Differentiating benign from malignant lung lesions using "quantitative" parameters of FDG PET images

In vivo evaluation of tumor uptake and bio-distribution of 99mTc-labeled 1-thio-β-D-glucose and 5-thio-D-glucose in mice model

BACKGROUND

To investigate the capacity of 99mTc-labeled 1-thio-β-D-glucose (1-TG) and 5-thio-D-glucose (5-TG) to act as a marker for glucose consumption in tumor cells in vivo as well as to evaluate the biodistribution of 1-TG and 5-TG. We investigated the biodistribution, including tumor uptake, of 1-TG and 5-TG at various time points after injection (0.5, 2 and 4 h) in human colorectal carcinoma (HCT-116) and human lung adenocarcinoma (A549) xenograft bearing nude mice (N = 4 per tracer and time point).

RESULTS

Ex vivo biodistribution studies revealed a moderate uptake with a maximum tumor-to-muscle ratio of 4.22 ± 2.7 and 2.2 ± 1.3 (HCT-116) and of 3.2 ± 1.1 and 4.1 ± 1.3 (A549) for 1-TG and 5-TG, respectively, with a peak at 4 h for 1-TG and 5-TG. Biodistribution revealed a significantly higher uptake compared to blood in kidneys (12.18 ± 8.77 and 12.69 ± 8.93%ID/g at 30 min) and liver (2.6 ± 2.8%ID/g) for 1-TG and in the lung (7.24 ± 4.1%ID/g), liver (6.38 ± 2.94%ID/g), and kidneys (4.71 ± 1.97 and 4.81 ± 1.91%ID/g) for 5-TG.

CONCLUSIONS

1-TG and 5-TG showed an insufficient tumor uptake with a moderate tumor-to-muscle ratio, not reaching the levels of commonly used tracer, for diagnostic use in human colorectal carcinoma and human lung adenocarcinoma xenograft model.

Diagnostic accuracy of visual analysis versus dual time-point imaging with 18F-FDG PET/CT for the characterization of indeterminate pulmonary nodules with low uptake

OBJECTIVE

To determine the accuracy of visual analysis and the retention index (RI) with dual-time point ¹⁸F-FDG PET/CT for the characterization of indeterminate pulmonary nodules (IPN) with low FDG uptake.

MATERIALS AND METHODS

A retrospective analysis was performed on 43 patients (28 men, 64 ± 11 years old, range 36-83 years) referred for IPN characterization with ¹⁸F-FDG-PET/CT and maximum standard uptake value ≤ 2.5 at 60 minutes post-injection (SUV_max1). Nodules were analyzed by size, visual score for FDG uptake on standard (OSEM 2,8) and high definition (HD) reconstructions, SUV_max1, SUV_max at 180 minutes post-injection (SUV_max2), and RI was calculated. The definitive diagnosis was based on histopathological confirmation (n = 28) or ≥ 2 years of follow-up.

RESULTS

Twenty-four (56%) nodules were malignant. RI ≥ 10% on standard reconstruction detected 18 nodules that would have been considered negative using the standard SUV_max ≥ 2.5 criterion for malignancy. RI ≥ 10% had a sensitivity, specificity, PPV, NPV and accuracy of 75, 73.7, 78.3, 70, and 74.4%, respectively, while for FDG uptake > liver on HD these were 79.1, 63.2, 73.1, 70.6, and 72.1%, respectively. SUV_max1 ≥ 2, SUV_max2 > 2.5 and FDG uptake > liver on standard reconstruction had a PPV of 100%. FDG uptake > mediastinum on HD had a NPV of 100%.

CONCLUSIONS

RI ≥ 10% was the most accurate criterion for malignancy, followed by FDG uptake > liver on HD reconstruction. On standard reconstruction, SUV_max1 ≥2 was highly predictive of malignancy, as well as SUV_max2 > 2.5 and FDG uptake > liver. FDG uptake < mediastinum on HD was highly predictive of benign nodules.

Diagnostic performance of a whole-body dynamic 68GA-DOTATOC PET/CT acquisition to differentiate physiological uptake of pancreatic uncinate process from pancreatic neuroendocrine tumor

To evaluate the diagnostic performance of net influx rate (Ki) values from a whole-body dynamic (WBD) Ga-DOTATOC-PET/CT acquisition to differentiate pancreatic neuroendocrine tumors (pNETs) from physiological uptake of pancreatic uncinate process (UP).Patients who were benefited from a WBD acquisition for the assessment of a known well-differentiated neuroendocrine tumor (NET)/suspicion of disease in the prospective GAPET-NET cohort were screened. Only patients with a confirmed pNET/UP as our gold standard were included. The positron emission tomography (PET) procedure consisted in a single-bed dynamic acquisition centered on the heart, followed by a whole-body dynamic acquisition and then a static acquisition. Dynamic (Ki calculated according to Patlak method), static (SUVmax, SUVmean, SUVpeak) parameters, and tumor-to-liver and tumor-to-spleen ratio (TLRKi and TSRKi (according to hepatic/splenic Ki)), tumor SUVmax to liver SUVmax (TM/LM), tumor SUVmax to liver SUVmean (TM/Lm), tumor SUVmax to spleen SUVmax (TM/SM), and tumor SUVmax to spleen SUVmean (TM/Sm) (according to hepatic/splenic SUVmax and SUVmean respectively) were calculated. A Receiver Operating Characteristic (ROC) analysis was performed to evaluate their diagnostic performance to distinguish UP from pNET.One hundred five patients benefited from a WBD between July 2018 and July 2019. Eighteen (17.1%) had an UP and 26 (24.8%) a pNET. For parameters alone, the Ki and SUVpeak had the best sensitivity (88.5%) while the Ki, SUVmax, and SUVmean had the best specificity (94.4%). The best diagnostic accuracy was obtained with Ki (90.9%). For ratios, the TLRKi and the TSRKi had the best sensitivity (95.7%) while the TM/SM and TM/Sm the best specificity (100%). TLRKi had the best diagnostic accuracy (95.1%) and the best area under the curve (AUC) (0.990).Our study is the first one to evaluate the interest of a WBD acquisition to differentiate UP from pNETs and shows excellent diagnostic performances of the Ki approach.

Impact of Enlarged Nonhypermetabolic Lymph Nodes on Outcomes After Stereotactic Body Radiotherapy for Early-Stage Non-Small-Cell Lung Cancer

BACKGROUND

Up to 15% of patients undergoing positron emission tomography (PET)/computed tomography (CT) before stereotactic body radiotherapy (SBRT) harbor occult nodal disease. In the absence of invasive mediastinal staging, the clinical significance of enlarged nonhypermetabolic lymph nodes (LNs) remains unclear. We performed what is to our knowledge the first study to address whether enlarged nonhypermetabolic LNs were associated with higher post-SBRT failure rates.

PATIENTS AND METHODS

Two academic centers assessed 157 consecutive patients treated with SBRT for cT1-2aN0M0 non-small-cell lung cancer who underwent PET/CT without pathologic nodal staging. The cutoff of an enlarged node was ≥ 1.0 cm, although a 7 mm threshold was also evaluated. Local recurrence-free survival (RFS), regional RFS, distant metastasis-free survival, RFS, and overall survival (OS) were calculated by Kaplan-Meier methodology. Multivariate Cox modeling addressed factors associated with RFS and OS.

RESULTS

There were 120 patients (76%) with LNs < 1 cm and 37 (24%) with nodes ≥ 1 cm. Most patients had peripheral and/or T1 tumors. Median follow-up was 25.5 months. There were no differences between cohorts in actuarial local RFS, regional RFS, distant metastasis-free survival, RFS, or OS (P > .05 for all). Thirteen percent of patients experienced any nodal relapse, 15% of which occurred in the same station as that of the largest pre-SBRT LN. Stratification by largest LN location in an N1 versus N2 station showed no differences in RFS or OS (P > .05 for both). A 7 mm cutoff also showed no differences in outcomes (P > .05 for all). LN size was not correlated with RFS/OS on multivariable analysis (P > .05 for both).

CONCLUSION

The presence of enlarged nonhypermetabolic LNs on PET/CT is not associated with increased post-SBRT failure rates.

Impact of PET/CT system, reconstruction protocol, data analysis method, and repositioning on PET/CT precision: An experimental evaluation using an oncology and brain phantom

Purpose

In longitudinal oncological and brain PET/CT studies, it is important to understand the repeatability of quantitative PET metrics in order to assess change in tracer uptake. The present studies were performed in order to assess precision as function of PET/CT system, reconstruction protocol, analysis method, scan duration (or image noise), and repositioning in the field of view.

Methods

Multiple (repeated) scans have been performed using a NEMA image quality (IQ) phantom and a 3D Hoffman brain phantom filled with ¹⁸F solutions on two systems. Studies were performed with and without randomly (< 2 cm) repositioning the phantom and all scans (12 replicates for IQ phantom and 10 replicates for Hoffman brain phantom) were performed at equal count statistics. For the NEMA IQ phantom, we studied the recovery coefficients (RC) of the maximum (SUV_max), peak (SUV_peak), and mean (SUV_mean) uptake in each sphere as a function of experimental conditions (noise level, reconstruction settings, and phantom repositioning). For the 3D Hoffman phantom, the mean activity concentration was determined within several volumes of interest and activity recovery and its precision was studied as function of experimental conditions.

Results

The impact of phantom repositioning on RC precision was mainly seen on the Philips Ingenuity PET/CT, especially in the case of smaller spheres (< 17 mm diameter, P < 0.05). This effect was much smaller for the Siemens Biograph system. When exploring SUV_max, SUV_peak, or SUV_mean of the spheres in the NEMA IQ phantom, it was observed that precision depended on phantom repositioning, reconstruction algorithm, and scan duration, with SUV_max being most and SUV_peak least sensitive to phantom repositioning. For the brain phantom, regional averaged SUVs were only minimally affected by phantom repositioning (< 2 cm).

Conclusion

The precision of quantitative PET metrics depends on the combination of reconstruction protocol, data analysis methods and scan duration (scan statistics). Moreover, precision was also affected by phantom repositioning but its impact depended on the data analysis method in combination with the reconstructed voxel size (tissue fraction effect). This study suggests that for oncological PET studies the use of SUV_peak may be preferred over SUV_max because SUV_peak is less sensitive to patient repositioning/tumor sampling.

[Analysis of the Role of PET/CT SUVmax in Prognosis and Its Correlation with Clinicopathological Characteristics in Resectable Lung Squamous Cell Carcinoma]

背景与目的

肺癌居于全球男性及女性癌症相关死亡原因的首位，大多数患者在确诊时已属晚期，5年生存率仅为18%。肺癌可分为非小细胞肺癌（non-small cell lung carcinoma, NSCLC）和小细胞癌（small cell lung carcinoma, SCLC），其中NSCLC占肺癌的80%-85%，NSCLC根据组织学可主要分为腺癌（约占40%），鳞状细胞癌（20%-30%）和大细胞癌（10%），针对驱动基因的靶向治疗在肺腺癌中取得一定成绩，但在肺鳞癌的治疗中收效甚微，肺鳞癌的诊治更需得到关注，¹⁸F-脱氧葡萄糖（fluorodeoxyglucose, FDG）正电子发射断层扫描/计算机体层摄影（positron emission tomography/computed tomography, PET/CT）越来越多地应用于肺癌的诊断与分期中，本研究旨在探讨¹⁸F-FDG PET/CT原发灶最大标准摄取值（maximum standardized uptake value, SUVmax）在肺鳞癌患者术后预后中的意义及与临床病理特征的关系。

方法

回顾分析2005年5月-2014年10月收治的182例初治、接受PET/CT检查、行根治术的原发肺鳞癌患者的临床影像病理及随访资料。采用Kaplan-Meier法及Cox模型分析患者生存情况，并分析原发灶SUVmax与各临床病理因素的关系。

结果

182例肺鳞癌患者原发灶SUVmax以13.0为界分为两组，SUVmax > 13.0组与≤13.0组患者的中位总生存期分别为56个月和87个月，差异具有统计学意义（P=0.022）。原发灶SUVmax与性别、肿瘤最大径、肿瘤-淋巴结-转移（tumor-node-metastasis, TNM）分期、中性粒细胞、中性粒细胞/淋巴细胞比例（neutrophil-lymphocyte ratio, NLR）存在正相关性，与血红蛋白呈负相关（P < 0.05）。Cox多因素分析显示SUVmax（HR=1.714, 95%CI: 1.021-2.876, P=0.042）、TNM分期（HR=1.677, 95%CI: 1.231-2.284, P=0.001）均为患者生存的独立预后影响因子，提示SUVmax有独立于病理TNM分期之外的预后价值。而且，SUVmax在Ⅰ期肺鳞癌患者的预后中有意义（P=0.045）。

结论

PET/CT SUVmax对肺鳞癌患者术后生存的预测有重要的价值，是独立于TNM分期之外的一个重要预后因素，并且原发灶SUVmax与多个临床病理因素间存在相关性。

Generalized whole-body Patlak parametric imaging for enhanced quantification in clinical PET

We recently developed a dynamic multi-bed PET data acquisition framework to translate the quantitative benefits of Patlak voxel-wise analysis to the domain of routine clinical whole-body (WB) imaging. The standard Patlak (sPatlak) linear graphical analysis assumes irreversible PET tracer uptake, ignoring the effect of FDG dephosphorylation, which has been suggested by a number of PET studies. In this work: (i) a non-linear generalized Patlak (gPatlak) model is utilized, including a net efflux rate constant kloss, and (ii) a hybrid (s/g)Patlak (hPatlak) imaging technique is introduced to enhance contrast to noise ratios (CNRs) of uptake rate Ki images. Representative set of kinetic parameter values and the XCAT phantom were employed to generate realistic 4D simulation PET data, and the proposed methods were additionally evaluated on 11 WB dynamic PET patient studies. Quantitative analysis on the simulated Ki images over 2 groups of regions-of-interest (ROIs), with low (ROI A) or high (ROI B) true kloss relative to Ki, suggested superior accuracy for gPatlak. Bias of sPatlak was found to be 16-18% and 20-40% poorer than gPatlak for ROIs A and B, respectively. By contrast, gPatlak exhibited, on average, 10% higher noise than sPatlak. Meanwhile, the bias and noise levels for hPatlak always ranged between the other two methods. In general, hPatlak was seen to outperform all methods in terms of target-to-background ratio (TBR) and CNR for all ROIs. Validation on patient datasets demonstrated clinical feasibility for all Patlak methods, while TBR and CNR evaluations confirmed our simulation findings, and suggested presence of non-negligible kloss reversibility in clinical data. As such, we recommend gPatlak for highly quantitative imaging tasks, while, for tasks emphasizing lesion detectability (e.g. TBR, CNR) over quantification, or for high levels of noise, hPatlak is instead preferred. Finally, gPatlak and hPatlak CNR was systematically higher compared to routine SUV values.

Dual time point fluorodeoxyglucose positron emission tomography/computed tomography in differentiation between malignant and benign lesions in cancer patients. Does it always work?

OBJECTIVES

Assess the added value of dual time point F-18-fluorodeoxyglucose positron emission tomography/computed tomography (DTP F-18-FDG-PET/CT) in the differentiation of malignant from a benign lesion in cancer patients.

MATERIALS AND METHODS

Totally, 140 F-18-FDG PET/CT scans of 60 cancer patients who underwent DTP protocol (early whole body PET/CT [E] at 60 min [range, 45-76 min] and delayed limited PET/CT [D] on areas of interest at 120 min [range, 108-153 min] after the tracer injection) were retrospectively reviewed. Visual and semi-quantitative analysis was performed on both early and delayed images. All findings were confirmed by histopathology and/or at least 3 months follow-up (F-18-FDG PET/CT, CT, or magnetic resonance imaging). The result was considered true positive (TP) if delayed standardized uptake value (SUV) of suspicious lesions increased and confirmed to be malignant, false positive (FP) if delayed SUV increased and confirmed to be benign, true negative (TN) if delayed SUV unchanged or decreased and confirmed to be benign, and false negative (FN) if delayed SUV unchanged or decreased and confirmed to be malignant.

RESULTS

A total of 164 suspicious lesions were detected (20 presacral lesions, 18 lung nodules, 18 Hodgkin's disease (HD) lesions, 16 rectal lesions, 16 head and neck (H and N) lesions, 14 hepatic lesions, 14 non-Hodgkin's lymphoma (NHL) lesions, 12 mediastinal lymph nodes (LNs), 10 focal gastric uptake, 10 soft tissue lesions, 8 breast lesions, 4 peritoneal nodule, and 4 others). Sixty-four lesions were pathologically confirmed, and 100 lesions were confirmed based on 3-6 months follow-up. There were 62 TP lesions, 44 FP, 58 TN and no FN results. The overall sensitivity was 100% of DTP F-18-FDG PET/CT in detecting suspicious lesions. The specificity was 57% in differentiating malignant from benign lesions, and the accuracy was 73%. Positive predictive value was 59%, negative predictive value (NPV) 100%. All hepatic lesions were TP. Accuracy in metastatic hepatic lesions HD, presacral soft tissue, lung nodules, H, and N cancer, breast cancer, NHL and mediastinal LN was100%, 88.8%, 80%, 78%, 75%, 75%, 71%, and 33.3%, respectively.

CONCLUSIONS

DTP F-18-FDG-PET/CT protocol does not always work in differentiation between benign and malignant lesions. However; it has high NPV, and promising results was noted in hepatic lesions, lymphoma, and recurrent rectal cancer.

Lung cancer imaging

Lung cancer remains the leading cause of cancer-related deaths in the US. Imaging plays an important role in the diagnosis, staging, and follow-up evaluation of patients with lung cancer. With recent advances in technology, it is important to update and standardize the radiological practices in lung cancer evaluation. In this article, the authors review the main clinical applications of different imaging modalities and the most common radiological presentations of lung cancer.

Kikuchi-Fujimoto disease mimicking malignant lymphoma with 2-[(18)F]fluoro-2-deoxy-D-glucose PET/CT in children

PURPOSE

Kikuchi-Fujimoto disease (KFD) is a benign disease, which is characterized by a cervical lymphadenopathy with fever, and it often mimics malignant lymphoma (ML). 2-[(18)F]fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) is a powerful imaging modality for the diagnosis, staging and monitoring of ML, with the limitations including the nonspecific FDG uptake in infectious or inflammatory processes. This study compared clinical manifestations and PET/CT findings between KFD and ML patients.

METHODS

We retrospectively reviewed the medical records of 23 patients with KFD and 33 patients with ML, diagnosed histopathologically, between January 2000 and May 2013 at the Department of Pediatrics, Yeungnam University Medical Center. Among them, we analyzed the clinical manifestations, laboratory findings and characteristics, and the amount of (18)F-FDG uptake between 8 KFD and 9 ML patients who had (18)F-FDG PET/CT.

RESULTS

The (18)F-FDG PET/CT maximum standardized uptake values (SUVmax) ranged from 8.3 to 22.5 (mean, 12.0) in KFDs, and from 5.8 to 34.3 (mean, 15.9) in MLs. There were no significant differences in SUVmax between KFDs and MLs. (18)F-FDG PET/CT with ML patients showed hot uptakes in the extranodal organs, such as bone marrow, small bowel, thymus, kidney, orbit and pleura. However, none of the KFD cases showed extranodal uptake (P<0.001). (18)F-FDG PET/CT findings of KFD with nodal involvement only were indistinguishable from those of ML.

CONCLUSION

Patients who had extranodal involvement on PET/CT were more likely to have malignancy than KFD.

Positron emission tomography in the evaluation of pulmonary nodules among patients living in a coccidioidal endemic region

BACKGROUND

Within a coccidioidal endemic region, pulmonary nodules due to coccidioidomycosis are common. Uptake of (18)fluorodeoxyglucose ((18)FDG) by positron emission tomography with computed axial tomography (PET/CT) has been used to assess whether pulmonary nodules are malignant but inflammatory lesions can be positive. The purpose of this study was to compare by PET/CT the (18)FDG uptake in pulmonary nodules likely due to coccidioidomycosis to that of nodules shown to be malignant among patients living in a coccidioidal endemic region.

METHODS

We retrospectively reviewed patients who underwent a PET/CT at the Southern Arizona Veterans Affairs Health Care System between January 2008 and March 2012 who were subsequently found on biopsy to have pulmonary nodules that were coccidioidal or granulomatous or were due to malignancy.

RESULTS

Among 245 diagnostic biopsies where the subject had a previous PET/CT, 15 (6.1 %) were either coccidioidal (n = 12) or granulomatous without an identified organism (n = 3). The median maximum standard unit of uptake (SUV(max)) on PET/CT of coccidioidal or granulomatous lesions was 2.0 compared to 9.8 for malignant lesions (P < 0.001). The maximum diameter of the coccidioidal or granulomatous nodules was 2.1 cm compared to 3.0 cm for the malignant lesions (P = 0.009). On multivariable analysis, an elevated SUV(max) was the only distinguishing feature between the malignant and the granulomatous lesions (OR 1.28, 95 % CI 1.05-1.55; P = 0.013).

CONCLUSIONS

Coccidioidal pulmonary nodules take up significantly less (18)FDG than those due to malignancies, but there is considerable overlap between granulomatous and malignant lesions at lower SUV(max).

Utility of 18F-FDG PET with a semi-quantitative index in the detection of sarcomatous transformation in patients with neurofibromatosis type 1

Background

Malignant peripheral nerve sheath tumors (MPNSTs) are a serious complications of neurofibromatosis type 1 associated with poor prognosis and deeper lesions can be difficult to diagnose. 18-FDG PET improves the detection of malignancies. However, the criteria for malignancy, notably the SUVmax threshold, are not standardized. Therefore, the aim of the study was to evaluate a semi-quantitative index for the reproducible detection of MPNST with FDG PET.

Methods

It is a multicenter retrospective study conducted between 2000 to 2012. All patients with NF1 referred for suspected MPNST underwent PET. Since SUVmax was not available until 2004 in our centers, we had to settle for the semi-quantitative method used at that time, the uptake ratio between the tumor and the normal liver (T/L ratio) with 1.5 as the cut-off for malignancy. When dedicated PET with SUVmax became available, the semi-quantitative analysis of PET images remained, along with SUVmax.

Results

113 patients with 145 tumors were included. PET assessment revealed 65 suspected lesions with T/L >1.5 and among these, 40 were MPNSTs. 80 tumors were classified as non-suspicious, and 79 were benign. The 1.5 T/L cut-off had a negative predictive value (NPV) of 98,8% and a positive predictive value of 61,5%. The positive likelihood ratio (LR) was 4,059, the negative LR was 0,032 with 97% sensitivity and 76% specificity.

Conclusions

This study, which is among the largest published, confirms the utility of PET for detecting NF1-associated MPNSTs. A semi-quantitative index, the T/L ratio with a cut-off of 1.5, allowed sensitive and specific differentiation of malignant from benign tumors better than SUVmax. When T/L was <1.5, MPNSTs were ruled out with 98,8% NPV. When T/L was >1.5, there was a strong suspicion of malignancy. This semi-quantitative analytical method is as simple as SUVmax, but is more sensitive, more reproducible and non-user-dependent.

Non-local means denoising of dynamic PET images. PLoS One. 2013;8:e81390. [PMID: 24339921 PMCID: PMC3855264 DOI: 10.1371/journal.pone.0081390]

Objective

Dynamic positron emission tomography (PET), which reveals information about both the spatial distribution and temporal kinetics of a radiotracer, enables quantitative interpretation of PET data. Model-based interpretation of dynamic PET images by means of parametric fitting, however, is often a challenging task due to high levels of noise, thus necessitating a denoising step. The objective of this paper is to develop and characterize a denoising framework for dynamic PET based on non-local means (NLM).

Theory

NLM denoising computes weighted averages of voxel intensities assigning larger weights to voxels that are similar to a given voxel in terms of their local neighborhoods or patches. We introduce three key modifications to tailor the original NLM framework to dynamic PET. Firstly, we derive similarities from less noisy later time points in a typical PET acquisition to denoise the entire time series. Secondly, we use spatiotemporal patches for robust similarity computation. Finally, we use a spatially varying smoothing parameter based on a local variance approximation over each spatiotemporal patch.

Methods

To assess the performance of our denoising technique, we performed a realistic simulation on a dynamic digital phantom based on the Digimouse atlas. For experimental validation, we denoised PET images from a mouse study and a hepatocellular carcinoma patient study. We compared the performance of NLM denoising with four other denoising approaches – Gaussian filtering, PCA, HYPR, and conventional NLM based on spatial patches.

Results

The simulation study revealed significant improvement in bias-variance performance achieved using our NLM technique relative to all the other methods. The experimental data analysis revealed that our technique leads to clear improvement in contrast-to-noise ratio in Patlak parametric images generated from denoised preclinical and clinical dynamic images, indicating its ability to preserve image contrast and high intensity details while lowering the background noise variance.

Diagnostic consideration for sinonasal Wegener's granulomatosis clinically mistaken for carcinoma

We report a case of Wegener's granulomatosis clinically mistaken for carcinoma in a 21-year-old girl presenting with an ulcerated mass of the nasopharynx associated with enlarged laterocervical nodes. The lesion was clinically suspected as malignant on the basis of clinical and radiological findings (namely, computed tomography scan and positron emission tomography). However, multiple biopsies were not conclusive for malignancy showing histological change suggestive of Wegener's granulomatosis. A serum determination of cANCA supported the diagnosis of Wegener's granulomatosis. Clinical findings and image studies suggested an erroneous diagnosis of malignancy whereas a definitive diagnosis of Wegener's granulomatosis was achieved only after repeated biopsies thus leading to a correct therapeutic approach. The Wegener granulomatosis must be added to the list of the differential diagnoses of the masses of the nasopharynx associated with or without enlarged laterocervical nodes.

Spreadsheet program for estimating recovery coefficient to get partial volume corrected standardized uptake value in clinical positron emission tomography-computed tomography studies

PURPOSE

To develop a spreadsheet program for estimation of recovery coefficient (RC) to get partial volume corrected (PVC) standardized uptake value (SUV) in clinical positron emission tomography-computed tomography (PET-CT) studies.

MATERIALS AND METHODS

For formulation of this program we used data from a phantom study conducted at our center in which a phantom with a sphere assembly (seven spheres-different diameters) was filled with 18F-Fluorodeoxyglucose solution to get a sphere/background ratio of 8:1, 10:1 and 12:1. PET-CT images were acquired. RC was then calculated from processed PET-CT images. We plotted graph of RC versus lesion-size at different sphere/background ratio using MS Excel function. There was logarithmic increase in RC with increase in lesion size. We fitted the data with a logarithmic equation and found optimum fit (least-square fit). We then validated this program with clinical data using 42 lung nodules in five patients.

RESULTS

The program estimates the value of RC and object to background ratio in PET-CT for the input lesion-size and displays graph with trendline. When the user enters SUV and background activity measured in clinical PET-CT, it provides the value of RC and PVC SUV. It also validates the data entry and displays appropriate message. It is consistent, reproducible, accurate and provides output for wide range of lesion-sizes (71% of lesions evaluated); however, program does not give output for lesion-size < 9 mm.

CONCLUSION

The present spreadsheet program is a useful and easy tool for calculating PVC SUV of clinical PET-CT lesions.

The value of delayed (18)F FDG-PET imaging in diagnosis of solitary pulmonary nodules: A preliminary study on 28 patients

OBJECTIVE

The aim of this study was to investigate whether adding delayed phase imaging can improve diagnostic ability of (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) in evaluating solitary pulmonary nodules (SPNs).

MATERIALS AND METHODS

28 patients with SPNs received dual-phase (18)F-FDG PET at 1h and 2h after (18)F-FDG injection during Feb 2009 to Jun 2011were included in this retrospective study. Their final diagnosis was confirmed by pathological examination in 27 cases and clinical follow-up in 1 case. The standardized uptake value (SUV) of early and delayed phases of all lesions was measured.

RESULTS

The 28 SPNs included 9 benign lesions and 19 malignant lesions. Using SUV ≥2.5 as a criteria for malignancy, the sensitivity, specificity, and accuracy were 52.6%, 55.6% and 53.6% respectively at early phase; 68.4%, 55.6% and 64.3% respectively at early and delayed phases combined. Combined early and delayed phase scans combined picked up 3 additional malignant lesions from the 14 lesions with an initial SUV value less than 2.5, and there was no additional false positive result with the benign lesions.

CONCLUSION

Adding delayed phase scanning resulted in correct diagnosis of three malignant lesions with an initial SUV value less than 2.5. Delayed phase scanning can be recommended in the SPNs with SUV less than 2.5 at early phase.

The clinical significance and management of lesion motion due to respiration during PET/CT scanning

Lesion movement during positron emission tomography (PET) scan acquisition due to normal respiration is a common source of artefact. A PET scan is acquired in multiple couch positions of between 2 and 5 min duration with the patient breathing freely. A PET-avid lesion will become blurred if affected by respiratory motion, an effect similar to that created when a person moves in a photograph. This motion also frequently causes misregistration between the PET and computed tomography (CT) scan acquired for attenuation correction and anatomical correlation on hybrid scanners. The compounding effects of blurring and misregistration in whole-body PET/CT imaging make accurate characterization of PET-avid disease in areas of high respiratory motion challenging. There is also increasing interest in using PET quantitatively to assess disease response in both clinical reporting and trials. However, at this stage, no response criteria take the effect of respiratory motion into account when calculating the standardized uptake value on a PET scan. A number of different approaches have been described in the literature to address the issue of respiratory motion in PET/CT scanning. This review details the clinical significance of lesion movement due to respiration and discusses various imaging techniques that have been investigated to manage the effects of respiratory motion in PET/CT scanning.

Is there a common SUV threshold in oncological FDG PET/CT, at least for some common indications? A retrospective study

PURPOSE

We retrospectively compared the maximum standard uptake value (SUVmax) of FDG PET in four different sites to evaluate whether a common diagnostic SUVmax threshold may exist in these tumor locations. We further postulate that the SUVmax thresholds are higher in thoracic lesions than in extrathoracic lesions.

MATERIAL AND METHODS

N = 143 patients in four subgroups underwent a FDG PET/CT: a) 42 patients for solitary pulmonary nodules (SPNs) characterization with b) respective mediastinal lymph nodes (LNs), c) 65 patients for LN staging of head and neck cancer, and d) 36 cancer patients diagnosed with adrenal lesions. Receiver operating characteristics of SUVmax values were evaluated.

RESULTS

The SUVmax were statistically significantly greater in malignant than in benign lesions. For SPNs and mediastinal LNs, a SUVmax > 3.6 each resulted in a sensitivity of 81% and 87%, and a specificity of 94% and 89%. For cervical LNs and adrenal glands, a SUVmax > 2.2 each showed a sensitivity of 98% and 100%, and a specificity of 83% and 93%.

CONCLUSION

A common SUVmax threshold did not exist in the four studied subgroups. The variable FDG uptake in SPNs and mediastinal LNs are associated with the high prevalence of inflammation/infection within the chest. Similar SUVmax thresholds however may exist for extrathoracic regions where the prevalence of inflammation/infection is low.

A pulmonary paragonimiasis case mimicking metastatic pulmonary tumor

Pulmonary paragonimiasis is a relatively rare cause of lung disease revealing a wide variety of radiologic findings, such as air-space consolidation, nodules, and cysts. We describe here a case of pulmonary paragonimiasis in a 27-year-old woman who presented with a 2-month history of cough and sputum. Based on chest computed tomography (CT) scans and fluorodeoxyglucose positron emission tomography (FDG-PET) findings, the patient was suspected to have a metastatic lung tumor. However, she was diagnosed as having Paragonimus westermani infection by an immunoserological examination using ELISA. Follow-up chest X-ray and CT scans after chemotherapy with praziquantel showed an obvious improvement. There have been several reported cases of pulmonary paragonimiasis mimicking lung tumors on FDG-PET. However, all of them were suspected as primary lung tumors. To our knowledge, this patient represents the first case of paragonimiasis mimicking metastatic lung disease on FDG-PET CT imaging.

Abnormal 18F-FDG Uptake Detected with Positron Emission Tomography in a Patient with Breast Cancer: A Case of Sarcoidosis and Review of the Literature

18F-FDG PET is a useful and sensitive imaging method for a variety of malignancies, however, the specificity is low in active infections and inflammatory diseases. We describe a female patient with stage IIIA breast cancer in first complete remission with combination chemotherapy who developed nodular formations in the lung and axilla 12 years later. Imaging studies as well as FDG PET showed nodular lesions and increased metabolic activity which was interpreted as the progression of the primary disease. She was first given combination chemotherapy and hormonal therapy but was proven thereafter to have sarcoidosis by pathologic examination and was successfully treated with corticosteroid treatment.

Dual-time point 18F-FDG PET/CT scan for differentiation between 18F-FDG-avid non-small cell lung cancer and benign lesions

OBJECTIVE

The aim of this study is to clarify the difference of F-18 FDG uptake kinetics between FDG-avid non-small-cell lung cancer (NSCLC) and benign lesions associated with various etiologies on dual-time point PET/CT scan, and to determine the optimal parameter for differentiation.

MATERIALS AND METHODS

The materials were 76 FDG-avid solitary NSCLC in 76 patients and 57 FDG-avid solitary benign lesions associated with various etiologies in 61 patients. FDG PET/CT scan was performed at 60 and 120 min after intravenous injection of 4.4 MBq/kg F-18 FDG. The maximum standardized uptake value (SUVmax) on early and delayed scans and the percent change of SUVmax (%DeltaSUVmax) between the two time points were measured. The optimal differential parameter was determined by receiver-operating characteristic curve analysis and evaluation of diagnostic accuracy.

RESULTS

The mean +/- SD of early SUV max, delayed SUVmax and %DeltaSUVmax were 8.3 +/- 5.2, and 10.2 +/- 6.5, and 21.9% +/- 18.9 in FDG-avid NSCLC, and 3.8 +/- 3.2, 4.0 +/- 3.7, and 11.3% +/- 26.0 in FDG-avid benign lesions, respectively. Delayed SUVmax in NSCLC was significantly higher than early SUVmax (P < 0.0001); while not different in benign lesions. Percent change of SUVmax in NSCLC was also significantly higher than that in benign lesions (P < 0.01). The optimal parameter for the differentiation was delayed SUVmax > 5.5 and yielded sensitivity of 77.6%, specificity of 80.7% and accuracy of 78.9%, which provided better differentiation than the use of %DeltaSUVmax or the traditional parameter of early SUVmax > 2.5. However, 11 (19.2%) benign lesions were indistinguishable from NSCLC.

CONCLUSION

Although delayed PET/CT scan enhances the difference of FDG uptake between FDG-avid NSCLC and benign lesions, and the use of delayed SUVmax > 5.5 appears to improve the differentiation of these hypermetabolic lesions compared with an early scan, careful interpretation and management for correct differentiation are still required.

Does the availability of positron emission tomography modify diagnostic strategies for solitary pulmonary nodules? An observational study in France

Background

Previous studies showed that at the individual level, positron emission tomography (PET) has some benefits for patients and physicians in terms of cancer management and staging. We aimed to describe the benefits of (PET) in the management of solitary pulmonary nodules (SPNs) in a population level, in terms of the number of diagnostic and invasive tests performed, time to diagnosis and factors determining PET utilization.

Methods

In an observational study, we examined reports of computed tomography (CT) performed and mentioning "spherical lesion", "nodule" or synonymous terms. We found 11,515 reports in a before-PET period, 2002–2003, and 20,075 in an after-PET period, 2004–2005. Patients were followed through their physician, who was responsible for diagnostic management.

Results

We had complete data for 112 patients (73.7%) with new cases of SPN in the before-PET period and 250 (81.4%) in the after-PET period. Patients did not differ in mean age (64.9 vs. 64.8 years). The before-PET patients underwent a mean of 4 tests as compared with 3 tests for the after-PET patients (p = 0.08). Patients in the before-PET period had to wait 41.4 days, on average, before receiving a diagnosis as compared with 24.0 days, on average, for patients in the after-PET period who did not undergo PET (p < 0.001). In the after-PET period, 11% of patients underwent PET during the diagnostic process. A spiculated nodule was more likely to determine prescription for PET (p < 0.001). Multivariate analysis revealed that patients in both periods underwent fewer tests when PET was prescribed by general practitioners (p < 0.001) and if the nodule was not spiculated (p < 0.001). The proportion of unnecessary invasive approaches prescribed (47% vs. 49%) did not differ between the groups.

Conclusion

In our study, 1 year after the availability of PET, the technology was not the first choice for diagnostic management of SPN. Even though we observed a tendency for reduced number of tests and mean time to diagnosis with PET, these phenomena did not fully relate to PET availability in health communities. In addition, the availability of PET in the management of SPN diagnosis did not reduce the overall rate of unnecessary invasive approaches.

The value of dual time point (18)F-FDG PET imaging for the differentiation between malignant and benign lesions

AIM

To assess the clinical value of dual time point 2-[(18)F]-fluoro-2-deoxy-d-glucose positron emission tomography ((18)F-FDG PET) imaging for the differentiation between malignant and benign lesions.

MATERIALS AND METHODS

Ninety-six patients (28 patients with primary lung cancer, 18 patients with digestive system carcinoma, 13 patients with other malignant tumours, and 37 patients with benign lesions) underwent FDG-PET/CT at two time points: examination 1 at 45-55 min and examination 2 at 160+/-24 (150-180) min after the intravenous injection of 233+/-52 (185-370)MBq (18)F-FDG. Reconstructed images were evaluated qualitatively and quantitatively. The maximum standardized uptake values (SUVmax) of the lesions were calculated for both time points. An increase was considered to have occurred if the SUVs at examination 2 had increased by >10% as compared with those at the examination 1.

RESULTS

The lesions in 24 of 28 (86%) patients with primary lung cancer had an SUVmax > or = 2.5 at examination 1. Of these, SUVmax values increased in 23 patients, but had not changed in one patient, at examination 2. The lesions in the other four patients with primary lung tumour had SUVmax values between 1.5 and 2.5 at examination 1, which were considered as suspected positive, increased SUVmax values were observed in three of these patients at examination 2. The malignant lesions in 17 of 18 patients with digestive system carcinoma showed SUVmax values > or = 2.5 and only one patient had an SUVmax value < 1.5 at examination 1; all lesions showed an increase in SUVmax values at examination 2. In 13 patients with other malignant tumours, all lesions had SUVmax values > or = 2.5 at examination 1 and the SUVmax values were further increased at examination 2. Therefore, the malignant lesions in 54/59 (92%) of patients had SUVmax values > or = 2.5 at examination 1 and showed a further increase in SUVmax value at examination 2. Only 12 of 37 (32%) patients with benign lesions showed SUVmax values > or = 2.5 at examination 1 and nine patients with benign lesions had SUVmax values > or = 2.5 in examination 2. The sensitivity, specificity, accuracy, positive and negative predictive values for the early and delayed imaging were 91.5, 67.6, 82.3, 81.8, and 83.3%, and 98.3, 75.7, 89.6, 86.6, and 96.6%, respectively.

CONCLUSION

The results of the present study provide further evidence that dual time point (18)F-FDG PET imaging is an important noninvasive method for the differentiation of malignant and nonmalignant lesions.

Performance of integrated FDG-PET/CT for differentiating benign and malignant lung lesions--results from a large prospective clinical trial

PURPOSE

The purpose of the study was to evaluate prospectively whether integrated 2-deoxy-2-[(18)F]fluoro-D-glucose positron emission tomography/computed tomography (FDG-PET/CT) is more accurate for determination of malignancy in newly diagnosed pulmonary lesions compared to separate interpretation of CT and FDG-PET.

PROCEDURES

Two hundred and seventy-six patients with newly diagnosed lung lesions underwent FDG-PET/CT. Helical CT, FDG-PET, and FDG-PET/CT were interpreted separately to determine the performance of each imaging modality. Histopathology served as reference in all patients, and in further 60 patients, a benign lesion was verified at follow-up (mean follow-up of 1,040 days).

RESULTS

Histology revealed malignant lung tumors in 216 of 276 patients. With PET and PET/CT, a significantly lower number of lesions were classified as equivocal compared to CT alone (p < 0.001). Assuming that equivocal lesions are benign, performance of diagnostic tests was as follows: sensitivity, specificity, and accuracy for CT was 94, 75, and 90%, for PET 97, 83, and 94% (p = 0.021), and for PET/CT 96, 87, and 94% (p = 0.010). Assuming that equivocal lesions are malignant, sensitivity, specificity, and accuracy for CT was 99, 37, and 86%, for PET 99, 77, and 94% (p < 0.001), and for PET/CT 98, 68, and 92% (p = 0.002). PET and PET/CT showed the highest concordance (K = 0.912; confidence interval 0.866-0.958). In lesions less than or equal to 3 cm, there was a significant difference in the performance of PET alone and multidetector row CT as well as PET/CT and multidetector row CT (p = 0.007), irrespective if equivocal findings were judged as malignant or benign.

CONCLUSION

For differentiation of benign from malignant lung lesions, integrated FDG-PET/CT imaging was significantly more accurate than CT but not FDG-PET. The addition of metabolic imaging (FDG-PET) to morphological imaging (CT) leads to an increase in specificity and significantly reduced equivocal findings and is therefore recommended to further specify newly diagnosed lung lesions.

Dual-time point FDG PET imaging in the evaluation of pulmonary nodules with minimally increased metabolic activity

PURPOSE

FDG PET has high accuracy in the evaluation of lung nodules. A standardized uptake value (SUV) > or =2.5 is frequently used as a criterion for malignancy in this setting. However, some malignant nodules have only mild FDG activity with a SUV less than 2.5. Assessment of the etiology of lung nodules with only mild metabolic activity remains difficult. This study was undertaken to compare the accuracy of dual-time point and standard single-time FDG PET imaging in the evaluation of such lung nodules.

METHODS

Four hundred fifty-seven dual-time FDG PET scans for lung nodules were retrospectively analyzed. Among them, 46 met the selection criteria and were included for the final analysis. Five methods of interpreting FDG PET results were compared. These methods included visual analysis for both initial and delayed images; SUV analysis for both initial and delayed images in which a SUV of 2.5 is regarded as criteria for malignancy; and finally, the retention index analysis in which a 10% increase in SUV on the delayed images was regarded as an indication of malignancy.

RESULTS

The lowest accuracies came from the visual and single SUV analysis on the initial images. The visual and single SUV analyses on the delayed images produced increased accuracy. The highest accuracy (84.8%) was obtained when a retention index of more than 10% was used as criteria for malignancy.

CONCLUSION

Dual-time FDG PET imaging has the potential for improving accuracy of a test in the evaluation of lung nodules with only borderline levels of increased metabolic activity.

Positron emission tomography imaging in nonsmall-cell lung cancer

Positron emission tomography (PET) using 18F-2-deoxy-D-glucose, a D-glucose analog labeled with fluorine-18, complements conventional radiologic assessment in the evaluation of patients with nonsmall-cell lung cancer (NSCLC). PET is being routinely used to improve the detection of nodal and extrathoracic metastases. PET is also currently being evaluated in the assessment of prognosis and therapeutic response and by potentially allowing an earlier assessment of response may prove invaluable in the oncologic management of patients. The article discusses the diagnosis, staging, and assessment of treatment response and prognosis with an emphasis on the appropriate clinical use of PET in management.

Additional value of integrated PET-CT in the detection and characterization of lung metastases: correlation with CT alone and PET alone

The purpose was evaluating retrospectively the additional value of integrated positron emission tomography (PET) and computed tomography (CT) in the detection of pulmonary metastases in comparison with CT and PET alone. Fifty-six lung nodules, divided into three groups according their size, detected in 24 consecutive patients with a known primary tumor were retrospectively evaluated with integrated PET-CT, CT and PET. The nature of these nodules was determined by either histopathology or a follow-up of at least 6 months. The CT and PET images of the integrated PET-CT were evaluated separately by a radiologist and a nuclear medicine physician, the integrated PET-CT images were evaluated by a chest radiologist and nuclear medicine physician in consensus. The investigators were asked to search lung nodules and to determine whether these nodules were metastases or not. Sensitivity and accuracy for CT, PET and integrated PET-CT for characterization of all pulmonary nodules were, respectively: 100%, 90%, 100% and 57%, 55%, 55%. There was no significant difference in the characterization of pulmonary nodules between integrated PET-CT and CT alone (P=1.000) and PET alone (P=0.1306). An accurate evaluation is only possible for lesions larger than 1 cm.

PET/CT today: System and its impact on cancer diagnosis

Over the past six years, PET/CT has spread rapidly and replaced conventional PET. Although PET/CT is a combination of PET for functional information and CT for morphological information, their combination is synergistic. PET/CT fusion images result in higher diagnostic accuracy with fewer equivocal findings. This results in a greater impact on cancer diagnosis. With attenuation correction performed by the CT component, PET/CT can provide higher quality images over shorter examination times than conventional PET. As with all modalities, PET/CT has several characteristic artifacts such as misregistration due to respiration, overattenuation correction due to metals, etc. Awareness of these pitfalls will help the imaging physician use PET/CT effectively in daily practice.

Two cases of pulmonary paragonimiasis on FDG-PET CT imaging

Positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) is useful in cancer diagnosis owing to its sensitivity to the differences in glucose metabolic rate between benign and malignant diseases, especially in the lung. One pitfall in PET imaging of lung disease, however, is the overlap in metabolic rate of inflammatory and neoplastic entities. Paragonimiasis is a food-borne parasitic disease that causes the pulmonary and pleural inflammation. We present two cases of pulmonary paragonimiasis that showed high uptake suggestive of tumor on FDG-PET CT images, both confirmed on histopathology by visualization of Paragonimus westermani eggs in the involved tissues.

Mediastinal Histoplasmosis: F-18 FDG PET and CT Findings Simulating Malignant Disease

We describe the computed tomography and F-18 FDG PET findings of a patient with extensive mediastinal nodal enlargement resulting from histoplasmosis. This patient with known metastatic melanoma presenting for restaging was initially considered to have widespread mediastinal and cervical metastases on the basis of the imaging findings. Bronchoalveolar lavage fluid and transbronchial lymph node biopsy were consistent with histoplasmosis. The imaging findings improved after treatment with antifungal medication. A relatively small area of pulmonary involvement proved to be the clue in the imaging studies that the disease was inflammatory rather than neoplastic.