Ralf Gutjahr
Technische Universität München
Imaging phantomOpticsPhysicsBiomedical engineeringArtificial intelligenceBilateral filterPixelNoise reductionPattern recognitionEnergy (signal processing)Materials scienceImage resolutionScannerPhoton countingNuclear medicineComputer scienceComputed tomographyImage qualityMedicineDetector
31Publications
7H-index
344Citations
Publications 23
Newest
#1Andrea Ferrero (Mayo Clinic)H-Index: 11
#2Ralf Gutjahr (TUM: Technische Universität München)H-Index: 7
Last. Cynthia H. McCollough (Mayo Clinic)H-Index: 92
view all 5 authors...
Rational and Objectives This study aims to investigate the performance of a whole-body, photon-counting detector (PCD) computed tomography (CT) system in differentiating urinary stone composition. Materials and Methods Eighty-seven human urinary stones with pure mineral composition were placed in four anthropomorphic water phantoms (35–50 cm lateral dimension) and scanned on a PCD-CT system at 100, 120, and 140 kV. For each phantom size, tube current was selected to match CTDIvol (volume CT dose...
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#1Wei Zhou (Mayo Clinic)H-Index: 14
#2J. Montoya (Mayo Clinic)H-Index: 4
Last. Shuai Leng (Mayo Clinic)H-Index: 57
view all 8 authors...
An ultra-high resolution (UHR) mode, with a detector pixel size of 0.25 mm×0.25 mm relative to isocenter, has been implemented on a whole body research photon-counting detector (PCD) computed tomography (CT) system. Twenty synthetic lung nodules were scanned using UHR and conventional resolution (macro) modes and reconstructed with medium and very sharp kernels. Linear regression was used to compare measured nodule volumes from CT images to reference volumes. The full-width-at-half-maximum of th...
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#1Christoph Polster (LMU: Ludwig Maximilian University of Munich)H-Index: 5
#2Ralf Gutjahr (TUM: Technische Universität München)H-Index: 7
Last. Olaf Dietrich (LMU: Ludwig Maximilian University of Munich)H-Index: 52
view all 8 authors...
Photon-counting detectors in computed tomography (CT) allow for measuring the energy of the incident xray photons within certain energy windows. This information can be used to enhance contrast or reconstruct CT images of different material bases. Compared to energy-integrating CT-detectors, pixel dimensions have to be smaller to limit the negative effect of pulse pile-up at high X-ray fluxes. Unfortunately, reducing the pixel size leads to increased K-escape and charge sharing effects. As a con...
Source
#1Wei Zhou (Mayo Clinic)H-Index: 14
#2J. Montoya (Mayo Clinic)H-Index: 4
Last. Shuai Leng (Mayo Clinic)H-Index: 57
view all 8 authors...
A new ultra high-resolution (UHR) mode has been implemented on a whole body photon counting-detector (PCD) CT system. The UHR mode has a pixel size of 0.25 mm by 0.25 mm at the iso-center, while the conventional (macro) mode is limited to 0.5 mm by 0.5 mm. A set of synthetic lung nodules (two shapes, five sizes, and two radio-densities) was scanned using both the UHR and macro modes and reconstructed with 2 reconstruction kernels (4 sets of images in total). Linear regression analysis was perfor...
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#1Ralf Gutjahr (TUM: Technische Universität München)H-Index: 7
#2Christoph Polster (Siemens)H-Index: 5
Last. T. G. Flohr (Siemens)H-Index: 1
view all 10 authors...
This study evaluates the capabilities of a whole-body photon counting CT system to differentiate between four common kidney stone materials, namely uric acid (UA), calcium oxalate monohydrate (COM), cystine (CYS), and apatite (APA) ex vivo. Two different x-ray spectra (120 kV and 140 kV) were applied and two acquisition modes were investigated. The macro-mode generates two energy threshold based image-volumes and two energy bin based image-volumes. In the chesspattern-mode four energy thresholds...
Source
#1Andrea Ferrero (Mayo Clinic)H-Index: 11
#2Ralf Gutjahr (TUM: Technische Universität München)H-Index: 7
Last. Cynthia H. McCollough (Mayo Clinic)H-Index: 92
view all 10 authors...
In addition to the standard-resolution (SR) acquisition mode, a high-resolution (HR) mode is available on a research photon-counting-detector (PCD) whole-body CT system. In the HR mode each detector consists of a 2x2 array of 0.225 mm x 0.225 mm subpixel elements. This is in contrast to the SR mode that consists of a 4x4 array of the same subelements, and results in 0.25 mm isotropic resolution at iso-center for the HR mode. In this study, we quantified ex vivo the capabilities of the HR mode to...
Source
#1Shuai Leng (Mayo Clinic)H-Index: 57
#2Ralf Gutjahr (TUM: Technische Universität München)H-Index: 7
Last. Cynthia H. McCollough (Mayo Clinic)H-Index: 92
view all 9 authors...
Two ultra-high-resolution (UHR) imaging modes, each with two energy thresholds, were implemented on a research, whole-body photon-counting-detector (PCD) CT scanner, referred to as sharp and UHR, respectively. The UHR mode has a pixel size of 0.25 mm at iso-center for both energy thresholds, with a collimation of 32 × 0.25 mm. The sharp mode has a 0.25 mm pixel for the low-energy threshold and 0.5 mm for the high-energy threshold, with a collimation of 48 × 0.25 mm. Kidney stones with mixed mine...
Source
#1Ralf Gutjahr (TUM: Technische Universität München)H-Index: 7
#2Ahmed F. HalaweishH-Index: 17
Last. Cynthia H. McColloughH-Index: 92
view all 10 authors...
ObjectivesThe purpose of this work was to measure and compare the iodine contrast-to-noise ratio (CNR) between a commercial energy-integrating detector (EID) computed tomography (CT) system and a photon-counting detector (PCD) CT scanner capable of human imaging at clinical dose rates, as well as to
Source
#1Christoph Polster (LMU: Ludwig Maximilian University of Munich)H-Index: 5
#2Katharina Hahn (Siemens)H-Index: 4
Last. T. G. Flohr (Siemens)H-Index: 1
view all 7 authors...
Photon counting detectors in computed tomography facilitate measurements of spectral distributions of detected X-ray quanta in discrete energy bins. Along with the dependency on wavelength and atomic number of the mass attenuation coefficient, this information allows for reconstruction of CT images of different material bases. Decomposition of two materials is considered standard in today’s dual-energy techniques. With photon-counting detectors the decomposition of more than two materials become...
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#1Ralf Gutjahr (TUM: Technische Universität München)H-Index: 7
#2Christoph Polster (LMU: Ludwig Maximilian University of Munich)H-Index: 5
Last. Bernhard Krauss (Siemens)H-Index: 34
view all 12 authors...
The energy resolving capabilities of Photon Counting Detectors (PCD) in Computed Tomography (CT) facilitate energy-sensitive measurements. The provided image-information can be processed with Dual Energy and Multi Energy algorithms. A research PCD-CT firstly allows acquiring images with a close to clinical configuration of both the X-ray tube and the CT-detector. In this study, two algorithms (Material Decomposition and Virtual Non-Contrast-imaging (VNC)) are applied on a data set acquired from ...
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