Modelling Automatic Exposure Control Response to the Presence of the Patient Scanning Bed in a Hybrid Pet/Ct Scanner

2021 ◽  
Author(s):  
Seán Cournane ◽  
Matthew Reade ◽  
Jackie McCavana ◽  
Julie Lucey
Keyword(s):  
Region Of Interest ◽  
Exposure Control ◽  
Automatic Exposure Control ◽  
Ct Scanner ◽  
Pet Ct ◽  
Control Response ◽  
Adequate Image Quality ◽  
Ct System ◽  
Attenuation Profiles

Abstract Automatic Exposure Control (AEC) systems optimise radiation dose to the patient while providing adequate image quality. This study examined the effect that the increased localiser region of interest of a hybrid PET/CT has on the CTDIvol, focussing on the role of extraneous objects and patient attenuation profiles. A Siemens Biograph™ 16 Horizon PET/CT system and a Siemens Somatom Sensation 64, both employing the Siemens CAREDose 4D AEC system, were used for acquisition of a range of phantoms. The effect of patient miscentring and effect of the patient bed impinging on the localiser was established and modelled. For PA localiser scans, a non-linear relationship between miscentring and CTDIvol was observed, attributable to the presence of the patient bed being misinterpreted as the patient width. The model identified how the presence of the patient bed led to an increase in the CTDIvol significantly larger than expected (~12%, or 1 mSv), particularly prevalent for smaller patients.

SU-F-I-31: Reproducibility of An Automatic Exposure Control Technique in the Low-Dose CT Scan of Cardiac PET/CT Exams

2016 ◽  
Vol 43 (6Part7) ◽  
pp. 3393-3394
Author(s):  
M Park ◽  
D Rosica ◽  
V Agarwal ◽  
M Di Carli ◽  
S Dorbala
Keyword(s):  
Ct Scan ◽  
Low Dose ◽  
Control Technique ◽  
Exposure Control ◽  
Automatic Exposure Control ◽  
Cardiac Pet ◽  
Low Dose Ct ◽  
Pet Ct ◽  
I 31

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

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Jenny Oddstig ◽  
Gustav Brolin ◽  
Elin Trägårdh ◽  
David Minarik
Keyword(s):  
Image Quality ◽  
Acquisition Time ◽  
Reconstruction Algorithms ◽  
Ct Scanner ◽  
Recovery Coefficient ◽  
Reconstruction Methods ◽  
Pet Ct ◽  
Significant Difference ◽  
Ct System ◽  
Bed Position

Abstract 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.

scholarly journals The role of activity, scan duration and patient's weight in the optimization of 18FDG imaging protocols on a TOF-PET/CT scanner

2020 ◽  
Author(s):  
Roberta Matheoud ◽  
Naema Al-Maymani ◽  
Alessia Oldani ◽  
Gian Mauro Sacchetti ◽  
Marco Brambilla ◽  
...  
Keyword(s):  
Image Quality ◽  
Activity Concentration ◽  
Whole Body ◽  
Internal Diameter ◽  
Ct Scanner ◽  
Recovery Coefficient ◽  
Pet Ct ◽  
Bed Position ◽  
Tof Pet

Abstract Background : Time-of-flight (TOF) PET technology determines a reduction in the noise and improves the reconstructed image quality , in low counts acquisitions, such as in overweight patients, allowing a reduction of administered activity and/or imaging time. However, international guidelines and recommendations on 18 F-fluoro-2-deoxyglucose (FDG) activity administration scheme are old or only partially account for TOF technology and advanced reconstruction modalities. The aim of this study was to optimize FDG whole-body studies on a TOF PET/CT scanner by using a multivariate approach to quantify how physical figures of merit related to image quality change with acquisition/reconstruction/patient-dependent parameters in a phantom experiment.Methods : The NEMA-IEC body phantom was used to evaluate contrast recovery coefficient (CRC), background variability (BV) and contrast-to-noise ratio (CNR) as a function of changing emission scan duration (ESD), activity concentration (AC), target internal diameter (ID), target-background activity ratio (TBR), and weight. The phantom was filled with 5.3 kBq/mL of FDG solution and the spheres with TBR of 21, 9, and 5 in 3 different sessions. Images were acquired at varying activity concentration from 5.1 to 1.3 kBq/mL and images were reconstructed for ESD of 30-151 seconds per bed position with and without Point Spread Function (PSF) correction. The parameters were all considered in simultaneous experiments and in a single analysis using multiple linear regression methods.Results : As expected, CRC depended only on sphere ID and on PSF application, while BV depended on sphere ID, ESD, AC and weight of the patient, in order of decreasing relevance. Noteworthy, ESD and AC resulted as the most significant predictors of CNR variability with a similar relevance, followed by the weight of the patient and TBR of the lesion.Conclusions : Due to the interchangeable role of AC and ESD in modulating CRC, ESD could be increased rather than AC to improve image quality in overweight/obese patients to fulfil ALARA principles.

scholarly journals Optimisation of CT protocols in PET-CT across different scanner models using different automatic exposure control methods and iterative reconstruction algorithms

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Sarah-May Gould ◽  
Jane Mackewn ◽  
Sugama Chicklore ◽  
Gary J. R. Cook ◽  
Andrew Mallia ◽  
...  
Keyword(s):  
Iterative Reconstruction ◽  
Significant Proportion ◽  
Exposure Control ◽  
Automatic Exposure Control ◽  
Reconstruction Algorithms ◽  
Patient Study ◽  
Percentage Difference ◽  
Pet Ct ◽  
Siemens Scanner ◽  
The Mean

Abstract Background A significant proportion of the radiation dose from a PET-CT examination is dependent on the CT protocol, which should be optimised for clinical purposes. Matching protocols on different scanners within an imaging centre is important for the consistency of image quality and dose. This paper describes our experience translating low-dose CT protocols between scanner models utilising different automatic exposure control (AEC) methods and reconstruction algorithms. Methods The scanners investigated were a newly installed Siemens Biograph mCT PET with 64-slice SOMATOM Definition AS CT using sinogram affirmed iterative reconstruction (SAFIRE) and two GE Discovery 710 PET scanners with 128-slice Optima 660 CT using adaptive statistical reconstruction (ASiR). Following exploratory phantom work, 33 adult patients of various sizes were scanned using the Siemens scanner and matched to patients scanned using our established GE protocol to give 33 patient pairs. A comparison of volumetric CT dose index (CTDIvol) and image noise within these patient pairs informed optimisation, specifically for obese patients. Another matched patient study containing 27 patient pairs was used to confirm protocol matching. Size-specific dose estimates (SSDEs) were calculated for patients in the second cohort. With the acquisition protocol for the Siemens scanner determined, clinicians visually graded the images to identify optimal reconstruction parameters. Results In the first matched patient study, the mean percentage difference in CTDIvol for Siemens compared to GE was − 10.7% (range − 41.7 to 50.1%), and the mean percentage difference in noise measured in the patients’ liver was 7.6% (range − 31.0 to 76.8%). In the second matched patient study, the mean percentage difference in CTDIvol for Siemens compared to GE was − 20.5% (range − 43.1 to 1.9%), and the mean percentage difference in noise was 19.8% (range − 27.0 to 146.8%). For these patients, the mean SSDEs for patients scanned on the Siemens and GE scanners were 3.27 (range 2.83 to 4.22) mGy and 4.09 (range 2.81 to 4.82) mGy, respectively. The analysis of the visual grading study indicated no preference for any of the SAFIRE strengths. Conclusions Given the different implementations of acquisition parameters and reconstruction algorithms between vendors, careful consideration is required to ensure optimisation and standardisation of protocols.

Quantitative accuracy of serotonergic neurotrans-mission imaging with high-resolution 123I SPECT

2004 ◽  
Vol 43 (06) ◽  
pp. 185-189 ◽  
Author(s):  
J. T. Kuikka
Keyword(s):  
High Resolution ◽  
Scatter Correction ◽  
Region Of Interest ◽  
Binding Potential ◽  
Partial Volume ◽  
Therapeutic Drugs ◽  
Quantitative Accuracy ◽  
Critical Error ◽  
Statistical Noise

Summary Aim: Serotonin transporter (SERT) imaging can be used to study the role of regional abnormalities of neurotransmitter release in various mental disorders and to study the mechanism of action of therapeutic drugs or drugs’ abuse. We examine the quantitative accuracy and reproducibility that can be achieved with high-resolution SPECT of serotonergic neurotransmission. Method: Binding potential (BP) of 123I labeled tracer specific for midbrain SERT was assessed in 20 healthy persons. The effects of scatter, attenuation, partial volume, mis-registration and statistical noise were estimated using phantom and human studies. Results: Without any correction, BP was underestimated by 73%. The partial volume error was the major component in this underestimation whereas the most critical error for the reproducibility was misplacement of region of interest (ROI). Conclusion: The proper ROI registration, the use of the multiple head gamma camera with transmission based scatter correction introduce more relevant results. However, due to the small dimensions of the midbrain SERT structures and poor spatial resolution of SPECT, the improvement without the partial volume correction is not great enough to restore the estimate of BP to that of the true one.

PET/CT IN THE DIAGNOSIS OF PANCREATIC CANCER: LITERATURE REVIEW

2018 ◽  
pp. 57-67
Author(s):  
P. E. Tulin ◽  
M. B. Dolgushin ◽  
D. I. Nevzorov ◽  
P. V. Kochergin ◽  
Yu. I. Patyutko
Keyword(s):  
Pancreatic Cancer ◽  
Literature Review ◽  
Pancreatic Neoplasms ◽  
Poor Prognosis ◽  
Modern Imaging ◽  
Pet Ct

Pancreatic cancer has a poor prognosis, often because most pancreatic neoplasms are found to be unresectable at diagnosis. Early staging of the tumor process can change the tactics of treatment and affect the survival of patients. The purpose of this review is to provide an overview of pancreatic cancer and the role of modern imaging in its diagnosis with an emphasis on PET/CT with a various radiopharmaceuticals.

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