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

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.

Download Full-text

The Role of Activity, Scan Duration and Patient's Body Mass Index in the Optimization of 18FDG Imaging Protocols on a TOF-PET/CT Scanner

10.21203/rs.3.rs-136005/v1 ◽

2020 ◽

Author(s):

Roberta Matheoud ◽

Naema Al-Maymani ◽

Alessia Oldani ◽

Gian Mauro Sacchetti ◽

Marco Brambilla ◽

...

Keyword(s):

Body Mass Index ◽

Image Quality ◽

Body Mass ◽

Activity Concentration ◽

Background Activity ◽

Whole Body ◽

Internal Diameter ◽

Ct Scanner ◽

Pet Ct ◽

Tof Pet

Abstract BackgroundTime-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 18F-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. MethodsThe NEMA-IQ 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 body mass index (BMI). The phantom was filled with an average concentration of 5.3 kBq/mL of FDG solution and the spheres with TBR of 21.2, 8.8, and 5.0 in 3 different sessions. Images were acquired at varying background 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 a single analysis using multiple linear regression methods. ResultsAs expected, CRC depended only on sphere ID and on PSF application, while BV depended on sphere ID, ESD, AC and BMI of the phantom, 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. ConclusionsAC and ESD proved to be effective tools in modulating CNR. ESD could be increased rather than AC to improve image quality in overweight/obese patients to fulfil ALARA principles.

Download Full-text

The role of activity, scan duration and patient’s body mass index in the optimization of FDG imaging protocols on a TOF-PET/CT scanner

EJNMMI Physics ◽

10.1186/s40658-021-00380-9 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Roberta Matheoud ◽

Naema Al-Maymani ◽

Alessia Oldani ◽

Gian Mauro Sacchetti ◽

Marco Brambilla ◽

...

Keyword(s):

Body Mass Index ◽

Image Quality ◽

Body Mass ◽

Activity Concentration ◽

Background Activity ◽

Whole Body ◽

Internal Diameter ◽

Ct Scanner ◽

Pet Ct ◽

Tof Pet

Abstract Background Time-of-flight (TOF) PET technology determines a reduction in the noise and improves the reconstructed image quality in low count acquisitions, such as in overweight patients, allowing a reduction of administered activity and/or imaging time. However, international guidelines and recommendations on the 18F-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-IQ 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 body mass index (BMI). The phantom was filled with an average concentration of 5.3 kBq/ml of FDG solution and the spheres with TBR of 21.2, 8.8 and 5.0 in 3 different sessions. Images were acquired at varying background activity concentration from 5.1 to 1.3 kBq/ml, and images were reconstructed for ESD of 30–151 s per bed position with and without point spread function (PSF) correction. The parameters were all considered 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 BMI of the phantom, 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 BMI of the patient and TBR of the lesion. Conclusions AC and ESD proved to be effective tools in modulating CNR. ESD could be increased rather than AC to improve image quality in overweight/obese patients to fulfil ALARA principles.

Download Full-text

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

EJNMMI Physics ◽

10.1186/s40658-021-00366-7 ◽

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.

Download Full-text

Comparing lesion detection efficacy and image quality across different PET system generations to optimize the iodine-124 PET protocol for recurrent thyroid cancer

EJNMMI Physics ◽

10.1186/s40658-021-00361-y ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

David Kersting ◽

Walter Jentzen ◽

Miriam Sraieb ◽

Pedro Fragoso Costa ◽

Maurizio Conti ◽

...

Keyword(s):

Thyroid Cancer ◽

Image Quality ◽

Neck Region ◽

Lesion Detection ◽

Whole Body ◽

Acquisition Time ◽

Region Detection ◽

Pet Ct ◽

Bed Position ◽

New Generation

Abstract Background In recurrent differentiated thyroid cancer patients, detectability in 124I PET is limited for lesions with low radioiodine uptake. We assess the improvements in lesion detectability and image quality between three generations of PET scanners with different detector technologies. The results are used to suggest an optimized protocol. Methods Datasets of 10 patients with low increasing thyroglobulin or thyroglobulin antibody levels after total thyroidectomy and radioiodine therapies were included. PET data were acquired and reconstructed on a Biograph mCT PET/CT (whole-body, 4-min acquisition time per bed position; OSEM, OSEM-TOF, OSEM-TOF+PSF), a non-TOF Biograph mMR PET/MR (neck region, 4 min and 20 min; OSEM), and a new generation Biograph Vision PET/CT (whole-body, 4 min; OSEM, OSEM-TOF, OSEM-TOF+PSF). The 20-min image on the mMR was used as reference to calculate the detection efficacy in the neck region. Image quality was rated on a 5-point scale. Results All detected lesions were in the neck region. Detection efficacy was 8/9 (Vision OSEM-TOF and OSEM-TOF+PSF), 4/9 (Vision OSEM), 3/9 (mMR OSEM and mCT OSEM-TOF+PSF), and 2/9 (mCT OSEM and OSEM-TOF). Median image quality was 4 (Vision OSEM-TOF and OSEM-TOF+PSF), 3 (Vision OSEM, mCT OSEM-TOF+PSF, and mMR OSEM 20-min), 2 (mCT OSEM-TOF), 1.5 (mCT OSEM), and 1 (mMR OSEM 4 min). Conclusion At a clinical standard acquisition time of 4 min per bed position, the new generation Biograph Vision using a TOF-based image reconstruction demonstrated the highest detectability and image quality and should, if available, be preferably used for imaging of low-uptake lesions. A prolonged acquisition time for the mostly affected neck region can be useful.

Download Full-text

New probe for the improvement of the Spatial Resolution in total-body PET (PROScRiPT)

EPJ Web of Conferences ◽

10.1051/epjconf/202125309004 ◽

2021 ◽

Vol 253 ◽

pp. 09004

Author(s):

A. Ros ◽

L. Barrientos ◽

M. Borja-Lloret ◽

J.V. Casaña ◽

E. Muñoz ◽

...

Keyword(s):

Spatial Resolution ◽

Whole Body ◽

Ct Scanner ◽

Scintillation Crystal ◽

Pet Ct ◽

Energy Peak ◽

Extended Field ◽

Total Body ◽

Bed Position ◽

Pet Scanners

In recent decades, PET scanners have been widely used for diagnosis and treatment monitoring in nuclear medicine. The continuous effort of the scientific community has led to improvements in scanner performance. Total-body PET is one of the latest upgrades in PET scanners. These kinds of scanners are able to scan the whole body of the patient with a single bed position, since the scanner tube is long enough for the patient to fit inside. While these scanners show unprecedented efficiency and extended field-of-view, a drawback is their low spatial resolution compared to dedicated scanners. In order to improve the spatial resolution of specific areas when measuring with a total-body PET scanner, the IRIS group at IFIC-Valencia is developing a probe. The proposed setup of the probe contains a monolithic scintillation crystal and a SiPM. The signal of the probe is read out by a TOFPET2 ASIC from PETsys, which has shown good performance for PET in terms of spatial and time resolutions. Furthermore, the PETsys technology generates a trigger signal that will be used to time synchronise the probe and the scanner. The proof-of-concept of the probe will be tested in a Preclinical Super Argus PET/CT scanner for small animals located at IFIC. Preliminary simulations of the scanner and the probe under ideal conditions show a slight improvement in the position reconstruction compared to the data obtained with the scanner, therefore we expect a considerable improvement when using the probe in a total-body PET scanner. Characterisation tests of the probe have been performed with a 22Na point-like source, obtaining an energy resolution of 9.09% for the 511 keV energy peak and a temporal resolution of 619 ps after time walk correction. The next step of the project is to test the probe measuring in temporal coincidence with the scanner.

Download Full-text

The effect of activity outside the field of view on image quality for a 3D LSO-based whole body PET/CT scanner

Physics in Medicine and Biology ◽

10.1088/0031-9155/54/19/013 ◽

2009 ◽

Vol 54 (19) ◽

pp. 5861-5872 ◽

Cited By ~ 8

Author(s):

R Matheoud ◽

C Secco ◽

P Della Monica ◽

L Leva ◽

G Sacchetti ◽

...

Keyword(s):

Image Quality ◽

Field Of View ◽

Whole Body ◽

Ct Scanner ◽

Pet Ct

Download Full-text

Minimisation of Acquisition Time in a TOF PET/CT Scanner Without Compromising Image Quality

VipIMAGE 2017 - Lecture Notes in Computational Vision and Biomechanics ◽

10.1007/978-3-319-68195-5_4 ◽

2017 ◽

pp. 27-42

Author(s):

J. Oliveira ◽

R. Parafita ◽

S. Branco

Keyword(s):

Image Quality ◽

Acquisition Time ◽

Ct Scanner ◽

Pet Ct ◽

Tof Pet

Download Full-text

Diagnostic challenges in neoplastic meningitis presenting as intracranial hypertension

BMJ Case Reports ◽

10.1136/bcr-2020-238808 ◽

2021 ◽

Vol 14 (3) ◽

pp. e238808

Author(s):

Santosh Sriram Andugulapati ◽

Akash Chheda ◽

Karan Desai ◽

Sangeeta Hasmukh Ravat

Keyword(s):

Cerebrospinal Fluid ◽

Intracranial Hypertension ◽

Neoplastic Meningitis ◽

Whole Body ◽

Csf Cytology ◽

Csf Analysis ◽

Pet Ct ◽

Pet Ct Scan ◽

Systemic Malignancy

A diagnosis of idiopathic intracranial hypertension should be considered only after careful exclusion of all possible aetiologies. We report a case of neoplastic meningitis presenting as intracranial hypertension with inconclusive repeated cerebrospinal fluid (CSF) cytology and MRI of brain, emphasising the importance of meticulous CSF analysis and role of early whole-body PET–CT scan for diagnosis of systemic malignancy.

Download Full-text

Optimizing reconstruction parameters for quantitative 124I-PET in the presence of therapeutic doses of 131I

10.21203/rs.3.rs-289963/v1 ◽

2021 ◽

Author(s):

Louise Fanchon ◽

Brad Beattie ◽

Keith Pentlow ◽

Steven Larson ◽

John Laurence Humm

Keyword(s):

Image Quality ◽

Dead Time ◽

Activity Level ◽

Ct Scanner ◽

Random Coincidence ◽

Quantitative Pet ◽

Quantitative Accuracy ◽

Pet Ct ◽

Therapeutic Doses ◽

Pet Detectors

Abstract Purpose To determine the accuracy of quantitative 124I PET imaging in the presence of therapeutic levels of 131I.Material and Methods Multiple PET images were acquired using a NEMA IEC phantom with spheres containing 0.4 MBq/cc of 124I and increasing amount of 131I activity in the phantom background (0 to 3.76 GBq). Acquisitions were performed on a GE Discovery 710 PET/CT scanner. At each 131I activity level two scans were acquired, one with the phantom at the center of the field of view (FOV) and one 11 cm off-center. Images were reconstructed with an ordered subset expectation maximization (OSEM) algorithm using between 1 and 25 iterations of 16 subsets. Results were evaluated visually and by comparing the 124I activity relative to the baseline PET performed in the absence of 131I.Results The presence of 131I within the PET FOV added to the random coincidence rate, to dead-time and to pile-up within the PET detectors. Using our standard clinical reconstruction parameters, the image quality and quantitative accuracy suffered at 131I background activities above 1.4 GBq. However, increasing the number of iterations resulted in dramatic improvements in image quality and quantitative accuracy. Projection space measurements suggest that the dead time corrections implemented on the scanner perform well even at the highest singles count rate tested (52 Mcps).Conclusion This study shows that 124I quantitative PET is feasible in the presence of large amounts of 131I on a GE D710. The high random coincidence fraction slows the reconstruction convergence rate, therefore iterations equivalent to at least 8x16 are recommended.

Download Full-text