The effect of modern PET technology and techniques on the EANM paediatric dosage card

Aim Recent advancements in PET technology have brought with it significant improvements in PET performance and image quality. In particular, the extension of the axial field of view of PET systems, and the introduction of semiconductor technology into the PET detector, initially for PET/MR, and more recently available long-field-of-view PET/CT systems (≥ 25 cm) have brought a step change improvement in the sensitivity of PET scanners. Given the requirement to limit paediatric doses, this increase in sensitivity is extremely welcome for the imaging of children and young people. This is even more relevant with PET/MR, where the lack of CT exposures brings further dose reduction benefits to this population. In this short article, we give some details around the benefits around new PET technology including PET/MR and its implications on the EANM paediatric dosage card. Material and methods Reflecting on EANM adult guidance on injected activities, and making reference to bed overlap and the concept of MBq.min bed−1 kg−1, we use published data on image quality from PET/MR systems to update the paediatric dosage card for PET/MR and extended axial field of view (≥ 25 cm) PET/CT systems. However, this communication does not cover the expansion of paediatric dosing for the half-body and total-body scanners that have recently come to market. Results In analogy to the existing EANM dosage card, new parameters for the EANM paediatric dosage card were developed (class B, baseline value: 10.7 MBq, minimum recommended activity 10 MBq). The recommended administered activities for the systems considered in this communication range from 11 MBq [18F]FDG for a child with a weight of 3 kg to 149 MBq [18F]FDG for a paediatric patient weight of 68 kg, assuming a scan of 3 min per bed position. The mean effective dose over all ages (1 year and older) is 2.85 mSv. Conclusion With this, recommendations for paediatric dosing are given for systems that have not been considered previously.

INERTIAL SENSOR-BASED MOTION ANALYSIS SYSTEM OF BRIDGE-STYLE MOVEMENT FOR REHABILITATION TREATMENTS

In the clinical course of the treatment, impartial representation of the patients’ rehabilitation state is a necessary condition for taking the best treatment to match the state of the current recovery. Bridge-style movement is one of the earliest training programs of the bed position change and is also the basis of successful standing and walking training because the bridge-style movement can inhibit the spasticity pattern of lower limb extensors and improve the control and coordination ability from the pelvis to lower limb. However, patients’ bridge-style movement planning for the current rehabilitation state largely depends on therapists’ clinical experience and subjective that may deteriorate the rehabilitation effect. Thus, it is necessary for hemiplegic patients to develop quantitative motor function assessment to judge its current rehabilitation state. This paper proposes a quantitative evaluating method to detect patients’ bridge-style movement posture and analyze their motion abilities. The real-time postural change of the bridge-style movement can be acquired by the inertial sensors attached to the waist, thigh, and crus. The bridge-style movement process of patients is recorded and analyzed by the software processing program. Finally, the experiment can be carried out to verify the feasibility and correctness of the evaluation method. The experimental results show that the evaluation method can judge patients’ current motion ability and rehabilitation state. And it is helpful for therapists to carry out targeted training for patients’ state.

Method to Determine the Statistical Technical Variability of SUV Parameters

Background: Some of the parameters used for the quantification of Positron Emission Tomography (PET) images are the Standardized Uptake Value (SUV)Max, SUVMean and SUVPeak. In order to assess the significance of an increasing or decreasing of these parameters for diagnostic purposes it is relevant to know their standard deviation. The sources of the standard deviation can be divided in biological and technical. In this study we present a method to determine the technical variation of the SUV in PET images.Results: This method was tested on images of a NEMA quality phantom with spheres of various diameters with full-length acquisition time of 150 s per bed position and foreground to background activity ratio of F18-2-fluoro-2-deoxy-D-glucose (FDG) of 10:1. Our method is based on dividing the full-length 150 s acquisition into subsets of shorter time length and reconstructing the images in the subsets. The SUVMax, Mean and Peak were calculated for each reconstructed image in a subset. The coefficient of deviation of the SUV parameters within each subset has then been used to estimate the expected standard deviation between images at 150 s reconstruction length. We report the largest technical variation of the SUV parameters for the smallest sphere, and the smallest variation for the largest sphere. The expected variation at 150 s reconstruction length does not exceed 6% for the smallest sphere and 2% for the largest sphere. Conclusions: With the presented method we are able to determine the technical variation of SUV. The method enables us to evaluate the effect of parameter selection and lesion size on the technical variation, and therefore to evaluate its relevance on the total variation of the SUV value between studies.

Yttrium-90 TOF-PET-Based EUD Predicts Response Post Liver Radioembolizations Using Recommended Manufacturer FDG Reconstruction Parameters

PurposeExplaining why 90Y TOF-PET based equivalent uniform dose (EUD) using recommended manufacturer FDG reconstruction parameters has been shown to predict response.MethodsThe hot rods insert of a Jaszczak deluxe phantom was partially filled with a 2.65 GBq 90Y - 300ml DTPA water solution resulting in a 100 Gy mean absorbed dose in the 6 sectors. A two bed 20min/position acquisition was performed on a 550ps- and on a 320ps- TOF-PET/CT and reconstructed with recommended manufacturer FDG reconstruction parameters, without and with additional filtering. The whole procedure was repeated on both PET after adding 300ml of water (50Gy setup). The phantom was acquired again after decay by a factor of 10 (5Gy setup), but with 200min per bed position. For comparison, the phantom was also acquired with 18F activity corresponding to a clinical FDG whole body acquisition.ResultsThe 100Gy-setup provided a hot rod sectors image almost as good as the 18F phantom. However, despite acquisition time compensation, the 5Gy-setup provides much lower quality imaging. TOF-PET based sectors EUDs for the three large rod sectors agreed with the actual EUDs computed with a radiosensitivity of 0.021Gy-1 well in the range observed in external beam radiotherapy (EBRT), i.e. 0.01-0.04Gy-1. This agreement explains the reunification of the dose-response relationships of the glass and resin spheres in HCC using the TOF-PET based EUD. Additional filtering reduced the EUDs agreement quality.ConclusionsRecommended manufacturer FDG reconstruction parameters are suitable in TOF-PET post 90Y liver radioembolization for accurate tumour EUD computation. The present results rule out the use of low specific activity phantom studies to optimize reconstruction parameters.

P054 The effect of head up bed-tilt (HUT) on sleep disordered breathing (SDB) in patients with supine dominant sleep apnoea (SDOSA): an exploratory study

SDB severity is reduced in SDOSA when posture changes from supine to lateral. Sleeping with a head up bed-tilt(HUT) is known to reduce SDB in some OSA patients. In this exploratory study, we tested whether HUT could be used to reduce SDB in SDOSA patients who had refused continuous positive airway pressure therapy(CPAP). We studied 5 male patients (age: 60 to 72years, BMI: 25.8 to 32.2kg/m2). Standard, in-laboratory, overnight-polysomnography was performed (Compumedics Ltd, Australia). Posture was monitored, but not restricted, and bed position was set at horizontal(HB) for half the night and at 7° HUT for the remainder (randomised). Polysomnograms were scored by a sleep technician using AASM criteria. SDB severity was quantified using the apnoea hypopnoea index(AHI) and apnoea index(AI). For this analysis, we focus on periods of supine, stage 2 sleep (S2S) only. Participants spent 23 to 60minutes (range) in S2S with HB and 11 to 36minutes with HUT. AHI was 49 to 138events/hr with HB and 24 to 120events/hr with HUT, representing a fall of 2 to 62events/hr across all patients. AI was 19 to 111events/hr with HB and 0 to 48 events/hr with HUT, a fall of 15 to 96events/hr across all patients. In these CPAP non-compliant, SDOSA patients, S2S in HUT was associated with a reduction in SDB severity that varied between individuals. Notably apnoeic events were reduced in all patients and eliminated in two patients. We conclude that HUT warrants further investigation as a potential alternative therapy for SDOSA patients intolerant of CPAP.

Post-reconstruction enhancement of [18F]FDG PET images with a convolutional neural network

Background The aim of the study was to develop and test an artificial intelligence (AI)-based method to improve the quality of [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) images. Methods A convolutional neural network (CNN) was trained by using pairs of excellent (acquisition time of 6 min/bed position) and standard (acquisition time of 1.5 min/bed position) or sub-standard (acquisition time of 1 min/bed position) images from 72 patients. A test group of 25 patients was used to validate the CNN qualitatively and quantitatively with 5 different image sets per patient: 4 min/bed position, 1.5 min/bed position with and without CNN, and 1 min/bed position with and without CNN. Results Difference in hotspot maximum or peak standardized uptake value between the standard 1.5 min and 1.5 min CNN images fell short of significance. Coefficient of variation, the noise level, was lower in the CNN-enhanced images compared with standard 1 min and 1.5 min images. Physicians ranked the 1.5 min CNN and the 4 min images highest regarding image quality (noise and contrast) and the standard 1 min images lowest. Conclusions AI can enhance [18F]FDG-PET images to reduce noise and increase contrast compared with standard images whilst keeping SUVmax/peak stability. There were significant differences in scoring between the 1.5 min and 1.5 min CNN image sets in all comparisons, the latter had higher scores in noise and contrast. Furthermore, difference in SUVmax and SUVpeak fell short of significance for that pair. The improved image quality can potentially be used either to provide better images to the nuclear medicine physicians or to reduce acquisition time/administered activity.

Head-to-head comparison of a Si-photomultiplier-based and a conventional photomultiplier-based PET-CT system

Background A novel generation of PET scanners based on silicon (Si)-photomultiplier (PM) technology has recently been introduced. Concurrently, there has been development of new reconstruction methods aimed at increasing the detectability of small lesions without increasing image noise. The combination of new detector technologies and new reconstruction algorithms has been found to increase image quality. However, it is unknown to what extent the demonstrated improvement of image quality is due to scanner hardware development or improved reconstruction algorithms. To isolate the contribution of the hardware, this study aimed to compare the ability to detect small hotspots in phantoms using the latest generation SiPM-based PET/CT scanner (GE Discovery MI) relative to conventional PM-based PET/CT scanner (GE Discovery 690), using identical reconstruction protocols. Materials and methods Two different phantoms (NEMA body and Jasczcak) with fillable spheres (31 μl to 26.5 ml) and varying sphere-to-background-ratios (SBR) were scanned in one bed position for 15–600 s on both scanners. The data were reconstructed using identical reconstruction parameters on both scanners. The recovery-coefficient (RC), noise level, contrast (spherepeak/backgroundpeak-value), and detectability of each sphere were calculated and compared between the scanners at each acquisition time. Results The RC-curves for the NEMA phantom were near-identical for both scanners at SBR 10:1. For smaller spheres in the Jaszczak phantom, the contrast was 1.22 higher for the DMI scanner at SBR 15:1. The ratio decreased for lower SBR, with a ratio of 1.03 at SBR 3.85:1. Regarding the detectability of spheres, the sensitivity was 98% and 88% for the DMI and D690, respectively, for SBR 15:1. For SBR 7.5, the sensitivity was 75% and 83% for the DMI and D690, respectively. For SBR 3.85:1, the sensitivity was 43% and 30% for the DMI and D690, respectively. Conclusion Marginally higher contrast in small spheres was seen for the SiPM-based scanner but there was no significant difference in detectability between the scanners. It was difficult to detect differences between the scanners, suggesting that the SiPM-based detectors are not the primary reason for improved image quality.

Assessment of Image Quality and Lesion Detectability With Digital PET/CT System

Purpose: The aim of this study was to assess image quality and lesion detectability acquired with a digital Positron Emission Tomography/Computed Tomography (PET/CT) Siemens Biograph Vision 600 system.Material and Methods: Consecutive patients who underwent a FDG PET/CT during the first week of use of a digital PET/CT (Siemens Biograph Vision 600) at the nuclear medicine department of the university hospital of Brest were analyzed. PET were realized using list mode acquisition. For all patients, 4 datasets were reconstructed. We determined, according to phantom measurements, an equivalent time acquisition/reconstruction parameters pair of the digital PET/CT corresponding to an analog PET/CT image quality (“analog-like”) as reference dataset. We compared the reference dataset with 3 others digital PET/CT reconstruction parameters, allowing a decrease of emission duration: 60, 90, and 120 s per bed position. Three nuclear medicine physicians evaluated independently, for each dataset, overall image quality [Maximal Intensity Projection (MIP), noise, sharpness] using a 4-point scale. Physicians assessed also lesion detection capability by reporting new visible lesions on each digital datasets with their confidence level in comparison with analog-like dataset.Results: Ninety-eight patients were analyzed. Image quality of MIP (IQMIP), sharpness (IQSHARPNESS), and noise (IQNOISE) of all digital datasets (60, 90, and 120 s) were better than those evaluated with analog-like reconstruction. Moreover, digital PET/CT system improved IQMIP, IQNOISE, and IQSHARPNESS whatever the BMI. Lesion detection capability and confidence level were higher for 60, 90, 120 s per bed position, respectively, than for analog-like images.Conclusion: Our study demonstrated an improvement of image quality and lesion detectability with a digital PET/CT system.