A comparison of the diagnostic accuracy of 18F-FDG PET and CT in the characterization of solitary pulmonary nodules.

CT and PET are widely used to characterize solitary pulmonary nodules (SPNs). However, most CT accuracy studies have been performed with outdated technology and methods, and previous PET studies have been limited by small sample sizes and incomplete masking. Our objective was to compare CT and PET accuracy in veterans with SPN. METHODS: Between January 1999 and June 2001, we recruited 532 participants with SPNs newly diagnosed on radiography and untreated. The SPNs were 7-30 mm. All patients underwent (18)F-FDG PET and CT. A masked panel of 3 PET and 3 CT experts rated the studies on a 5-point scale. SPN tissue diagnosis or 2-y follow-up established the final diagnosis. RESULTS: A definitive diagnosis was established for 344 participants. The prevalence of malignancy was 53%. The average size was 16 mm. Likelihood ratios (LRs) for PET and CT results for combined ratings of either definitely benign (33% and 9% of patients, respectively) or probably benign (27% and 12%) were 0.10 and 0.11, respectively. LRs for PET and CT results for combined ratings of indeterminate (1% and 25%), probably malignant (21% and 39%), or definitely malignant (35% and 15%) were 5.18 and 1.61, respectively. Area under the receiver operating characteristic curve was 0.93 (95% confidence interval, 0.90-0.95) for PET and 0.82 (95% confidence interval, 0.77-0.86) for CT (P < 0.0001 for the difference). PET inter- and intraobserver reliability was superior to CT. CONCLUSION: Definitely and probably benign results on PET and CT strongly predict benign SPN. However, such results were 3 times more common with PET. Definitely malignant results on PET were much more predictive of malignancy than were these results on CT. A malignant final diagnosis was approximately 10 times more likely than a benign final diagnosis in participants with PET results rated definitely malignant.     

Recent progress in computer-aided diagnosis of lung nodules on thin-section CT.

Computer-aided diagnosis (CAD) provides a computer output as a "second opinion" in order to assist radiologists in the diagnosis of various diseases on medical images. Currently, a significant research effort is being devoted to the detection and characterization of lung nodules in thin-section computed tomography (CT) images, which represents one of the newest directions of CAD development in thoracic imaging. We describe in this article the current status of the development and evaluation of CAD schemes for the detection and characterization of lung nodules in thin-section CT. We also review a number of observer performance studies in which it was attempted to assess the potential clinical usefulness of CAD schemes for nodule detection and characterization in thin-section CT. Whereas current CAD schemes for nodule characterization have achieved high performance levels and would be able to improve radiologists' performance in the characterization of nodules in thin-section CT, current schemes for nodule detection appear to report many false positives, and, therefore, significant efforts are needed in order further to improve the performance levels of current CAD schemes for nodule detection in thin-section CT.     

CT resolution and diagnostic accuracy.

To justify CT purchases and document certificates of need, the clinical effectiveness of CT scanners with different cost and resolution must be compared. The diagnostic accuracy and anatomic detail in three scanners with different resolution were studied. Seventeen patients were studied with both a first or a second generation CT scanner and a third-generation scanner. Appearance of normal and pathologic structures was compared. Cerebral sulci, corticomedullary discrimination, basal cistern vessels, and some pathologic lesions were seen in third generation images that were not seen in the others. Higher resolution scans provide significantly better anatomic detail and accuracy in detecting pathologic processes.     

PET-CT: accuracy of PET and CT spatial registration of lung lesions

PET-CT scanners offer the unique ability to acquire PET and CT data with rapid full body registration. The purpose of this study was to evaluate the accuracy of spatial registration between PET and CT data in patients with fluorine-18 fluoro-2-deoxy- D-glucose (FDG)-avid lung lesions. PET, CT and fused PET-CT images from 244 consecutive clinical patients undergoing whole-body FDG PET-CT imaging (GE Discovery LS, CT attenuation correction, OSEM reconstruction) were evaluated. Inclusion criteria for this analysis were lung lesions clearly defined on both PET and CT, lesion diameter less than 5 cm and clear borders. Patients were allowed to breathe freely during both PET and CT image acquisitions. The spatial coordinates of the visually estimated centers of the lesion were determined independently for PET and CT images and compared. Thirty-six patients (26 females, 10 males) with a total of 48 lesions were included (19 lung cancer patients with 26 lesions, 17 patients with 22 lung metastases). The average lung lesion diameter was 15.6+/-9 mm. The mean distance between the center of lesions independently determined for both PET and CT was 7.55+/-4.73 mm. Misregistration tended to be more pronounced in the lower lungs (10.2+/-6.55 mm) than in the upper lungs (6.67+/-4.28 mm) ( P=0.063). Misregistration also tended to be slightly more pronounced in the left lung (8.33+/-5.05 mm) than in the right lung (6.25+/-3.92 mm) ( P=0.059). In conclusion, with a dedicated PET-CT scanner and this clinically practical imaging algorithm, registration is usually accurate, but spatial misregistration of primary lung lesions does occur.     

Development of computer-aided diagnostic system for detection of lung nodules in three-dimensional computed tomography images

We have developed an automated computerized method for the detection of lung nodules in three-dimensional (3D) computed tomography (CT) images obtained by helical CT. In this scheme, a lung segmentation technique for the determination of the nodule search area is performed based on a gray-level thresholding technique. To enhance lung nodules, we employed the 3D cross-correlation method by using a 3D Gaussian template with zero-surrounding as a model of lung nodule. False positives are then eliminated by using a rule-base with 53 features. For further reduction of false positives, we performed linear discriminant analysis using these 53 features. The average number of false positives was 6.7 per case at a percent sensitivity of 85.0%. This computerized scheme will be useful to radiologists by providing a "second opinion" in case of possible early lung cancer.     

New methods for using computer-aided detection information for the detection of lung nodules on chest radiographs

Objective:

To investigate two new methods of using computer-aided detection (CAD) system information for the detection of lung nodules on chest radiographs. We evaluated an interactive CAD application and an independent combination of radiologists and CAD scores.

Methods:

300 posteroanterior and lateral digital chest radiographs were selected, including 111 with a solitary pulmonary nodule (average diameter, 16 mm). Both nodule and control cases were verified by CT. Six radiologists and six residents reviewed the chest radiographs without CAD and with CAD (ClearRead +Detect™ 5.2; Riverain Technologies, Miamisburg, OH) in two reading sessions. The CAD system was used in an interactive manner; CAD marks, accompanied by a score of suspicion, remained hidden unless the location was queried by the radiologist. Jackknife alternative free response receiver operating characteristics multireader multicase analysis was used to measure detection performance. Area under the curve (AUC) and partial AUC (pAUC) between a specificity of 80% and 100% served as the measure for detection performance. We also evaluated the results of a weighted combination of CAD scores and reader scores, at the location of reader findings.

Results:

AUC for the observers without CAD was 0.824. No significant improvement was seen with interactive use of CAD (AUC = 0.834; p = 0.15). Independent combination significantly improved detection performance (AUC = 0.834; p = 0.006). pAUCs without and with interactive CAD were similar (0.128), but improved with independent combination (0.137).

Conclusion:

Interactive CAD did not improve reader performance for the detection of lung nodules on chest radiographs. Independent combination of reader and CAD scores improved the detection performance of lung nodules.

Advances in knowledge:

(1) Interactive use of currently available CAD software did not improve the radiologists'' detection performance of lung nodules on chest radiographs. (2) Independently combining the interpretations of the radiologist and the CAD system improved detection of lung nodules on chest radiographs.Chest radiography can be considered the workhorse of the radiology department. It is being used for the detection and diagnosis of multiple diseases, including lung nodules, which may represent early lung cancer. Since a chest radiograph is a two-dimensional image, overprojection of multiple anatomical structures is inevitable. This so-called anatomical noise substantially impedes interpretation of chest radiographs. Multiple studies have shown that a substantial amount of lung cancers are missed, ranging from 19% to 26%,^1,2 and even up to 90%.^3–5 More recent studies have shown that the problem of missing lung nodules is still present with the most modern digital radiographic technology.^6,7 Abnormalities can be missed as a result of inadequate search, perception errors or interpretation errors. It has been stated that interpretation by the radiologist is the most important factor for missing lung cancer on chest radiographs.^8,9To reduce miss rates, computer-aided detection (CAD) systems have been developed. Thus far, all studies dealing with chest radiography apply CAD as a second reader to the radiologist, meaning that the CAD marks are made available only after the radiologist has made a primary review. It remains the reader''s discretion to accept or disregard the CAD marks. Results of these studies were contradictory: some found an increased accuracy for the detection of lung nodules,^10–12 whereas other studies reported an increase in sensitivity only at the expense of loss in specificity.^13–16 One problem ameliorating the potential of CAD is the radiologist''s limited ability to reliably discriminate between true-positive (TP) and false-positive (FP) CAD marks.We therefore decided to explore alternative methods of using CAD information. First, we used CAD interactively. In the interactive mode, CAD marks remained hidden unless the radiologist queried a position in the image by clicking with the mouse on that location. If a CAD mark was present in this location, it was shown to the radiologist together with a score of suspicion. Such an interactive CAD system had been shown to be beneficial in chest radiography in an observer study that only used non-radiologists.¹⁷ Second, we computed a mathematical combination of reader and CAD scores. With this method, observers did not need to view the CAD marks at all during their reading of the images, but a mathematical combination of the reader and the CAD scores was computed afterwards. Both methods have been reported to outperform the use of CAD as a second reader for lesion detection in mammograms.^18–20The purpose of this observer study was to test the impact of these two alternative methods of using CAD information on nodule detection on chest radiographs. To optimize baseline performance without CAD, digitally bone-suppressed images (BSIs) were added to the original chest radiographs. BSIs have been shown to improve accuracy for the detection of focal lesions on chest radiographs;^21–24 a further increase in detection performance beyond that of BSIs by adding CAD has also been documented.²⁵     

Integrated PET/CT in differentiated thyroid cancer: diagnostic accuracy and impact on patient management.

The aim of this study was to investigate the diagnostic accuracy and impact on patient management of the new integrated PET/CT modality in patients with suspected iodine-negative, differentiated thyroid carcinoma (DTC). METHODS: Forty patients with DTC and a suggestion of iodine-negative tumor tissue underwent PET/CT examination (370 MBq (18)F-FDG, coregistered PET/CT whole-body images). As the first step of analysis, PET and CT images were scored blindly and independently by 2 nuclear medicine physicians and 2 radiologists. A 5-point scale was used. The second step consisted of a consensus reading, during which a virtual side-by-side fusion of PET and CT images was initially evaluated and afterward the "real" fusion (i.e., coregistered) PET/CT images were also scored with the same 5-point scale. The imaging results were compared with histopathologic findings and the course of disease during further follow-up examinations. RESULTS: One hundred twenty-seven lesions in 40 patients were evaluated. Diagnostic accuracy was 93% and 78% for PET/CT and PET, respectively (P = 0.049, per-patient analysis). In 17 (74%) of 23 patients with suspicious (18)F-FDG foci, integrated PET/CT added relevant information to the side-by-side interpretation of PET and CT images by precisely localizing the lesion(s). In tumor-positive PET patients, PET/CT fusion by coregistration led to a change of therapy in 10 (48%) patients. Futile surgery was prevented in an additional 3 patients. CONCLUSION: Integrated PET/CT is able to improve diagnostic accuracy in a therapeutically relevant way in patients with iodine-negative DTC. By precisely localizing tumor tissue, image fusion by integrated PET/CT is clearly superior to side-by-side interpretation of PET and CT images.     

High-risk melanoma: accuracy of FDG PET/CT with added CT morphologic information for detection of metastases

PURPOSE: To prospectively determine the accuracy of positron emission tomography (PET)/computed tomography (CT) with added CT morphologic information for depiction of metastases in patients with high-risk melanoma and negative findings for metastases at PET, by using histologic findings or additional imaging and/or follow-up findings as reference standard. MATERIALS AND METHODS: Institutional review board approval was obtained. Informed consent was obtained from patients. One hundred twenty-four consecutive high-risk melanoma patients (65 female, 59 male; mean age, 54.4 years; range, 15-82 years) were included. Fluorine 18 fluorodeoxyglucose (FDG) PET/CT was performed. First, PET/CT scans were evaluated for presence of metastases with increased FDG uptake; CT anatomic location was determined. Lesions were considered metastases if there was focal uptake higher than that of background tissue. Second, coregistered CT images of combined PET/CT scans were evaluated for presence of lesions without FDG uptake. Findings were compared with reference standard findings to determine the accuracy of each evaluation. McNemar test was used to assess statistical differences in accuracy. RESULTS: In 53 of 124 patients, metastases were found. In 46 of 53 patients with metastases, lesions had increased FDG uptake. In seven patients with metastatic disease, metastases did not have increased FDG uptake (maximum standard uptake value [SUV], <1.5; n = 5) or had faint FDG uptake (maximum SUV, 2.5 and 2.9; n = 2)-findings that were inconclusive with PET alone. These lesions were interpreted as metastases only with coregistered CT images. Lesions missed with PET were located in the lungs, iliac lymph nodes, subcutis, and psoas muscle. Sensitivity, specificity, and accuracy, respectively, of PET/CT for depiction of metastases were 85%, 96%, and 91%, and those of PET/CT with dedicated CT interpretation were 98%, 94%, and 96% (P = .016). CONCLUSION: Dedicated analysis of coregistered CT images significantly improves the accuracy of integrated PET/CT for depiction of metastases in patients with high-risk melanoma.     

Eosinophilic lung diseases: diagnostic accuracy of thin-section CT in 111 patients

PURPOSE: To determine whether various eosinophilic lung diseases can be differentiated by means of thin-section computed tomography (CT). MATERIALS AND METHODS: Thin-section CT scans in 111 patients with eosinophilic lung diseases-40 with chronic eosinophilic pneumonia, 16 with Churg-Strauss syndrome, 16 with allergic bronchopulmonary aspergillosis (ABPA), 13 with acute eosinophilic pneumonia, 12 with simple pulmonary eosinophilia, 11 with drug-induced eosinophilic pneumonia, and three with hypereosinophilic syndrome-were assessed independently by two observers. The observers recorded the abnormalities, diagnosis, and degree of confidence in the diagnosis. RESULTS: The two observers made a correct first-choice diagnosis on average in 61% of readings. The correct diagnosis was made in 78% of cases of chronic eosinophilic pneumonia; 81%, acute eosinophilic pneumonia; 44%, Churg-Strauss syndrome; 84%, ABPA; 17%, simple pulmonary eosinophilia; 27%, drug-induced eosinophilic pneumonia; and 33%, hypereosinophilic syndrome. The two observers made a correct diagnosis with a high degree of confidence in 36% of readings. There was moderate agreement between the observers for the correct diagnosis (kappa, 0.47) and for the correct diagnosis with a high degree of confidence (kappa, 0.59). CONCLUSION: Although eosinophilic lung diseases often can be differentiated by means of thin-section CT, correlation between CT findings and careful clinical evaluation are required for a definitive diagnosis.     

PET和PET/CT对孤立性肺结节的对照研究

目的探讨PET／CT对孤立性肺结节（SPN）定性诊断的准确性。方法行PET／CT检查并经手术或随访证实的良恶性SPN患者各30例，PET诊断由2位核医学科医生以标准摄取值（SUV）max〉12．5作为良恶性结节鉴别标准，PET／CT诊断由2位有经验的放射科医生与2位核医学科医生综合评价结节的SUV和形态学特点后做出。并分析SPN的形态学特征，包括分叶、短毛刺、棘突、结节空泡、空洞、钙化、胸膜凹陷、支气管截断、支气管血管集束征、卫星灶等。统计各种征象在良性和恶性SPN中的出现频率，并用x^2检验分析其统计学意义。结果SPNPET诊断的灵敏度、特异性和准确性分别为86．7％、90．0％和88．3％，PET／CT诊断的灵敏度、特异性和准确性分别为90．0％、93．3％和91．7％。排在前五位的恶性征象依次是短毛刺（63．3％）、支气管截断（50．0％）、棘突（46．7％）、典型分叶（36．7％）和胸膜凹陷（26．7％），与良性SPN比较差异均有显著性。在7例PET诊断错误的SPN患者中，有4例PET／CT诊断改变了治疗决策，其中2例PET／CT诊断正确，另有2例诊断可疑，建议随访。结论PET／CT对SPN定性诊断的准确性较PET有所提高。     

Lymph node staging with dual-modality PET/CT: enhancing the diagnostic accuracy in oncology

Lymph node staging according to the TNM criteria is an essential part of tumor evaluation. Several morphological and functional imaging procedures are used complementarily in this setting. Dual-modality PET/CT scanners are able to provide anatomical and functional data sets in a single session with accurate image co-registration. Comparative studies between morphological imaging procedures, such as MRI and CT, with co-registered PET/CT demonstrated significantly better lymph node staging with PET/CT than with anatomical procedures alone, regardless of the staged body compartment (head and neck, thorax or abdominal area). Based on more accurate staging results, PET/CT was able to alter the patients' therapy in a significant number of studies. Functional imaging with FDG-PET ([(18)F]-2-fluoro-2-desoxy-D-glucose-positron emission tomography) demonstrated outstanding results in lymph node staging of different tumor diseases. By adding anatomical information to PET, PET/CT outperforms PET alone when assessing the TNM-stage of different malignant diseases. This paper provides an overview concerning the performance of PET/CT in staging lymph nodes for malignant spread and points out benefits and limitations of this new imaging modality.     

Acute parenchymal lung disease in immunocompetent patients: diagnostic accuracy of high-resolution CT

OBJECTIVE: The purpose of this study was to determine whether acute parenchymal lung diseases can be differentiated on the basis of the pattern and distribution of abnormalities revealed on high-resolution CT. MATERIALS AND METHODS: High-resolution CT scans of 90 patients with acute parenchymal lung diseases (19 with bacterial pneumonia, 13 with mycoplasmal pneumonia, 21 with acute interstitial pneumonia, 18 with hypersensitivity pneumonitis, 10 with acute eosinophilic pneumonia, and nine with pulmonary hemorrhage) were independently assessed by two observers who had no knowledge of clinical or pathologic data. The observers recorded abnormalities, their first-choice diagnosis, and their degree of confidence in their first-choice diagnosis. RESULTS: The two observers made a correct first-choice diagnosis in an average of 55 (61%) of 90 cases. Correct first-choice diagnosis was made in 50% of cases of bacterial pneumonia, 62% of mycoplasmal pneumonia, 90% of acute interstitial pneumonia, 72% of hypersensitivity pneumonitis, 30% of acute eosinophilic pneumonia, and 28% of pulmonary hemorrhage. CT findings allowed distinction between infectious and noninfectious causes in 81 (90%) of 90 cases. CONCLUSION: High-resolution CT is helpful in the differential diagnosis of infectious from noninfectious acute parenchymal lung disease. However, high-resolution CT is of limited value in making a specific diagnosis.     

Chronic cystic lung disease: diagnostic accuracy of high-resolution CT in 92 patients

OBJECTIVE: The objective of this study was to determine whether the various chronic cystic lung diseases can be differentiated on the basis of the pattern and distribution of abnormalities on high-resolution CT. MATERIALS AND METHODS: High-resolution CT scans in 92 patients with chronic cystic lung diseases (18 with pulmonary Langerhans cell histiocytosis, 18 with pulmonary lymphangioleiomyomatosis, 17 with usual interstitial pneumonia, 16 with lymphocytic interstitial pneumonia, 15 with emphysema, and eight with desquamative interstitial pneumonia or respiratory bronchiolitis interstitial lung disease) were retrospectively assessed by two independent observers without knowledge of the clinical or pathologic data. The observers recorded the abnormalities, the most likely diagnosis, and the degree of confidence in that diagnosis. RESULTS: The two observers made a correct first-choice diagnosis in 148 (80%) of 184 interpretations. The correct diagnosis was made in 100% of interpretations of usual interstitial pneumonia, 81% of desquamative interstitial pneumonia or respiratory bronchiolitis interstitial lung disease, 81% of lymphocytic interstitial pneumonia, 77% of emphysema, 72% of lymphangioleiomyomatosis, and 72% of Langerhans cell histiocytosis. The two observers made a diagnosis with a high degree of confidence in 105 (57%) of 184 interpretations. The confident diagnosis was correct in 98 (93%) of 105 interpretations. CONCLUSION: Although various chronic cystic lung diseases often have a characteristic appearance that allows their distinction on high-resolution CT, considerable overlap exists among the CT findings. Therefore, lung biopsy is often required for a definitive diagnosis.     

Reassessment of CT images to improve diagnostic accuracy in patients with suspected acute appendicitis and an equivocal preoperative CT interpretation

Objectives

To identify CT features that discriminate individuals with and without acute appendicitis in patients with equivocal CT findings, and to assess whether knowledge of these findings improves diagnostic accuracy.

Methods

53 patients that underwent appendectomy with an indeterminate preoperative CT interpretation were selected and allocated to an acute appendicitis group or a non-appendicitis group. The 53 CT examinations were reviewed by two radiologists in consensus to identify CT findings that could aid in the discrimination of those with and without appendicitis. In addition, two additional radiologists were then requested to evaluate independently the 53 CT examinations using a 4-point scale, both before and after being informed of the potentially discriminating criteria.

Results

CT findings found to be significantly different in the two groups were; the presence of appendiceal wall enhancement, intraluminal air in appendix, a coexistent inflammatory lesion, and appendiceal wall thickening (P?P?=?0.0193 and P?=?0.0397, respectively).

Conclusions

Knowledge of the identified CT findings was found to improve diagnostic accuracy for acute appendicitis in patients with equivocal CT findings.

Key Points

? Numerous patients with clinically equivocal appendicitis do not have acute appendicitis ? Computed tomography (CT) helps to reduce the negative appendectomy rate ? CT is not always infallible and may also demonstrate indeterminate findings ? However knowledge of significant CT variables can further reduce negative appendectomy rate ? An equivocal CT interpretation of appendicitis should be reassessed with this knowledge     

肺癌病人或可疑肺癌病人FDGPET／CT检查发现肾上腺结节：有效诊断方案的提议

目的 通过定义的衰减和标准摄取率标准制定一项最大限度提高PET／CT诊断率的规则。方法 研究获机构审查委员会批准，免除知情同意，符合HIPAA法案。复习了1388例患有或疑有肺癌的连续病人的PET／CT检查，147例病人中发现187个肾上腺结节。结节性质通过病理或大小变化（恶性，n=37）或1年以上稳定性（良性，n=58）确定，未进行活检且随访不足1年者定义为不确定（n=92）。