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Recently introduced PET systems using silicon photomultipliers with digital readout (dPET) have an improved timing and spatial resolution, aiming at a better image quality than conventional PET (cPET) systems. We prospectively evaluated the performance of a dPET system in patients with cancer, as compared with high-resolution (HR) cPET imaging. Methods: After a single 18F-FDG injection, 66 patients underwent dPET and cPET imaging in randomized order. We used HR reconstructions (2 × 2 × 2 mm voxels) for both scanners and determined SUVmax, SUVmean, lesion-to-background ratio (LBR), metabolic tumor volume (MTV), and lesion diameter in up to 5 18F-FDG-positive lesions per patient. Furthermore, we counted the number of visible and measurable lesions on each PET scan. Two nuclear medicine specialists determined, in a masked manner, the TNM score from both image sets in 30 patients referred for initial staging. For all 66 patients, these specialists separately evaluated image quality (4-point scale) and determined the scan preference. Results: We included 238 lesions that were visible and measurable on both PET scans. For 27 patients, we found 37 additional lesions on dPET (41%) that were unmeasurable (n = 14) or invisible (n = 23) on cPET. Mean (±SD) SUVmean, SUVmax, LBR, and MTV on cPET were 5.2 ± 3.9, 6.9 ± 5.6, 5.0 ± 3.6, and 2,991 ± 13,251 mm3, respectively. On dPET, SUVmean, SUVmax, and LBR increased by 24%, 23%, and 27%, respectively (P < 0.001) whereas MTV decreased by 13% (P < 0.001), compared with cPET. Visual analysis showed TNM upstaging with dPET in 13% of the patients (4/30). dPET images also had higher scores for quality (P = 0.003) and were visually preferred in most cases (65%). Conclusion: dPET improved the detection of small lesions, upstaged the disease, and produced images that were visually preferred to those from HR cPET. More studies are necessary to confirm the superior diagnostic performance of dPET.Keywords: digital PET; conventional PET; FDG PET; lesion detection; cancer imaging.

Background PET scanners using silicon photomultipliers with digital readout (SiPM PET) have an improved temporal and spatial resolution compared to PET scanners using conventional photomultiplier tubes (PMT PET). However, the effect on image quality and visibility of perfusion defects in myocardial perfusion imaging (MPI) is unknown. Our aim was to determine the value of a SiPM PET scanner in MPI. Methods We prospectively included 30 patients who underwent rest and regadenoson-induced stress Rubidium-82 (Rb-82) MPI on the D690 PMT PET (GE Healthcare) and within three weeks on the Vereos SiPM PET (Philips Healthcare). Two expert readers scored the image quality and assessed the existence of possible defects. In addition, interpreter’s confidence, myocardial blood flow (MBF), and myocardial flow reserve (MFR) values were compared. Results Image quality improved (P = 0.03) using the Vereos as compared to the D690. Image quality of the Vereos and the D690 was graded fair in 20% and 10%, good in 60% and 50%, and excellent in 20% and 40%, respectively. Defect interpretation and interpreter’s confidence did not differ between the D690 and the Vereos (P > 0.50). There were no significant differences in rest MBF (P ≥ 0.29), stress MBF (P ≥ 0.11), and MFR (P ≥ 0.51). Conclusion SiPM PET provides an improved image quality in comparison with PMT PET. Defect interpretation, interpreter’s confidence, and absolute blood flow measurements were comparable between both systems. SiPM PET is therefore a reliable technique for MPI using Rb-82. Trial registration ToetsingOnline NL63853.075.17. Registered 13 November, 2017.

Background A high SUV-reproducibility is crucial when different PET scanners are in use. We evaluated the SUV variability in whole-body FDG-PET scans of patients with suspected or proven cancer using an EARL-accredited conventional and digital PET scanner. In a head-to-head comparison we studied images of 50 patients acquired on a conventional scanner (cPET, Ingenuity TF PET/CT, Philips) and compared them with images acquired on a digital scanner (dPET, Vereos PET/CT, Philips). The PET scanning order was randomised and EARL-compatible reconstructions were applied. We measured SUVmean, SUVpeak, SUVmax and lesion diameter in up to 5 FDG-positive lesions per patient. The relative difference ΔSUV between cPET and dPET was calculated for each SUV-parameter. Furthermore, we calculated repeatability coefficients, reflecting the 95% confidence interval of ΔSUV. Results We included 128 lesions with an average size of 19 ± 14 mm. Average ΔSUVs were 6-8% with dPET values being higher for all three SUV-parameters (p < 0.001). ΔSUVmax was significantly higher than ΔSUVmean (8% vs. 6%, p = 0.002) and than ΔSUVpeak (8% vs. 7%, p = 0.03). Repeatability coefficients across individual lesions were 27% (ΔSUVmean and ΔSUVpeak) and 33% (ΔSUVmax) (p < 0.001). Conclusions With EARL-accredited conventional and digital PET, we found a limited SUV variability with average differences up to 8%. Furthermore, only a limited number of lesions showed a SUV difference of more than 30%. These findings indicate that EARL standardisation works. Trial registration This prospective study was registered on the 31th of October 2017 at ClinicalTrials.cov. URL: https://clinicaltrials.gov/ct2/show/NCT03457506?id=03457506&rank=1.

To derive and validate a practical patient-specific dose protocol to obtain an image quality, expressed by the image noise, independent of patients’ size and a better radiation dose justification in coronary CT angiography (CCTA) using prospective ECG triggering. 43 patients underwent clinically indicated CCTA. The image noise, defined as the standard deviation of pixel attenuation values in a homogeneous region in the liver, was determined in all scans. Subsequently, this noise was normalized to the radiation exposure. Next, three patient-specific parameters, body weight, body mass index and mass per length (MPL), were tested for the best correlation with normalized image noise. From these data, a new dose protocol to provide a less variable image noise was derived and subsequently validated in 84 new patients. The normalized image noise increased for heavier patients for all patients’ specific parameters (p < 0.001). MPL correlated best with the normalized image noise and was selected for dose protocol optimization. This new protocol resulted in image noise levels independent of patients’ MPL (p = 0.28). A practical method to obtain CCTA images with noise levels independent of patients’ MPL was derived and validated. It results in a less variable image quality and better radiation exposure justification and can also be used for CT scanners from other vendors.

Background We evaluated the diagnostic implications of a small-voxel reconstruction for lymph node characterization in breast cancer patients, using state-of-the-art FDG-PET/CT. We included 69 FDG-PET/CT scans from breast cancer patients. PET data were reconstructed using standard 4 × 4 × 4 mm3 and small 2 × 2 × 2 mm3 voxels. Two hundred thirty loco-regional lymph nodes were included, of which 209 nodes were visualised on PET/CT. All nodes were visually scored as benign or malignant, and SUVmax and TBratio(=SUVmax/SUVbackground) were measured. Final diagnosis was based on histological or imaging information. We determined the accuracy, sensitivity and specificity for both reconstruction methods and calculated optimal cut-off values to distinguish benign from malignant nodes. Results Sixty-one benign and 169 malignant lymph nodes were included. Visual evaluation accuracy was 73% (sensitivity 67%, specificity 89%) on standard-voxel images and 77% (sensitivity 78%, specificity 74%) on small-voxel images (p = 0.13). Across malignant nodes visualised on PET/CT, the small-voxel score was more often correct compared with the standard-voxel score (89 vs. 76%, p

Previously, several studies have reported that a decreasing image quality in heavier patients in myocardial perfusion imaging (MPI) using single-photon emission computed tomography (SPECT) can be compensated by using a body-weight-dependent tracer activity or scan time,1-3 as illustrated in Figure 1. Although we derived and validated a activity-scan-time formula for a conventional SPECT scanner, this formula cannot simply be used for all SPECT scanners.1 Differences in detector sensitivity, technical specifications such a collimator design and geometrical detector configuration, and acquisition and reconstruction settings limit the generalizability of the derived formula. Ideally, a tracer activity-scan-time formula should therefore be derived for each SPECT scanner using the method as described previously.1 However, this could be technically challenging and is time consuming. In this technical note, we therefore introduce, as a first-order approach, an alternative simplified method to obtain a body-weight-dependent protocol, which can easily be adopted in every day patient care. Figuer 1 Example of constant image quality in MPI SPECT scans of three male patients without any perfusion defects with varying body weights. From left to right: 66 kg (22.6 kg·m−2), 85 kg (25.1 kg·m−2 ... Deriving a Body-Weight-Dependent Protocol In cardiac SPECT, the application of a fixed tracer activity and scan-time protocol results in a decreasing number of photon counts in heavier patients due to increased photon attenuation, as demonstrated earlier1,3 and illustrated in Figure 2A, D. As image quality primarily depends on the number of measured photon counts, a constant number of detected photon counts provides an image quality less dependent on patients’ size.1,3 Figure 2 Schematic overview of the transition from a fixed tracer activity and scan-time product (A×T) to a minimized patient-specific A×T. From left to right: a fixed A×T (A) resulting in a decreasing number of photon counts and image ... A patient-specific protocol will allow obtaining a constant number of detected photons independent of patients’ size.1,3 A method to derive such a protocol is described recently.1 Ideally, the derivation and validation of a patient-specific protocol are performed for each SPECT scanner to account for differences in hardware, software, and acquisition and reconstruction settings. However, to limit the burden of using this extended method, we hereby introduce an alternative, simplified approach, which can easily be adopted in every day patient care. In this approach, we assume that local physicians consider their SPECT image quality of patients with average body weight, AVGweight, to be adequate, using the local tracer activity and scan-time combination. To convert this to other patients, a multiplication factor (MF) can be determined using MF=0.13AVGweight0.64×bodyweight(kg)+1-0.13×AVGweight0.36. 1a This formula is derived from the validated tracer activity and scan-time formula as presented in our recent study by normalizing it to an average patient.1 In a patient population with an average body weight of 80 kg, the MF formula can be described by MF = body weight (kg) × 0.0079 + 0.37 1b In the next step, the body-weight-specific tracer activity or scan time can be calculated using Patient-specific tracer activity (using a fixed scan time) = standard activity × MF 2a Patient-specific scan time (using a fixed tracer activity) = standard scan time × MF 2b As can be seen, MF is 1.0 for a patient of 80 kg when applying Eq. 1b. In that case, the patient-specific tracer activity (or scan time) is the same as the standard administered activity (or scan time). For heavier patients MF is higher than 1, and for less heavy patients it is lower than 1. Table 1 shows an example with the outcome of these equations in practice. The suggested MF is only eligible for conventional SPECT cameras1 and patients weighing between 60 and 130 kg, as weights outside this range were not used in deriving the formula.1 One could worry that the application of a patient-specific tracer activity or scan-time protocol deviates from the current guidelines.4,5 However, these guidelines are relatively old and partly outdated due to technological advances and revised insights. Motivated deviation can therefore be justified. Table 1 Multiplication factors to adjust the tracer dose or scan time per projection angle as a function of patient’s weight, using Eq. 1b. Furthermore, two examples for introducing either a patient-specific tracer activity or scan-time protocol ... Beneficial Effect of Patient-Specific Tracer Activities Introducing a body-weight-dependent protocol will not only result in image quality that depends less on patients’ size, it also allows for a reduction in the administered activity and, hence, radiation dose to the patient, as shown in a previous study6 and illustrated in Figure 2C, F. Nowadays, leaner patients are generally administered a higher activity than clinically necessary. In heavier patients, the currently applied fixed tracer activity is generally low or at best just sufficient. Implementing a patient-specific protocol will therefore result in a better image quality independent of patients’ size. It might even allow an overall tracer activity or scan-time reduction, without compromising diagnostic accuracy.

Purpose: New X-ray technology providing new image processing techniques may reduce radiation exposure. The aim of this study was to quantify this radiation exposure reduction for patients during pacemaker and implantable cardioverter defibrillator (ICD) implantation. Methods: In this retrospective study, 1185 consecutive patients who had undergone de novo pacemaker or ICD implantation during a 2-year period were included. All implantations in the first year were performed using the reference technology (Allura Xper), whereas in the second year, the new X-ray technology (AlluraClarity) was used. Radiation exposure, expressed as the dose area product (DAP), was compared between the two time periods to determine the radiation exposure reduction for pacemaker and ICD implantations without cardiac resynchronization therapy (CRT) and with CRT. Procedure duration and contrast volume were used as measures to compare complexity and image quality. Results: The study population consisted of 591 patients who had undergone an implantation using the reference technology, and 594 patients with the new X-ray technology. The two groups did not differ in age, gender, or body mass index. The DAP decreased with 69 % from 16.4 ± 18.5 to 5.2 ± 6.6 Gy cm2 for the non-CRT implantations (p < 0.001). The DAP decreased with 75 % from 72.1 ± 60.0 to 17.8 ± 17.4 Gy cm2 for the CRT implantations (p < 0.001). Nevertheless, procedure duration and contrast volume did not differ when using the new technology (p = 0.09 and p = 0.20, respectively). Conclusions: Introduction of new X-ray technology resulted in a radiation exposure reduction of more than 69 % for patients during pacemaker and ICD implantation while image quality was unaffected.

To assess the capability of a zero coronary artery calcium (CAC) score to help exclude flow-limiting coronary artery disease (CAD) in a homogeneous population with stable anginal complaints and a low-to-intermediate pretest likelihood.The study protocol had institutional ethics committee approval, with written informed consent from all patients. Between 2009 and 2011, a total of 3501 consecutive stable patients without known CAD underwent prospectively simultaneous myocardial perfusion imaging and CAC scoring on a hybrid, 64-section single photon emission computed tomography (SPECT)/computed tomography (CT) scanner. In 868 (25%) of 3501 patients, the CAC score was zero, and these patients constituted the current study population. When feasible, additional coronary CT angiography was performed in those with abnormal SPECT findings. Clinical follow-up was recorded with regard to invasive coronary angiography, coronary revascularization, nonfatal myocardial infarction, or death. Results were analyzed by using descriptive statistics.In 868 patients (mean age, 54 years ± 11 [standard deviation]; 610 [70%] female, 258 [30%] male), SPECT findings were normal in 766 (88%) and abnormal in 102 (12%), with equivocal results in 41 (5%), persistent defect in 35 (4%), and ischemia in 26 (3%). In the group with abnormal SPECT findings, additional coronary CT angiography was performed in 93 patients (91%), showing nonobstructive CAD in eight patients (9%) and normal coronary arteries in 85 patients (91%). In the other nine patients (9%), invasive angiography was used to exclude obstructive CAD. At a median follow-up of 17 months (25th percentile, 11; 75th percentile, 24 months), no coronary events were recorded.A CAC score of zero in stable patients at low or intermediate risk excludes flow-limiting CAD. These findings support the possibility of CAC scoring as a simple and safe tool to select patients for additional testing or discharge, as recommended in the literature.

Background For tumour imaging with PET, the literature proposes to administer a patient-specific FDG activity that depends quadratically on a patient’s body weight. However, a practical approach on how to implement such a protocol in clinical practice is currently lacking. We aimed to provide a practical method to determine a FDG activity formula for whole-body PET examinations that satisfies both the EANM guidelines and this quadratic relation. Results We have developed a methodology that results in a formula describing the patient-specific FDG activity to administer. A PET study using the NEMA NU-2001 image quality phantom forms the basis of our method. This phantom needs to be filled with 2.0 and 20.0 kBq FDG/mL in the background and spheres, respectively. After a PET acquisition of 10 min, a reconstruction has to be performed that results in sphere recovery coefficients (RCs) that are within the specifications as defined by the EANM Research Ltd (EARL). By performing reconstructions based on shorter scan durations, the minimal scan time per bed position (Tmin) needs to be extracted using an image coefficient of variation (COV) of 15 %. At Tmin, the RCs should be within EARL specifications as well. Finally, the FDG activity (in MBq) to administer can be described by \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ A=c \cdot {w}^2\cdot \frac{T_{\min }}{t} $$\end{document}A=c⋅w2⋅Tmint with c a constant that is typically 0.0533 (MBq/kg2), w the patient’s body weight (in kg), and t the scan time per bed position that is chosen in a clinical setting (in seconds). We successfully demonstrated this methodology using a state-of-the-art PET/CT scanner. Conclusions We provide a practical method that results in a formula describing the FDG activity to administer to individual patients for whole-body PET examinations, taking into account both the EANM guidelines and a quadratic relation between FDG activity and patient’s body weight. This formula is generally applicable to any PET system, using a specified image reconstruction and scan time per bed position.

Background— The prognostic value of coronary artery calcium (CAC) scoring on top of myocardial perfusion imaging with single-photon emission computed tomography (SPECT) in patients suspected for coronary artery disease is not well established. Methods and Results— Four thousand eight hundred ninety-seven symptomatic patients without a history of coronary artery disease referred for SPECT and CAC scoring were included. Major adverse cardiac events (MACEs) were defined as late revascularization (>90 days after scanning), nonfatal myocardial infarction, and all-cause mortality. The frequency of abnormal SPECT increased with higher CAC scores, from 12% in patients with CAC scores of 0 to 19%, 32%, 37%, and 50% among those with CAC scores 1 to 99, 100 to 399, 400 to 999, and ≥1000, respectively ( P P P Conclusions— CAC score and SPECT are independent predictors of MACE in patients suspected for coronary artery disease. Our findings strongly support performing a CAC score in addition to SPECT in symptomatic patients to better define the risk of events during follow-up.

Objective: Modern PET/CT scanners have significantly improved detectors and fast time-of-flight (TOF) performance and this may improve clinical performance. The aim of this study was to analyze the impact of a current generation TOF PET/CT scanner on standardized uptake values (SUV), lesion-background contrast and characterization of the adrenal glands in patients with suspected lung cancer, in comparison with literature data and commonly used SUV cut-off levels. Methods: We included 149 adrenal glands from 88 patients with suspected lung cancer, who underwent 18F-FDG PET/CT. We measured the SUVmax in the adrenal gland and compared this with liver SUVmean to calculate the adrenal-to-liver ratio (AL ratio). Results were compared with literature derived with older scanners, with SUVmax values of 1.0 and 1.8 for normal glands [1, 2]. Final diagnosis was based on histological proof or follow-up imaging. We proposed cut-off values for optimal separation of benign from malignant glands. Results: In 127 benign and 22 malignant adrenal glands, SUVmax values were 2.3 ± 0.7 (mean ± SD) and 7.8 ± 3.2 respectively (p < 0.01). Corresponding AL ratios were 1.0 ± 0.3 and 3.5 ± 1.4 respectively (p < 0.01). With a SUVmax cut-off value of 3.7, 96 % sensitivity and 96 % specificity was reached. An AL ratio cut-off value of 1.8 resulted in 91 % sensitivity and 97 % specificity. The ability of both SUVmax and AL ratio to separate benign from malignant glands was similar (AUC 0.989 vs. 0.993, p = 0.22). Conclusions: Compared with literature based on the previous generation of PET scanners, current generation TOF 18F-FDG PET/CT imaging provides higher SUVs for benign adrenal glands, while it maintains a highly accurate distinction between benign and malignant glands. Clinical implementation of current generation TOF PET/CT requires not only the use of higher cut-off levels but also visual adaptation by PET readers.

Background: Attenuation correction (AC) improves the diagnostic outcome of stress-only myocardial perfusion imaging (MPI) using conventional SPECT. Our aim was to determine the value of AC using a cadmium zinc telluride-based (CZT)-SPECT camera. Methods and results: We retrospectively included 107 consecutive patients who underwent stress-optional rest MPI CZT-SPECT/CT. Next, we created three types of images for each patient; (1) only displaying reconstructed data without the CT-based AC (NC), (2) only displaying AC, and (3) with both NC and AC (NC + AC). Next, two experienced physicians visually interpreted these 321 randomized images as normal, equivocal, or abnormal. Image outcome was compared with all hard events over a mean follow-up time of 47.7 ± 9.8 months. The percentage of images interpreted as normal increased from 45% using the NC images to 72% using AC and to 67% using NC + AC images (P

Background Our aim was to evaluate if a recently introduced TOF PET system with digital photon counting technology (Philips Healthcare), potentially providing an improved image quality over analogue systems, can fulfil EANM research Ltd (EARL) accreditation specifications for tumour imaging with FDG-PET/CT. Findings We have performed a phantom study on a digital TOF PET system using a NEMA NU2-2001 image quality phantom with six fillable spheres. Phantom preparation and PET/CT acquisition were performed according to the European Association of Nuclear Medicine (EANM) guidelines. We made list-mode ordered-subsets expectation maximization (OSEM) TOF PET reconstructions, with default settings, three voxel sizes (4 × 4 × 4 mm3, 2 × 2 × 2 mm3 and 1 × 1 × 1 mm3) and with/without point spread function (PSF) modelling. On each PET dataset, mean and maximum activity concentration recovery coefficients (RCmean and RCmax) were calculated for all phantom spheres and compared to EARL accreditation specifications. The RCs of the 4 × 4 × 4 mm3 voxel dataset without PSF modelling proved closest to EARL specifications. Next, we added a Gaussian post-smoothing filter with varying kernel widths of 1–7 mm. EARL specifications were fulfilled when using kernel widths of 2 to 4 mm. Conclusions TOF PET using digital photon counting technology fulfils EARL accreditation specifications for FDG-PET/CT tumour imaging when using an OSEM reconstruction with 4 × 4 × 4 mm3 voxels, no PSF modelling and including a Gaussian post-smoothing filter of 2 to 4 mm.

Background Correction of motion has become feasible on cadmium-zinc-telluride (CZT)-based SPECT cameras during myocardial perfusion imaging (MPI). Our aim was to quantify the motion and to determine the value of automatic correction using commercially available software. Methods and Results We retrospectively included 83 consecutive patients who underwent stress-rest MPI CZT-SPECT and invasive fractional flow reserve (FFR) measurement. Eight-minute stress acquisitions were reformatted into 1.0- and 20-second bins to detect respiratory motion (RM) and patient motion (PM), respectively. RM and PM were quantified and scans were automatically corrected. Total perfusion deficit (TPD) and SPECT interpretation—normal, equivocal, or abnormal—were compared between the noncorrected and corrected scans. Scans with a changed SPECT interpretation were compared with FFR, the reference standard. Average RM was 2.5 ± 0.4 mm and maximal PM was 4.5 ± 1.3 mm. RM correction influenced the diagnostic outcomes in two patients based on TPD changes ≥7% and in nine patients based on changed visual interpretation. In only four of these patients, the changed SPECT interpretation corresponded with FFR measurements. Correction for PM did not influence the diagnostic outcomes. Conclusion Respiratory motion and patient motion were small. Motion correction did not appear to improve the diagnostic outcome and, hence, the added value seems limited in MPI using CZT-based SPECT cameras. Electronic supplementary material The online version of this article (doi:10.1007/s12350-016-0571-7) contains supplementary material, which is available to authorized users.