BackgroundThe purpose of the study is to evaluate the physical performance of a Biograph mCT Flow 64-4R PET/CT system (Siemens Healthcare, Germany) and to compare clinical image quality in step-and-shoot (SS) and continuous table motion (CTM) acquisitions.MethodsThe spatial resolution, sensitivity, count rate curves, and Image Quality (IQ) parameters following the National Electrical Manufactures Association (NEMA) NU2-2012 standard were evaluated. For resolution measurements, an 18F point source inside a glass capillary tube was used. Sensitivity measurements were based on a 70-cm-long polyethylene tube, filled with 4.5 MBq of FDG. Scatter fraction and count rates were measured using a 70-cm-long polyethylene cylinder with a diameter of 20 cm and a line source (1.04 GBq of FDG) inserted axially into the cylinder 4.5 cm off-centered. A NEMA IQ phantom containing six spheres (10- to 37-mm diameter) was used for the evaluation of the image quality. First, a single-bed scan was acquired (NEMA standard), followed by a two-bed scan (4 min each) of the IQ phantom with the image plane containing the spheres centered in the overlap region of the two bed positions. In addition, a scan of the same region in CTM mode was performed with a table speed of 0.6 mm/s. Furthermore, two patient scans were performed in CTM and SS mode. Image contrasts and patient images were compared between SS and CTM acquisitions.ResultsFull Width Half Maximum (FWHM) of the spatial resolution ranged from 4.3 to 7.8 mm (radial distance 1 to 20 cm). The measured sensitivity was 9.6 kcps/MBq, both at the center of the FOV and 10 cm off-center. The measured noise equivalent count rate (NECR) peak was 185 kcps at 29.0 kBq/ml. The scatter fraction was 33.5 %. Image contrast recovery values (sphere-to-background of 8:1) were between 42 % (10-mm sphere) to 79 % (37-mm sphere). The background variability was between 2.1 and 5.3 % (SS) and between 2.4 and 6.9 % (CTM). No significant difference in image quality was observed between SS and CTM mode.ConclusionsThe spatial resolution, sensitivity, scatter fraction, and count rates were in concordance with the published values for the predecessor system, the Biograph mCT. Contrast recovery values as well as image quality obtained in SS and CTM acquisition modes were similar.

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Abstract:Objective: The objective of this work was to determine any changes in HRV (heart rate variability) using shorttime measurements (140 seconds) in a quasi-experimental therapeutic application study on Reiki.Method: HRV was determined using a ready at hand electrocardiogram device the size of a cellular phone, which requires a measuring time of 140 seconds and electrode contact only with the finger tips. Measurements were performed on healthy test subjects, before and after a defined control rest period and a defined test intervention period (Reiki treatment). 27 test subjects were enrolled.Results: SDNN (the standard deviation of all heartbeat intervals in ms) and TP (total power of heartbeat interval variability in the frequency range 0.003 -0.4 Hz in ms 2 ) were together interpreted as an indicator of test subjects' autonomic nervous activity and as a measure of their ability to cope with demands on their health (regulatory capacity). These values increased both in the control (p < 0.05) and in the test intervention period (p < 0.01). However the increase was more marked after the Reiki intervention (57.8% / 81.7%) than it was after the control rest period (19.6% / 42.8%) (interactions: p < 0.01 / p > 0.05). The LF/HF ratio (sympathico-vagal balance) was interpreted as a measure of the balance between activation and relaxation. No changes in the LF/HF ratio were observed in the course of the control or the test intervention period (p > 0.05). Conclusion:Both control rest and Reiki treatment had a favourable effect on heart rate variability, but the effect of Reiki treatment was markedly stronger. The measurement device used seems to be a promising tool for practical application studies of this kind.