Current generation time-of-flight 18F-FDG PET/CT provides higher SUVs for normal adrenal glands, while maintaining an accurate characterization of benign and malignant glands

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 (18)F-FDG PET/CT. We measured the SUV(max) in the adrenal gland and compared this with liver SUV(mean) to calculate the adrenal-to-liver ratio (AL ratio). Results were compared with literature derived with older scanners, with SUV(max) 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, SUV(max) 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 SUV(max) 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 SUV(max) 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 (18)F-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

Impact of new X-ray technology on patient dose in pacemaker and implantable cardioverter defibrillator (ICD) implantations

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 cm(2) for the non-CRT implantations (p < 0.001). The DAP decreased with 75 % from 72.1 ± 60.0 to 17.8 ± 17.4 Gy cm(2) 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

Free radicals and stroke

De formatie van vrije radicalen heeft waarschijnlijk een initïerende rol in de pathofysiologie van enkele neurologische ziekten. Het CerebroVasculair Accident (CVA, beroerte of hersenbloeding) is een voorbeeld van een ziekte waarbij vrije radicalen mede verantwoordelijk worden gehouden voor het ontstaan van de beschadiging. Cerebrovasculaire accidenten zijn de derde doodsoorzaak en de belangrijkste veroorzaker van ernstige handicaps. De therapie in deze patiënten is tot nu toe voornamelijk gelimiteerd tot de preventie van nieuwe complicaties in plaats van de (farmacologische) beperking van de hersenschade (appendix l). Het gebrek aan effectieve chirurgische of farmacologische behandelingen is enerzijds gelegen in de beperkte pathofysiologische kennis over herseninfarcten en wordt anderzijds veroorzaakt door de problemen met de interpretatie en implementatie van data verkregen uit dierexperimenten. In dit proefschrift is veel aandacht besteed aan het ontrafelen van de mogelijke pathofysiologische mechanismen in een rat hypoxie/ischemie/reperfusie model.... Zie: Samenvatting

SUV variability in EARL-accredited conventional and digital PET

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

Performance of Digital PET Compared with High-Resolution Conventional PET in Patients with Cancer

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

Down-regulation of the hypothalamo-pituitary-adrenal axis reduces brain damage and number of seizures following hypoxia/ischaemia in rats

Several reports suggest that the activity of the hypothalamo-pituitary-adrenal axis (HPA-axis) is increased following hypoxia/ischaemia and that this might be associated with increased neuronal vulnerability. The main goal of this study was to examine the effects of down-regulation of the HPA-axis on the hypoxia/ischaemia-induced (1) rise of plasma corticosterone levels, (2) seizures, and (3) brain damage. Down-regulation of the HPA-axis was induced by prolonged corticosterone treatment lasting until 24 h before hypoxia/ischaemia exposure. When compared to 8 days vehicle (sesame oil)-treated animals (CONT), 8 days daily corticosterone (40 mg/animal)-treated animals (CORT) showed significantly reduced adrenal-and thymus weight. Shortly after hypoxia/ischaemia plasma corticosterone levels in CORT animals were significantly reduced (17.30 mu g/dl +/- 3.50) when compared to CONT animals (54.80 mu g/dl +/- 7.78). This correlated with the brain damage which is expressed as the ratio between the damaged area and the total area. The total brain damage was significantly less in CORT-treated animals (28% +/- 11%) than in CONT animals (69% +/- 2%). Following hypoxia/ischaemia the number of seizures was significantly reduced in CORT animals (56 +/- 26) when compared to CONT animals (217 +/- 50). We conclude that prolonged corticosterone treatment resulting in down-regulation of the HPA-axis leads to (1) lower plasma corticosterone levels during hypoxia/ischaemia, (2) a reduction in brain damage following hypoxia/ischaemia, and (3) less hypoxia/ischaemia-induced seizures

Value of automatic patient motion detection and correction in myocardial perfusion imaging using a CZT-based SPECT camera

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

Technical note: how to determine the FDG activity for tumour PET imaging that satisfies European guidelines

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 A ¼ c ⋅w2⋅ Tmin t 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