Standardized uptake value-based evaluations of solitary pulmonary nodules using F-18 fluorodeoxyglucose-PET/computed tomography

Timing of fluorodeoxyglucose positron emission tomography maximum standardized uptake value for diagnosis of local recurrence of non-small cell lung cancer after stereotactic body radiation therapy

Introduction

After treatment with stereotactic body radiation therapy (SBRT), local recurrence of non‐small cell cancer (NSCLC) can be difficult to differentiate from radiation‐induced changes. Maximum standardized uptake value (SUVmax), measured with 18‐F‐Fluorodeoxyglucose positron emission tomography (FDG‐PET), can have false positives due to acute radiation inflammation. The primary study objective was to determine the utility of SUVmax > 5 to identify local recurrence later than 9 months after SBRT.

Method

A retrospective review was performed of FDG‐PET scans for suspicious CT findings after SBRT treatment of stage 1 NSCLC. SUVmax was measured including surrounding opacification. Outcome measures were local recurrence, progression free survival, and overall survival. Receiver operator curve analysis, sensitivity, specificity, and Kaplan‐Meier analysis were performed.

Results

Of 118 patients treated, 42 patients had eligible FDG‐PET scans. They received SBRT (48‐60Gy in 3‐8 fractions) for 49 NSCLC and had 101 follow‐up PET scans. The median time to first PET scan was 9.3 months, and the median follow‐up period was 22.4 months. Local recurrence was diagnosed in 12 patients, at a median of 16 months. Due to selection bias, the included patients had poorer outcomes than the entire cohort, with progression free survival (PFS) at 1, 2, and 3 years of 82.7%, 57.8%, and 45.8%; and overall survival of 97.9%, 79.9%, and 59.1%, respectively. Thirty FDG‐PET scans were performed within 9 months, of which 17% were false positives. A total of 71 FDG‐PET scans were performed beyond 9 months, and the median SUVmax was significantly higher for patients with local recurrence (7.48 vs. 2.14, P < .0001). SUVmax > 5 has a sensitivity of 91% (95% CI 62%‐99.8%) and 100% (89.1%‐100%).

Conclusion

For local recurrence of NSCLC, SUVmax > 5 on FDG‐PET scan has good sensitivity and specificity after 6 months, but is highest beyond 9 months after SBRT.

Comparing the diagnostic value of 18F-FDG-PET/CT versus CT for differentiating benign and malignant solitary pulmonary nodules: a meta-analysis

Background

This quantitative meta-analysis was conducted to provide an indirect comparison of the diagnostic value of computed tomography (CT) with positron emission tomography (PET)/CT for differentiating benign and malignant solitary pulmonary nodules (SPNs).

Methods

PubMed, Embase, and the Cochrane Library were searched to identify eligible studies throughout November 2018, which differentiated benign and malignant SPNs using CT or PET/CT. The summary sensitivity, specificity, positive and negative likelihood ratio (PLR and NLR), diagnostic odds ratio (DOR), and area under the receiver operating characteristic curve (AUC) were calculated using bivariate generalized linear mixed model and random-effects model. The diagnostic value of CT with PET/CT was indirectly evaluated using the ratio for diagnostic parameters.

Results

The sensitivity, specificity, PLR, NLR, DOR, and AUC for CT were 0.94 [95% confidence interval (CI): 0.87-0.97], 0.73 (95% CI: 0.64-0.80), 3.45 (95% CI: 2.60-4.58), 0.09 (95% CI: 0.04-0.17), 32.01 (95% CI: 15.10-67.86), and 0.89 (95% CI: 0.86-0.91), respectively. The pooled sensitivity, specificity, PLR, NLR, DOR, and AUC for PET/CT were 0.89 (95% CI: 0.85-0.92), 0.78 (95% CI: 0.66-0.86), 3.97 (95% CI: 2.57-6.13), 0.15 (95% CI: 0.10-0.20), 24.04 (95% CI: 12.71-45.48), and 0.91 (95% CI: 0.89-0.94), respectively. No significant differences were observed between CT and PET/CT for sensitivity, specificity, PLR, NLR, DOR, and AUC.

Conclusions

This study used both CT and PET/CT with a moderate-to-high diagnostic value for differentiating benign and malignant SPNs and showed no significant differences in diagnostic parameters between CT and PET/CT.

Clinically simplified screening methods to evaluate maximum standard uptake value from F-18-FDG-PET/CT in patients with non-small-cell lung cancer

Maximum standard uptake value (SUVmax) of F-18-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) is reportedly useful for evaluating regional lymph nodes (RLNs) of non-small-cell lung cancer (NSCLC) to predict malignancy. However, it is difficult for clinicians to measure SUVmax (mSUVmax) as calculated by a workstation.We assessed the utility of simplified SUVmax (sSUVmax) in screening RLNs for pathologic malignancy. The highest color was visually defined in the region of interest. The resulting color can be quantified using the color bar, and interpreted as sSUVmax. Patients in respiratory medicine and surgery who underwent both contrast-enhanced CT and FDG-PET/CT within 3 months before radical lobectomy were evaluated retrospectively. The correlation was examined by regression analysis and receiver operating characteristic (ROC) curve analyses.Participants comprised 69 patients with NSCLC treated between May 2009 and April 2016. Medical group comprised 22 patients from respiratory medicine. The prediction model could be written as a linear relationship (mSUVmax = 1.019 × sSUVmax; R = 0.930). A total of 316 RLNs resected by surgery in total cohort were pathologically determined. From ROC curves, area under curve for sSUVmax was 0.72 (95% confidence interval, 0.61-0.83; P < .0002). The cutoff sSUVmax was 2.42 (sensitivity, 52%; specificity, 88%; accuracy, 85%).The sSUVmax allows quantification of colors from FDG-PET/CT and shows a close correlation to mSUVmax. This value may have potential in screening for RLNs, and thoracic clinicians can readily determine the value. These findings may facilitate better planning of therapeutic strategy in the real world.

The value of 18F-FDG-PET/CT in the diagnosis of solitary pulmonary nodules: A meta-analysis

BACKGROUND

Solitary pulmonary nodules (SPNs) are common imaging findings. Many studies have indicated that F-fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG-PET/CT) is an accurate test for distinguishing benign and malignant SPNs. The aim of this study was to investigate the value of F-FDG-PET/CT in the diagnosis of malignant SPNs.

METHODS

We systematically searched the PubMed and Embase databases up to March 2017, and published data on sensitivity, specificity, and other measures of diagnostic accuracy of F-FDG-PET/CT in the diagnosis of malignant SPNs were meta-analyzed. Statistical analyses were undertaken using Meta-DiSc 1.4 software and Stata version 12.0. The measures of accuracy of F-FDG-PET/CT in the diagnosis of malignant SPNs were pooled using random-effects models.

RESULTS

A total of 20 publications reporting 21 studies were identified. Pooled results indicated that F-FDG-PET/CT showed a diagnostic sensitivity of 0.89 (95% confidence interval [CI], 0.87-0.91) and a specificity of 0.70 (95% CI, 0.66-0.73). The positive likelihood ratio was 3.33 (95% CI, 2.35-4.71) and the negative likelihood ratio was 0.18 (95% CI, 0.13-0.25). The diagnostic odds ratio was 22.43 (95% CI, 12.55-40.07).

CONCLUSIONS

F-FDG-PET/CT showed insufficient sensitivity and specificity for diagnosing malignant SPNs; it cannot replace the "gold standard" pathology by resection or percutaneous biopsy. Larger studies are required for further evaluation.

Impact of partial-volume correction in oncological PET studies: a systematic review and meta-analysis

Purpose

Positron-emission tomography can be useful in oncology for diagnosis, (re)staging, determining prognosis, and response assessment. However, partial-volume effects hamper accurate quantification of lesions <2–3× the PET system’s spatial resolution, and the clinical impact of this is not evident. This systematic review provides an up-to-date overview of studies investigating the impact of partial-volume correction (PVC) in oncological PET studies.

Methods

We searched in PubMed and Embase databases according to the PRISMA statement, including studies from inception till May 9, 2016. Two reviewers independently screened all abstracts and eligible full-text articles and performed quality assessment according to QUADAS-2 and QUIPS criteria. For a set of similar diagnostic studies, we statistically pooled the results using bivariate meta-regression.

Results

Thirty-one studies were eligible for inclusion. Overall, study quality was good. For diagnosis and nodal staging, PVC yielded a strong trend of increased sensitivity at expense of specificity. Meta-analysis of six studies investigating diagnosis of pulmonary nodules (679 lesions) showed no significant change in diagnostic accuracy after PVC (p = 0.222). Prognostication was not improved for non-small cell lung cancer and esophageal cancer, whereas it did improve for head and neck cancer. Response assessment was not improved by PVC for (locally advanced) breast cancer or rectal cancer, and it worsened in metastatic colorectal cancer.

Conclusions

The accumulated evidence to date does not support routine application of PVC in standard clinical PET practice. Consensus on the preferred PVC methodology in oncological PET should be reached. Partial-volume-corrected data should be used as adjuncts to, but not yet replacement for, uncorrected data.

Electronic supplementary material

The online version of this article (doi:10.1007/s00259-017-3775-4) contains supplementary material, which is available to authorized users.

Contribution of nonattenuation-corrected images on FDG-PET/CT in the assessment of solitary pulmonary nodules

In this study, we aim to determine the diagnostic performance of nonattenuation-corrected (NAC) and attenuation-corrected (AC) FDG-PET/CT images in the assessment of solitary pulmonary nodule (SPN). We reviewed the images of 41 patients who underwent FDG-PET/CT to diagnose SPNs. The visual analysis of FDG uptake intensity in SPN on AC and NAC PET images was made using a four-point score from 1 to 4 on both AC and NAC PET images. The cutoff value of SUVmax and visual uptake scores for malignancy were defined as ≥2.5 and ≥3, respectively. The significant visual uptake (≥2 visual point score) on AC and NAC PET images was considered to be positive 18F-FDG PET findings for lesion detectability. The sensitivity, specificity and diagnostic accuracy were calculated for AC and NAC PET images. Based on the histopathology and imaging data, 22 of the SPNs (54 %) were malignant and 19 of them (46 %) were benign. The sensitivity and NPV were found to be 100 % in the detection of SPNs for AC and NAC PET images. For all SPNs and SPNs ≤2 cm, NAC PET image had a higher diagnostic performance for the SPN characterization as malignant or benign, when compared with AC PET image. The success rates of AC and NAC PET images were found to be similar for the detection of SPNs. NAC PET image had a higher diagnostic performance for the SPN characterization. It is thought that NAC PET image may provide additional contributions for characterization of SPNs.

Indolent, Potentially Inconsequential Lung Cancers in the Pittsburgh Lung Screening Study

RATIONALE

The finding of indolent, potentially inconsequential cancers (overdiagnosis) is inherent to cancer screening in general, and there is a growing body of literature about this concept in lung cancer screening.

OBJECTIVES

We report on indolent, potentially inconsequential lung cancers in the Pittsburgh Lung Screening Study (PLuSS) population screened for lung cancer with annual low-dose computed tomography.

METHODS

We identified 93 subjects with screen-detected prevalence cancers in PLuSS. We defined indolent, potentially inconsequential cancers as stage I prevalence lung cancer cases that had volumetric doubling time >400 days (when available) and maximal standardized uptake value max on positron emission tomography (PET) scan ≤1 (when available).

MEASUREMENTS AND MAIN RESULTS

Approximately 18.5% (n = 17) of all 93 screen-detected prevalence lung cancers in PLuSS were indolent, potentially inconsequential cancers. All such cancers except for one were adenocarcinomas by histology. Median tumor size of such cancers at the time of final diagnosis was 10 mm (range, 7-22 mm). Median doubling time was significantly longer in this group when compared with the rest of the prevalence stage 1 cancers (752 vs. 284.5 d).

CONCLUSIONS

Although the precise definitions may vary, the existence of indolent, potentially inconsequential cancers in low-dose computed tomography lung cancer screening is real. Clinicians involved in managing patients with low-dose computed tomography-detected slow-growing nodules, especially with a standardized uptake value ≤1 on PET scan, should consider the possibility of indolent, potentially inconsequential cancer in the longitudinal management of these nodules.

Accuracy of FDG-PET to diagnose lung cancer in areas with infectious lung disease: a meta-analysis

IMPORTANCE

Positron emission tomography (PET) combined with fludeoxyglucose F 18 (FDG) is recommended for the noninvasive diagnosis of pulmonary nodules suspicious for lung cancer. In populations with endemic infectious lung disease, FDG-PET may not accurately identify malignant lesions.

OBJECTIVES

To estimate the diagnostic accuracy of FDG-PET for pulmonary nodules suspicious for lung cancer in regions where infectious lung disease is endemic and compare the test accuracy in regions where infectious lung disease is rare.

DATA SOURCES AND STUDY SELECTION

Databases of MEDLINE, EMBASE, and the Web of Science were searched from October 1, 2000, through April 28, 2014. Articles reporting information sufficient to calculate sensitivity and specificity of FDG-PET to diagnose lung cancer were included. Only studies that enrolled more than 10 participants with benign and malignant lesions were included. Database searches yielded 1923 articles, of which 257 were assessed for eligibility. Seventy studies were included in the analysis. Studies reported on a total of 8511 nodules; 5105 (60%) were malignant.

DATA EXTRACTION AND SYNTHESIS

Abstracts meeting eligibility criteria were collected by a research librarian and reviewed by 2 independent reviewers. Hierarchical summary receiver operating characteristic curves were constructed. A random-effects logistic regression model was used to summarize and assess the effect of endemic infectious lung disease on test performance.

MAIN OUTCOME AND MEASURES

The sensitivity and specificity for FDG-PET test performance.

RESULTS

Heterogeneity for sensitivity (I2 = 87%) and specificity (I2 = 82%) was observed across studies. The pooled (unadjusted) sensitivity was 89% (95% CI, 86%-91%) and specificity was 75% (95% CI, 71%-79%). There was a 16% lower average adjusted specificity in regions with endemic infectious lung disease (61% [95% CI, 49%-72%]) compared with nonendemic regions (77% [95% CI, 73%-80%]). Lower specificity was observed when the analysis was limited to rigorously conducted and well-controlled studies. In general, sensitivity did not change appreciably by endemic infection status, even after adjusting for relevant factors.

CONCLUSIONS AND RELEVANCE

The accuracy of FDG-PET for diagnosing lung nodules was extremely heterogeneous. Use of FDG-PET combined with computed tomography was less specific in diagnosing malignancy in populations with endemic infectious lung disease compared with nonendemic regions. These data do not support the use of FDG-PET to diagnose lung cancer in endemic regions unless an institution achieves test performance accuracy similar to that found in nonendemic regions.

Infection dynamics and response to chemotherapy in a rabbit model of tuberculosis using [¹⁸F]2-fluoro-deoxy-D-glucose positron emission tomography and computed tomography

With a host of new antitubercular chemotherapeutics in development, methods to assess the activity of these agents beyond mouse efficacy are needed to prioritize combinations for clinical trials. Lesions in Mycobacterium tuberculosis-infected rabbits are hypoxic, with histopathologic features that closely resemble those of human tuberculous lesions. Using [(18)F]2-fluoro-deoxy-d-glucose ([(18)F]FDG) positron emission tomography-computed tomography (PET-CT) imaging, we studied the dynamics of tuberculosis infection in rabbits, revealing an initial inflammatory response followed by a consolidative chronic disease. Five weeks after infection, as much as 23% of total lung volume was abnormal, but this was contained and to some extent reversed naturally by 9 weeks. During development of this chronic state, individual lesions in the same animal had very different fates, ranging from complete resolution to significant progression. Lesions that remained through the initial stage showed an increase in volume and tissue density over time by CT. Initiation of chemotherapy using either isoniazid (INH) or rifampin (RIF) during chronic infection reduced bacterial load with quantitative changes in [(18)F]FDG uptake, lesion density and total lesion volume measured by CT. The [(18)F]FDG PET uptake in lesions was significantly reduced with as little as 1 week of treatment, while the volume and density of lesions changed more slowly. The results from this study suggest that rabbits may be a useful surrogate species for evaluating novel chemotherapies and understanding changes in both PET and CT scans in human clinical trials.

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 < 0.0001), respectively, with an average percentage increase of 30.8 %. In 3-D PET/CT, 86 of 206 (41.7 %) lesions were considered positive, 70 of 206 (34 %) negative and 50 of 206 (24.3 %) equivocal, while in 4-D PET/CT 117 of 206 (56.8 %) lesions were defined as positive, 80 of 206 (38.8 %) negative and 9 of 206 (4.4 %) equivocal. In 34 of 50 (68 %) 3-D equivocal lesions follow-up data were available and the presence of malignancy was confirmed in 21 of 34 (61.8 %) lesions, while in 13 of 34 (38.2 %) was excluded. In 31 of these 34 controlled lesions, 20 of 34 (58.8 %) and 11 of 34 (32.4 %) were correctly classified by 4-D PET/CT as positive and negative, respectively; 3 of 34 (8.8 %) remained equivocal. With equivocal lesions classified as positive, the overall accuracy of 3-D and 4-D was 85.7 and 92.8 %, respectively, while the same figures were 80.5 and 94.2 % when equivocal lesions were classified as negative.

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.

Kikuchi-Fujimoto disease: PET/CT assessment of a rare cause of cervical lymphadenopathy

PURPOSE

Kikuchi-Fujimoto disease (KFD), formerly called subacute necrotizing lymphadenitis, is a rare cause of cervical lymphadenopathy. The purpose of this study was to evaluate the usefulness of FDG PET/CT for distinguishing KFD from non-Hodgkin lymphoma (NHL).

MATERIALS AND METHODS

Twenty-two patients with cervical lymphadenopathy (8 with KFD and 14 with NHL) underwent CT and FDG PET/CT scans to examine the cervical lymphadenopathy. Regional values of FDG uptake were evaluated using the standardized uptake value (SUV) and partial volume corrected SUV (corSUV) based on the count recovery coefficient. Tumor size (mm), SUV, and corSUV were compared among KFD, indolent NHL, and aggressive NHL.

RESULTS

KFD lesions tended to be smaller (13.8 ± 5.4 mm) than those of indolent (25.4 ± 11.8) and aggressive (29.7 ± 18.8) NHL, whereas there were no significant differences in size. As for SUV, a significant difference was observed only between indolent and aggressive (6.4 ± 1.5 and 17.3 ± 9.3, P < 0.05) NHL; however, KFD showed a significantly greater corSUV (23.8 ± 10.6) as compared with indolent NHL (9.2 ± 5.1, P < 0.05), which did not show a significant difference from aggressive NHL (21.4 ± 10.2). FDG PET/CT detected thoracoabdominal lesions in 2 patients (25%) with KFD.

CONCLUSIONS

KFD shows high FDG uptake for size, which may reflect the pathologic characteristics, including necrotizing lymphocytes and numerous histiocytes (macrophages) surrounding small necrotic foci. FDG PET/CT will be useful for detecting noncervical lesions of KFD and distinguishing KFD from NHLs using both SUV and corSUV.

Is there any maximum standardized uptake value variation among positron emission tomography scanners for mediastinal staging in non-small cell lung cancer?

The maximum standardized uptake value (SUV(max)) varies among positron emission tomography-integrated computed tomography (PET/CT) centers in the staging of non-small cell lung cancer. We evaluated the ratio of the optimum SUV(max) cut-off for the lymph nodes to the median SUV(max) of the primary tumor (ratioSUV(max)) to determine SUV(max) variations between PET/CT scanners. The previously described PET predictive ratio (PPR) was also evaluated. PET/CT and mediastinoscopy and/or thoracotomy were performed on 337 consecutive patients between September 2005 and March 2009. Thirty-six patients were excluded from the study. The pathological results were correlated with the PET/CT findings. Histopathological examination was performed on 1136 N2 lymph nodes using 10 different PET/CT centers. The majority of patients (group A: 240) used the same PET/CT scanner at four different centers. Others patients were categorized as group B. The ratioSUV(max) for groups A and B was 0.18 and 0.22, respectively. The same ratio for centers 1, 2, 3 and 4 was 0.2, 0.21, 0.21, and 0.23, respectively. The optimal cut-off value of the PPR to predict mediastinal lymph node pathology for malignancy was 0.49 (likelihood ratio +2.02; sensitivity 70%, specificity 65%). We conclude that the ratioSUV(max) was similar for different scanners. Thus, SUV(max) is a valuable cut-off for comparing-centers.

The role of (18)F-FDG PET in the differentiation between lung metastases and synchronous second primary lung tumours

Purpose

In lung cancer patients with multiple lesions, the differentiation between metastases and second primary tumours has significant therapeutic and prognostic implications. The aim of this retrospective study was to investigate the potential of ¹⁸F-FDG PET to discriminate metastatic disease from second primary lung tumours.

Methods

Of 1,396 patients evaluated by the thoracic oncology group between January 2004 and April 2009 at the Radboud University Nijmegen Medical Centre, patients with a synchronous second primary lung cancer were selected. Patients with metastatic disease involving the lungs served as the control group. Maximum standardized uptake values (SUVs) measured with ¹⁸F-FDG PET were determined for two tumours in each patient. The relative difference between the SUVs of these tumours (∆SUV) was determined and compared between the second primary group and metastatic disease group. Receiver-operating characteristic (ROC) curve analysis was performed to determine the sensitivity and specificity of the ∆SUV for an optimal cut-off value.

Results

A total of 37 patients (21 metastatic disease, 16 second primary cancer) were included for analysis. The ∆SUV was significantly higher in patients with second primary cancer than in those with metastatic disease (58 vs 28%, respectively, p < 0.001). The area under the ROC curve was 0.81 and the odds ratio for the optimal cut-off was 18.4.

Conclusion

SUVs from ¹⁸F-FDG PET images can be helpful in differentiating metastatic disease from second primary tumours in patients with synchronous pulmonary lesions. Further studies are warranted to confirm the consistency of these results.

[PET-CT for evaluation of the solitary pulmonary nodule: an update]

INTRODUCTION

Positron emission tomography (PET) with 18F-FDG has become an important tool for the characterization of solitary pulmonary nodules (SPN).

BACKGROUND

The results of the main meta-analyses show that the sensitivity and specificity of 18F-FDG PET for determining malignancy of SPN are close to 95% and 80% respectively. The limits of the technology are now well known. False negative results are mainly due to certain histological types with low metabolic activity (such as bronchiolo-alveolar carcinoma and typical carcinoid), or small size (nodules less than 8 mm). False positives are mainly represented by granulomatous and infectious processes.

VIEWPOINTS

A gain in accuracy occurred with the advent of hybrid PET/CT machines that combine the functional data from 18FDG-PET and the morphological data of computed tomography. Improved imaging protocols (eg. injection of iodinated contrast media) could further enhance the performance of PET-CT. Further improvements will rely on respiratory synchronization protocols and on the advent of new PET tracers.

CONCLUSION

18F-FDG PET-CT should be performed for any nodule over 8 mm in size when the pre-test probability of malignancy is not deemed negligible.

Contrast material injection protocol with the dose adjusted to the body surface area for MDCT aortography

OBJECTIVE

The objective of our study was to investigate the effect on aortic enhancement of contrast material volumes adjusted for a patient's body surface area (BSA) at CT angiography (CTA).

SUBJECTS AND METHODS

A 64-MDCT scanner was used to perform CTA of the whole aorta in 89 patients (mean age, 68.7 years) with confirmed or suspected aortoiliac disease. The patients were divided into groups: a body weight (BW) group (n = 45) and a BSA (n = 44) group. The contrast dose was 360 mg I/kg BW in the BW group and 12,753 mg I/m(2) BSA in the BSA group. Because the average BW of Japanese adults is approximately 60 kg, the contrast dose in the two protocols was identical in patients weighing 60 kg. We compared aortic enhancement achieved with the two protocols using the two-tailed Student's t test, and we used the generalized linear model to analyze the effect of patient age, sex, and BW on aortic enhancement in each protocol group.

RESULTS

The mean aortic enhancement in the BW and BSA groups was 324.2 and 311.7 HU, respectively; the difference was not significant (p = 0.26). In the BW group, BW had a statistically significant effect on aortic enhancement (p < 0.01), whereas neither patient age nor sex did (p = 0.08 and 0.07, respectively). In the BSA group, the age, sex, BW, and BW by sex had no statistically significant effect on aortic enhancement (p = 0.33, 023, 0.10, and 0.16, respectively).

CONCLUSION

Under the BSA protocol, aortic enhancement tended to be consistent and adequate regardless of patient BW.

(18)F-FDG PET-CT respiratory gating in characterization of pulmonary lesions: approximation towards clinical indications

AIM

To evaluate the effect of the 18F-FDG PET-CT respiratory gating (4D) study in the correct documentation of pulmonary lesions with faint uptake in standard PET-CT.

METHODS

Forty-two pulmonary lesions with a low or no detectable uptake of FDG (SUV(max) < 2.5) in 3D PET-CT were prospectively evaluated in 28 patients (19 males and 9 females), mean age 66.5 years (41-81). 22 patients had neoplastic background. A conventional PET-CT (3D) total body scan was performed approximately 60 min after iv injection of a mean dose of 370 MBq. Furthermore, a 4D PET-CT (synchronized with respiratory movement) thorax study was acquired. SUV(max) was determined for each lesion in both studies. For the 4D studies, we selected the SUV(max) in respiratory period with the highest uptake ("best bin"). We calculated the SUV(max) percentage difference between 3D and 4D PET-CT (% difference = SUV(max) 4D - SUV(max) 3D/SUV(max) 3D x 100) and the relation of this value with the size and locations of the lesions. In 4D study, any lesion with SUV(max) > or = 2.5 was classified as malignant. We assessed the changes of lesion classification (from benign to malignant) applying the 4D technique. The final diagnosis was obtained by histological assessment or clinical and radiological follow-up longer than 12 months.

RESULTS

Forty out of 42 lesions showed an increase of SUV(max) in the 4D study with respect to 3D. The mean SUV(max) in the 3D and 4D PET-CT studies were 1.33 (+/-0.59) and 2.26 (+/-0.87), respectively. The SUV(max) percentage difference mean between both techniques was 83.3% (+/-80.81).The smaller the lesion the greater was the SUV(max) percentage difference (P < 0.05). No differences were observed depending on the location of the lesion. In 40% of cases, there was a change in the final classification of lesions from benign to malignant. In the final diagnosis, 24 lesions were malignant. 4D PET-CT diagnosed correctly the 52% of them.

CONCLUSIONS

The 4D PET-CT study permitted a better characterization of malignant lung lesions compared with the standard PET-CT, because of its higher sensitivity. 4D PET-CT is a recommendable technique in the early diagnosis of malignant lesions.