The Netherlands protocol for standardisation and quantification of FDG whole body PET studies in multi-centre trials

Imaging angiogenesis in patients with head and neck squamous cell carcinomas by [68Ga]Ga-DOTA-E-[c(RGDfK)]2 PET/CT

Purpose

Angiogenesis plays an important role in the growth and metastatic spread of solid tumours and is characterised by the expression of integrins on the cell surface of endothelial cells. Radiolabelled RGD peptides specifically target angiogenesis-related α_vβ₃ integrins, expressed on the activated endothelial cells of sprouting blood vessels. Here, we validated the feasibility of ⁶⁸Ga[Ga]-DOTA-E-[c(RGDfK)]₂ (⁶⁸Ga-RGD) PET/CT to visualise angiogenesis in patients with oral squamous cell carcinoma (OSCC).

Methods

Ten patients with OSCC and scheduled for surgical resection including elective neck dissection received an intravenously administration of ⁶⁸Ga-RGD (42 ± 8 μg; 214 ± 9 MBq). All patients subsequently underwent dynamic (n = 5) or static PET/CT imaging (n = 5) for 60 min or for 4 min/bed position at 30, 60 and 90 min after injection, respectively. Quantitative tracer uptake in tumour lesions was expressed as standardised uptake values (SUV). Additionally, tumour tissue was immunohistochemically stained for α_vβ₃ integrin to assess the expression pattern.

Results

⁶⁸Ga-RGD tumour accumulation was observed in all patients. At 60 min post injection, tumour SUV_max ranged between 4.0 and 12.7. Tracer accumulation in tumour tissue plateaued at 10 min after injection. Uptake in background tissue did not change over time, resulting in tumour-to-muscle tissue of 6.4 ± 0.7 at 60 min post injection.

Conclusions

⁶⁸Ga-RGD PET/CT of α_vβ₃ integrin expression in OSCC patients is feasible with adequate tumour-to-background ratios. It will provide more insight in angiogenesis as a hallmark of the head and neck squamous cell carcinomas’ tumour microenvironment.

Trial registration

https://eudract.ema.europa.eu no. 2015-000917-31

Electronic supplementary material

The online version of this article (10.1007/s00259-020-04766-2) contains supplementary material, which is available to authorized users.

The QIBA Profile for FDG PET/CT as an Imaging Biomarker Measuring Response to Cancer Therapy

The Quantitative Imaging Biomarkers Alliance (QIBA) Profile for fluorodeoxyglucose (FDG) PET/CT imaging was created by QIBA to both characterize and reduce the variability of standardized uptake values (SUVs). The Profile provides two complementary claims on the precision of SUV measurements. First, tumor glycolytic activity as reflected by the maximum SUV (SUVmax) is measurable from FDG PET/CT with a within-subject coefficient of variation of 10%-12%. Second, a measured increase in SUVmax of 39% or more, or a decrease of 28% or more, indicates that a true change has occurred with 95% confidence. Two applicable use cases are clinical trials and following individual patients in clinical practice. Other components of the Profile address the protocols and conformance standards considered necessary to achieve the performance claim. The Profile is intended for use by a broad audience; applications can range from discovery science through clinical trials to clinical practice. The goal of this report is to provide a rationale and overview of the FDG PET/CT Profile claims as well as its context, and to outline future needs and potential developments.

Quantification of 18F-fluorodeoxyglucose uptake to detect residual nodal disease in locally advanced head and neck squamous cell carcinoma after chemoradiotherapy: results from the ECLYPS study

BACKGROUND

The Hopkins criteria were introduced for nodal response evaluation after therapy in head and neck cancer, but its superiority over quantification is not yet confirmed.

METHODS

SUV_{body weight} thresholds and lesion-to-background ratios were explored in a prospective multicenter study of standardized FDG-PET/CT 12 weeks after CRT in newly diagnosed locally advanced head and neck squamous cell carcinoma (LAHNSCC) patients (ECLYPS). Reference standard was histology, negative FDG-PET/CT at 12 months after treatment or ≥ 2 years of negative follow-up. Area under the receiver operator characteristics curves (AUROC) were estimated and obtained thresholds were validated in an independent cohort of HNSCC patients (n = 127).

RESULTS

In ECLYPS, 124 patients were available for quantification. With a median follow-up of 20.4 months, 23 (18.5%) nodal neck recurrences were observed. A SUV₇₀ threshold of 2.2 (AUROC = 0.89; sensitivity = 79.7%; specificity = 80.8%) was identified as optimal metric to identify nodal recurrence within 1 year after therapy. For lesion-to-background ratios, an SUV₅₀/SUV_liver threshold of 0.96 (AUROC = 0.89; sensitivity = 79.7%; specificity = 82.8%) had the best performance. Compared with Hopkins criteria (AUROC = 0.81), SUV₇₀ and SUV₅₀/SUV_liver provided a borderline significant (p = 0.040 and p = 0.094, respectively) improvement. Validation of thresholds yielded similar AUROC values (SUV₇₀ = 0.93, SUV₅₀/SUV_liver = 0.95), and were comparable to the Hopkins score (AUROC = 0.91; not statistically significant).

CONCLUSION

FDG quantification detects nodal relapse in LAHNSCC patients. When using EARL standardized PET acquisitions and reconstruction, absolute SUV metrics (SUV₇₀ threshold 2.2) prove robust, yet ratios (SUV₅₀/SUV_liver, threshold 0.96) may be more useful in routine clinical care. In this setting, the diagnostic value of quantification is comparable to the Hopkins criteria.

TRIAL REGISTRATION

US National Library for Medicine, NCT01179360. Registered 11 August 2010, https://clinicaltrials.gov/ct2/show/NCT01179360.

Influx rate constant of 18F-FDG increases in metastatic lymph nodes of non-small cell lung cancer patients

PURPOSE

Primary tumor (PT) and metastatic lymph node (MLN) status have a great influence on diagnosis and treatment of lung cancer. Our main purpose was to investigate the imaging characteristics of PT or MLN by applying the ¹⁸F-FDG PET dynamic modeling approach for non-small cell lung cancer (NSCLC).

METHODS

Dynamic ¹⁸F-FDG PET scans were performed for 76 lung cancer patients, and 62 NSCLC cases were finally included in this study: 37 with newly diagnosed early and locally advanced lung cancer without distant metastases (group M0) and 25 metastatic lung cancer (group M1). Patlak graphic analysis (K_i calculation) based on the dynamic modeling and SUV analysis from conventional static data were performed.

RESULTS

For PT, both K_i^PT (0.050 ± 0.005 vs 0.026 ± 0.004 min^-1, p < 0.001) and SUV^PT (8.41 ± 0.64 vs 5.23 ± 0.73, p < 0.01) showed significant higher values in group M1 than M0. For MLN, K_i^MLN showed significant higher values in M1 than M0 (0.033 ± 0.005 vs 0.016 ± 0.003 min^-1, p < 0.01), while no significant differences were found for SUV^MLN between M0 and M1 (4.22 ± 0.49 vs 5.57 ± 0.59, p > 0.05). Both SUV ^PT and K_i^PT showed significant high values in squamous cell carcinoma than adenocarcinoma, but neither SUV^PT nor K_i^PT showed significant differences between EGFR mutants versus wild types. The overall Spearman analysis for SUV and K_i from different groups showed variable correlation (r = 0.46-0.94).

CONCLUSION

The dynamic modeling for MLN (K_i^MLN) showed more sensitive than the static analysis (SUV) to detect metastatic lymph nodes in NSCLC, although both methods were sensitive for PT. This methodology of non-invasive imaging may become an important tool to evaluate MLN and PT status for patients who cannot undergo histological examination.

CLINICAL TRIAL REGISTRATION

The clinical trial registration number is NCT03679936 (http://www.clinicaltrials.gov/).

177Lu-DOTATATE Peptide Receptor Radionuclide Therapy: Dose Response in Small Intestinal Neuroendocrine Tumors

INTRODUCTION

Peptide receptor radionuclide therapy (PRRT) has during the last few years been frequently used in patients with progressive, disseminating, well-differentiated neuroendocrine tumors (NETs).

OBJECTIVE

To study whether the absorbed dose in small intestinal NET (SI-NET) metastases from PRRT with 177Lu-DOTATATE is related to tumor shrinkage.

MATERIALS AND METHODS

Dosimetry for 1 tumor was performed in each of 25 SI-NET patients based on sequential SPECT/CT 1, 4, and 7 days after 177Lu-DOTATATE infusion. The SPECT data were corrected for the partial volume effect based on previous phantom measurements, and the unit density sphere model from OLINDA was used for absorbed dose calculations. Morphological therapy response was assessed by CT/MRI regarding tumor diameter, tumor volume, total liver tumor volume, liver volume, and overall tumor response according to RECIST 1.1. Plasma chromogranin A and urinary 5-hydroxy-indole-acetic-acid were measured during PRRT and follow-up to assess biochemical response.

RESULTS

At the time of best response with respect to tumor diameter and volume shrinkage, the median absorbed dose was 128.6 Gy (range 28.4-326.9) and 140 Gy (range 50.9-487.4), respectively. All metrics regarding tumor shrinkage and biochemical response were unrelated to the absorbed dose. A correlation was, however, found between the administered radioactivity and the tumor volume shrinkage (p = 0.01) and between the administered radioactivity and RECIST 1.1 response (p = 0.01).

CONCLUSIONS

It was not possible to demonstrate a tumor dose-response relationship in SI-NET metastases with the applied dosimetry method, contrary to what was previously shown for pancreatic NETs.

Image Quality and Activity Optimization in Oncologic 18F-FDG PET Using the Digital Biograph Vision PET/CT System

The first Biograph Vision PET/CT system (Siemens Healthineers) was installed at the University Medical Center Groningen. Improved performance of this system could allow for a reduction in activity administration or scan duration. This study evaluated the effects of reduced scan duration in oncologic ¹⁸F-FDG PET imaging on quantitative and subjective imaging parameters and its influence on clinical image interpretation. Methods: Patients referred for a clinical PET/CT scan were enrolled in this study, received a weight-based ¹⁸F-FDG injected activity, and underwent list-mode PET acquisition at 180 s per bed position (s/bp). Acquired PET data were reconstructed using the vendor-recommended clinical reconstruction protocol (hereafter referred to as "clinical"), using the clinical protocol with additional 2-mm gaussian filtering (hereafter referred to as "clinical+G2"), and-in conformance with European Association of Nuclear Medicine Research Ltd. (EARL) specifications-using different scan durations per bed position (180, 120, 60, 30, and 10 s). Reconstructed images were quantitatively assessed for comparison of SUVs and noise. In addition, clinically reconstructed images were qualitatively evaluated by 3 nuclear medicine physicians. Results: In total, 30 oncologic patients (22 men, 8 women; age: 48-88 y [range], 67 ± 9.6 y [mean ± SD]) received a single weight-based (3 MBq/kg) ¹⁸F-FDG injected activity (weight: 45-123 kg [range], 81 ± 15 kg [mean ± SD]; activity: 135-380 MBq [range], 241 ± 47.3 MBq [mean ± SD]). Significant differences in lesion SUV_max were found between the 180-s/bp images and the 30- and 10-s/bp images reconstructed using the clinical protocols, whereas no differences were found in lesion SUV_peak EARL-compliant images did not show differences in lesion SUV_max or SUV_peak between scan durations. Quantitative parameters showed minimal deviation (∼5%) in the 60-s/bp images. Therefore, further subjective image quality assessment was conducted using the 60-s/bp images. Qualitative assessment revealed the influence of personal preference on physicians' willingness to adopt the 60-s/bp images in clinical practice. Although quantitative PET parameters differed minimally, an increase in noise was observed. Conclusion: With the Biograph Vision PET/CT system for oncologic ¹⁸F-FDG imaging, scan duration or activity administration could be reduced by a factor of 3 or more with the use of the clinical+G2 or the EARL-compliant reconstruction protocol.

Standardization of Preclinical PET/CT Imaging to Improve Quantitative Accuracy, Precision, and Reproducibility: A Multicenter Study

Preclinical PET/CT is a well-established noninvasive imaging tool for studying disease development/progression and the development of novel radiotracers and pharmaceuticals for clinical applications. Despite this pivotal role, standardization of preclinical PET/CT protocols, including CT absorbed dose guidelines, is essentially nonexistent. This study (1) quantitatively assesses the variability of current preclinical PET/CT acquisition and reconstruction protocols routinely used across multiple centers and scanners; and (2) proposes acquisition and reconstruction PET/CT protocols for standardization of multicenter data, optimized for routine scanning in the preclinical PET/CT laboratory. Methods: Five different commercial preclinical PET/CT scanners in Europe and the United States were enrolled. Seven different PET/CT phantoms were used for evaluating biases on default/general scanner protocols, followed by developing standardized protocols. PET, CT, and absorbed dose biases were assessed. Results: Site default CT protocols were the following: greatest extracted Hounsfield units (HU) were 133 HU for water and −967 HU for air; significant differences in all tissue equivalent material (TEM) groups were measured. The average CT absorbed doses for mouse and rat were 72 mGy and 40 mGy, respectively. Standardized CT protocol were the following: greatest extracted HU were −77 HU for water and −990 HU for air; TEM precision improved with a reduction in variability for each tissue group. The average CT absorbed dose for mouse and rat decreased to 37 mGy and 24 mGy, respectively. Site default PET protocols were the following: uniformity was substandard in one scanner, recovery coefficients (RCs) were either over- or underestimated (maximum of 43%), standard uptake values (SUVs) were biased by a maximum of 44%. Standardized PET protocols were the following: scanner with substandard uniformity improved by 36%, RC variability decreased by 13% points, and SUV accuracy improved to 10%. Conclusion: Data revealed important quantitative biases in preclinical PET/CT and absorbed doses with default protocols. Standardized protocols showed improvements in measured PET/CT accuracy and precision with reduced CT absorbed dose across sites. Adhering to standardized protocols generates reproducible and consistent preclinical imaging datasets, thus augmenting translation of research findings to the clinic.

Physics aspects of setting up a multicenter clinical trial involving internal dosimetry of radioiodine treatment of differentiated thyroid cancer

The field of molecular radiotherapy is expanding rapidly, with the advent of many new radiotherapeutics for the treatment of common as well as for rare cancers. Treatment outcome is dependent on the absorbed doses delivered to target volumes and to healthy organs-at-risk, which are shown to vary widely from fixed administrations of activity. There have been significant developments in quantitative imaging and internal dosimetry in recent years, although clinical implementation of these methods has been slow in comparison with external beam radiotherapy, partly due to there being relatively few patients treated at single centers. Multicenter clinical trials are therefore essential to acquire the data required to ensure best practice and to develop the personalized treatment planning that this area is well suited to, due to the unrivalled opportunity to image the therapeutic drug in vivo. Initial preparation for such trials requires a significant effort in terms of resources and trial design. Imaging systems in participating centers must be characterized and set up for quantitative imaging to allow for collation of data. Data transfer for centralized processing is usually necessary but is hindered in some cases by data protection regulations and local logistics. Recent multicenter clinical trials involving radioiodine therapy have begun to establish the procedures necessary for quantitative SPECT imaging in a multicenter setting using standard and anthropomorphic phantoms. The establishment of national and international multicenter imaging and dosimetry networks will provide frameworks to develop and harmonize best practice with existing therapeutic procedures and to ensure rapid and optimized clinical implementation of new radiotherapeutics across all centers of excellence that offer molecular radiotherapy. This will promote networks and collaborations that can provide a sound basis for further developments and will ensure that nuclear medicine maintains a key role in future developments.

U.S. PET/CT and Gamma Camera Diagnostic Reference Levels and Achievable Administered Activities for Noncardiac Nuclear Medicine Studies

Existing surveys of radiopharmaceutical doses for U.S. nuclear medicine laboratories are of limited scope and size. Dose data are important because they can be used to benchmark individual laboratories, understand geographic variations in practice, and provide source data for societal guidelines and appropriateness criteria. Diagnostic reference levels (DRLs) and achievable administered activities (AAAs) for 13 noncardiac adult gamma camera and PET/CT examinations were derived retrospectively from American College of Radiology accreditation data (January 1, 2015, to December 31, 2017). The calculated DRL and AAA are consistent with previously published surveys. The distributions of radiopharmaceutical doses across facilities are in general consistent but show variation within a particular examination. Analysis of dose distribution suggests this variation results from differences in clinical protocols, educational gaps, and/or equipment factors. The AAA for the surveyed facilities exceeds dose ranges proposed in societal practice guidelines for several common nuclear medicine studies. Compared with similar surveys from Europe and Japan, geographic variation is observed, with some doses greater and others lower than used in the United States. Overall, radiopharmaceutical dose variation within the United States and internationally, and deviation from societal guidelines, imply that these dose-related benchmarks may be used to further standardize and improve clinical practice.

Relationship between semiquantitative 18F-fluorodeoxyglucose positron emission tomography metrics and necrosis in classical Hodgkin lymphoma

Semiquantitative 18F-fluoro-2-deoxy-D-glucose positron emission tomography (18F-FDG PET) parameters have been proposed as prognostic markers in classical Hodgkin lymphoma (cHL). In non-Hodgkin lymphoma necrosis as assessed by 18F-FDG PET or computed tomography (CT) (necrosisvisual) correlates with an adverse prognosis. We investigated whether semiquantitative 18F-FDG PET metrics correlate with necrosisvisual, determined the incidence of necrosisvisual and explored the prognostic impact of these factors in cHL. From 87 cHL cases treated with ABVD, (escalated) BEACOPP or CHOP chemotherapy between 2010 and 2017, 71 had both a NEDPAS/EARL accredited 18F-FDG PET and a contrast enhanced CT scan. Semiquantitative 18F-FDG PET parameters were determined using Hermes Hybrid 3D software. Necrosisvisual, defined by photopenic tumor areas on 18F-FDG PET and attenuation values between 10 and 30 Hounsfield units (HUs) on CT, was assessed blinded to outcome. Univariate Cox regression survival analyses of progression free survival (PFS) were performed. Necrosisvisual was observed in 18.3% of cHL patients. Bulky disease (tumor mass >10 cm in any direction) (P = 0.002) and TLG (P = 0.041) but no other semiquantitative parameters were significantly associated with necrosisvisual. In exploratory univariate survival analysis for PFS the covariates IPS, bulky disease, MTV and TLG were prognostic, while necrosisvisual was not.

Randomised phase 3 study of adjuvant chemotherapy with or without nadroparin in patients with completely resected non-small-cell lung cancer: the NVALT-8 study

Background

Retrospective studies suggest that low molecular weight heparin may delay the development of metastasis in patients with resected NSCLC.

Methods

Multicentre phase 3 study with patients with completely resected NSCLC who were randomised after surgery to receive chemotherapy with or without nadroparin. The main exclusion criteria were R1/2 and wedge/segmental resection. FDG-PET was required. The primary endpoint was recurrence-free survival (RFS).

Results

Among 235 registered patients, 202 were randomised (nadroparin: n = 100; control n = 102). Slow accrual enabled a decrease in the number of patients needed from 600 to 202, providing 80% power to compare RFS with 94 events (α = 0.05; 2-sided). There were no differences in bleeding events between the two groups. The median RFS was 65.2 months (95% CI, 36—NA) in the nadroparin arm and 37.7 months (95% CI, 22.7—NA) in the control arm (HR 0.77 (95% CI, 0.53–1.13, P = 0.19). FDG-PET SUVmax ≥10 predicted a greater likelihood of recurrence in the first year (HR 0.48, 95% CI 0.22–0.9, P = 0.05).

Conclusions

Adjuvant nadroparin did not improve RFS in patients with resected NSCLC. In this study, a high SUVmax predicted a greater likelihood of recurrence in the first year.

Clinical trial registration

Netherlands Trial registry: NTR1250/1217.

Tumor-to-Blood Ratio for Assessment of Somatostatin Receptor Density in Neuroendocrine Tumors Using 68Ga-DOTATOC and 68Ga-DOTATATE

PET/CT with ⁶⁸Ga-DOTA-somatostatin analogs has been tested for therapy monitoring in patients with neuroendocrine tumors (NETs). However, SUVs in tumors do not correlate with the net influx rate (K_i), as a representation of the somatostatin receptor expression. In this study, tumor-to-blood ratio (TBR) was evaluated as an alternative tool for semiquantitative assessment of ⁶⁸Ga-DOTATOC and ⁶⁸Ga-DOTATATE tumor uptake and as a therapy monitoring tool for patients with NETs. Methods: Twenty-two NET patients underwent a 45-min dynamic PET/CT scan after injection of ⁶⁸Ga-DOTATOC or ⁶⁸Ga-DOTATATE. K_i was determined using the Patlak method, and TBR was calculated for the 40- to 45-min interval. Results: A linear relation was found between K_i and TBR, with a square of Pearson correlation of 0.98 and 0.93 for ⁶⁸Ga-DOTATOC and ⁶⁸Ga-DOTATATE, respectively. Conclusion: A high correlation was found between K_i and TBR. Hence, TBR reflects somatostatin receptor density more accurately than SUV and is suggested as the preferred metric for semiquantitative assessment of ⁶⁸Ga-DOTATOC and ⁶⁸Ga-DOTATATE tumor uptake.

Screening for brain metastases in patients with stage III non-small-cell lung cancer, magnetic resonance imaging or computed tomography? A prospective study

INTRODUCTION

Non-small-cell lung cancer (NSCLC) guidelines advise to screen stage III NSCLC patients for brain metastases (BMs), preferably by magnetic resonance imaging (MRI) or when contraindicated or not accessible a dedicated contrast enhanced-computed tomography (dCE-CT), which can be incorporated in the staging ¹⁸Fluodeoxoglucose-positron emission tomography (¹⁸FDG-PET-CE-CT). In daily practice, often a dCE-CT is performed instead of a MRI. The aim of the current study is to evaluate the additive value of MRI after dCE-CT, incorporated in the ¹⁸FDG-PET-CE-CT.

PATIENTS AND METHODS

It is an observational prospective multicentre study (NTR3628). Inclusion criteria included stage III NSCLC patients with a dCE-CT of the brain incorporated in the ¹⁸FDG-PET and an additional MRI of the brain. Primary end-point is percentage of patients with BM on MRI without suspect lesions on dCE-CT. Secondary end-points are percentage of patients with BM on dCE-CT and percentage of patients with BM ≤ 1 year of a negative staging MRI.

RESULTS

Sixteen (7%) patients with extracranial stage III had BM on dCE-CT and were excluded. One hundred forty-nine patients were enrolled. 7/149 (4.7%) had BM on MRI without suspect lesions on dCE-CT. One hundred eighteen patients had a follow-up of at least 1 year (four with BM on baseline MRI); eight of the remaining 114 (7%) patients developed BM ≤ 1 year after a negative staging brain MRI.

CONCLUSION

Although in 7% of otherwise stage III NSCLC patients, BMs were detected on staging dCE-CT, MRI brain detected BMs in an additional 4.7%, which we consider clinically relevant. Within 1 year after a negative staging MRI, 7% developed BM.

Absolute radiotracer concentration measurement using whole-body solid-state SPECT/CT technology: in vivo/in vitro validation

The accuracy of recently approved quantitative clinical software was determined by comparing in vivo/in vitro measurements for a solid-state cadmium-zinc-telluride SPECT/CT (single photon emission computed tomography/x-ray computed tomography) camera. Bone SPECT/CT, including the pelvic region in the field of view, was performed on 16 patients using technetium-99m methylene diphosphonic acid as a radiotracer. After imaging, urine samples from each patient provided for the measurement of in vitro radiopharmaceutical concentrations. From the SPECT/CT images, three users measured in vivo radiotracer concentration and standardized uptake value (SUV) for the bladder using quantitative software (Q.Metrix, GE Healthcare). Linear regression was used to validate any in vivo/in vitro identity relations (ideally slope = 1, intercept = 0), within a 95% confidence interval (CI). Thirteen in vivo/in vitro pairs were available for further analysis, after rejecting two as clinically irrelevant (SUVs > 100 g/mL) and one as an outlier (via Cook's distance calculations). All linear regressions (R² ≥ 0.85, P < 0.0001) provided identity in vivo/in vitro relations (95% CI), with SUV averages from all users giving a slope of 0.99 ± 0.25 and intercept of 0.14 ± 5.15 g/mL. The average in vivo/in vitro residual difference was < 20%. Solid-state SPECT/CT imaging can reliably provide in vivo urinary bladder radiotracer concentrations within approximately 20% accuracy. This practical, non-invasive, in vivo quantitation method can potentially improve diagnosis and assessment of response to treatment. Graphical abstract.

Adrenal tracer uptake by 18F-FDOPA PET/CT in patients with pheochromocytoma and controls

Context

¹⁸F-FDOPA PET/CT accurately localizes pheochromocytoma in patients with an established biochemical diagnosis. However, cut-off ¹⁸F-FDOPA levels of standardized uptake values (SUV_max) for both normal adrenal glands and pheochromocytoma are lacking.

Objective

Objectives of this study were to determine (1) reference maximum standardized uptake values (SUVmax) for normal adrenal ¹⁸F-DOPA tracer uptake and (2) the optimal diagnostic approach for pheochromocytoma localization by using ¹⁸F-DOPA SUVmax across a series of cut-off points: the affected adrenal gland (inter-individual analysis), the difference in SUVmax between the affected adrenal gland and the contralateral normal adrenal gland (intra-individual analysis), or a combination of these two.

Patients and methods

All patients with histologically confirmed pheochromocytoma diagnosed at our center between November 2009 and December 2017 were retrospectively analysed. Only those patients who underwent an ¹⁸F-FDOPA PET/CT-scan for localization purposes before adrenalectomy were included for further analysis. The control group consisted of patients who underwent ¹⁸F-FDOPA PET/CT for other indications and who had no genetic susceptibility for developing a pheochromocytoma. SUV_max of the volume of interest surrounding the adrenal glands was determined on EARL reconstructed images. Receiver operating characteristic (ROC) analysis was performed for adrenal gland SUV_max and intra-individual difference in SUV_max between affected and normal adrenal gland. In addition, binary logistic regression was performed for ROC analysis of the combined parameters.

Results

In total, 47 histologically confirmed pheochromocytomas were diagnosed in 45 patients, and 245 disease control patients were identified. In the control group, no statistical differences between the SUV_max of left and right adrenal glands were observed, and uptake values in both adrenal glands correlated significantly with each other (r = 0.865, p < 0.001). Median (range) adrenal gland SUV_max in pheochromocytomas and in the control group was 12 (2.6–50) and 2.9 (1.1–6.6), respectively (p < 0.001). ROC analysis revealed 93% sensitivity and 85% specificity at an SUV_max cut-off value of 4.1 (area under the curve (AUC) = 0.951), and 93% sensitivity and 96% specificity at an intra-individual SUV_max difference between the affected and normal adrenal gland of 1.0 (AUC = 0.992). The combination of both variables increased the AUC to 0.995.

Conclusions

¹⁸F-FDOPA PET/CT distinguishes pheochromocytoma from normal adrenal glands with the highest diagnostic accuracy when combining the SUVmax of the affected adrenal gland with the difference in SUV_max between affected and normal adrenal gland.

Verification of image quality and quantification in whole-body positron emission tomography with continuous bed motion

OBJECTIVE

Whole-body dynamic imaging using positron emission tomography (PET) facilitates the quantification of tracer kinetics. It is potentially valuable for the differential diagnosis of tumors and for the evaluation of therapeutic efficacy. In whole-body dynamic PET with continuous bed motion (CBM) (WBDCBM-PET), the pass number and bed velocity are key considerations. In the present study, we aimed to investigate the effect of a combination of pass number and bed velocity on the quantitative accuracy and quality of WBDCBM-PET images.

METHODS

In this study, WBDCBM-PET imaging was performed at a body phantom using seven bed velocity settings in combination with pass numbers. The resulting image quality was evaluated. For comparing different acquisition settings, the dynamic index (DI) was obtained using the following formula: [P/S], where P represents the pass number, and S represents the bed velocity (mm/s). The following physical parameters were evaluated: noise equivalent count at phantom (NEC_phantom), percent background variability (N_10 mm), percent contrast of the 10 mm hot sphere (Q_{H, 10 mm}), the Q_{H, 10 mm}/N_10 mm ratio, and the maximum standardized uptake value (SUV_max). Furthermore, visual evaluation was performed.

RESULTS

The NEC_phantom was equivalent for the same DI settings regardless of the bed velocity. The N_10 mm exhibited an inverse correlation (r < - 0.89) with the DI. Q_H,10 mm was not affected by DI, and a correlation between Q_H,10 mm/N_10 mm ratio and DI was found at all the velocities (r > 0.93). The SUV_max of the spheres was not influenced by the DI. The coefficient of variations caused by bed velocity decreased in larger spheres. There was no significant difference between the bed velocities on visual evaluation.

CONCLUSION

The quantitative accuracy and image quality achieved with WBDCBM-PET was comparable to that achieved with non-dynamic CBM, regardless of the pass number and bed velocity used during imaging for a given acquisition time.

Metabolic tumour volume is prognostic in patients with non-small-cell lung cancer treated with stereotactic ablative radiotherapy

Introduction

Stereotactic ablative radiotherapy (sabr) is a relatively new technique for the curative-intent treatment of patients with inoperable early-stage non-small-cell lung cancer (nsclc). Previous studies have demonstrated a prognostic value for positron emission tomography-computed tomography (pet/ct) parameters, including maximal standardized uptake value (suv_max), metabolic tumour volume (mtv), and total lesion glycolysis (tlg) in lung cancer patients. We aimed to determine which pet/ct parameter is most prognostic of local control (lc) and overall survival (os) in patients treated with sabr for nsclc.

Methods

We conducted a retrospective review of patients treated with sabr for stage I inoperable nsclc at BC Cancer between 2009 and 2013. The Akaike information criterion was used to compare the prognostic value of the various pet/ct parameters.

Results

The study included 134 patients with a median age of 76 years. Median tumour diameter was 2.2 cm, gross tumour volume was 8.1 mL, suv_max was 7.9, mtv was 2.4 mL, and tlg was 10.9 suv·mL. The 2-year lc was 92%, and os was 66%. On univariate and multivariate analysis, imaging variables including tumour size, gross tumour volume, suv_max, mtv, and tlg were all associated with worse lc. Tumour size was not associated with significantly worse os, but other imaging variables were. The pet/ct parameter most prognostic of lc was mtv. Compared with suv_max, tlg and mtv were more prognostic of os.

Conclusions

In patients with early-stage nsclc treated with sabr, mtv appears to be prognostic of lc and os.

Healthy Tissue Uptake of 68Ga-Prostate-Specific Membrane Antigen, 18F-DCFPyL, 18F-Fluoromethylcholine, and 18F-Dihydrotestosterone

PET is increasingly used for prostate cancer (PCa) diagnostics. Important PCa radiotracers include ⁶⁸Ga-prostate-specific membrane antigen HBED-CC (⁶⁸Ga-PSMA), ¹⁸F-DCFPyL, ¹⁸F-fluoromethylcholine (¹⁸F-FCH), and ¹⁸F-dihydrotestosterone (¹⁸F-FDHT). Knowledge on the variability of tracer uptake in healthy tissues is important for accurate PET interpretation, because malignancy is suspected only if the uptake of a lesion contrasts with its background. Therefore, the aim of this study was to quantify uptake variability of PCa tracers in healthy tissues and identify stable reference regions for PET interpretation. Methods: A total of 232 PCa PET/CT scans from multiple hospitals was analyzed, including 87 ⁶⁸Ga-PSMA scans, 50 ¹⁸F-DCFPyL scans, 68 ¹⁸F-FCH scans, and 27 ¹⁸F-FDHT scans. Tracer uptake was assessed in the blood pool, lung, liver, bone marrow, and muscle using several SUVs (SUV_max, SUV_mean, SUV_peak). Variability in uptake between patients was analyzed using the coefficient of variation (COV%). For all tracers, SUV reference ranges (95th percentiles) were calculated, which could be applicable as image-based quality control for future PET acquisitions. Results: For ⁶⁸Ga-PSMA, the lowest uptake variability was observed in the blood pool (COV, 19.9%), which was significantly more stable than all other tissues (COV, 29.8%-35.2%; P = 0.001-0.024). For ¹⁸F-DCFPyL, the lowest variability was observed in the blood pool and liver (COV, 14.4% and 21.7%, respectively; P = 0.001-0.003). The least variable ¹⁸F-FCH uptake was observed in the liver, blood pool, and bone marrow (COV, 16.8%-24.2%; P = 0.001-0.012). For ¹⁸F-FDHT, low uptake variability was observed in all tissues, except the lung (COV, 14.6%-23.6%; P = 0.001-0.040). The different SUV types had limited effect on variability (COVs within 3 percentage points). Conclusion: In this multicenter analysis, healthy tissues with limited uptake variability were identified, which may serve as reference regions for PCa PET interpretation. These reference regions include the blood pool for ⁶⁸Ga-PSMA and ¹⁸F-DCFPyL and the liver for ¹⁸F-FCH and ¹⁸F-FDHT. Healthy tissue SUV reference ranges are presented and applicable as image-based quality control.

F8-IL10: A New Potential Antirheumatic Drug Evaluated by a PET-Guided Translational Approach

Antibody fragment F8-mediated interleukin 10 (IL10) delivery is a novel treatment for rheumatoid arthritis (RA). F8 binds to the extra-domain-A of fibronectin (ED-A). In this study, in vivo biodistribution and arthritis targeting of radiolabeled F8-IL10 were investigated in RA patients, followed by further animal studies. Therefore, three RA patients (DAS28 > 3.2) received 0.4 mg of 30–74 megabecquerel [¹²⁴I]I–F8–IL10 for PET-CT and blood sampling. In visually identified PET-positive joints, target-to-background was calculated. Healthy mice, rats, and arthritic rats were injected with iodinated F8-IL10 or KSF-IL10 control antibody. Various organs were excised, weighed, and counted for radioactivity. Tissue sections were stained for fibronectin ED-A. In RA patients, [¹²⁴I]I–F8–IL10 was cleared rapidly from the circulation with less than 1% present in blood after 5 min. PET-CT showed targeting in 38 joints (11–15 per patient) and high uptake in the liver and spleen. Mean target-to-background ratios of PET-positive joints were 2.5 ± 1.2, 1.5 times higher for clinically active than clinically silent joints. Biodistribution of radioiodinated F8-IL10 in healthy mice showed no effect of the radioiodination method. [¹²⁴I]I–F8–IL10 joint uptake was also demonstrated in arthritic rats, ∼14-fold higher than that of the control antibody [¹²⁴I]I-KSF-IL10 (p < 0.001). Interestingly, liver and spleen uptake were twice as high in arthritic than in healthy rats and were related to increased (∼7×) fibronectin ED-A expression in these tissues. In conclusion, [¹²⁴I]I–F8–IL10 uptake was observed in arthritic joints in RA patients holding promise for visualization of inflamed joints by PET-CT imaging and therapeutic targeting. Patient observations and, subsequently, arthritic animal studies pointed to awareness of increased [¹²⁴I]I–F8–IL10 uptake in the liver and spleen associated with moderate systemic inflammation. This translational study demonstrated the value of in vivo biodistribution and PET-CT-guided imaging in development of new and potential antirheumatic drugs’.

Use of a Qualification Phantom for PET Brain Imaging in a Multicenter Consortium: A Collaboration Between the Pediatric Brain Tumor Consortium and the SNMMI Clinical Trials Network

The purpose of this study was to assess image quality and quantitative brain PET across a multicenter consortium. Methods: All academic centers and children's hospitals in the Pediatric Brain Tumor Consortium (PBTC) scanned a phantom developed by the Society of Nuclear Medicine and Molecular Imaging Clinical Trials Network (SNMMI CTN) for the validation of brain PET studies associated with clinical trials. The phantom comprises 2 separate, fillable sections: a resolution/uniformity section and a clinical simulation section. The resolution/uniformity section is a cylinder 12.7 cm long and 20 cm in diameter; spatial resolution is evaluated subjectively with 2 sets of rods (hot and cold) of varying diameter (4.0, 5.0, 6.25, 7.81, 9.67, and 12.2 mm) and spacing (twice the rod diameter). The clinical simulation section simulates a transverse section of midbrain with ventricles and gray and white matter compartments. If properly filled, hot rods have a 4:1 target-to-background ratio, and gray-to-white matter sections have a 4:1 ratio. Uniformity and image quality were evaluated using the SUV in a small volume of interest as well as subjectively by 2 independent observers using a 4-point scale. Results: Eleven PBTC sites scanned the phantom on 13 PET scanners. The phantom's complexity led to suboptimal filling, particularly of the hot rod section, in 5 sites. The SUV in the uniformity section was within 10% of unity on only 5 of 13 scanners, although 12 of 13 were subjectively judged to have very good to excellent uniformity. Four of 6 hot rods were discernable by all 13 scanners, whereas 3 of 6 cold rods were discernable by only 5 scanners. Four of 13 scanners had a gray-to-white matter ratio between 3.0 and 5.0 (4.0 is truth); however, 11 of 13 scanners were subjectively judged to have very good or excellent image quality. Conclusion: Eleven sites were able to image a powerful phantom developed by the SNMMI CTN that evaluated image uniformity, spatial resolution, and image quality of brain PET. There was considerable variation in PET data across the PBTC sites, possibly resulting from variations in scanning across the sites due to challenges in filling the phantom.

Is C-11 Methionine PET an alternative to 18-F FDG-PET for identifying recurrent laryngeal cancer after radiotherapy?

OBJECTIVE

18F FDG-PET is superior to other imaging techniques in revealing residual laryngeal cancer after radiotherapy. Unfortunately, its specificity is low, due to FDG uptake in inflammation and in anaerobic conditions. PET imaging with the amino acid-based radiopharmaceutical C11-methionine (MET) should be less influenced by post-radiation conditions. The aim of this study was to investigate the potential of MET in diagnosing recurrent laryngeal cancer after radiotherapy as compared to 18F-FDG.

METHODS

Forty-eight patients with a clinical suspicion of local residual disease at least 3 months after completion of radiotherapy or chemoradiotherapy for a T2-4 laryngeal carcinoma, along with an indication for direct laryngoscopy, were included. They received MET-PET and FDG-PET prior to the direct laryngoscopy. One senior nuclear medicine physician assessed both the FDG-PET and MET-PET images visually for the degree of abnormal uptake. The gold standard was a biopsy-proven recurrence 12 months after PET. The nuclear physician had no access to the medical charts and was blinded to the results of the other PET. Sensitivity, specificity and positive and negative predictive value were calculated.

RESULTS

The sensitivity of FDG was 77.3% and the specificity 56.0% after the conservative reading, with these values equalling 54.5% and 76.0% for MET. The positive predictive value of FDG was 60.7% and the negative predictive value 73.7%. The PPV of MET was 66.7%, and the NPV was 65.5%. The McNemar test within diseased (sensitivity comparison) shows a p-value of 0.125, and the McNemar test within non-diseased (specificity comparison) shows a P-value of 0.180.

CONCLUSION

MET-PET is not superior to FDG-PET in terms of identifying recurrent laryngeal cancer.

The acute and late toxicity results of a randomized phase II dose-escalation trial in non-small cell lung cancer (PET-boost trial)

BACKGROUND AND PURPOSE

The PET-boost randomized phase II trial (NCT01024829) investigated dose-escalation to the entire primary tumour or redistributed to regions of high pre-treatment FDG-uptake in inoperable non-small cell lung cancer (NSCLC) patients. We present a toxicity analysis of the 107 patients randomized in the study.

MATERIALS AND METHODS

Patients with stage II-III NSCLC were treated with an isotoxic integrated boost of ≥72 Gy in 24 fractions, with/without chemotherapy and strict dose limits. Toxicity was scored until death according to the CTCAEv3.0.

RESULTS

77 (72%) patients were treated with concurrent chemoradiotherapy. Acute and late ≥G3 occurred in 41% and 25%. For concurrent (C) and sequential or radiotherapy alone (S), the most common acute ≥G3 toxicities were: dysphagia in 14.3% (C) and 3.3% (S), dyspnoea in 2.6% (C) and 6.7% (S), pneumonitis in 0% (C) and 6.7% (S), cardiac toxicity in 6.5% (C) and 3.3% (S). Seventeen patients died of which in 13 patients a possible relation to treatment could not be excluded. In 10 of these 13 patients progressive disease was scored. Fatal pulmonary haemorrhages and oesophageal fistulae were observed in 9 patients.

CONCLUSION

Personalized dose-escalation in inoperable NSCLC patients results in higher acute and late toxicity compared to conventional chemoradiotherapy. The toxicity, however, was within the boundaries of the pre-defined stopping rules.

An account of data entry inconsistencies and their impact on positron emission tomography quantification

Reproducibility is essential to clinical application of positron emission tomography (PET) quantification. Human lapses in data registration and protocol compliance are pervasive sources of intrasite quantification variability. Although rarely assessed or reported, these lapses are ultimately a limitation to harmonization in multicenter clinical trials. A comprehensive account of their possible extent is relayed here.This is a retrospective audit of errors in manual registration of study parameters and in protocol adherence across a sample of in-center research projects over one year (201 patients, 222 PET/CT scans). Discrepancies in patient height and weight; tracer type; dose; injection; and scan times were listed. Correspondent variances in standardized uptake values (SUVs) normalized by body weight, SUV (BW), and body surface area, SUV (BSA), were assessed.Manual misregistrations totalled 41.8%. These were mainly small, but with a few large deviations, and most significant in weight (range: -1-100 kg) and dose (-19 to 12 MBq). Errors were more frequent and generally larger in non-routine studies. This also applied to protocol compliance. A 50.7% noncompliance was found with significant deviations in dose (-106 to 208 MBq) and especially in early scan uptake times (-37 to 54 min). Although misregistrations did not overall translate into significant SUV variability, noncompliance did. These errors contributed a factor 0.02 to 1.45 and 0.71 to 3.09 SUV (BW) change, respectively. SUV (BSA) saw a significant 21% to 22% decrease with mistyped height and weight.Inconsistency was frequent but less prominent in data entry than in protocol compliance. As both caused some substantial SUV variances, intra-site assessments and data checking are required for clinical trials.

Standardization of 64Cu activity

The complex decay scheme that makes 64Cu promising as both an imaging and therapeutic agent in medicine also makes the absolute measurement of its activity challenging. The National Institute of Standards and Technology (NIST) has completed a primary activity standardization of a 64CuCl2 solution using the 4πβ(LS)-γ(NaI) live-timed anticoincidence (LTAC) counting method with a combined standard uncertainty of 0.51 %. Two liquid scintillation (LS) counting methods were employed for confirmatory measurements. Secondary measurements were made by high-purity germanium detectors, pressurized ionization chambers (IC), and a well-type NaI(Tl) counter. Agreement between the LTAC-based standard and standards from other laboratories was established via IC calibration factors. Poor agreement between methods and with theoretical IC responses may indicate a need for improved β+/- branching probabilities and a better treatment of β+/- spectra.

Longitudinal PET imaging of tumor hypoxia during the course of radiotherapy

Hypoxia results from an imbalance between oxygen supply and consumption. It is a common phenomenon in solid malignant tumors such as head and neck cancer. As hypoxic cells are more resistant to therapy, tumor hypoxia is an indicator for poor prognosis. Several techniques have been developed to measure tissue oxygenation. These are the Eppendorf O2 polarographic needle electrode, immunohistochemical analysis of endogenous (e.g., hypoxia-inducible factor-1α (HIF-1a)) and exogenous markers (e.g., pimonidazole) as well as imaging methods such as functional magnetic resonance imaging (e.g., blood oxygen level dependent (BOLD) imaging, T1-weighted imaging) and hypoxia positron emission tomography (PET). Among the imaging modalities, only PET is sufficiently validated to detect hypoxia for clinical use. Hypoxia PET tracers include 18F-fluoromisonidazole (FMISO), the most commonly used hypoxic marker, 18F-flouroazomycin arabinoside (FAZA), 18Ffluoroerythronitroimidazole (FETNIM), 18F-2-nitroimidazolpentafluoropropylacetamide (EF5) and 18F-flortanidazole (HX4). As technical development provides the opportunity to increase the radiation dose to subregions of the tumor, such as hypoxic areas, it has to be ensured that these regions are stable not only from imaging to treatment but also through the course of radiotherapy. The aim of this review is therefore to characterize the behavior of tumor hypoxia during radiotherapy for the whole tumor and for subregions by using hypoxia PET tracers, with focus on head and neck cancer patients.

Metformin Discontinuation prior to FDG PET/CT: A Randomized Controlled Study to Compare 24- and 48-hour Bowel Activity

Purpose To investigate the relationship of 24- and 48-hour metformin discontinuation to bowel uptake of fluorine 18 fluorodeoxyglucose (FDG) on PET/CT scans. Materials and Methods Patients with diabetes who were treated with metformin and referred for FDG PET/CT were randomized to three equal groups based on duration of metformin discontinuation: 24 hours, 48 hours, and no discontinuation (control group). Two interpreters blinded to the study groups assessed FDG uptake in multiple segments of small and large bowel qualitatively and semiquantitatively by using maximum standardized uptake values (SUVs_max). Differences in age, sex, weight, dose of metformin, duration of metformin treatment, blood glucose levels, and FDG dose injected were assessed. Data were analyzed with analysis of variance when passing normality, and by nonparametric testing when not. Results Ninety study participants (62 male, 28 female; median age, 70 years) were enrolled from July 2010 through March 2012. There were no differences between study groups in weight, blood glucose levels 3 days prior to scanning, or normal organ uptake. Large bowel SUV_max was lower after 24 hours (4.10 ± 2.00 vs 5.42 ± 2.36; P = .020) and 48 hours (2.63 ± 0.88 vs 5.42 ± 2.36; P ˂ .001) of metformin discontinuation than for no discontinuation (control), and for 48 hours versus 24 hours of discontinuation (P = .0015). Small bowel SUV_max was lower after 24 hours (2.86 ± 0.67 vs 3.73 ± 1.08 [control]; P ˂ .001) and 48 hours (2.78 ± 0.73 vs 3.73 ± 1.08 [control]; P ˂ .001) of metformin discontinuation versus no metformin discontinuation, but not for 48 hours versus 24 hours of discontinuation (P = .57). Examination-day blood glucose levels increased after 48-hour withdrawal of metformin (8.41 mmol/L ± 2.86 vs 6.83 mmol/L ± 2.13 [control]; P = .002). Conclusion Metformin discontinuation for 48 hours prior to PET/CT was associated with lower accumulation of fluorodeoxyglucose in the bowel, compared to when there was no discontinuation (control group) or 24-hour discontinuation of metformin. © RSNA, 2018.

Serial FLT PET imaging to discriminate between true progression and pseudoprogression in patients with newly diagnosed glioblastoma: a long-term follow-up study

Purpose

Response evaluation in patients with glioblastoma after chemoradiotherapy is challenging due to progressive, contrast-enhancing lesions on MRI that do not reflect true tumour progression. In this study, we prospectively evaluated the ability of the PET tracer ¹⁸F-fluorothymidine (FLT), a tracer reflecting proliferative activity, to discriminate between true progression and pseudoprogression in newly diagnosed glioblastoma patients treated with chemoradiotherapy.

Methods

FLT PET and MRI scans were performed before and 4 weeks after chemoradiotherapy. MRI scans were also performed after three cycles of adjuvant temozolomide. Pseudoprogression was defined as progressive disease on MRI after chemoradiotherapy with stabilisation or reduction of contrast-enhanced lesions after three cycles of temozolomide, and was compared with the disease course during long-term follow-up. Changes in maximum standardized uptake value (SUV_max) and tumour-to-normal uptake ratios were calculated for FLT and are presented as the mean SUV_max for multiple lesions.

Results

Between 2009 and 2012, 30 patients were included. Of 24 evaluable patients, 7 showed pseudoprogression and 7 had true progression as defined by MRI response. FLT PET parameters did not significantly differ between patients with true progression and pseudoprogression defined by MRI. The correlation between change in SUV_max and survival (p = 0.059) almost reached the standard level of statistical significance. Lower baseline FLT PET uptake was significantly correlated with improved survival (p = 0.022).

Conclusion

Baseline FLT uptake appears to be predictive of overall survival. Furthermore, changes in SUV_max over time showed a tendency to be associated with improved survival. However, further studies are necessary to investigate the ability of FLT PET imaging to discriminate between true progression and pseudoprogression in patients with glioblastoma.

Simultaneous Estimation of Bias and Resolution in PET Images With a Long-Lived "Pocket" Phantom System

A challenge in multicenter trials that use quantitative positron emission tomography (PET) imaging is the often unknown variability in PET image values, typically measured as standardized uptake values, introduced by intersite differences in global and resolution-dependent biases. We present a method for the simultaneous monitoring of scanner calibration and reconstructed image resolution on a per-scan basis using a PET/computed tomography (CT) "pocket" phantom. We use simulation and phantom studies to optimize the design and construction of the PET/CT pocket phantom (120 × 30 × 30 mm). We then evaluate the performance of the PET/CT pocket phantom and accompanying software used alongside an anthropomorphic phantom when known variations in global bias (±20%, ±40%) and resolution (3-, 6-, and 12-mm postreconstruction filters) are introduced. The resulting prototype PET/CT pocket phantom design uses 3 long-lived sources (15-mm diameter) containing germanium-68 and a CT contrast agent in an epoxy matrix. Activity concentrations varied from 30 to 190 kBq/mL. The pocket phantom software can accurately estimate global bias and can detect changes in resolution in measured phantom images. The pocket phantom is small enough to be scanned with patients and can potentially be used on a per-scan basis for quality assurance for clinical trials and quantitative PET imaging in general. Further studies are being performed to evaluate its performance under variations in clinical conditions that occur in practice.

[Administration Accuracy of Automated Infusion Device for PET Using Improved Disposable Kit]

PURPOSE

The AI-300 automated infusion device (Sumitomo Heavy Industries, Ltd., Tokyo, Japan) is subject to administration error as a function of smaller volumes of ¹⁸F-FDG dispensed via a three-way cock supplied with a disposable kit. The present study aimed to validate the administration accuracy of the AI-300 using an improved disposable kit for quantitative positron emission tomography (PET) assessment.

METHODS

We determined administration accuracy between the improved and previous disposable kits by measuring variations in dispensed volumes and radioactive concentrations of ¹⁸F-FDG according to the criteria of the Japanese Society of Nuclear Medicine. A reference value was generated by measuring radioactivity using a standard dose calibrator.

RESULTS

The values obtained using the previous kit deviated from the reference values by a maximum of -10.6%, and the deviation depended on dispensed volumes of ¹⁸F-FDG<0.25 mL. In contrast, the values were relatively stable when using the improved kit with dispensed ¹⁸F-FDG volumes < 0.25 mL. Variations in radioactive concentrations were relatively stable using the improved kit, whereas that of the previous kit was slightly unstable at high radioactive concentrations.

CONCLUSION

The administration accuracy of the AI-300 using the previous kit varied considerably according to smaller dispensed volumes, but the improved kit might alleviate this problem. The present results indicated that the improved disposal kit should be immediately implemented to eliminate uncertainty surrounding quantitative PET findings.

Monitoring scanner calibration using the image-derived arterial blood SUV in whole-body FDG-PET

Background

The current de facto standard for quantification of tumor metabolism in oncological whole-body PET is the standardized uptake value (SUV) approach. SUV determination requires accurate scanner calibration. Residual inaccuracies of the calibration lead to biased SUV values. Especially, this can adversely affect multicenter trials where it is difficult to ensure reliable cross-calibration across participating sites. The goal of the present work was the evaluation of a new method for monitoring scanner calibration utilizing the image-derived arterial blood SUV (BSUV) averaged over a sufficiently large number of whole-body FDG-PET investigations.

Data of 681 patients from three sites which underwent routine ¹⁸F-FDG PET/CT or PET/MR were retrospectively analyzed. BSUV was determined in the descending aorta using a three-dimensional ROI concentric to the aorta’s centerline. The ROI was delineated in the CT or MRI images and transferred to the PET images. A minimum ROI volume of 5 mL and a concentric safety margin to the aortic wall was observed. Mean BSUV, standard deviation (SD), and standard error of the mean (SE) were computed for three groups of patients at each site, investigated 2 years apart, respectively, with group sizes between 53 and 100 patients. Differences of mean BSUV between the individual groups and sites were determined.

Results

SD (SE) of BSUV in the different groups ranged from 14.3 to 20.7% (1.7 to 2.8%). Differences of mean BSUV between intra-site groups were small (1.1–6.3%). Only one out of nine of these differences reached statistical significance. Inter-site differences were distinctly larger (12.6–25.1%) and highly significant (P<0.001).

Conclusions

Image-based determination of the group-averaged blood SUV in modestly large groups of whole-body FDG-PET investigations is a viable approach for ensuring consistent scanner calibration over time and across different sites. We propose this approach as a quality control and cross-calibration tool augmenting established phantom-based procedures.

Interobserver Agreement of Interim and End-of-Treatment 18F-FDG PET/CT in Diffuse Large B-Cell Lymphoma: Impact on Clinical Practice and Trials

We aimed to assess the interobserver agreement of interim PET (I-PET) and end-of-treatment PET (EoT-PET) using the Deauville score (DS) in first-line diffuse large B-cell lymphoma (DLBCL) patients. Methods: I-PET and EoT-PET scans of DLBCL patients were performed in the HOVON84 study (2007-2012), an international multicenter randomized controlled trial. Patients received R-CHOP14 and were randomized to receive rituximab intensification in the first 4 cycles or not. I-PET was performed after 4 cycles (for observational purposes), and EoT-PET after 6 or 8 cycles. Two independent central reviewers retrospectively scored all scans according to the DS system, masked to clinical outcomes. Results were dichotomized as negative (DS of 1-3) or positive (DS of 4-5). Besides percentage overall agreement (OA), we calculated agreement for positive and negative scores, expressed as positive agreement (PA) and negative agreement (NA), respectively. Results: 465 I-PET and 457 EoT-PET scans were centrally reviewed; baseline ¹⁸F-FDG PET or PET/CT was available in 75%-77%, and CT in the remaining cases. Percentage OA for I-PET and EoT-PET were 87.7% and 91.7% (P = 0.049), with NA of 92.0% and 95.0% (P = 0.091), and PA of 73.7% and 76.3% (P = 0.656), respectively. Conclusion: Interobserver agreement using DS in DLBCL patients in I-PET and EoT-PET yields high OA and NA. The lower PA suggests that EoT-PET/CT treatment evaluation in daily practice and I-PET-adapted trials may benefit from dual reads and central review, respectively.

Biological imaging for individualized therapy in radiation oncology: part I physical and technical aspects

Recently, there has been an increase in the imaging modalities available for radiotherapy planning and radiotherapy prognostic outcome: dual energy computed tomography (CT), dynamic contrast enhanced CT, dynamic contrast enhanced magnetic resonance imaging (MRI), diffusion-weighted MRI, positron emission tomography-CT, dynamic contrast enhanced ultrasound, MR spectroscopy and positron emission tomography-MR. These techniques enable more precise gross tumor volume definition than CT alone and moreover allow subvolumes within the gross tumor volume to be defined which may be given a boost dose or an individual voxelized dose prescription may be derived. With increased plan complexity care must be taken to immobilize the patient in an accurate and reproducible manner. Moreover the physical and technical limitations of the entire treatment planning chain need to be well characterized and understood, interdisciplinary collaboration ameliorated (physicians and physicists within nuclear medicine, radiology and radiotherapy) and image protocols standardized.

18F-fluorodeoxyglucose positron-emission tomography (FDG-PET)-Radiomics of metastatic lymph nodes and primary tumor in non-small cell lung cancer (NSCLC) - A prospective externally validated study

BACKGROUND

Lymph node stage prior to treatment is strongly related to disease progression and poor prognosis in non-small cell lung cancer (NSCLC). However, few studies have investigated metabolic imaging features derived from pre-radiotherapy 18F-fluorodeoxyglucose (FDG) positron-emission tomography (PET) of metastatic hilar/mediastinal lymph nodes (LNs). We hypothesized that these would provide complementary prognostic information to FDG-PET descriptors to only the primary tumor (tumor).

METHODS

Two independent cohorts of 262 and 50 node-positive NSCLC patients were used for model development and validation. Image features (i.e. Radiomics) including shape and size, first order statistics, texture, and intensity-volume histograms (IVH) (http://www.radiomics.io/) were evaluated by univariable Cox regression on the development cohort. Prognostic modeling was conducted with a 10-fold cross-validated least absolute shrinkage and selection operator (LASSO), automatically selecting amongst FDG-PET-Radiomics descriptors from (1) tumor, (2) LNs or (3) both structures. Performance was assessed with the concordance-index. Development data are publicly available at www.cancerdata.org and Dryad (doi:10.5061/dryad.752153b).

RESULTS

Common SUV descriptors (maximum, peak, and mean) were significantly related to overall survival when extracted from LNs, as were LN volume and tumor load (summed tumor and LNs' volumes), though this was not true for either SUV metrics or tumor's volume. Feature selection exclusively from imaging information based on FDG-PET-Radiomics, exhibited performances of (1) 0.53 -external 0.54, when derived from the tumor, (2) 0.62 -external 0.56 from LNs, and (3) 0.62 -external 0.59 from both structures, including at least one feature from each sub-category, except IVH.

CONCLUSION

Combining imaging information based on FDG-PET-Radiomics features from tumors and LNs is desirable to achieve a higher prognostic discriminative power for NSCLC.

Reduced cognitive function, increased blood-brain-barrier transport and inflammatory responses, and altered brain metabolites in LDLr -/-and C57BL/6 mice fed a western diet

Recent work suggests that diet affects brain metabolism thereby impacting cognitive function. Our objective was to determine if a western diet altered brain metabolism, increased blood-brain barrier (BBB) transport and inflammation, and induced cognitive impairment in C57BL/6 (WT) mice and low-density lipoprotein receptor null (LDLr -/-) mice, a model of hyperlipidemia and cognitive decline. We show that a western diet and LDLr -/- moderately influence cognitive processes as assessed by Y-maze and radial arm water maze. Also, western diet significantly increased BBB transport, as well as microvessel factor VIII in LDLr -/- and microglia IBA1 staining in WT, both indicators of activation and neuroinflammation. Interestingly, LDLr -/- mice had a significant increase in ¹⁸F- fluorodeoxyglucose uptake irrespective of diet and brain ¹H-magnetic resonance spectroscopy showed increased lactate and lipid moieties. Metabolic assessments of whole mouse brain by GC/MS and LC/MS/MS showed that a western diet altered brain TCA cycle and β-oxidation intermediates, levels of amino acids, and complex lipid levels and elevated proinflammatory lipid mediators. Our study reveals that the western diet has multiple impacts on brain metabolism, physiology, and altered cognitive function that likely manifest via multiple cellular pathways.

Influence of PET reconstruction para meters on the TrueX algorithm

With the increasing use of functional imaging in modern radiotherapy (RT) and the envisaged automated integration of PET into target definition, the need for reliable quantification of PET is growing. Reconstruction algorithms in new PET scanners employ pointspread-function (PSF) based resolution recovery, however, their impact on PET quantification still requires thorough investigation. Patients, material, methods: Measurements were performed on a Siemens PET/CT using an IEC phantom filled with varying activity. Data were reconstructed using the OSEM (Gauss filter) and the PSF TrueX (Gauss and Allpass filter) algorithm with all available products of iterations (i) and subsets (ss). The recovery coeffcient (RC) and threshold defining the real sphere volume were determined for all settings and compared to the clinical standard (4i21ss). PET acquisitions of eight lung patients were reconstructed using all algorithms with 4i21ss. Volume size and tracer uptake were determined with different segmentation methods. Results: The threshold for the TrueX was lower (up to 40%) than for the OSEM. The RC for the different algorithms and filters varied. TrueX was more sensitive to permutations of i and ss and only the RC of the OSEM stabilised with increasing number. For patient scans the difference of the volume and activity between TrueX and OSEM could be reduced by applying an adapted threshold and activity correction. Conclusion: The TrueX algorithm results in excellent diagnostic image quality, however, guidelines for native algorithms have to be extended for PSF based reconstruction methods. For appropriate tumour delineation, for the TrueX a lower threshold than the 42% recommended for the OSEM is necessary. These filter dependent thresholds have to be verified for different scanners prior to using them in multicenter trials.

Baseline PET as prognostic marker for Hodgkin?

In this issue of Blood, Akhtari et al present a retrospective analysis of baseline positron emission tomography-computed tomography (PET-CT) in Hodgkin lymphoma (HL) in relation to the prognostic significance of the metabolic tumor volume (MTV) in risk classification of early-stage HL.1 These measurements yield estimates of the total tumor burden, which has previously been demonstrated to be one of the most significant prognostic factor in HL.2 A more precise discrimination between low-risk vs high-risk HL using baseline PET-CT characteristics could be clinically useful and might inform treatment decisions.

Variation of system performance, quality control standards and adherence to international FDG-PET/CT imaging guidelines

Aim: To gather information on clinical operations, quality control (QC) standards and adoption of guidelines for FDG-PET/CT imaging in Austrian PET/CT centres. Methods: A written survey composed of 68 questions related to A) PET/CT centre and installation, B) standard protocol parameters for FDG-PET/CT imaging of oncology patients, and C) standard QC procedures was conducted between November and December 2013 among all Austrian PET/CT centres. In addition, a NEMA-NU2 2012 image quality phantom test was performed using standard whole-body imaging settings on all PET/CT systems with a lesion-to- background ratio of 4. Recovery coefficients (RC) were calculated for each lesion and PET/ CT system. Resu lts: A) 13 PET/CT systems were installed in 12 nuclear medicine departments at public hospitals. B) Average fasting prior to FDG-PET/CT was 7.6 (4-12) h. All sites measured blood glucose levels while using different cut-off levels (64%: 150 mg/dl). Weight- based activity injection was performed at 83% sites with a mean FDG activity of 4.1 MBq/kg. Average FDG uptake time was 55 (45-75) min. All sites employed CT contrast agents (variation from 1 %-95% of the patients). All sites reported SUV-max. C) Frequency of QC tests varied significantly and QC phantom measurements revealed significant differences in RCs. Conclusion: Significant variations in FDG-PET/CT protocol parameters among all Austrian PET/CT users were observed. subsequently, efforts need to be put in place to further standardize imaging protocols. At a minimum clinical PET/CT operations should ensure compliance with existing guidelines. Further, standardized QC procedures must be followed to improve quantitative accuracy across PET/CT centres.

Diagnostic accuracy of C-11 choline and C-11 acetate for lymph node staging in patients with bladder cancer: a systematic review and meta-analysis

OBJECTIVE

We aimed to assess the diagnostic accuracy of C-11 choline and C-11 acetate positron emission tomography/computed tomography (PET/CT) for lymph node (LN) staging in bladder cancer (BC) patients through a systematic review and meta-analysis.

METHODS

The MEDLINE, EMBASE, and Cochrane Library database, from the earliest available date of indexing through June 30, 2017, were searched for studies evaluating the diagnostic performance of C-11 choline and C-11 acetate PET/CT for LN staging in BC. We determined the sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LR+ and LR-), and constructed summary receiver operating characteristic curves.

RESULTS

Across 10 studies (282 patients), the pooled sensitivity was 0.66 (95% CI 0.54-0.75) without heterogeneity (χ² = 12.4, p = 0.19) and a pooled specificity of 0.89 (95% CI 0.76-0.95) with heterogeneity (χ² = 29.1, p = 0.00). Likelihood ratio (LR) syntheses gave an overall positive likelihood ratio (LR+) of 5.8 (95% CI 2.7-12.7) and negative likelihood ratio (LR-) of 0.39 (95% CI 0.28-0.53). The pooled diagnostic odds ratio (DOR) was 15 (95% CI 6-38). In meta-regression analysis, the study design (prospective vs retrospective) was the source of the study heterogeneity.

CONCLUSION

C-11 choline and C-11 acetate PET/CT shows a low sensitivity and moderate specificity for the detection of metastatic LNs in patients with BC. Moreover, heterogeneity among the studies should be considered a limitation. Further large multicenter studies would be necessary to substantiate the diagnostic accuracy of C-11 choline and C-11 acetate PET/CT for this purpose.

Hybrid 18F-FDG PET/CT of colonic anastomosis

18F-fluorodeoxyglucose positron emission tomography (FDG-PET) is a known method to diagnose inflammatory processes and thus may be a promising imaging technique to detect anastomotic bowel leak. The aim of this study was to assess postoperative FDG uptake in colorectal anastomosis in patients without suspicion of active infection or anastomotic leakage. Patients, methods: Design of a prospective observational pilot study in order to assess normal FDG uptake in the patient anastomosis after colorectal surgery. Patients that underwent colorectal surgery with primary anastomosis received FDG-PET of the abdomen, 2–6 days postoperatively. Results: 35 patients met the inclusion criteria. Three patients were not scanned for various reasons. Of the remaining 32 patients, one demonstrated an increased uptake of FDG at the site of the anastomosis. In the other 31 patients FDG uptake was negligible (n = 17) or scored as physiological (n = 14). None of the scanned patients developed a clinical relevant anastomotic leakage within the first 30 days after surgery. Conclusion: The present study shows that FDG uptake in colorectal anastomosis remains low within the first six days after surgery in patients without anastomotic leakage. Therefore, FDG-PET might be useful to investigate further as a tool to detect anastomotic leakage in an the early postoperative phase.

Quality assessment of positron emission tomography scans: recommendations for future multicentre trials

BACKGROUND

Standardization protocols and guidelines for positron emission tomography (PET) in multicenter trials are available, despite a large variability in image acquisition and reconstruction parameters exist. In this study, we investigated the compliance of PET scans to the guidelines of the European Association of Nuclear Medicine (EANM). From these results, we provide recommendations for future multicenter studies using PET.

MATERIAL AND METHODS

Patients included in a multicenter randomized phase II study had repeated PET scans for early response assessment. Relevant acquisition and reconstruction parameters were extracted from the digital imaging and communications in medicine (DICOM) header of the images. The PET image parameters were compared to the guidelines of the EANM for tumor imaging version 1.0 recommended parameters.

RESULTS

From the 223 included patients, 167 baseline scans and 118 response scans were available from 15 hospitals. Scans of 19% of the patients had an uptake time that fulfilled the Uniform Protocols for Imaging in Clinical Trials response assessment criteria. The average quality score over all hospitals was 69%. Scans with a non-compliant uptake time had a larger standard deviation of the mean standardized uptake value (SUVmean) of the liver than scans with compliant uptake times.

CONCLUSIONS

Although a standardization protocol was agreed on, there was a large variability in imaging parameters. For future, multicenter studies including PET imaging a prospective central quality review during patient inclusion is needed to improve compliance with image standardization protocols as defined by EANM.

Predicting tumor hypoxia in non-small cell lung cancer by combining CT, FDG PET and dynamic contrast-enhanced CT

BACKGROUND

Most solid tumors contain inadequately oxygenated (i.e., hypoxic) regions, which tend to be more aggressive and treatment resistant. Hypoxia PET allows visualization of hypoxia and may enable treatment adaptation. However, hypoxia PET imaging is expensive, time-consuming and not widely available. We aimed to predict hypoxia levels in non-small cell lung cancer (NSCLC) using more easily available imaging modalities: FDG-PET/CT and dynamic contrast-enhanced CT (DCE-CT).

MATERIAL AND METHODS

For 34 NSCLC patients, included in two clinical trials, hypoxia HX4-PET/CT, planning FDG-PET/CT and DCE-CT scans were acquired before radiotherapy. Scans were non-rigidly registered to the planning CT. Tumor blood flow (BF) and blood volume (BV) were calculated by kinetic analysis of DCE-CT images. Within the gross tumor volume, independent clusters, i.e., supervoxels, were created based on FDG-PET/CT. For each supervoxel, tumor-to-background ratios (TBR) were calculated (median SUV/aorta SUV_mean) for HX4-PET/CT and supervoxel features (median, SD, entropy) for the other modalities. Two random forest models (cross-validated: 10 folds, five repeats) were trained to predict the hypoxia TBR; one based on CT, FDG, BF and BV, and one with only CT and FDG features. Patients were split in a training (trial NCT01024829) and independent test set (trial NCT01210378). For each patient, predicted, and observed hypoxic volumes (HV) (TBR > 1.2) were compared.

RESULTS

Fifteen patients (3291 supervoxels) were used for training and 19 patients (1502 supervoxels) for testing. The model with all features (RMSE training: 0.19 ± 0.01, test: 0.27) outperformed the model with only CT and FDG-PET features (RMSE training: 0.20 ± 0.01, test: 0.29). All tumors of the test set were correctly classified as normoxic or hypoxic (HV > 1 cm³) by the best performing model.

CONCLUSIONS

We created a data-driven methodology to predict hypoxia levels and hypoxia spatial patterns using CT, FDG-PET and DCE-CT features in NSCLC. The model correctly classifies all tumors, and could therefore, aid tumor hypoxia classification and patient stratification.

Interim 18F-FDG-PET/CT during chemo-radiotherapy in the management of oesophageal cancer patients. A systematic review

Oesophageal cancer is an aggressive disease. The possibility to early stratify patients as responsive and non-responsive with a non-invasive method is extremely appealing. The uptake of Fluorodeoxyglucose (¹⁸F-FDG) in tumours, provided by positron emission tomography (PET) images, has been proved to be useful to assess the initial staging of the disease, recurrence, and response to chemotherapy and chemo-radiotherapy (CRT). In the last years, efforts have been focused on the possibility to use ad interim ¹⁸F-FDG-PET/CT (PET_int) to evaluate response during radiation therapy. However, controversial findings have been reported, although some relevant results would support its use for individual therapeutic decision. The present review assembles the comprehensive literature of the last decade to evaluate whether and in which cases PET_int may offer predictive potential in oesophageal cancer. All the analysed studies (13 studies, 697 patients) denoted PET_int as a challenging examination for early assessment of outcomes during CRT. In particular, 8 studies advocated the predictivity of PET_int, whilst 5 did not find any correlation between the interim variation of PET parameters and the pathological complete response and/or the clinical outcome. The reasons that possibly have caused contradictions among the studies demand further research with prospective and uniform protocols and methods of analysis to assess the predictive and prognostic value of PET_int in oesophageal cancer.

Difference in F-18 FDG Uptake After Esophagogastroduodenoscopy and Colonoscopy in Healthy Sedated Subjects

PURPOSE

We aimed to evaluate the difference in fluorodeoxyglucose (FDG) uptake in sedated healthy subjects after they underwent esophagogastroduodenoscopy (EGD) and colonoscopy procedures.

METHODS

The endoscopy group (n = 29) included healthy subjects who underwent screening via F-18 FDG positron emission tomography/computed tomography (PET/CT) after an EGD and/or colonoscopy under sedation on the same day. The control group (n = 35) included healthy subjects who underwent screening via PET/CT only. FDG uptake in the tongue, uvula, epiglottis, vocal cords, esophagus, stomach, duodenum, liver, cecum, colon, anus, and muscle were compared between the two groups.

RESULTS

Maximum standardized uptake value (SUVmax) in the tongue, pharynx, larynx, and esophagus did not significantly differ between the endoscopy and control groups. In contrast, mean SUVmax in the whole stomach was 18 % higher in the endoscopy group than in the control group (SUVmax: 2.96 vs. 2.51, P = 0.010). In the lower gastrointestinal track, SUVmax from the cecum to the rectum was not significantly different between the two groups, whereas SUVmax in the anus was 20 % higher in the endoscopy group than in the control group (SUVmax: 4.21 vs. 3.50, P = 0.002). SUVmax in the liver and muscle was not significantly different between the two groups. Mean volume of the stomach and mean cross section of the colon was significantly higher in the endoscopy group than in the control group (stomach: 313.28 cm³ vs. 209.93 cm³, P < 0.001, colon: 8.82 cm² vs. 5.98 cm², P = 0.001).

CONCLUSIONS

EGD and colonoscopy under sedation does not lead to significant differences in SUVmax in most parts of the body. Only gastric FDG uptake in the EGD subjects and anal FDG uptake in the colonoscopy subjects was higher than uptake in those regions in the control subjects.

FDG PET for therapy monitoring in Hodgkin and non-Hodgkin lymphomas

PET using 18F-FDG for treatment monitoring in patients with lymphoma is one of the most well-developed clinical applications. PET/CT is nowadays used during treatment to assess chemosensitivity, with response-adapted therapy given according to 'interim' PET in clinical practice to adults and children with Hodgkin lymphoma. PET is also used to assess remission from disease and to predict prognosis in the pretransplant setting. Mature data have been reported for the common subtypes of aggressive B-cell lymphomas, with more recent data also supporting the use of PET for response assessment in T-cell lymphomas. The Deauville five-point scale incorporating the Deauville criteria (DC) is recommended for response assessment in international guidelines. FDG uptake is graded in relation to the reference regions of normal mediastinum and liver. The DC have been validated in most lymphoma subtypes. The DC permit the threshold for adequate or inadequate response to be adapted according to the clinical context or research question. It is important for PET readers to understand how the DC have been applied in response-adapted trials for correct interpretation and discussion with the multidisciplinary team. Quantitative methods to perform PET in standardized ways have also been developed which may further improve response assessment including a quantitative extension to the DC (qPET). This may have advantages in providing a continuous scale to refine the threshold for adequate/inadequate response in specific clinical situations or treatment optimization in trials. qPET is also less observer-dependent and limits the problem of optical misinterpretation due to the influence of background activity.