Optimization and impact of sensitivity mode on abbreviated scan protocols with population-based input function for parametric imaging of [18F]-FDG for a long axial FOV PET scanner.

BACKGROUND: The long axial field of view, combined with the high sensitivity of the Biograph Vision Quadra PET/CT scanner enables the precise deviation of an image derived input function (IDIF) required for parametric imaging. Traditionally, this requires an hour-long dynamic PET scan for [18F]-FDG, which can be significantly reduced by using a population-based input function (PBIF). In this study, we expand these examinations and include the scanner's ultra-high sensitivity (UHS) mode in comparison to the high sensitivity (HS) mode and evaluate the potential for further shortening of the scan time. METHODS: Patlak Ki and DV estimates were determined by the indirect and direct Patlak methods using dynamic [18F]-FDG data of 6 oncological patients with 26 lesions (0-65 min p.i.). Both sensitivity modes for different number/duration of PET data frames were compared, together with the potential of using abbreviated scan durations of 20, 15 and 10 min by using a PBIF. The differences in parametric images and tumour-to-background ratio (TBR) due to the shorter scans using the PBIF method and between the sensitivity modes were assessed. RESULTS: A difference of 3.4 ± 7.0% (Ki) and 1.2 ± 2.6% (DV) was found between both sensitivity modes using indirect Patlak and the full IDIF (0-65 min). For the abbreviated protocols and indirect Patlak, the UHS mode resulted in a lower bias and higher precision, e.g., 45-65 min p.i. 3.8 ± 4.4% (UHS) and 6.4 ± 8.9% (HS), allowing shorter scan protocols, e.g. 50-65 min p.i. 4.4 ± 11.2% (UHS) instead of 7.3 ± 20.0% (HS). The variation of Ki and DV estimates for both Patlak methods was comparable, e.g., UHS mode 3.8 ± 4.4% and 2.7 ± 3.4% (Ki) and 14.4 ± 2.7% and 18.1 ± 7.5% (DV) for indirect and direct Patlak, respectively. Only a minor impact of the number of Patlak frames was observed for both sensitivity modes and Patlak methods. The TBR obtained with direct Patlak and PBIF was not affected by the sensitivity mode, was higher than that derived from the SUV image (6.2 ± 3.1) and degraded from 20.2 ± 12.0 (20 min) to 10.6 ± 5.4 (15 min). Ki and DV estimate images showed good agreement (UHS mode, RC: 6.9 ± 2.3% (Ki), 0.1 ± 3.1% (DV), peak signal-to-noise ratio (PSNR): 64.5 ± 3.3 dB (Ki), 61.2 ± 10.6 dB (DV)) even for abbreviated scan protocols of 50-65 min p.i. CONCLUSIONS: Both sensitivity modes provide comparable results for the full 65 min dynamic scans and abbreviated scans using the direct Patlak reconstruction method, with good Ki and DV estimates for 15 min short scans. For the indirect Patlak approach the UHS mode improved the Ki estimates for the abbreviated scans.

Impact of the maximum ring difference on image quality and noise characteristics of a total-body PET/CT scanner.

The sensitivity of a PET system highly depends on the axial acceptance angle or maximum ring difference (MRD), which can be particularly high for total-body scanners due to their larger axial field of views (aFOVs). This study aims to evaluate the impact on image quality (IQ) and noise performance when MRD85 (18°), the current standard for clinical use, is increased to MRD322 (52°) for the Biograph Vision Quadra (Siemens Healthineers). METHODS: Studies with a cylindrical phantom covering the 106 cm aFOV and an IEC phantom filled with 18F, 68Ga and 89Zr were performed for acquisition times from 60 to 1800 s and activity concentrations from 0.4 to 3 kBq/ml to assess uniformity, contrast recovery coefficients (CRCs) and to characterize noise by coefficient of variation (CV). Spatial resolution was compared for both MRDs by sampling a quadrant of the FOV with a point source. Further IQ, CV, liver SUVmean and SUVmax were compared for a cohort of 5 patients scanned with [18F]FDG (3 MBq/kg, 1 h p.i.) from 30 to 300 s. RESULTS: CV was improved by a factor of up to 1.49 and is highest for short acquisition times, peaks at the center field of view and mitigates parabolic in axial direction with no difference to MRD85 beyond the central 80 cm. No substantial differences between the two evaluated MRDs in regards to uniformity, SUVmean or CRC for the different isotopes were observed. A degradation of the average spatial resolution of 0.9 ±â€¯0.2 mm in the central 40 cm FOV was determined with MRD322. Depending on the acquisition time MRD322 resulted in a decrease of SUVmax between 23.8% (30 s) and 9.0% (300 s). CONCLUSION: Patient and phantom studies revealed that scan time could be lowered by approximately a factor of two with MRD322 while maintaining similar noise performance. The moderate degradation in spatial resolution for MRD322 is worth to exploit the full potential of the Quadra by either shorten scan times or leverage noise performance in particular for low count scenarios such as ultra-late imaging or dynamic studies with high temporal resolution.

Evaluation of a modular all-in-one high-resolution PET detector and readout electronics setup.

Objective. The all-in-one solution and modularity of the C13500 series TOF-PET detector modules (Hamamatsu Photonics K.K., Hamamatsu, Japan) make them a highly attractive candidate for the development of positron emission tomography (PET) systems. However, the commercially available portfolio targets clinical whole-body PET systems with a scintillation crystal cross area of 3.1 × 3.1 mm2. To extend the modules for high resolution (preclinical or organ specific) systems, the support for smaller scintillation crystals is required.Approach.In this work, a PET detector was developed based on the TOF-PET modules using a light sharing approach, 16 × 16 lutetium oxyorthosilicate (LSO) scintillation crystals with a size of 1.51 × 1.51 × 10.00 mm3readout with 8 × 8 photosensor channels of size 3.0 × 3.0 mm2. In addition to hardware and software development, the optimized parameter settings for the adapted configuration were evaluated.Main Results.A factor of two in amplification of the analog signal compared to the minimum gain setting was necessary for an accurate crystal identification (peak-to-valley ratio 14.9 ± 5.9). A further increase to a factor of three was not determined as optimum as the time over threshold duration, thus pile-up probability, increased from 1032.1 ± 109.5 to 1789.5 ± 218.5 ns (photopeak position). With this amplification a full width at half maximum (FWHM) energy resolution of 14.1 ± 2.0% and a high linearity of the energy detection was obtained. A FWHM coincidence resolving time (CRT) of 313 ps was achieved by using a low timing threshold, increasing the bandwidth of the front-end circuit and using a narrow ± 1σenergy window. To approximately double the sensitivity and reduce the power consumption, the timing parameters were adjusted resulting in a FWHM CRT of 354 ps (±2σ).Significance.Based on the results obtained with the proof-of-concept detector setup, we confirm the modularity and flexibility of the all-in-one TOF-PET detector modules for the future development of application-specific high-resolution PET systems.

Design and performance simulation studies of a breast PET insert integrable into a clinical whole-body PET/MRI scanner.

Objective. Three different breast positron emission tomography (PET) insert geometries are proposed for integration into an existing magnetic resonance imaging (MRI) breast coil (Breast Biopsy Coil, NORAS MRI products) to be used inside a whole-body PET/MRI scanner (Biograph mMR, Siemens Healthineers) to enhance the sensitivity and spatial resolution of imaging inside the breast.Approach. Monte Carlo simulations were performed to predict and compare the performance characteristics of the three geometries in terms of the sensitivity, spatial resolution, scatter fraction, and noise equivalent count rate (NECR). In addition, the background single count rate due to organ uptake in a clinical scan scenario was predicted using a realistic anthropomorphic phantom.Main results. In the center of the field of view (cFOV), absolute sensitivities of 3.1%, 2.7%, and 2.2% were found for Geometry A (detectors arranged in two cylinders), Geometry B (detectors arranged in two partial cylinders), and Geometry C (detectors arranged in two half cylinders combined with two plates), respectively. The full width at half maximum spatial resolution was determined to be 1.7 mm (Geometry A), 1.8 mm (Geometry B) and 2.0 mm (Geometry C) at 5 mm from the cFOV. Designs with multiple scintillation-crystal layers capable of determining the depth of interaction (DOI) strongly improved the spatial resolution at larger distances from the transaxial cFOV. The system scatter fractions were 33.1% (Geometries A and B) and 32.3% (Geometry C). The peak NECRs occurred at source activities of 300 MBq (Geometry A), 310 MBq (Geometry B) and 340 MBq (Geometry C). The background single-event count rates were 17.1 × 106cps (Geometry A), 15.3 × 106cps (Geometry B) and 14.8 × 106cps (Geometry C). Geometry A in the three-layer DOI variant exhibited the best PET performance characteristics but could be challenging to manufacture. Geometry C had the lowest impact on the spatial resolution and the lowest sensitivity among the investigated geometries.Significance. Geometry B in the two-layer DOI variant represented an effective compromise between the PET performance and manufacturing difficulty and was found to be a promising candidate for the future breast PET insert.

Optimization, evaluation and calibration of a cross-strip DOI detector.

This study depicts the evaluation of a SiPM detector with depth of interaction (DOI) capability via a dual-sided readout that is suitable for high-resolution positron emission tomography and magnetic resonance (PET/MR) imaging. Two different 12 × 12 pixelated LSO scintillator arrays with a crystal pitch of 1.60 mm are examined. One array is 20 mm-long with a crystal separation by the specular reflector Vikuiti enhanced specular reflector (ESR), and the other one is 18 mm-long and separated by the diffuse reflector Lumirror E60 (E60). An improvement in energy resolution from 22.6% to 15.5% for the scintillator array with the E60 reflector is achieved by taking a nonlinear light collection correction into account. The results are FWHM energy resolutions of 14.0% and 15.5%, average FWHM DOI resolutions of 2.96 mm and 1.83 mm, and FWHM coincidence resolving times of 1.09 ns and 1.48 ns for the scintillator array with the ESR and that with the E60 reflector, respectively. The measured DOI signal ratios need to be assigned to an interaction depth inside the scintillator crystal. A linear and a nonlinear method, using the intrinsic scintillator radiation from lutetium, are implemented for an easy to apply calibration and are compared to the conventional method, which exploits a setup with an externally collimated radiation beam. The deviation between the DOI functions of the linear or nonlinear method and the conventional method is determined. The resulting average of differences in DOI positions is 0.67 mm and 0.45 mm for the nonlinear calibration method for the scintillator array with the ESR and with the E60 reflector, respectively; Whereas the linear calibration method results in 0.51 mm and 0.32 mm for the scintillator array with the ESR and the E60 reflector, respectively; and is, due to its simplicity, also applicable in assembled detector systems.

Admission heart rate in relation to presentation and prognosis in patients with acute myocardial infarction. Treatment regimens in German chest pain units.

BACKGROUND: Higher heart rates on admission have been associated with poor outcomes in patients with an acute coronary syndrome in previous cohorts. Whether such a linear relationship still exists in contemporary high-level care is unclear. METHODS: Prospectively collected data from patients presenting with myocardial infarction (MI) in centers participating in the Chest Pain Unit (CPU) Registry between December 2008 and July 2014 were analyzed. Patients were classified according to their initial heart rate (I: < 50; II: 50-69; III: 70-89; IV: ≥ 90 bpm). A total of 6,168 patients out of 30,339 patients presenting to 38 centers were included in the study. RESULTS: Patients in group IV had more comorbidities, while patients in group I more often had a history of MI. Patients in the lowest heart rate group presented significantly earlier to the hospital (4 h 31 min vs. 7 h 37 min; p < 0.05) and had the highest rate of interventions. The overall survival after 3 months was significantly worse in group IV after adjusting for baseline variables. In the subgroup analysis, heart rate was a prognostic factor in the non-ST-segment elevation MI group but not in the ST-segment elevation MI group. The correlation between heart rate and major adverse cardiac events followed a J-shaped curve with worst outcomes in the lowest and highest heart rate groups. CONCLUSION: Patients admitted to a dedicated CPU with the diagnosis of MI and a heart rate > 90 bpm experience reduced survival at 3 months despite optimal treatment. Patients with bradycardia also seem to be at increased risk for cardiovascular events despite much earlier presentation and treatment.

["Do-not-rescuscitate"--Results of introducing a standardized order sheet on documentation quality]. / "Do not rescuscitate"--Auswirkungen der Einführung eines standardisierten Formulars auf Therapiebegrenzungen in der klinischen Praxis.

INTRODUCTION: DNR orders have been used internationally since the 1970 s. Despite the growing importance of patient preference in German law, there is little data on DNR orders in Germany Methods: The prevalence of DNR orders was assessed on the hospital wards. Healthcare were asked about their experiences and opinions in two polls. The charts of all deceased patients were reviewed for DNR notes for 9 month before and after introduction of the new DNR order sheets. RESULTS: The prevalence of DNR orders remained constant at 8% of patients. In 12,4% of these DNR status was not known by the nursing staff. After introduction of the order sheet, the percentage of orders with comprehensive documentation increased from 5.9 to 65.4% of orders (p < 0.001). In the polls the healthcare workers saw a significant improvement in information content of DNR orders after introduction of the new order sheets. The chart review documented an improved documentation of DNR status going up from 28.8 to 40.8% of deceased patients (p < 0.001). The fraction of comprehensive orders increased from 32% to 84.6% (p < 0.001). CONCLUSION: INTRODUCTION of DNR order sheets in a German hospital lead to objective improvements in the quality of end-of life care documentation while the prevalence of DNR orders remained unchanged.

Surgery for acquired cardiovascular disease: antiseptic treatment of contaminated vein grafts.

AIM: Saphenous vein grafts harvested for use as bypass conduits can be contaminated intraoperatively, e.g. by being inadvertently dropped to the floor of the operating room (OR). This study was performed to investigate microorganisms most likely contaminating vein grafts and to assess the possible efficacy of measures to treat potentially contaminated vein grafts antiseptically for further use. METHODS: In a first step we determined the microbiological flora of the OR using surface cultures and cultures from intentionally dropped vein grafts. Several antiseptic agents (PVP-iodine 10%, octenidinhydrochloride 0.1%, polyhexanide 1%) were evaluated for their in vitro efficacy to disinfect artificially contaminated vein segments. The most promising antiseptic regimen was tested on veins contaminated in a real OR setting. Finally, we tested for possible alterations in mechanical properties of the veins caused by antiseptic treatment. RESULTS: Coagulase-negative staphylococci where the predominant bacteria recovered from the OR with 59.9%. Antiseptic treatment with a combination of octenidine and PVP-iodine resulted in a higher rate of negative cultures than any single agent. Treatment of 50 saphenous vein grafts contaminated in the OR with the combination regimen resulted in only 3 positive cultural results within 7 days. Mechanical tear-stress testing comparing antiseptically treated vein grafts with controls showed no difference in their resistance to tear stress. CONCLUSION: Antiseptic treatment of contaminated vein grafts was shown to be effective in a high percentage of cases without altering mechanical properties of grafts and may be an option for the surgeon in case of a contamination.

[Protein Z deficiency in unexplained affinity to thromboses, bleedings or abortions]. / Protein-Z-Mangel bei ungeklärter Neigung zu Thrombosen, Blutungen oder Aborten.

UNLABELLED: A protein Z deficiency is presumably related with a threefold risk of venous and arterial thrombosis. Mucosal bleedings and post-operative haematomas can occur more frequently. This is seen in an increased in vivo bleeding time without other plasmatic coagulation disorders or thrombopathies. Pregnancy complications, especially abortions before the 15th week of gestation, are described as well. PATIENTS, METHODS: Since May 2011 the plasmatic concentration of protein Z has been tested in 684 patients of the Hämostaseologicum. RESULTS: In 74 patients a protein Z deficiency has been found. In other 45 patients protein Z was reduced because of the intake of phenprocoumon or coumadin. Of the 74 patients with diminished protein Z concentration 39 were marginally decreased (protein Z 1000-1500 µg/l). Of the 35 patients with a protein Z concentration <1000 µg/l 12 had had a thrombosis before (6 strokes, 3 DVT or PE, 1 arterial thrombosis, 1 retinal branch vein occlusion, 1 acute hearing loss). 7 had arterial hypertension, 2 suffered from diabetes mellitus. Of the patients who had a thrombosis 6 had a heterozygous factor V Leiden mutation. 10 had a microcirculation disorder (Raynaud's phenomenon), 4 had had bleeding complications before, 3 had a von Willebrand disease type I, 6 patients had had abortions and 4 were healthy. Of the 39 patients with protein Z concentrations between 1000 and 1500 µg/l 18 had experienced a thrombosis before (9 DVT or PE, 3 myocardial infarctions, 1 CHD, 3 strokes, 1 retinal branch vein occlusion, 1 PAOD I, 1 tinnitus). 5 additionally had arterial hypertension. 13 suffered from Raynaud's phenomenon, of which 7 had a hypotension. Of the patients with thromboses 3 had a heterozygous factor V Leiden mutation and one a protein C deficiency. 7 patients had had an abortion before. Bleeding complications were seen in 4 patients, of which 3 suffered from von Willebrand disease type 1.

[Risk pregnancies and how to treat them]. / Risikoschwangerschaften und deren Therapie.

UNLABELLED: Recurrent abortions are a common problem. A therapy with low-molecular- weight heparin is usual in deep vein thrombosis with thrombophilia, in woman with recurrent abortions or other risks, like EPH-gestosis or HELLP-Syndrom. PATIENTS, METHOD: The efficacy of a mono-therapy with LMWH (3000-16000 daily) in women with risk pregnancies has been examined prospectively. The dates of 676 pregnant women have been analysed and compared to the current literature about live birth rates without therapy and tot he results of other, similar studies. The live birth rate has been the target variable. RESULTS: We obtained main a live birth rate of 98.6%. There has been no record of serious adverse effects. We obtained a live birth rate of 95.8% if NMH therapy starts early, and a live birth rate of 100% if NMH therapy starts between week 20 and 25. For the live birth rate the existence of thrombophilic gene polymorphisms is irrelevant. CONCLUSION: The high live birth weight is depended on early starting the therapy with NMH. For the late risk it is favourable to start the therapy with heparin between week 20 and 25 week of pregnancy.

[Automatic blood group determination in the ABO- and Rh-system using conductometry]. / Automatisierte Blutgruppenbestimmung im AB0- und Rh-System mittels Konduktometrie.

A method was developed and tested on the basis of conductometry for determining blood group-specific agglutinates in the AB0 and Rh-system (D). By comparing the measured particle numbers before and after administration of specific antisera or test erythrocytes and objective evaluation can be made whether agglutination has occurred or not. The calculated degrees of agglutination were compared depending on the method, sex, and age of patients. The method can be automated.