Elsevier

Molecular Imaging & Biology

Volume 4, Issue 2, March–April 2002, Pages 171-178
Molecular Imaging & Biology

Original article
Reproducibility of Common Semi-quantitative Parameters for Evaluating Lung Cancer Glucose Metabolism with Positron Emission Tomography using 2-Deoxy-2-[18F]Fluoro-D-Glucose

https://doi.org/10.1016/S1536-1632(01)00004-XGet rights and content

Abstract

Purpose: Positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose (FDG) has been used for various cancers, but reproducibility of common utilized semi-quantitative parameters, such as the maximal single pixel standardized uptake value (SUV) and effective glycolytic volume (EGV), remains unknown. Knowledge of precision is essential for applying these parameters to treatment monitoring. The purpose of this investigation was to assess the precision of PET results obtained by repeated examinations of patients with untreated lung cancer.

Patients and Methods: Ten patients with lung cancer underwent two PET examinations within a week with no intervening treatment. The reproducibility of three parameters:((1) maximal SUV of 1 × 1 pixel anywhere in the tumor, calculated on the basis of predicted lean body mass [SULmax]; (2) highest average SUV at 4 × 4 pixels in the tumor adjusted by predicted lean body mass [SULmean]; and (3) EGV calculated by multiplying SUL by tumor volume), using PET images obtained at 50–60 min post-injection, were examined. Plasma glucose, insulin and free fatty acid levels were also monitored.

Results: The SULmax, SULmean, and EGV were measured with a mean ± S.D. difference of 11.3% ± 8.0, 10.1% ± 8.2, and 10.1% ± 8.0%, respectively. By multiplying SUL by plasma glucose concentration, the mean differences were slightly reduced to 7.2% ± 5.8, 6.7% ± 6.2, and 9.5% ± 8.2, respectively.

Conclusion: These data indicate that commonly used semi-quantitative indices of glucose metabolism on PET show high reproducibly. This supports their use in sequential quantitative analysis in PET, such as in treatment response monitoring. (Mol Imag Biol 2002;4:171–178)

Introduction

Positron emission tomography (PET) using 2-deoxy-2-[18F]fluoro-D-glucose (FDG) is an established diagnostic tool for oncological imaging. 1, 2, 3 In lung cancer, PET can provide useful information regarding differentiation,4, 5, 6, 7, 8, 9 staging,10, 11, 12, 13 recurrence,14 and prognosis.15 PET has also been reported to reduce the cost for management of patients with lung cancer.16

In evaluating lesions with PET, semi–quantitative analysis, including standardized uptake value (SUV), has been often applied for attenuation corrected images. For example, most reports showed higher values of radioactivity in malignant lesions than in benign lesions. In addition, an optimal cut-off value for differentiation between malignant and benign lesions has been suggested.6, 7 In assessment of therapies using quantitative parameters in PET, reproducibility of such parameters is critically important. In order to determine if a tumor has responded to therapy by PET, it is necessary to know how much normal variability there is in the measurement of semiquantitative parameters of glycolysis. We have previously reported the reproducibility of kinetic behavior and SUV on the basis of predicted lean body mass (SUL) of 16 pixels in size within lesions.17 A comparison between the volumes of metabolically active tumors estimated by PET and anatomical volume of the tumor by CT was also reported.18 Effective glycolytic volume (EGV) that is formed by multiplying total tumor average SUL by total tumor volume (Fig. 1), is considered to be a potential measure of active viable cancer cells.19 Therefore, it may be a useful parameter especially when monitoring cancer treatments. Its reproducibility, however, is unknown. Similarly, commercial software available with most PET systems does not routinely provide the maximum 16 pixel ROI in tumor, but generally does provide the maximal single pixel value in a tumor ROI. The reproducibility of the single pixel value, however, has not been assessed. In this work, we investigated the reproducibility of three parameters: maximum single pixel SUL, highest average SUL for 4 × 4 pixels, and EGV for patients with histologically-proven untreated lung cancer.

Section snippets

Patients

The group consisted of 10 patients who were admitted to this investigation if they had a newly detected primary lung cancer or a lung nodule with a high suspicion of malignancy. The patients' profile is shown in Table 1. These patients were prospectively recruited and initial analyses were performed.17 Only patients with a primary lesion diameter measuring at least 2.0 cm in all three orthogonal dimensions (as measured from a CT scan) were included to avoid the need for correction of partial

Results

We summarized sequential quantitative data in 10 patients with lung cancer in Table 2 and mean ± S.D. for each PET study as demonstrated in [ID] Table 3. There were no parameters that showed a significant difference between the two PET studies. Reproducibility between the two PET studies is shown in Figure 2 as to the SULmax, SULmean, EGV, and TV. Figure 3 revealed those data after the adjustment by glucose concentration. All parameters showed high reproducibility, as all ICCs were >0.9.

Discussion

PET enables us to directly quantify lesion radioactivity levels, as an alternative to measuring tumor size. SUV, a commonly used semi-quantative parameter, is also referred to as the dose uptake ratio (DUR), i.e. radioactivity concentration adjusted by body weight and injected dose. There have been several reports describing its characteristics, significance and limitations.23, 24 Indeed, this value acquired in static images is sometimes criticized for its oversimplifications, and kinetic

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