Repeatability of image features extracted from FET PET in application to post-surgical glioblastoma assessment.

Positron emission tomography (PET) imaging using the amino acid tracer O-[2-(18F)fluoroethyl]-L-tyrosine (FET) has gained increased popularity within the past decade in the management of glioblastoma (GBM). Radiomics features extracted from FET PET images may be sensitive to variations when imaging at multiple time points. It is therefore necessary to assess feature robustness to test-retest imaging. Eight patients with histologically confirmed GBM that had undergone post-surgical test-retest FET PET imaging were recruited. In total, 1578 radiomic features were extracted from biological tumour volumes (BTVs) delineated using a semi-automatic contouring method. Feature repeatability was assessed using the intraclass correlation coefficient (ICC). The effect of both bin width and filter choice on feature repeatability was also investigated. 59/106 (55.7%) features from the original image and 843/1472 (57.3%) features from filtered images had an ICC ≥ 0.85. Shape and first order features were most stable. Choice of bin width showed minimal impact on features defined as stable. The Laplacian of Gaussian (LoG, σ = 5 mm) and Wavelet filters (HLL and LHL) significantly improved feature repeatability (p ≪ 0.0001, p = 0.003, p = 0.002, respectively). Correlation of textural features with tumour volume was reported for transparency. FET PET radiomic features extracted from post-surgical images of GBM patients that are robust to test-retest imaging were identified. An investigation with a larger dataset is warranted to validate the findings in this study.

Is Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography Imaging Cost-effective in Prostate Cancer: An Analysis Informed by the proPSMA Trial.

BACKGROUND: Before integrating prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) into routine care, it is important to assess if the benefits justify the differences in resource use. OBJECTIVE: To determine the cost-effectiveness of PSMA-PET/CT when compared with conventional imaging. DESIGN, SETTING, AND PARTICIPANTS: A cost-effectiveness analysis was developed using data from the proPSMA study. proPSMA included patients with high-risk prostate cancer assigned to conventional imaging or 68Ga-PSMA-11 PET/CT with planned health economics data collected. The cost-effectiveness analysis was conducted from an Australian societal perspective. INTERVENTION: 68Ga-PSMA-11 PET/CT compared with conventional imaging (CT and bone scan). OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The primary outcome from proPSMA was diagnostic accuracy (nodal and distant metastases). This informed a decision tree analysis of the cost per accurate diagnosis. RESULTS AND LIMITATIONS: The estimated cost per scan for PSMA PET/CT was AUD$1203, which was less than the conventional imaging cost at AUD$1412. PSMA PET/CT was thus dominant, having both better accuracy and a lower cost. This resulted in a cost of AUD$959 saved per additional accurate detection of nodal disease, and AUD$1412 saved for additional accurate detection of distant metastases. The results were most sensitive to variations in the number of men scanned for each 68Ga-PSMA-11 production run. Subsequent research is required to assess the long-term costs and benefits of PSMA PET/CT-directed care. CONCLUSIONS: PSMA PET/CT has lower direct comparative costs and greater accuracy compared to conventional imaging for initial staging of men with high-risk prostate cancer. This provides a compelling case for adopting PSMA PET/CT into clinical practice. PATIENT SUMMARY: The proPSMA study demonstrated that prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) better detects disease that has spread beyond the prostate compared with conventional imaging. Our analysis shows that PSMA PET/CT is also less costly than conventional imaging for the detection of disease spread. This research was presented at the European Association of Nuclear Medicine Scientific Meeting in October 2020.

Accuracy of Dose Calibrators for 68Ga PET Imaging: Unexpected Findings in a Multicenter Clinical Pretrial Assessment.

We report the discovery of a systematic miscalibration during the work-up process for site validation of a multicenter clinical PET imaging trial using 68Ga, which manifested as a consistent and reproducible underestimation in the quantitative accuracy (assessed by SUV) of a range of PET systems from different manufacturers at several different facilities around Australia. Methods: Sites were asked to follow a strict preparation protocol to create a radioactive phantom with 68Ga to be imaged using a standard clinical protocol before commencing imaging in the trial. All sites had routinely used 68Ga for clinical PET imaging for many years. The reconstructed image data were transferred to an imaging core laboratory for analysis, along with information about ancillary equipment such as the radionuclide dose calibrator. Fourteen PET systems were assessed from 10 nuclear medicine facilities in Australia, with the aim for each PET system being to produce images within 5% of the true SUV. Results: At initial testing, 10 of the 14 PET systems underestimated the SUV by 15% on average (range, 13%-23%). Multiple PET systems at one site, from two different manufacturers, were all similarly affected, suggesting a common cause. We eventually identified an incorrect factory-shipped dose calibrator setting from a single manufacturer as being the cause. The calibrator setting for 68Ga was subsequently adjusted by the users so that the reconstructed images produced accurate values. Conclusion: PET imaging involves a chain of measurements and calibrations to produce accurate quantitative performance. Testing of the entire chain is simple, however, and should form part of any quality assurance program or prequalifying site assessment before commencing a quantitative imaging trial or clinical imaging.

68 Ga-somatostatin analogue PET-CT: Analysis of costs and benefits in a public hospital setting.

INTRODUCTION: Between 2009 and 2012, 68 Ga-somatostatin analogue PET-CT progressively replaced 111 In-octreotide scintigraphy for imaging neuroendocrine tumours in WA public hospitals due to published literature demonstrating improved diagnostic accuracy and increased availability. Despite significantly improved sensitivity and specificity, 68 Ga-somatostatin analogue PET is currently unfunded in Australia. This study sought to undertake cost analysis of the two modalities in a public hospital setting and to compare them with regard to patient factors such as imaging time and radiation dose. METHODS: This analysis was based on retrospective clinical data from 95 111 In-octreotide scintigraphies performed in 2007 and 2008 at Sir Charles Gairdner (SCGH) and Royal Perth (RPH) hospitals and 219 68 Ga-somatostatin analogue PET-CT studies performed in 2013 at SCGH. Whole body effective radiation dose was derived from the radiopharmaceutical and low-dose CT scan. The cost analysis included radiopharmaceutical and imaging costs. RESULTS: The median imaging time for an 111 In-octreotide scintigraphy was 152 min at SCGH, 100 min at RPH and 20 min for a 68 Ga-somatostatin analogue PET-CT scan. The mean effective radiation dose for 111 In-octreotide scintigraphy was 18.1 mSv at SCGH and 13.8 mSv at RPH. The effective dose for 68 Ga-somatostatin analogue PET-CT was 8.7-10.8 mSv. The average cost of 68 Ga-somatostatin analogue PET-CT was four times less than 111 In-octreotide scintigraphy. CONCLUSION: 68 Ga-somatostatin analogue PET-CT is not only more accurate than 111 In-octreotide scintigraphy, this study has also shown that it is significantly less expensive, delivers a lower radiation dose to patients and requires less imaging time for patients and staff. 68 Ga-somatostatin PET-CT provides an important combination of both reduced cost and improved clinical care for patients.

A Multimodality Imaging Review of Malignant Pleural Mesothelioma Response Assessment.

Assessment of response is important to interpret early phase clinical trial results and to guide individual patient management. In malignant pleural mesothelioma (MPM), the circumferential growth pattern of the disease, the presence of pleural effusion and atelectasis, and the common use of pleurodesis make this a challenging task for imaging specialists and clinicians. This article reviews the current evidence for radiological and positron emission tomography (PET) response assessment in MPM, and the pitfalls and challenges in its application. Current research and future directions in radiological and PET response are discussed, including the use of novel radiotracers.