification that are not visible on thin-section CT scans. Since 1986, the reference nodules have been manufactured with a nominal composition of 185 H. The multicenter study published in 1986 used nodules with a nominal composition of 264 H, 100 H more than the threshold value reported by Siegelman et al. in 1980. In the multicenter study, one of 37 nodules diagnosed as benign with the phantom proved to be malignant. The purpose of this study was to determine the misdiagnosis rate with the 185-H phantom and to ascertain whether the malignant tumors predicted to be benign actually contained calcification. We retrospectively reviewed 296 cases in which examinations had been performed with the 185-H nodules since 1986. Eighty-five nodules were diagnosed as benign by comparison to the reference phantom. These 85 contained no visible calcification on thin-section CT scans. Ten of the 85 cases were shown to be malignant tumors. Eight were diagnosed as having a high probability of benignity. Two were diagnosed as having a moderate probability of benignity. Calcium was present in the tissue of all six nodules available for review. Fifty-nine of the 85 nodules were still clinically indeterminate at the time of this review. Even if all of the clinically indeterminate nodules are benign, the misdiagnosis rate would be significantly higher than in most previous studies. Although analysis by using the reference phantom with 185-H nodules may indicate a high probability of benignity, close radiologic follow-up is necessary.     

Kurtosis and skewness assessments of solid lung nodule density histograms: differentiating malignant from benign nodules on CT

Purpose

The purpose of our study was to assess pulmonary nodule characteristics using density histogram kurtosis and skewness and to distinguish malignant from benign nodules.

Materials and methods

Ninety-three lung nodules on CT were analyzed, including 72 malignant and 21 benign nodules. They were completely solid or solid with limited ground-glass opacity. Based on their CT characteristics, nodules were categorized into type A, homogeneous nodules with uniform internal structures and clear margins, and type B, inhomogeneous nodules with heterogeneous structures or uneven margins. Kurtosis and skewness were calculated from density histograms to compare type A and B nodules and malignant and benign nodules. Receiver-operating characteristic (ROC) curves were generated to assess kurtosis and skewness for discriminating between different nodule types.

Results

Type A nodules (n = 35) had greater kurtosis and reduced skewness (p < 0.001) compared to type B nodules (n = 58). Malignant tumor kurtosis was greater than that of benign nodules (type A, p < 0.05; type B, p = 0.001). Type B malignant tumors had reduced skewness compared to benign nodules (p < 0.05). ROC curves provided relatively high values for the area under the curve (0.71–0.83).

Conclusion

Kurtosis and skewness assessments of density histograms may be useful for differentiating malignant from benign nodules.     

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.     

Lung nodules: dual-kilovolt peak analysis with CT--multicenter study

PURPOSE: To test the following hypothesis: The greater the increase in the mean computed tomographic (CT) number of a radiologically indeterminate lung nodule from the CT number on a 140-kVp CT image to that on an 80-kVp CT image, the more likely the nodule is benign (ie, contains calcium). MATERIALS AND METHODS: Two hundred forty indeterminate lung nodules were prospectively studied at four institutions: Mayo Clinic Scottsdale, Ariz (n = 160); Mayo Clinic Rochester, Minn (n = 50); Shiga Health Insurance Hospital, Otsu, Japan (n = 25); and Duke University Medical Center, Durham, NC (n = 5). Of the 240 nodules, 157 met the entrance criteria for this study and had a diagnosis. All nodules included were solid, 5-40-mm diameter, relatively spherical, homogeneous, and without visible evidence of calcification or fat. Each nodule was evaluated by using 3-mm-collimation, nonenhanced CT scans with both 140- and 80-kVp x-ray beams. RESULTS: There were 86 (55%) benign and 71 (45%) malignant nodules. The median increase in the nodule mean CT number from the CT number on 140-kVp images to that on 80-kVp images was 2 HU for benign nodules and 3 HU for malignant nodules. This difference was not statistically significant. The area under the receiver operating characteristic curve was 0.505. CONCLUSION: Dual-kilovolt peak analysis with current CT technology does not appear to be helpful in the identification of benign lung nodules.     

孤立性肺结节CT征像在鉴别良恶性结节中的价值

目的 探讨孤立性肺结节的各种CT征像对良恶性结节鉴别的意义.方法 选取41例术后病理结果的孤立性肺结节CT征像,依据病理结果把病例分成恶性结节组23例,良性结节组18例,对两组患者的性别、年龄及结节直径对比分析,对孤立性肺结节的毛刺征、分叶征、胸膜尾征、血管集束征、空泡征、磨玻璃结节及钙化等CT征像进行单一CT征像及组...     

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.     

双源CT双能量技术鉴别甲状腺良恶性结节的临床应用研究

目的 探讨双源CT能量成像在鉴别甲状腺良恶性结节中的临床应用价值.方法 收集91例经双源CT双能量扫描的甲状腺结节患者,获得单能量40~190 keV图像及碘图,计算线性融合图像与各单能量图像对比噪声比(CNR),测量动静脉期良恶性结节各单能量图像CT值、碘图正常甲状腺、结节、同层面颈动脉碘浓度值,绘制良恶性结节CT值衰减趋势图,计算曲线斜率、正常甲状腺与甲状腺结节内碘浓度差异(ICD)、碘浓度差异比(ICDNR)、标准化碘浓度比(NIC),采用配对样本t检验并绘制受试者工作特征(ROC)曲线比较上述定量参数值诊断恶性结节效能.结果 动、静脉期甲状腺结节在不同能量水平下CNR均有统计学差异(P<0.0001),动脉期最佳CNR在70 keV为11.61±1.71,静脉期最佳CNR在60 keV为10.55±1.09;良恶性结节动脉期单能谱曲线斜率(λ)分别为1.66±0.48,3.31±1.33,ICD分别为(2.83±1.23)mg/mL,(2.10±0.98)mg/mL,ICDNR分别为0.50±0.23,0.38±0.27,差异均有统计学意义(F=-89.43,4.036,2.791,P均<0.05),λ恶性结节大于良性,ICD及ICDNR良性结节大于恶性;静脉期曲线斜率分别为3.85±2.47,1.24±1.26,NIC分别为0.57±0.32,0.39±0.13,差异有统计学意义(F=8.651,4.893,P均<0.05),均良性结节大于恶性;动脉期ICDNR曲线下面积(AUC)最大为0.913,诊断敏感度为100%,特异度为87.5%.结论 动、静脉期分别采用70 keV及60 keV单能量图像可提高甲状腺结节检出率,能量相关定量参数值对良恶性结节鉴别诊断有较大临床应用价值.     

Fractal analysis of small peripheral pulmonary nodules in thin-section CT: evaluation of the lung-nodule interfaces

OBJECTIVES: To analyze the lung-nodule interfaces on small peripheral pulmonary nodules (<2 cm) in thin-section CT (HRCT) images with fractal analysis. METHODS: Thin-section CT images from 70 patients with bronchogenic carcinomas (61 adenocarcinomas and 9 squamous cell carcinomas) and 47 patients with benign pulmonary nodules (23 hamartomas, 13 organizing pneumonias, and 11 tuberculomas) were used. For calculation of fractal dimensions (FDs), the authors used a box-counting method for binary- and gray-scale images of nodules. FD(two-dimensional [2D]) was an FD obtained from the binary image, and FD(three-dimensional [3D]) was an FD obtained from the gray-scale image. RESULTS: The FD(2D)s of hamartomas were smaller than those of other nodules ( < 0.05). The FD(3D)s obtained from the gray-scale images of organizing pneumonias and tuberculomas were greater than those of bronchogenic carcinomas ( < 0.0001) and hamartomas ( < 0.0001). In bronchogenic carcinomas, FD(3D)s of adenocarcinomas were greater than those of squamous cell carcinomas ( < 0.05). CONCLUSIONS: Fractal dimensions reflect the characteristics of the lung-nodule interfaces of small peripheral pulmonary nodules. The FD(2D)s revealed the irregularities of the contours. On the other hand, FD(3D)s revealed the complexities of the heterogeneous textures. With use of FD(2D) and FD(3D), it may be possible to distinguish bronchogenic carcinomas from benign pulmonary nodules. Moreover, FD(3D) may make it possible to distinguish between adenocarcinomas and squamous cell carcinomas.     

Frequency and significance of pulmonary nodules on thin-section CT in patients with extrapulmonary malignant neoplasms

Purpose

To determine the frequency and significance of pulmonary nodules detected on thin-section CT in patients with extrapulmonary malignant neoplasms.

Materials and methods

The institutional review board approved this study. This study retrospectively evaluated 308 patients with extrapulmonary carcinomas or sarcomas and had undergone thin-section chest CT (2 mm slice thickness) for staging. Three radiologists identified non-calcified nodules and evaluated the size, the growth and the distance from the nearest pleural surface. The characteristics of the nodules were defined based on the results of either a diagnostic biopsy or nodule growth.

Results

One or more non-calcified pulmonary nodules were detected in 75% of the patients (233/308). One hundred and thirty-seven of these patients had nodules that met the criteria of either benign or malignant nodules. Nodules smaller than 10 mm were more likely to be benign, whereas those 10 mm or greater were more likely to be malignant (22/26, 85%; P < .0001). Most nodules less than 10 mm from the pleura were benign (91%), whereas approximately half of the nodules 10 mm or more away from the pleura were malignant (20/43, 47%; P < .0001). Patients with melanoma, sarcoma, or testicular carcinoma were more likely to have malignant nodules. A multivariable analysis demonstrated the nodule size (P < .0001) and distance from the pleura were predictive of malignancy.

Conclusion

The nodule detection rate on thin-section CT in patients with extrapulmonary malignancy is high. Most of the nodules smaller than 10 mm or less than 10 mm from the pleura are benign.     

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.     

Positron emission tomography of incidentally detected small pulmonary nodules

The aim of this study was to assess the value of fluorodeoxyglucose positron emission tomography (FDG PET) imaging of small pulmonary nodules incidentally detected by spiral computed tomography (CT) in a high-risk population. Ten patients (five females, five males, aged 54-72 years) were recruited from an ongoing 4-year placebo controlled intervention study of the effect of inhaled steroids in 300 smokers with moderate to severe chronic obstructive pulmonary disease. The participants received yearly CT scans of the chest. Patients with a negative chest radiograph at the time of inclusion, but with pulmonary nodules indeterminate for malignancy detected by conventional spiral CT on a subsequent scan, were referred for FDG PET. Histological diagnoses were sought for all nodules with FDG uptake or where CT showed that they had grown. Ten patients had pulmonary nodules indeterminate for malignancy (approx. 3.3% of the entire study population). The prevalence of malignancy in this group was 50%. The accuracy of PET was high, in spite of the fact that seven patients had nodules smaller than 15 mm and two patients had bronchoalveolar cell carcinoma. This small prospective study indicates that subsequent assessment with FDG PET of small pulmonary nodules incidentally detected by CT has the potential to minimize the numbers of invasive procedures performed in individuals with a benign pulmonary lesion. FDG PET also increases the possibility of an early diagnosis as compared to the strategy of watchful waiting.     

Solitary pulmonary nodules: comparison of classification with standard, thin-section, and reference phantom CT

Standard, thin-section, and reference phantom computed tomography (CT) were performed to evaluate 75 consecutive patients with solitary pulmonary nodules. Follow-up was available for 62 nodules in 59 patients; 53 of the nodules were benign and nine were malignant. Twenty-one of the 62 nodules were assessed as benign with thin-section CT, while 33 of the 62 nodules were assessed as benign with reference phantom CT. Two of the nodules classified as benign with both thin-section and reference phantom CT proved to be malignant (a peripheral, ossified carcinoid and a 3.5-cm-diameter calcified carcinoma). The sensitivity of reference phantom CT (58%) for classification of benign nodules was higher than the sensitivity of thin-section CT (36%). The sensitivity of standard CT was lowest (12%). The presence of fat at thin-section CT was a reliable criterion for benignancy in six hamartomas. While both thin-section and reference phantom CT were useful in the identification of benign pulmonary nodules, reference phantom CT increased sensitivity by 22% compared with thin-section CT.     

CT纹理分析技术鉴别甲状腺良恶性结节可行性研究

目的探讨CT纹理分析技术在鉴别甲状腺良恶性结节中的价值。方法回顾性分析经我院手术病理证实的甲状腺病变病人35例,共42个病灶,其中恶性结节26个,良性结节16个。所有病人治疗前均行颈部增强CT扫描。将DICOM格式的CT增强图像(层厚和层间距均为5 mm)导入CT Kinetics软件进行纹理及直方图分析得到未经滤过的原始细纹理图像。CT纹理分析主要参数包括熵值、偏度、峰态、平均像素值和像素分布的标准差。甲状腺良恶性结节间纹理参数比较采用独立样本t检验或Mann-Whitney U检验,并对有统计学意义的纹理参数进行受试者操作特征(ROC)曲线分析,确定诊断阈值。结果甲状腺恶性结节的熵值、偏度、峰态、像素值和标准差分别为6.65±0.92、0.63±1.37、0.69±1.23、84.08±23.36和18.14±3.31;良性结节分别为5.96±0.54、0.59±1.42、0.51±1.17、72.00±24.52和20.05±6.10。熵值在甲状腺良恶性结节间差异有统计学意义(P0.05),偏度、峰态、像素值和标准差在甲状腺良恶性结节间差异均无统计学意义(均P0.05)。ROC曲线分析显示,以熵值6.09为鉴别甲状腺结节良恶性的阈值,其ROC曲线下面积、敏感度和特异度分别为0.733、71.3%和70.0%。结论 CT纹理参数对鉴别甲状腺结节的良恶性有一定帮助。     

Prevalence of air bronchograms in small peripheral carcinomas of the lung on thin-section CT: comparison with benign tumors

Despite improved techniques--such as bronchoscopy and percutaneous needle biopsy--to evaluate pulmonary nodules, there are still many cases in which surgical resection is necessary before carcinoma can be differentiated from benign lesions. The present study was undertaken to determine if the presence of an air bronchogram or air bronchiologram (patent visible bronchus or bronchiole) is useful in distinguishing small lung cancers from benign nodules. Thin-section chest CT scans were obtained in patients with 20 peripheral lung cancers less than 2 cm in diameter (18 adenocarcinomas, one squamous cell carcinoma, and one large cell carcinoma) and 20 small benign nodules (eight hamartomas, seven tuberculomas, two foci of aspergillosis, one focus of cryptococcosis, one chronic focal interstitial pneumonitis, and one plasma cell granuloma). The images were compared with regard to the patency of any bronchus or bronchiole within the lesions. After surgical resection, the specimens were inflated with agar and sectioned transversely to correlate gross morphology and low-power histologic sections with the CT appearance. An air bronchogram or air bronchiologram was seen in the tumors on 65% of CT scans and 70% of histologic sections. Benign nodules had a patent bronchus or bronchiole on CT scans and histologic sections in only one case (5%). These findings suggest that the presence of an air bronchogram in a lung nodule is a useful finding to help differentiate adenocarcinomas from benign lesions.     

Prospective evaluation of solitary thyroid nodule on 18F-FDG PET/CT and high-resolution ultrasonography

Purpose

The utility of 18F-FDG PET/CT in the assessment of thyroid nodules is unclear as there are several conflicting reports on the usefulness of SUV as an indicator to distinguish benign from malignant thyroid lesions. This study incorporated an additional parameter, namely dual time point imaging, to determine the diagnostic accuracy of PET/CT imaging. The performance of 18F-FDG PET/CT was compared to that of high-resolution ultrasound which is routinely used for the evaluation of thyroid nodules.

Methods

Two hundred patients with incidentally detected solitary thyroid nodules were included in the study. Each patient underwent ultrasound and PET/CT evaluation within 7 days of each other, reported by an experienced radiologist and nuclear medicine specialist, respectively, in a blinded manner. The PET/CT criteria employed were maximum SUV (SUV_max) at 60 min and change in SUV_max at delayed (120 min) imaging. Final diagnosis was based on pathological evaluation and follow-up.

Results

Of the 200 patients, 26 had malignant and 174 had benign nodules. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of ultrasound were 80.8, 81.6, 39.6, 96.6 and 81.5%, respectively. Using SUV_max at 60 min as the diagnostic criterion, the above indices were 80.8, 84.5, 43.8, 96.7 and 84%, respectively, for PET/CT. The SUV_max of malignant thyroid lesions was significantly higher than benign lesions (16.2 ± 10.6 vs. 4.5 ± 3.1, respectively; p = 0.0001). Incorporation of percentage change in SUV_max at delayed imaging as the diagnostic criterion yielded a slightly improved sensitivity, specificity, PPV, NPV and accuracy of 84.6, 85.6, 46.8, 97.4 and 85.5%, respectively. There was a significant difference in percentage change in SUV_max between malignant and benign thyroid lesions (14.9 ± 11.4 vs. ?1.6 ± 13.7, respectively; p = 0.0001). However, there was no statistically significant difference (95% confidence interval) between the diagnostic performance of PET/CT and ultrasound.

Conclusions

Routine use of 18F-FDG PET/CT with SUV_max at 60 min as the sole diagnostic criterion does not appear to have a significant advantage over high-resolution ultrasound in the evaluation of thyroid nodules. Incorporation of dual time point imaging enhances image interpretation, and yields a higher diagnostic performance, yet it is not statistically significant. Bearing in mind the cost, limited availability and radiation exposure, routine use of 18F-FDG PET/CT for distinguishing benign from malignant thyroid nodules cannot be recommended.     

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.