TY  - JOUR
A1  - Nehr, Sascha
A1  - Baus, Lukas
A1  - Çinar, Hasan
A1  - Elsen, Ingo
A1  - Frauenrath, Tobias
T1  - Indoor environmental quality assessment in passively ventilated classrooms in Germany and estimation of ventilation energy losses
JF  - Journal of Building Engineering
N2  - In this field study we present an approach for the comprehensive and room-specific assessment of
parameters with the overall aim to realize energy-efficient provision of hygienically harmless and
thermally comfortable indoor environmental quality in naturally ventilated non-residential
buildings. The approach is based on (i) conformity assessment of room design parameters, (ii)
empirical determination of theoretically expected occupant-specific supply air flow rates and
corresponding air exchange rates, (iii) experimental determination of real occupant-specific
supply air flow rates and corresponding air exchange rates, (iv) measurement of indoor environmental
exposure conditions of T, RH, cCO2 , cPM2.5 and cTVOC, and (v) determination of real
energy demands for the prevailing ventilation scheme. Underlying assessment criteria comprise
the indoor environmental parameters of category II of EN 16798-1: Temperature T = 20 ◦C–24 ◦C,
and relative humidity RH = 25 %–60 % as well as the guide values of the German Federal
Environment Agency for cCO2 cPM2.5 and cTVOC of 1000 ppm, 15 μg m⁻³, and 1 mg m ⁻³,
respectively.
Investigation objects are six naturally ventilated classrooms of a German secondary school.
Major factors influencing indoor environmental quality in these classrooms are the specific room
volume per occupant and the window opening area. It is concluded that the rigorous implementation
of ventilation recommendations laid down by the German Federal Environment
Agency is ineffective with respect to anticipated indoor environmental parameters and inefficient
with respect to ventilation energy losses on the order of about 10 kWh m⁻² a ⁻¹ to 30 kWh m⁻²
a ⁻¹.
KW  - Indoor air quality
KW  - Indoor environmental quality
KW  - Energy-efficient ventilation
KW  - CO2
KW  - PM2.5
Y1  - 2024
SN  - 2352-7102
VL  - 97
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Gong, Jing
A1  - Raut, Amod
A1  - Pelzer, Marcel
A1  - Hüning, Felix
T1  - Marking-based perpendicular parking slot detection algorithm using LiDAR sensors
JF  - Vehicles
N2  - The emergence of automotive-grade LiDARs has given rise to new potential methods to develop novel advanced driver assistance systems (ADAS). However, accurate and reliable parking slot detection (PSD) remains a challenge, especially in the low-light conditions typical of indoor car parks. Existing camera-based approaches struggle with these conditions and require sensor fusion to determine parking slot occupancy. This paper proposes a parking slot detection (PSD) algorithm which utilizes the intensity of a LiDAR point cloud to detect the markings of perpendicular parking slots. LiDAR-based approaches offer robustness in low-light environments and can directly determine occupancy status using 3D information. The proposed PSD algorithm first segments the ground plane from the LiDAR point cloud and detects the main axis along the driving direction using a random sample consensus algorithm (RANSAC). The remaining ground point cloud is filtered by a dynamic Otsu’s threshold, and the markings of parking slots are detected in multiple windows along the driving direction separately. Hypotheses of parking slots are generated between the markings, which are cross-checked with a non-ground point cloud to determine the occupancy status. Test results showed that the proposed algorithm is robust in detecting perpendicular parking slots in well-marked car parks with high precision, low width error, and low variance. The proposed algorithm is designed in such a way that future adoption for parallel parking slots and combination with free-space-based detection approaches is possible. This solution addresses the limitations of camera-based systems and enhances PSD accuracy and reliability in challenging lighting conditions.
KW  - point cloud processing
KW  - RANSAC
KW  - line detection
KW  - automated parking
KW  - LiDAR
KW  - parking slot detection
Y1  - 2024
U6  - https://doi.org/10.3390/vehicles6040083
SN  - 2624-8921
N1  - Corresponding author: Felix Hüning
VL  - 6
IS  - 4
SP  - 1717
EP  - 1729
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Windmüller, Anna
A1  - Schaps, Kristian
A1  - Zantis, Frederik
A1  - Domgans, Anna
A1  - Taklu, Bereket Woldegbreal
A1  - Yang, Tingting
A1  - Tsai, Chih-Long
A1  - Schierholz, Roland
A1  - Yu, Shicheng
A1  - Kungl, Hans
A1  - Tempel, Hermann
A1  - Dunin-Borkowski, Rafal E.
A1  - Hüning, Felix
A1  - Hwang, Bing Joe
A1  - Eichel, Rüdiger-A.
T1  - Electrochemical activation of LiGaO2: implications for ga-doped garnet solid electrolytes in li-metal batteries
JF  - ACS Applied Materials & Interfaces
N2  - Ga-doped Li7La3Zr2O12 garnet solid electrolytes exhibit the highest Li-ion conductivities among the oxide-type garnet-structured solid electrolytes, but instabilities toward Li metal hamper their practical application. The instabilities have been assigned to direct chemical reactions between LiGaO2 coexisting phases and Li metal by several groups previously. Yet, the understanding of the role of LiGaO2 in the electrochemical cell and its electrochemical properties is still lacking. Here, we are investigating the electrochemical properties of LiGaO2 through electrochemical tests in galvanostatic cells versus Li metal and complementary ex situ studies via confocal Raman microscopy, quantitative phase analysis based on powder X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electron energy loss spectroscopy. The results demonstrate considerable and surprising electrochemical activity, with high reversibility. A three-stage reaction mechanism is derived, including reversible electrochemical reactions that lead to the formation of highly electronically conducting products. The results have considerable implications for the use of Ga-doped Li7La3Zr2O12 electrolytes in all-solid-state Li-metal battery applications and raise the need for advanced materials engineering to realize Ga-doped Li7La3Zr2O12for practical use.
KW  - LiGaO2
KW  - garnet solid electrolyte
KW  - ga-doping
KW  - Li7La3Zr2O12
KW  - solid-state battery
Y1  - 2024
U6  - https://doi.org/10.1021/acsami.4c03729
SN  - 39181–3919
VL  - 16
IS  - 30
PB  - ACS Publications
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Droop, Philipp
A1  - Chen, Shaohuang
A1  - Radford, Melissa J.
A1  - Paulßen, Elisabeth
A1  - Gates, Byron D.
A1  - Reilly, Raymond M.
A1  - Radchenko, Valery
A1  - Hoehr, Cornelia
T1  - Synthesis of 197m/gHg labelled gold nanoparticles for targeted radionuclide therapy
JF  - Radiochimica Acta
N2  - Meitner-Auger-electron emitters have a promising potential for targeted radionuclide therapy of cancer because of their short range and the high linear energy transfer of Meitner-Auger-electrons (MAE). One promising MAE candidate is 197m/gHg with its half-life of 23.8 h and 64.1 h, respectively, and high MAE yield. Gold nanoparticles (AuNPs) that are labelled with 197m/gHg could be a helpful tool for radiation treatment of glioblastoma multiforme when infused into the surgical cavity after resection to prevent recurrence. To produce such AuNPs, 197m/gHg was embedded into pristine AuNPs. Two different syntheses were tested starting from irradiated gold containing trace amounts of 197m/gHg. When sodium citrate was used as reducing agent, no 197m/gHg labelled AuNPs were formed, but with tannic acid, 197m/gHg labeled AuNPs were produced. The method was optimized by neutralizing the pH (pH = 7) of the Au/197m/gHg solution, which led to labelled AuNPs with a size of 12.3 ± 2.0 nm as measured by transmission electron microscopy. The labelled AuNPs had a concentration of 50 μg (gold)/mL with an activity of 151 ± 93 kBq/mL (197gHg, time corrected to the end of bombardment).
KW  - 197m/gHg
KW  - Gold nanoparticle (AuNP)
KW  - Meitner-Auger-electron (MAE)
KW  - Targeted radionuclide therapy (TRT)
Y1  - 2023
U6  - https://doi.org/10.1515/ract-2023-0144
SN  - 2193-3405
VL  - 111
IS  - 10
SP  - 773
EP  - 779
PB  - De Gruyter
CY  - Berlin [u.a.]
ER  - 
TY  - JOUR
A1  - Fiedler, Thomas M.
A1  - Orzada, Stephan
A1  - Flöser, Martina
A1  - Rietsch, Stefan H. G.
A1  - Quick, Harald H.
A1  - Ladd, Mark E.
A1  - Bitz, Andreas
T1  - Performance analysis of integrated RF microstrip transmit antenna arrays with high channel count for body imaging at 7 T
JF  - NMR in Biomedicine
N2  - The aim of the current study was to investigate the performance of integrated RF
transmit arrays with high channel count consisting of meander microstrip antennas
for body imaging at 7 T and to optimize the position and number of transmit ele-
ments. RF simulations using multiring antenna arrays placed behind the bore liner
were performed for realistic exposure conditions for body imaging. Simulations were
performed for arrays with as few as eight elements and for arrays with high channel
counts of up to 48 elements. The B1+ field was evaluated regarding the degrees of
freedom for RF shimming in the abdomen. Worst-case specific absorption rate
(SARwc ), SAR overestimation in the matrix compression, the number of virtual obser-
vation points (VOPs) and SAR efficiency were evaluated. Constrained RF shimming
was performed in differently oriented regions of interest in the body, and the devia-
tion from a target B1+ field was evaluated. Results show that integrated multiring
arrays are able to generate homogeneous B1+ field distributions for large FOVs, espe-
cially for coronal/sagittal slices, and thus enable body imaging at 7 T with a clinical
workflow; however, a low duty cycle or a high SAR is required to achieve homoge-
neous B1+ distributions and to exploit the full potential. In conclusion, integrated
arrays allow for high element counts that have high degrees of freedom for the pulse
optimization but also produce high SARwc , which reduces the SAR accuracy in the
VOP compression for low-SAR protocols, leading to a potential reduction in array
performance. Smaller SAR overestimations can increase SAR accuracy, but lead to a
high number of VOPs, which increases the computational cost for VOP evaluation
and makes online SAR monitoring or pulse optimization challenging. Arrays with
interleaved rings showed the best results in the study.
KW  - body imaging at UHF MRI
KW  - integrated transmit coil arrays
KW  - VOP compression
Y1  - 2021
U6  - https://doi.org/10.1002/nbm.4515
SN  - 0952-3480 (ISSN)
SN  - 1099-1492 (eISSN)
VL  - 34
IS  - 7
PB  - Wiley
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Frauenrath, Tobias
A1  - Niendorf, Thoralf
A1  - Kob, Malte
T1  - Acoustic method for synchronization of Magnetic Resonance Imaging (MRI)
JF  - Acta Acustica
N2  - Magnetic Resonance Imaging (MRI) of moving organs requires synchronization with physiological motion or flow, which dictate the viable window for data acquisition. To meet this challenge, this study proposes an acoustic gating device (ACG) that employs acquisition and processing of acoustic signals for synchronization while providing MRI compatibility, immunity to interferences with electro-magnetic and acoustic fields and suitability for MRI at high magnetic field strengths. The applicability and robustness of the acoustic gating approach is examined in a pilot study, where it substitutes conventional ECG-gating for cardiovascular MR. The merits and limitations of the ACG approach are discussed. Implications for MR imaging in the presence of physiological motion are considered including synchronization with other structure- or motion borne sounds.
Y1  - 2008
U6  - https://doi.org/10.3813/AAA.918017
SN  - 1861-9959
VL  - 94
IS  - 1
SP  - 148
EP  - 155
PB  - Hirzel
CY  - Stuttgart
ER  - 
TY  - JOUR
A1  - Heinrichs, Uwe
A1  - Utting, Jane F.
A1  - Frauenrath, Tobias
A1  - Hezel, Fabian
A1  - Krombach, Gabriele A.
A1  - Hodenius, Michael A. J.
A1  - Kozerke, Sebastian
A1  - Niendorf, Thoralf
T1  - Myocardial T2 mapping free of distortion using susceptibility-weighted fast spin-echo imaging: A feasibility study at 1.5 T and 3.0 T
JF  - Magnetic Resonance in Medicine
N2  - This study demonstrates the feasibility of applying free-breathing, cardiac-gated, susceptibility-weighted fast spin-echo imaging together with black blood preparation and navigator-gated respiratory motion compensation for anatomically accurate T₂ mapping of the heart. First, T₂ maps are presented for oil phantoms without and with respiratory motion emulation (T₂ = (22.1 ± 1.7) ms at 1.5 T and T₂ = (22.65 ± 0.89) ms at 3.0 T). T₂ relaxometry of a ferrofluid revealed relaxivities of R2 = (477.9 ± 17) mM⁻¹s⁻¹ and R2 = (449.6 ± 13) mM⁻¹s⁻¹ for UFLARE and multiecho gradient-echo imaging at 1.5 T. For inferoseptal myocardial regions mean T₂ values of 29.9 ± 6.6 ms (1.5 T) and 22.3 ± 4.8 ms (3.0 T) were estimated. For posterior myocardial areas close to the vena cava T₂-values of 24.0 ± 6.4 ms (1.5 T) and 15.4 ± 1.8 ms (3.0 T) were observed. The merits and limitations of the proposed approach are discussed and its implications for cardiac and vascular T₂-mapping are considered.
Y1  - 2009
U6  - https://doi.org/10.1002/mrm.22054
SN  - 1522-2594
VL  - 62
IS  - 3
SP  - 822
EP  - 828
PB  - Wiley-Liss
CY  - New York
ER  - 
TY  - JOUR
A1  - Kob, Malte
A1  - Frauenrath, Tobias
T1  - A system for parallel measurement of glottis opening and larynx position
JF  - Biomedical Signal Processing and Control
N2  - The simultaneous assessment of glottal dynamics and larynx position can be beneficial for the diagnosis of disordered voice or speech production and swallowing. Up to now, methods either concentrate on assessment of the glottis opening using optical, acoustical or electrical (electroglottography, EGG) methods, or on visualisation of the larynx position using ultrasound, computer tomography or magnetic resonance imaging techniques.

The method presented here makes use of a time-multiplex measurement approach of space-resolved transfer impedances through the larynx. The fast sequence of measurements allows a quasi simultaneous assessment of both larynx position and EGG signal using up to 32 transmit–receive signal paths. The system assesses the dynamic opening status of the glottis as well as the vertical and back/forward motion of the larynx.

Two electrode-arrays are used for the measurement of the electrical transfer impedance through the neck in different directions. From the acquired data the global and individual conductivity is calculated as well as a 2D point spatial representation of the minimum impedance.

The position information is shown together with classical EGG signals allowing a synchronous visual assessment of glottal area and larynx position. A first application to singing voice analysis is presented that indicate a high potential of the method for use as a non-invasive tool in the diagnosis of voice, speech, and swallowing disorders.
KW  - EGG
KW  - Transfer impedance
KW  - Tomography
KW  - Larynx position
KW  - Voice assessment
Y1  - 2009
U6  - https://doi.org/10.1016/j.bspc.2009.03.004
SN  - 1746-8108
VL  - 4
IS  - 3
SP  - 221
EP  - 228
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - von Knobelsdorf-Brenkenhoff, Florian
A1  - Frauenrath, Tobias
A1  - Prothmann, Marcel
A1  - Dieringer, Matthias A.
A1  - Hezel, Fabian
A1  - Renz, Wolfgang
A1  - Kretschel, Kerstin
A1  - Niendorf, Thoralf
A1  - Schulz-Menger, Jeanette
T1  - Cardiac chamber quantification using magnetic resonance imaging at 7 Tesla—a pilot study
N2  - Objectives
Interest in cardiovascular magnetic resonance (CMR) at 7 T is motivated by the expected increase in spatial and temporal resolution, but the method is technically challenging. We examined the feasibility of cardiac chamber quantification at 7 T.

Methods
A stack of short axes covering the left ventricle was obtained in nine healthy male volunteers. At 1.5 T, steady-state free precession (SSFP) and fast gradient echo (FGRE) cine imaging with 7 mm slice thickness (STH) were used. At 7 T, FGRE with 7 mm and 4 mm STH were applied. End-diastolic volume, end-systolic volume, ejection fraction and mass were calculated.

Results
All 7 T examinations provided excellent blood/myocardium contrast for all slice directions. No significant difference was found regarding ejection fraction and cardiac volumes between SSFP at 1.5 T and FGRE at 7 T, while volumes obtained from FGRE at 1.5 T were underestimated. Cardiac mass derived from FGRE at 1.5 and 7 T was larger than obtained from SSFP at 1.5 T. Agreement of volumes and mass between SSFP at 1.5 T and FGRE improved for FGRE at 7 T when combined with an STH reduction to 4 mm.

Conclusions
This pilot study demonstrates that cardiac chamber quantification at 7 T using FGRE is feasible and agrees closely with SSFP at 1.5 T.
Y1  - 2010
U6  - https://doi.org/10.1007/s00330-010-1888-2
SN  - 0938-7994
VL  - 20
SP  - 2844
EP  - 2852
PB  - Springer
CY  - Berlin, Heidelberg
ER  - 
TY  - JOUR
A1  - Frauenrath, Tobias
A1  - Hezel, Fabian
A1  - Renz, Wolfgang
A1  - de Geyer d'Orth, Thibaut
A1  - Dieringer, Matthias
A1  - von Knobelsdorf-Brenkenhoff, Florian
A1  - Prothmann, Marcel
A1  - Schulz-Menger, Jeanette
A1  - Niendorf, Thoralf
T1  - Acoustic cardiac triggering: a practical solution for synchronization and gating of cardiovascular magnetic resonance at 7 Tesla
JF  - Journal of Cardiovascular Magnetic Resonance
N2  - Background
To demonstrate the applicability of acoustic cardiac triggering (ACT) for imaging of the heart at ultrahigh magnetic fields (7.0 T) by comparing phonocardiogram, conventional vector electrocardiogram (ECG) and traditional pulse oximetry (POX) triggered 2D CINE acquisitions together with (i) a qualitative image quality analysis, (ii) an assessment of the left ventricular function parameter and (iii) an examination of trigger reliability and trigger detection variance derived from the signal waveforms.

Results
ECG was susceptible to severe distortions at 7.0 T. POX and ACT provided waveforms free of interferences from electromagnetic fields or from magneto-hydrodynamic effects. Frequent R-wave mis-registration occurred in ECG-triggered acquisitions with a failure rate of up to 30% resulting in cardiac motion induced artifacts. ACT and POX triggering produced images free of cardiac motion artefacts. ECG showed a severe jitter in the R-wave detection. POX also showed a trigger jitter of approximately Δt = 72 ms which is equivalent to two cardiac phases. ACT showed a jitter of approximately Δt = 5 ms only. ECG waveforms revealed a standard deviation for the cardiac trigger offset larger than that observed for ACT or POX waveforms.

Image quality assessment showed that ACT substantially improved image quality as compared to ECG (image quality score at end-diastole: ECG = 1.7 ± 0.5, ACT = 2.4 ± 0.5, p = 0.04) while the comparison between ECG vs. POX gated acquisitions showed no significant differences in image quality (image quality score: ECG = 1.7 ± 0.5, POX = 2.0 ± 0.5, p = 0.34).

Conclusions
The applicability of acoustic triggering for cardiac CINE imaging at 7.0 T was demonstrated. ACT's trigger reliability and fidelity are superior to that of ECG and POX. ACT promises to be beneficial for cardiovascular magnetic resonance at ultra-high field strengths including 7.0 T.
KW  - Interval Time Series
KW  - Image Quality Score
KW  - Image Quality Assessment
KW  - Sound Pressure Level
KW  - Cardiovascular Magnetic Resonance
Y1  - 2010
U6  - https://doi.org/10.1186/1532-429X-12-67
SN  - 1532-429X
VL  - 12
IS  - 1
PB  - Elsevier
CY  - Amsterdam
ER  -