CT appearance of bone metastases detected with FDG PET as part of the same PET/CT examination

PURPOSE: To retrospectively evaluate lesion findings at computed tomography (CT) performed as part of a combined positron emission tomography (PET)/CT examination in patients suspected of having metastatic bone lesions-lesions that were detected with fluorine 18 fluorodeoxyglucose (FDG) PET as part of the same examination-and to correlate the CT and FDG PET findings. MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval, and the need for patient informed consent was waived. Three hundred fifty-nine consecutive patients (191 male patients, 168 female patients; mean age, 56.9 years; age range, 8-92 years) underwent PET/CT. PET images were first reviewed by nuclear medicine physicians who had no clinical information regarding the presence or absence of bone metastasis by using a five-point grading system (0, a lesion was definitely negative for metastasis; 1, a lesion was probably negative; 2, a lesion was equivocal; 3, a lesion was probably positive; and 4, a lesion was definitely positive). For lesions assigned a grade of 3 or 4 at PET, CT characteristics such as the presence or absence of morphologic changes or accompanying findings (including bone destruction) were assessed by radiologists on the CT images obtained during the same imaging session. RESULTS: One hundred seventy-nine lesions in 55 patients were considered to be probable or definite bone metastases at PET. One hundred thirty-three of these lesions in 33 patients were clinically confirmed to be bone metastases at follow-up and/or histopathologic examination. CT revealed osteolytic changes in 41 (31%) and osteoblastic changes in 21 (16%) of the 133 lesions, but no or nonspecific changes were seen at CT in 49 (37%) and 22 lesions (17%), respectively. Of the 179 lesions suspected at PET, 46 ultimately proved to be nonosseous or false-positive for bone metastasis. Of these 46 lesions, 38 were not located in the bone but in adjacent tissues such as the pleura. CONCLUSION: CT images obtained as part of PET/CT scanning were useful in yielding the precise location of bone lesions and thus helping avoid misdiagnosis of bone metastasis; however, CT revealed morphologic changes in only half of the lesions assigned a grade of 3 or 4 at PET.     

Clinical performance of PET/CT in evaluation of cancer: additional value for diagnostic imaging and patient management.

This study assessed the clinical performance of a combined PET/CT system using (18)F-FDG in oncologic patients. METHODS: (18)F-FDG PET/CT was used to evaluate 204 patients with 586 suspicious lesions. All patients had available follow-up data, enabling assessment of the clinical significance of hybrid PET/CT findings. Differences in interpretation between PET, CT, and fused PET/CT data were prospectively documented for detection, localization, and characterization of each evaluated site. The additional value of PET/CT for data interpretation over that of separate PET and CT was classified into several criteria, including change in lesion characterization to either definitely benign or definitely malignant, precise anatomic localization of malignant (18)F-FDG uptake, and retrospective lesion detection on PET and CT. The clinical impact of information provided by PET/CT on patient management was assessed on the basis of follow-up data concerning further diagnostic or therapeutic approach. Analysis of data was performed for the whole study population, for different types of cancer, and for different anatomic sites. RESULTS: PET/CT provided additional information over the separate interpretation of PET and CT in 99 patients (49%) with 178 sites (30%). PET/CT improved characterization of equivocal lesions as definitely benign in 10% of sites and as definitely malignant in 5% of sites. It precisely defined the anatomic location of malignant (18)F-FDG uptake in 6%, and it led to retrospective lesion detection on PET or CT in 8%. The results of PET/CT had an impact on the management of 28 patients (14%). Hybrid PET/CT data obviated the need for further evaluation in 5 patients, guided further diagnostic procedures in 7 patients, and assisted in planning therapy for 16 patients. CONCLUSION: Hybrid PET/CT improves the diagnostic interpretation of (18)F-FDG PET and CT in cancer patients and has an impact on both diagnostic and therapeutic aspects of patient management.     

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.     

Head and neck imaging with PET and PET/CT: artefacts from dental metallic implants

Germanium-68 based attenuation correction (PET(Ge68)) is performed in positron emission tomography (PET) imaging for quantitative measurements. With the recent introduction of combined in-line PET/CT scanners, CT data can be used for attenuation correction. Since dental implants can cause artefacts in CT images, CT-based attenuation correction (PET(CT)) may induce artefacts in PET images. The purpose of this study was to evaluate the influence of dental metallic artwork on the quality of PET images by comparing non-corrected images and images attenuation corrected by PET(Ge68) and PET(CT). Imaging was performed on a novel in-line PET/CT system using a 40-mAs scan for PET(CT) in 41 consecutive patients with high suspicion of malignant or inflammatory disease. In 17 patients, additional PET(Ge68) images were acquired in the same imaging session. Visual analysis of fluorine-18 fluorodeoxyglucose (FDG) distribution in several regions of the head and neck was scored on a 4-point scale in comparison with normal grey matter of the brain in the corresponding PET images. In addition, artefacts adjacent to dental metallic artwork were evaluated. A significant difference in image quality scoring was found only for the lips and the tip of the nose, which appeared darker on non-corrected than on corrected PET images. In 33 patients, artefacts were seen on CT, and in 28 of these patients, artefacts were also seen on PET imaging. In eight patients without implants, artefacts were seen neither on CT nor on PET images. Direct comparison of PET(Ge68) and PET(CT) images showed a different appearance of artefacts in 3 of 17 patients. Malignant lesions were equally well visible using both transmission correction methods. Dental implants, non-removable bridgework etc. can cause artefacts in attenuation-corrected images using either a conventional 68Ge transmission source or the CT scan obtained with a combined PET/CT camera. We recommend that the non-attenuation-corrected PET images also be evaluated in patients undergoing PET of the head and neck.     

Accuracy of PET/CT in characterization of solitary pulmonary lesions.

Characterization of a pulmonary lesion is a well-established indication for metabolic imaging with 18F-FDG. There is extensive literature on the use of PET and CT in the characterization of a solitary pulmonary nodule (SPN). The performance of dual-modality imaging with PET/CT for characterizing SPNs was investigated in a clinical referral setting. METHODS: We performed a retrospective study involving patients referred for SPN characterization with PET/CT between September 2002 and June 2004, for whom a pathologic diagnosis was available. The group consisted of 12 men and 30 women whose age ranged from 35 to 84 y (mean age +/- SD, 67 +/- 11 y). A dual-slice CT/lutetium oxyorthosilicate PET system was used for imaging. CT images were acquired without intravenous contrast. Blinded interpretation was performed by 1 chest radiologist for CT and 2 nuclear medicine physicians for PET. PET/CT images were read in consensus. Lesions were analyzed by location, texture, axial dimension, and metabolic activity and visually scored on a 5-point scale from benign to malignant; the maximum standardized uptake value (SUVmax) was measured. RESULTS: Lesion diameter varied from 7 to 30 mm (mean +/- SD, 15 +/- 6 mm). The SUVmax ranged from 0.5 to 17.2 (mean +/- SD, 3.0 +/- 3.0). SUVmax corrected for lean body mass was 0.4-12.1 (mean +/- SD, 2.1 +/- 2.0). Comparison of CT versus PET versus PET/CT yielded accuracies of 74%, 74%, and 93%, respectively. PET and CT correctly characterized 31 and PET/CT correctly characterized 39 of the 42 lesions as malignant or benign. The sensitivity and specificity for CT, PET, and PET/CT was 93%/31%, 69%/85%, and 97%/85%, respectively. There were significant differences (P < 0.05) between PET/CT and PET for accuracy, sensitivity, and specificity. Accuracy did not improve by quantitative analysis using an SUVmax cutoff of 2.0 for malignancy. Lean body mass correction of the SUVmax did not change accuracy. CONCLUSION: PET/CT demonstrates an excellent performance in classifying SPNs as benign or malignant. The combination of anatomic and metabolic imaging is synergistic by maintaining the sensitivity of CT and the specificity of PET, resulting in an overall significantly improved accuracy. Visual interpretation is sufficient for characterizing an SPN. Quantitative analysis does not improve accuracy of PET/CT for SPN characterization.     

Increased 18F-FDG uptake in degenerative disease of the spine: Characterization with 18F-FDG PET/CT.

We determined the prevalence of abnormal spinal 18F-FDG uptake and assessed the relationship between the severity of findings on 18F-FDG PET and the severity of degenerative spinal disease (DSD) on CT. METHODS: PET/CT scans of 150 patients >18 y old, referred for whole-body 18F-FDG PET/CT for evaluation of known or suspected malignancy from June to July 2002, were analyzed retrospectively for the presence of increased 18F-FDG uptake in the spine and for anatomic correlates. Initially, PET images were examined and foci of 18F-FDG uptake in the spine were graded on a 0-4 scale based on intensity of 18F-FDG uptake (0 = definitely normal, 1 = probably normal, 2 = equivocal, 3 = probably abnormal, 4 = definitely abnormal). From PET alone, an impression as to whether lesions were most likely metastases or degenerative, as well the level of the spine involved, was also recorded. CT images of all 150 patients were reviewed independently by a musculoskeletal radiologist, who was unaware of patient identification, history, and findings of other imaging modalities, with the location recorded and severity graded on a 4-point-scale (0 = normal, 1 = mild, 2 = moderate, 3 = severe for both degenerative disk and facet disease). The relationship between PET and CT findings was then determined. RESULTS: Of the 150 patients, 63 (42.0%) had no abnormal findings in the spine on PET (grade 0), 27 (18.0%) had grade 1, 25 (16.7%) had grade 2, 17 (11.3%) had grade 3, and 16 patients (10.7%) had grade 4 18F-FDG uptake for DSD. Two additional patients had apparent spinal metastases with no degenerative changes. Five patients had metastases and DSD (included above). Of the patients who had abnormal spinal findings graded as probable or definite for DSD on CT (grades 3-4), 11 had abnormal findings in the cervical spine, 16 in the thoracic spine, and 23 patients in the lumbosacral spine. Seven patients (4.7%) had PET findings suggestive of spinal metastases. For patients with a maximum regional DSD score of 3, the mean 18F-FDG uptake for that spinal level was 1.4 +/- 1.5, whereas for patients with a maximum regional DSD score of 0, the mean PET grade was significantly lower at 0.4 +/- 0.9 (P = 0.0001). CONCLUSION: Incidental findings on PET suggestive of DSD are common (22% of patients), most common in the lumbosacral spine, and can be recognized on CT. The severity of PET findings correlates with the severity of degenerative disk and facet disease as graded by CT, likely due to the fact that the inflammatory process that accompanies DSD is evident on PET. Increased 18F-FDG uptake in DSD should not be confused with metastatic disease.     

PET/CT诊断恶性肿瘤及其转移灶的价值

目的探讨PET／CT对恶性肿瘤及其转移灶的检测效能。方法恶性肿瘤患者65例皆行PET／CT检查，原发灶皆经病理组织学确诊，转移灶的诊断综合组织病理学结果及多种影像学检查而定。行^18F-脱氧葡萄糖(FDG)PET／CT融合图像、唧图像和CT图像帧对帧对比分析。结果初诊恶性肿瘤患者59例，有恶性病灶264个。264个病灶中，唧与平扫CT阅片均有肯定诊断结论者128个，占48．4％；而唧有肯定诊断结论，但CT难以有肯定诊断结论者111个，占42．0％；唧显像为阴性或难以确定，而CT有肯定诊断结论者11例共25个病灶．占9．6％。PET／CT的总检出率高于PET和CT。6例治疗后患者，CT难以确定肿瘤残余和坏死区域，而PET／CT能清楚区分。结论PET／CT可提高对恶性肿瘤诊断及分期的准确性。     

Respiratory gated PET/CT in a European multicentre retrospective study: added diagnostic value in detection and characterization of lung lesions

Purpose

The aim of our work is to evaluate the added diagnostic value of respiratory gated (4-D) positron emission tomography/computed tomography (PET/CT) in lung lesion detection/characterization in a large patient population of a multicentre retrospective study.

Methods

The data of 155 patients (89 men, 66 women, mean age 63.9?±?11.1?years) from 5 European centres and submitted to standard (3-D) and 4-D PET/CT were retrospectively analysed. Overall, 206 lung lesions were considered for the analysis (mean ± SD lesions dimension 14.7 ± 11.8?mm). Maximum standardized uptake values (SUV_max) and lesion detectability were assessed for both 3-D and 4-D PET/CT studies; 3-D and 4-D PET/CT findings were compared to clinical follow-up as standard reference.

Results

Mean ± SD 3-D and 4-D SUV_max values were 5.2 ± 5.1 and 6.8 ± 6.1 (p?Conclusion The respiratory gated PET/CT technique is a valuable clinical tool in diagnosing lung lesions, improving quantification and confidence in reporting, reducing 3-D undetermined findings and increasing the overall accuracy in lung lesion detection and characterization.     

PET recognition of pulmonary metastases on PET/CT imaging: impact of attenuation-corrected and non-attenuation-corrected PET images

Purpose The aims of this study were to assess the performance of FDG PET at PET/CT imaging for the detection of pulmonary metastases and to evaluate differences in lesion detectability on attenuation-corrected (AC) and non-attenuation corrected (NAC) PET images.Methods The institutional PET/CT database was searched for patients with pulmonary metastases of 3–60 mm in diameter. Ninety-two patients with 438 metastases to the lungs were included in the study. The primary tumours were 33 malignant melanomas, 12 carcinomas of unknown primary, 11 colorectal carcinomas, eight differentiated thyroid carcinomas, seven aggressive non-Hodgkins lymphomas, six head and neck cancers, three breast cancers, two prostate cancers and ten others. Lesion detectability was visually compared between PET and CT and between AC and NAC PET images using a five-point scale.Results Of the 438 pulmonary metastases, 174 were detected with FDG PET (39.7%), six of them on NAC images only (not significant). Visual scores were higher on NAC images in 41.4% and equal in 54.6% of lesions. The sensitivity of FDG PET increased significantly from 0.405 for metastases of 5–7 mm in diameter to 0.784 for lesions of 8–10 mm and to 0.935 for lesions measuring 11–29 mm in diameter. No metastases smaller than 5 mm in diameter were seen on PET images.Conclusion FDG PET/CT is useful for the assessment of pulmonary metastases. The frequency of lesion detection is similar for AC and NAC PET images. A reduced sensitivity of FDG PET has to be considered for lesions smaller than 11 mm in diameter.     

Head and neck cancer: clinical usefulness and accuracy of PET/CT image fusion

PURPOSE: To compare diagnostic accuracy of attenuation-corrected positron emission tomography (PET) with fused PET and computed tomography (CT) in patients with head and neck cancer and to evaluate the effect of PET/CT findings on patient care. MATERIALS AND METHODS: Studies of 68 patients were reviewed by two physicians in consensus. Focal fluorodeoxyglucose (FDG) uptake in the head and neck on attenuation-corrected PET images was graded as benign, equivocal, or malignant. CT and PET/CT images were then reviewed, and initial findings were amended if necessary. Comparison was performed on a lesion-by-lesion basis. Accuracy was evaluated on the basis of follow-up and histopathologic findings. Potential effects on patient care were assessed by a head and neck surgeon. PET and PET/CT accuracy was compared with a McNemar test adjusted for clustering. RESULTS: A total of 157 foci with abnormal FDG uptake were noted, two of which were seen only on PET/CT images. PET/CT images were essential in determining the exact anatomic location for 100 lesions (74% better localization in regions previously treated surgically or with irradiation vs 58% in untreated areas; P =.06). On the basis of PET findings alone, 45 lesions were considered benign; 39, equivocal; and 71, malignant. With PET/CT, the fraction of equivocal lesions decreased by 53%, from 39 of 155 to 18 of 157 (P <.01). PET/CT had a higher accuracy of depicting cancer than did PET (96% vs 90%, P =.03). Six proved malignancies were missed with PET, but only one was missed with PET/CT. PET/CT findings altered the care for 12 (18%) of 68 patients. CONCLUSION: PET/CT is more accurate than PET alone in the detection and anatomic localization of head and neck cancer and has the clear potential to affect patient care.     

(18)F-FDG PET versus (18)F-FDG PET/CT for adrenal gland lesion characterization: a comparison of diagnostic efficacy in lung cancer patients.

OBJECTIVE: The aim of this study was to assess the diagnostic efficacy of integrated PET/CT using fluorodeoxyglucose (FDG) for the differentiation of benign and metastatic adrenal gland lesions in patients with lung cancer and to compare the diagnostic efficacy with the use of PET alone. MATERIALS AND METHODS: Sixty-one adrenal lesions (size range, 5-104 mm; mean size, 16 mm) were evaluated retrospectively in 42 lung cancer patients. Both PET images alone and integrated PET/CT images were assessed, respectively, at two-month intervals. PET findings were interpreted as positive if the FDG uptake of adrenal lesions was greater than or equal to that of the liver, and the PET/CT findings were interpreted as positive if an adrenal lesion show attenuation > 10 HU and showed increased FDG uptake. Final diagnoses of adrenal gland lesions were made at clinical follow-up (n = 52) or by a biopsy (n = 9) when available. The diagnostic accuracies of PET and PET/CT for the characterization of adrenal lesions were compared using the McNemar test. RESULTS: Thirty-five (57%) of the 61 adrenal lesions were metastatic and the remaining 26 lesions were benign. For the depiction of adrenal gland metastasis, the sensitivity, specificity, and accuracy of PET were 74%, 73%, and 74%, respectively, whereas those of integrated PET/CT were 80%, 89%, and 84%, respectively (p values; 0.5, 0.125, and 0.031, respectively). CONCLUSION: The use of integrated PET/CT is more accurate than the use of PET alone for differentiating benign and metastatic adrenal gland lesions in lung cancer patients.     

18F-FDG PET/CT与PET/MRI在结直肠癌肝转移诊断中的比较分析

目的:比较 18F-氟脱氧葡萄糖（FDG） PET/CT与PET/MRI显像对结直肠癌肝转移的诊断价值。 方法:回顾性分析2018年9月至2019年9月于宁波明州医院行全身 18F-FDG PET/CT显像及上腹部 18F-FDG PET/MRI显像,并疑似有结直肠癌肝转移...     

PET/CT colonography in patients with colorectal polyps: a feasibility study

PURPOSE: To examine: (1) the feasibility of PET/CT colonography (PET/CTc) in patients with colorectal polyps; (2) the impact of metabolic information on CTc interpretation and, conversely, the impact of morphological information on PET characterisation of focal colorectal uptake. METHODS: Ten patients with colorectal polyps underwent PET/CTc, followed within 3 h by therapeutic conventional colonoscopy (CC). A radiologist and a nuclear medicine physician analysed the PET/CTc images. The agreement of morphological and metabolic information in the colon and rectum was evaluated. The sensitivity and specificity of PET, CT and PET/CT were calculated for colorectal polyps. RESULTS: Seventeen polypoid lesions were identified at CC: six< or =5 mm, six between 6 and 9 mm, and five > or =10 mm (four hyperplastic polyps, 11 tubular adenomas, one adenocarcinoma and one submucosal lipoma). A total of 20 scans (supine and prone) were performed in the ten patients: the agreement of morphological and metabolic information was excellent in 17 scans, good in two and moderate in one. PET/CTc showed a sensitivity of 91% for lesions > or =6 mm and a specificity of 100%. The metabolic information did not disclose any further polyps missed on CTc. The morphological information permitted correct classification of all eight instances of focal radiotracer uptake. CONCLUSION: PET/CTc is a feasible study. Adding a colonographic protocol to PET/CT images seems to allow correct characterisation of all cases of colorectal focal radiotracer uptake. The metabolic information does not seem to increase the accuracy of CTc.     

Role of 11C-choline PET/CT in the restaging of prostate cancer patients showing a single lesion on bone scintigraphy

Aim

To assess the utility of ¹¹C-choline PET/CT in the restaging of prostate cancer (PC) patients who showed a single finding on bone scintigraphy (BS) that was classified as equivocal or suspected for metastatic lesion.

Materials and methods

A total of 25 PC patients with biochemical failure (mean PSA value 11.1 ng/mL; median value 6.3 ng/mL; range 0.2–37.7 ng/mL) after primary treatment were included in this retrospective study. All of them showed a single lesion on BS reported as suspected for metastatic lesion or as equivocal finding. Patients underwent ¹¹C-choline PET/CT within 1–4 months from BS. Validation was established by follow-up for at least 6 months.

Results

On the basis of biopsy confirmation and/or 6-month follow-up, 22 of 25 patients were classified as positive for the presence of metastatic bone lesions: 13 with a single lesion and 9 with multiple lesions. ¹¹C-choline PET/CT was positive in 19/25 patients and, on a lesion basis, it showed 50 positive findings. BS results were confirmed in 8/25 (32%) patients. ¹¹C-choline PET/CT detected multiple sites of relapse in 11/25 (44%) patients: in 2/11, a single bone lesion associated with other extraosseous sites of relapse; in 6/11, multiple bone lesions; in 3/11, multiple bone lesions and other extraosseous localizations. Finally, 6/25 patients were negative on ¹¹C-choline PET/CT. In 3/6 patients, an osteoblastic lesion was seen on CT attenuation correction images (PET false negative; BS true positive), while in 3/6 patients only findings suggestive of the presence of degenerative disease were found (PET true negative; BS false positive). On a patient basis, ¹¹C-choline PET/CT showed a diagnostic sensitivity of 86% (19/22) and a specificity of 100% (19/19).

Conclusions

In our study, ¹¹C-choline PET/CT detected unknown lesions in 11/25 patients. Patients with a single equivocal finding on BS could have important additional information from ¹¹C-choline PET/CT study, especially in the detection of additional metastases, to choose an appropriate treatment.     

Correction for oral contrast artifacts in CT attenuation-corrected PET images obtained by combined PET/CT.

Recent studies have shown increased artifacts in CT attenuation-corrected (CTAC) PET images acquired with oral contrast agents because of misclassification of contrast as bone. We have developed an algorithm, segmented contrast correction (SCC), to properly transform CT numbers in the contrast regions from CT energies (40-140 keV) to PET energy at 511 keV. METHODS: A bilinear transformation, equivalent to that supplied by the PET/CT scanner manufacturer, for the conversion of linear attenuation coefficients of normal tissues from CT to PET energies was optimized for BaSO(4) contrast agent. This transformation was validated by comparison with the linear attenuation coefficients measured for BaSO(4) at concentrations ranging from 0% to 80% at 511 keV for PET transmission images acquired with (68)Ge rod sources. In the CT images, the contrast regions were contoured to exclude bony structures and then segmented on the basis of a minimum threshold CT number (300 Hounsfield units). The CT number in each pixel identified with contrast was transformed into the corresponding effective bone CT number to produce the correct attenuation coefficient when the data were translated by the manufacturer software into PET energy during the process of CT attenuation correction. CT images were then used for attenuation correction of PET emission data. The algorithm was validated with a phantom in which a lesion was simulated within a volume of BaSO(4) contrast and in the presence of a human vertebral bony structure. Regions of interest in the lesion, bone, and contrast on emission PET images reconstructed with and without the SCC algorithm were analyzed. The results were compared with those for images obtained with (68)Ge-based transmission attenuation-corrected PET. RESULTS: The SCC algorithm was able to correct for contrast artifacts in CTAC PET images. In the phantom studies, the use of SCC resulted in an approximate 32% reduction in the apparent activity concentration in the lesion compared with data obtained from PET images without SCC and a <7.6% reduction compared with data obtained from (68)Ge-based attenuation-corrected PET images. In one clinical study, maximum standardized uptake value (SUV(max)) measurements for the lesion, bladder, and bowel were, respectively, 14.52, 13.63, and 13.34 g/mL in CTAC PET images, 59.45, 26.71, and 37.22 g/mL in (68)Ge-based attenuation-corrected PET images, and 11.05, 6.66, and 6.33 g/mL in CTAC PET images with SCC. CONCLUSION: Correction of oral contrast artifacts in PET images obtained by combined PET/CT yielded more accurate quantitation of the lesion and other, normal structures. The algorithm was tested in a clinical case, in which SUV(max) measurements showed discrepancies of 2%, 1.3%, and 5% between (68)Ge-based attenuation-corrected PET images and CTAC PET images with SCC for the lesion, bladder, and bowel, respectively. These values correspond to 6.5%, 62%, and 66% differences between CTAC-based measurements and (68)Ge-based ones.     

Significant benefit of multimodal imaging: PET/CT compared with PET alone in staging and follow-up of patients with Ewing tumors.

Hybrid PET/CT was compared with PET alone in the staging and restaging of patients with Ewing tumor to assess the benefit of the combined imaging technique. METHODS: A total of 163 (18)F-FDG PET/CT studies performed in 53 patients (age: range, 4-38 y; median, 16.5 y) with histopathologically confirmed Ewing tumor were evaluated retrospectively. All PET/CT studies included low-dose CT for attenuation correction; in 91 examinations, additional diagnostic chest CT was performed. PET and CT data were assessed independently by 2 nuclear medicine physicians and 2 radiologists, respectively. Finally, both datasets were fused by use of software and analyzed by all 4 reviewers (consensus reading). Each lesion was scored with a 5-point scale. Biopsy, imaging, or clinical follow-up served as a standard of reference. Receiver operating characteristic (ROC) analyses were performed to evaluate PET and PET/CT performance characteristics. To measure the abilities to detect and correctly localize tumor foci, localization ROC (L-ROC) curves were generated for PET. RESULTS: A total of 609 lesions were detected by PET alone. The hybrid PET/CT technique resulted in a change of score in 160 of these lesions (26%): higher scores in 23 lesions (4%) and lower scores in 137 lesions (23%). In 49 lesions detected by PET (8%), the localization had to be changed after image fusion. Additionally, 124 (21%) more lesions were found by PET/CT than by PET alone, resulting in a total of 733 lesions. As determined by lesion-based analysis, the sensitivity, specificity, and accuracy of PET were 71%, 95%, and 88%, respectively; the corresponding values for the hybrid PET/CT technique were 87%, 97%, and 94% (P < 0.0001). The areas under the curve in the ROC analysis were 0.82 for PET and 0.92 for PET/CT (P < 0.0001), and that in the L-ROC analysis was 0.66 for PET. CONCLUSION: PET/CT is significantly more accurate than PET alone for the detection and localization of lesions and improves staging for patients with Ewing tumor. The hybrid technique is superior to PET alone in terms of sensitivity, specificity, and accuracy, mainly because of the detection of new lesions.     

ROC曲线评价18F—FDGPET／CT、99Tcm—MDP骨显像及二者联合对骨转移的检出效能

目的采用ROC曲线比较18F-FDGPET／CT、99TcmMDP骨显像及二者联合对骨转移患者的检出效能。方法296例恶性肿瘤患者在2个月内同时接受了18F-FDGPET／CT和99TcmMDP骨显像,对2种显像结果按5分法（0分：骨转移阴性,1分：可能阴性,2分：不能确定,3分：可能阳性,4分：肯定阳性）分别评分,两者之和为联合评分值。以病理诊断或临床随访为确诊“金标准”,采用。检验比较ROC曲线下面积,以评价骨显像、PET／CT及联合评分法对骨转移患者的检出效能,采用r检验比较不同方法在各自最佳诊断阈值下的灵敏度、特异性、准确性、阳性预测值、阴性预测值。结果296例患者中,确诊骨转移阳性61例（占20．6％）、阴性235例（占79．4％）。骨显像、PET／CT及联合评分诊断骨转移的ROC曲线下面积（95％可信区间）分别为0．919（0．867—0．971）、0．949（0．906～0．991）、0．994（0．988～0．999）,联合评分法的曲线下面积明显大于骨显像（z=2．866,P=0．004）和PET／CT（z=2．027,P=0．043）各自单独评分法,骨显像和PET／CT法曲线下面积差异没有统计学意义（z=0．881,P=0．378）。最佳阈值点下,骨显像和PET／CT单独检出骨转移患者的灵敏度、特异性、准确性、阳性预测值、阴性预测值分别为90．2％（55／61）、85．1％（200／235）、86．1％（255／296）、61．1％（55／90）、97．1％（200／206）和88．5％（54／61）、97．0％（228／235）、95．3％（282／296）、88．5％（54／61）、97．0％（228／235）,而联合评分检出的结果分别为98．4％（60／61）、95．7％（225／235）、96．3％（285／296）、85．7％（60／70）、99．6％（225／226）。PET／CT对骨转移患者检出的特异性（X2=19．600,P〈0．001）、准确性（X2=13．755,P〈0．001）、阳性预测值（x2=13．608,P〈0．001）均高于骨显像,灵敏度（r=0,P=1．000）差异无统计学意义;与骨显像、PET／CT单独评分比较,联合评分法检出的特异性（X2=19．862,P〈0．001）、准确性（x2=23．361,P〈0．001）和阳性预测值（x2=11．791,P=0．001）均明显高于骨显像,灵敏度明显高于PET／CT（x2=4．167,P=0．031）。结论18F—FDGPET／CT对骨转移患者的检出效能优于99Tcm—MDP骨显像,二者联合明显提高了对骨转移患者的检出率。     

PET/CT与HRCT在孤立型细支气管肺泡癌诊断中的协同应用价值

目的探讨正电子发射计算机体层成像(PET/CT)与高分辨率CT(HRCT)在孤立型细支气管肺泡癌(sol-itary bronchioloalveolar carcinoma,SBAC)诊断中协同应用的价值,以提高对该病的诊断准确率。方法搜集经手术病理证实的28例SBAC患者的PET/CT及HRCT影像资料,患者均先行PET/CT显像,其中16例根据诊断需要于0～3天内行HRCT检查,分析两者对SBAC的协同诊断价值。结果 28例中,PET/CT显像确切诊断肺癌者15例(53.6%),恶性不除外5例(17.9%),良性病变8例(28.6%),误诊率较高。16例HRCT协同PET/CT确切诊断肺癌15例,其中1例初诊良性病变,后经HRCT结合图像后处理技术诊断为肺癌,1例伴右肺门淋巴结转移者,HRCT图像仅显示形态正常淋巴结影,而PET/CT诊断淋巴结转移,后经病理证实;PET/CT与HRCT协同诊断正确率达100%。结论 PET/CT显像诊断SBAC易出现假阴性,误诊率较高;PET/CT与HRCT在SBAC诊断中的协同应用能够弥补常规PET/CT显像中的不足,达到优势互补并充分发挥PET/CT的资源优势,有助于提高对SBAC的诊断准确率。     

Sensitivity of PET/MR images in liver metastases from colorectal carcinoma

Our aim was to evaluate the sensitivity of positron emission tomography/magnetic resonance image (PET/MRI) in the detection of liver metastases in patients from colorectal cancer as compared with computed tomography (CT), magnetic resonance imaging (MRI), PET and PET/CT images. From April 2008 to April 2010, twenty-four patients (mean age 56.5±10.5 years) with liver metastases from colorectal cancer diagnosed by pathology were retrospectively studied as above. All image data were respectively collected and fused. PET/CT and PET/MRI fusion images were successfully performed with a PET-MR-CT robot transmission-fusion imaging system. Pathologic findings and clinical follows-up were performed as referenced standards. Images were reviewed independently by at least three experts. We found a total number of 121 metastatic lesions and 35 of them, with a maximum diameter less than 1cm. According to a per-lesion analysis, the sensitivity on liver metastases was 64.5%, 80.2% and 54.5% on CT, MRI and PET, respectively. Based on reconstruction imaging analysis, PET/CT and PET/MRI showed sensitivities of 84.2% and 98.3%. Sensitivity comparison of PET/MRI had superior sensitivity of 98.08%. Paired data analysis (McNemar) resulted a type I error which equated to 0.05. There was a statistically significant difference between CT and MRI or PET for the detection of patients with liver metastatic lesions (P<0.05). However, PET/MRI can efficiently detect more metastatic lesions than PET/CT (P<0.05) among those with diameter <1cm. In conclusion, PET/MRI was a quite efficient diagnostic modality compared to conventional imaging modalities and should be considered the procedure of choice in the detection of liver metastatic lesions from colorectal cancer.     

CT vs 68Ge attenuation correction in a combined PET/CT system: evaluation of the effect of lowering the CT tube current

With the introduction of combined positron emission tomography/computed tomography (PET/CT) systems, several questions have to be answered.In this work we addressed two of these questions: (a) to what value can the CT tube current be reduced while still yielding adequate maps for the attenuation correction of PET emission scans and (b) how do quantified uptake values in tumours derived from CT and germanium-68 attenuation correction compare. In 26 tumour patients, multidetector CT scans were acquired with 10, 40, 80 and 120 mA (CT10, CT40, CT80 and CT120) and used for the attenuation correction of a single FDG PET emission scan, yielding four PET scans designated PET(CT10)-PET(CT120). In 60 tumorous lesions, FDG uptake and lesion size were quantified on PET(CT10)-PET(CT120). In another group of 18 patients, one CT scan acquired with 80 mA and a standard transmission scan acquired using 68Ge sources were employed for the attenuation correction of the FDG emission scan (PET(CT80), PET(68Ge)). Uptake values and lesion size in 26 lesions were compared on PET(CT80) and PET(68Ge). In the first group of patients, analysis of variance revealed no significant effect of CT current on tumour FDG uptake or lesion size. In the second group, tumour FDG uptake was slightly higher using CT compared with 68Ge attenuation correction, especially in lesions with high FDG uptake. Lesion size was similar on PET(CT80) and PET(68Ge). In conclusion, low CT currents yield adequate maps for the attenuation correction of PET emission scans. Although the discrepancy between CT- and 68Ge-derived uptake values is probably not relevant in most cases, it should be kept in mind if standardised uptake values derived from CT and 68Ge attenuation correction are compared.