Partial volume correction strategies for quantitative FDG PET in oncology

Purpose: Quantitative accuracy of positron emission tomography (PET) is affected by partial volume effects resulting in increased underestimation of the standardized uptake value (SUV) with decreasing tumour volume. The purpose of the present study was to assess accuracy and precision of different partial volume correction (PVC) methods. Methods: Three methods for PVC were evaluated: (1) inclusion of the point spread function (PSF) within the reconstruction, (2) iterative deconvolution of PET images and (3) calculation of spill-in and spill-out factors based on tumour masks. Simulations were based on a mathematical phantom with tumours of different sizes and shapes. Phantom experiments were performed in 2-D mode using the National Electrical Manufacturers Association (NEMA) NU2 image quality phantom containing six differently sized spheres. Clinical studies (2-D mode) included a test-retest study consisting of 10 patients with stage IIIB and IV non-small cell lung cancer and a response monitoring study consisting of 15 female breast cancer patients. In all studies tumour or sphere volumes of interest (VOI) were generated using VOI based on adaptive relative thresholds. Results: Simulations and experiments provided similar results. All methods were able to accurately recover true SUV within 10% for spheres equal to and larger than 1 ml. Reconstruction-based recovery, however, provided up to twofold better precision than image-based methods. Cl

Recurrent differentiated thyroid cancer: Towards personalized treatment based on evaluation of tumor characteristics with PET (THYROPET Study): Study protocol of a multicenter observational cohort study

Background: After initial treatment of differentiated thyroid carcinoma (DTC) patients are followed with thyroglobulin (Tg) measurements to detect recurrences. In case of elevated levels of Tg and negative neck ultrasonography, patients are treated 'blindly' with Iodine-131 (131I). However, in up to 50% of patients, the post-therapy scan reveals no 131I-targeting of tumor lesions. Such patients derive no benefit from the blind therapy but are exposed to its toxicity. Alternatively, iodine-124 (124I) Positron Emission Tomography/Computed Tomography (PET/CT) has become available to visualize DTC lesions and without toxicity. In addition to this, 18F-fluorodeoxyglucose (18F-FDG) PET/CT detects the recurrent DTC phenotype, which lost the capacity to accumulate iodine. Taken together, the combination of 124I and 18F-FDG PET/CT has potential to stratify patients for treatment with 131I.Methods/Design: In a multicenter prospective observational cohort study the hypothesis that the combination of 124I and 18F-FDG PET/CT can avoid futile 131I treatments in patients planned for 'blind' therapy with 131I, is tested.One hundred patients planned for 131I undergo both 124I and 18F-FDG PET/CT after rhTSH stimulation. Independent of the outcome of the scans, all patients will subsequently receive, after thyroid hormone withdrawal, the 131I therapy. The post 131I therapeutic scintigraphy is compared with the outcome of the 124I and 18F-FDG PET/CT in order to evaluate the diagnostic value of the combined PET modalities.This study primary aims to reduce the number of futile 131I therapies. Secondary aims are the nationwide introduction of 124I PET/CT by a quality assurance and quality control (QA/QC) program, to correlate imaging outcome with histopathological features, to compare 124I PET/CT after rhTSH and after withdrawal of thyroid hormone, and to compare 124I and 131I dosimetry.Discussion: This study aims to evaluate the potential value of the combination of 124I and 18F-FDG PET/CT in the prevention of futile 131I therapies in patients with biochemically suspected recurrence of DTC. To our best knowledge no studies addressed this in a prospective cohort of patients. This is of great clinical importance as a futile 131I is a costly treatment associated with morbidity and therefore should be restricted to those likely to benefit from this treatment.Trial registration: Clinicaltrials.gov identifier: NCT01641679

FDG PET and PET/CT: EANM procedure guidelines for tumour PET imaging: version 1.0

The aim of this guideline is to provide a minimum standard for the acquisition and interpretation of PET and PET/CT scans with [18F]-fluorodeoxyglucose (FDG). This guideline will therefore address general information about [18F]-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) and is provided to help the physician and physicist to assist to carrying out, interpret, and document quantitative FDG PET/CT examinations, but will concentrate on the optimisation of diagnostic quality and quantitative information

How should we analyse FDG PET studies for monitoring tumour response?

FDG PET is a promising technique for monitoring tumour response early during anticancer therapy. Progress, however, has been limited owing to the multitude of methods currently in use. Here, the most promising techniques for multi-centre trials are discussed briefly, with emphasis on the need for standardisation. In addition, an approach is presented for response monitoring studies using newly developed drugs. This approach makes use of a large database of response monitoring studies, which defines the relationship between simplified clinical methods and full quantitative analysis for classic cytotoxic drugs. For a new drug, first a pilot study is performed to assess whether it affects this relationship. Based on this pilot, it is decided whether or not a simplified clinical method can be used in further studies

Erratum: Effects of ROI definition and reconstruction method on quantitative outcome and applicability in a response monitoring trial (European Journal of Nuclear Medicine and Molecular Imaging (2005) 32 (294-301) DOI: http://dx.doi.org/10.1007/s00259-004-1566-1)

Purpose: Quantitative measurement of tracer uptake in a tumour can be influenced by a number of factors, including the method of defining regions of interest (ROIs) and the reconstruction parameters used. The main purpose of this study was to determine the effects of different ROI methods on quantitative outcome, using two reconstruction methods and the standard uptake value (SUV) as a simple quantitative measure of FDG uptake. Methods: Four commonly used methods of ROI definition (manual placement, fixed dimensions, threshold based and maximum pixel value) were used to calculate SUV (SU

Measurement of perfusion in stage IIIA-N2 non-small cell lung cancer using H215O and positron emission tomography

Purpose: As the interest in antiangiogenesis therapy in oncology is rising, the need for in vivo techniques to monitor such therapy is obvious. Measurement of tumor perfusion using positron emission tomography and H215O potentially is such a technique. The objective of the present study was to assess whether it is feasible to measure perfusion in vivo in non-small cell lung cancer (NSCLC) using H215O and positron emission tomography. Experimental Design: Fifteen dynamic H215O and [18F]2-fluoro-2-deoxy-D-glucose (18FDG) studies were performed in 10 patients with stage IIIA-N2 NSCLC. Blood flow (BF) data were correlated with simplified methods of analysis (tumor:normal tissue ratio and standardized uptake value) and with glucose metabolism (MRglu). Results: 18FDG data were required for accurate definition of tumor and mediastinal lymph node metastases. There was large intertumor variation in BF. Correlation of simplified methods of analysis with quantitative BF was poor. In addition, BF and MRglu were not correlated. Conclusion: Measurement of BF in NSCLC using H215O and 18FDG is feasible. Simple uptake analysis, however, cannot be used as an indicator of perfusion. Whether BF can be used for response monitoring needs to be evaluated in a large patient study, where results can be compared with outcome

Methods to monitor response to chemotherapy in non-small cell lung cancer with 18F-FDG PET

PET using 18F-FDG is a promising technique to monitor response in oncology. Unfortunately, a multitude of analytic methods is in use. To date, it is not clear whether simplified methods could replace complex quantitative methods in routine clinical practice. The aim of this study was to select those methods that would qualify for further assessment in a future prospective response-monitoring study by comparing results with patient outcome. Methods: Dynamic 18F-FDG PET scans were obtained on 2 groups of patients. First, 10 patients with advanced non-small cell lung cancer (NSCLC) were scanned on consecutive days before treatment to assess test-retest variability. Second, 30 scans were obtained on 19 patients with locally advanced NSCLC as part of an ongoing response-monitoring study. These scans were analyzed by 2 observers to assess observer variability. In addition, these studies were used to compare various methods with the gold standard, full kinetic analysis (nonlinear regression [NLR]). Results: Using an imagederived input function, NLR showed excellent test-retest and observer agreement confirming that it could be used as a gold standard method. From a total of 34 analytic methods, 10 showed good correlation with NLR. Taking into account the degree of complexity of the methods, 4 remain for further evaluation. Conclusion: The optimal method for analysis of 18F-FDG PET data was determined for several levels of complexity. Four methods need to be evaluated further to determine the optimal trade-off between simplicity and accuracy for routine clinical practice