Daniel (Danny) Ruijters is employed by Philips Healthcare since 2001. Currently he is working as Principal Scientist in the domain of 3D Imaging Applications at the iXR innovation department in Best, the Netherlands. His responsibilities comprise heading the interventional neurological radiology study, developing interventional image guided interventions and therapy prototypes, and staying in touch with the scientific developments in this field. He received his engineering degree at the University of Technology Aachen (RWTH), and performed his master thesis at ENST in Paris. Next to his work for Philips, he has performed a joint PhD thesis at the Katholieke Universiteit Leuven and the University of Technology Eindhoven (TU/e). His primary research interest areas are medical image processing, 3D visualization, image registration, fast algorithms and hardware acceleration.
Poster: "ECR 2008 / C-591 / XperGuide: C-arm needle guidance" by: "D. Ruijters1, L... more Poster: "ECR 2008 / C-591 / XperGuide: C-arm needle guidance" by: "D. Ruijters1, L. Spelle2, J. Moret2, D. Babic1, R. Homan1, P. Mielekamp1, B. M. ter Haar Romeny3, P. Suetens4; 1Best/NL, 2Paris/FR, 3Eindhoven/NL, 4Leuven/BE"
BackgroundX‐ray digital subtraction angiography (DSA) is the imaging modality for peri‐procedural... more BackgroundX‐ray digital subtraction angiography (DSA) is the imaging modality for peri‐procedural guidance and treatment evaluation in (neuro‐) vascular interventions. Perfusion image construction from DSA, as a means of quantitatively depicting cerebral hemodynamics, has been shown feasible. However, the quantitative property of perfusion DSA has not been well studied.PurposeTo comparatively study the independence of deconvolution‐based perfusion DSA with respect to varying injection protocols, as well as its sensitivity to alterations in brain conditions.MethodsWe developed a deconvolution‐based algorithm to compute perfusion parametric images from DSA, including cerebral blood volume (CBV), cerebral blood flow (CBF), time to maximum (Tmax), and mean transit time (MTT) and applied it to DSA sequences obtained from two swine models. We also extracted the time intensity curve (TIC)‐derived parameters, that is, area under the curve (AUC), peak concentration of the curve, and the time to peak (TTP) from these sequences. Deconvolution‐based parameters were quantitatively compared to TIC‐derived parameters in terms of consistency upon variations in injection profile and time resolution of DSA, as well as sensitivity to alterations of cerebral condition.ResultsComparing to TIC‐derived parameters, the standard deviation (SD) of deconvolution‐based parameters (normalized with respect to the mean) are two to five times smaller, indicating that they are more consistent across different injection protocols and time resolutions. Upon ischemic stroke induced in a swine model, the sensitivities of deconvolution‐based parameters are equal to, if not higher than, those of TIC‐derived parameters.ConclusionsIn comparison to TIC‐derived parameters, deconvolution‐based perfusion imaging in DSA shows significantly higher quantitative reliability against variations in injection protocols across different time resolutions, and is sensitive to alterations in cerebral hemodynamics. The quantitative nature of perfusion angiography may allow for objective treatment assessment in neurovascular interventions.
BackgroundDesign of flow-diverter stents for flexibility, tractability, and low profile limits th... more BackgroundDesign of flow-diverter stents for flexibility, tractability, and low profile limits their radiopacity on conventional digital subtraction angiography. Cone-beam computed tomography (CBCT) offers higher spatial resolution for the evaluation of flow-diverter stents. However, CBCT requires optimal dilution and timing of contrast medium for simultaneous visualization of the stent, arterial lumen, and vessel wall. There are only limited data on the effects of different contrast dilutions on CBCT image quality in neurointerventional applications.Materials and methodsIn our institution, intra-arterial CBCTs were acquired during stent deployment and at follow-ups with 10% diluted contrast. We had recently started acquiring intra-arterial CBCTs with non-diluted contrast. Retrospective analysis of our flow-diverter data identified eight cases with different aneurysm locations who had intra-arterial CBCT with 10% diluted contrast immediately after flow-diverter stent deployment and with non-diluted contrast technique during follow-ups. For each case, the image quality between diluted and non-diluted contrast techniques was compared qualitatively by assessing stent visualization and quantitatively by plotting gray-scale intensity values along the vessel lumen.ResultsIn two sets of CBCT images per each case, there was no substantial difference between diluted and non-diluted CBTC techniques for the evaluation of stent architecture and lumen opacification. Gray-scale intensity values perpendicular to the lumen revealed similar intensity values along the neighboring parenchyma, vessel wall, and lumen for the two different contrast techniques.ConclusionIntra-arterial CBCT angiography can be performed without contrast dilution and still achieve adequate image quality in certain cerebral aneurysms treated with flow diverter. The non-diluted contrast technique avoids the time loss during preparation of diluted contrast and installation of diluted contrast to the injector in angiography suites with a single power injector.
Intracranial vessel perforation is a peri-procedural complication during endovascular therapy (EV... more Intracranial vessel perforation is a peri-procedural complication during endovascular therapy (EVT). Prompt recognition is important as its occurrence is strongly associated with unfavorable treatment outcomes. However, perforations can be hard to detect because they are rare, can be subtle, and the interventionalist is working under time pressure and focused on treatment of vessel occlusions. Automatic detection holds potential to improve rapid identification of intracranial vessel perforation. In this work, we present the first study on automated perforation detection and localization on X-ray digital subtraction angiography (DSA) image series. We adapt several state-of-the-art single-frame detectors and further propose temporal modules to learn the progressive dynamics of contrast extravasation. Application-tailored loss function and post-processing techniques are designed. We train and validate various automated methods using two national multi-center datasets (i.e., MR CLEAN Registry and MR CLEAN-NoIV Trial), and one international multi-trial dataset (i.e., the HERMES collaboration). With ten-fold cross-validation, the proposed methods achieve an area under the curve (AUC) of the receiver operating characteristic of 0.93 in terms of series level perforation classification. Perforation localization precision and recall reach 0.83 and 0.70 respectively. Furthermore, we demonstrate that the proposed automatic solutions perform at similar level as an expert radiologist.
A Dual-Energy CT (DECT) with a spectral detector greatly extends the capabilities of CT by incorp... more A Dual-Energy CT (DECT) with a spectral detector greatly extends the capabilities of CT by incorporating energy-dependent information of the X-ray attenuation. In order to fully exploit DECT capabilities, it is required to perform a process known as spectral decomposition. However, this process is sensitive to noise, suffers from reduced photon count per layer in DECT scans and generates anti-correlated noise in the estimated material specific images. In order to overcome these problems, the Anti-Correlated Rudin, Osher and Fatemi (AC-ROF) model is applied for noise reduction, exploiting the relationship between the material-specific images. However, this model deteriorates the structural information with intense noise. In this paper we propose to extend this method by integrating it into an iterative reconstruction procedure to improve the noise reduction performance. The resulting algorithm is called Iterative Reconstruction AC-ROF, or IR-AC-ROF. We have tested AC-ROF and IR-AC-RO...
In this study, a novel anthropomorphic head phantom for quantitative image quality assessment in ... more In this study, a novel anthropomorphic head phantom for quantitative image quality assessment in cone beam computed tomography (CBCT) is proposed. The phantom is composed of tissue equivalent materials (TEMs) which are suitable for cost-efficient fabrication methods such as silicone casting and 3D printing. A monocalcium phosphate/gypsum mixture (MCPHG), nylon and a silyl modified polymer gel (SMP) are proposed as bone, muscle and brain equivalent materials respectively. The TEMs were evaluated for their radiodensity in terms of Hounsfield Units (HU) and their X-ray scatter characteristics. The median radiodensity and inter quartile range (IQR) of the MCPHG and SMP were found to be within the range of the theoretical radiodensity for bone and brain tissue: 922 (IQR = 156) and 47 (IQR = 7) HU respectively. The median radiodensity of nylon was slightly outside of the HU range of muscle tissue, but within the HU range of a combination of muscle and adipose tissue: -18 (IQR = 40) HU. Th...
Poster: "ECR 2008 / C-591 / XperGuide: C-arm needle guidance" by: "D. Ruijters1, L... more Poster: "ECR 2008 / C-591 / XperGuide: C-arm needle guidance" by: "D. Ruijters1, L. Spelle2, J. Moret2, D. Babic1, R. Homan1, P. Mielekamp1, B. M. ter Haar Romeny3, P. Suetens4; 1Best/NL, 2Paris/FR, 3Eindhoven/NL, 4Leuven/BE"
BackgroundX‐ray digital subtraction angiography (DSA) is the imaging modality for peri‐procedural... more BackgroundX‐ray digital subtraction angiography (DSA) is the imaging modality for peri‐procedural guidance and treatment evaluation in (neuro‐) vascular interventions. Perfusion image construction from DSA, as a means of quantitatively depicting cerebral hemodynamics, has been shown feasible. However, the quantitative property of perfusion DSA has not been well studied.PurposeTo comparatively study the independence of deconvolution‐based perfusion DSA with respect to varying injection protocols, as well as its sensitivity to alterations in brain conditions.MethodsWe developed a deconvolution‐based algorithm to compute perfusion parametric images from DSA, including cerebral blood volume (CBV), cerebral blood flow (CBF), time to maximum (Tmax), and mean transit time (MTT) and applied it to DSA sequences obtained from two swine models. We also extracted the time intensity curve (TIC)‐derived parameters, that is, area under the curve (AUC), peak concentration of the curve, and the time to peak (TTP) from these sequences. Deconvolution‐based parameters were quantitatively compared to TIC‐derived parameters in terms of consistency upon variations in injection profile and time resolution of DSA, as well as sensitivity to alterations of cerebral condition.ResultsComparing to TIC‐derived parameters, the standard deviation (SD) of deconvolution‐based parameters (normalized with respect to the mean) are two to five times smaller, indicating that they are more consistent across different injection protocols and time resolutions. Upon ischemic stroke induced in a swine model, the sensitivities of deconvolution‐based parameters are equal to, if not higher than, those of TIC‐derived parameters.ConclusionsIn comparison to TIC‐derived parameters, deconvolution‐based perfusion imaging in DSA shows significantly higher quantitative reliability against variations in injection protocols across different time resolutions, and is sensitive to alterations in cerebral hemodynamics. The quantitative nature of perfusion angiography may allow for objective treatment assessment in neurovascular interventions.
BackgroundDesign of flow-diverter stents for flexibility, tractability, and low profile limits th... more BackgroundDesign of flow-diverter stents for flexibility, tractability, and low profile limits their radiopacity on conventional digital subtraction angiography. Cone-beam computed tomography (CBCT) offers higher spatial resolution for the evaluation of flow-diverter stents. However, CBCT requires optimal dilution and timing of contrast medium for simultaneous visualization of the stent, arterial lumen, and vessel wall. There are only limited data on the effects of different contrast dilutions on CBCT image quality in neurointerventional applications.Materials and methodsIn our institution, intra-arterial CBCTs were acquired during stent deployment and at follow-ups with 10% diluted contrast. We had recently started acquiring intra-arterial CBCTs with non-diluted contrast. Retrospective analysis of our flow-diverter data identified eight cases with different aneurysm locations who had intra-arterial CBCT with 10% diluted contrast immediately after flow-diverter stent deployment and with non-diluted contrast technique during follow-ups. For each case, the image quality between diluted and non-diluted contrast techniques was compared qualitatively by assessing stent visualization and quantitatively by plotting gray-scale intensity values along the vessel lumen.ResultsIn two sets of CBCT images per each case, there was no substantial difference between diluted and non-diluted CBTC techniques for the evaluation of stent architecture and lumen opacification. Gray-scale intensity values perpendicular to the lumen revealed similar intensity values along the neighboring parenchyma, vessel wall, and lumen for the two different contrast techniques.ConclusionIntra-arterial CBCT angiography can be performed without contrast dilution and still achieve adequate image quality in certain cerebral aneurysms treated with flow diverter. The non-diluted contrast technique avoids the time loss during preparation of diluted contrast and installation of diluted contrast to the injector in angiography suites with a single power injector.
Intracranial vessel perforation is a peri-procedural complication during endovascular therapy (EV... more Intracranial vessel perforation is a peri-procedural complication during endovascular therapy (EVT). Prompt recognition is important as its occurrence is strongly associated with unfavorable treatment outcomes. However, perforations can be hard to detect because they are rare, can be subtle, and the interventionalist is working under time pressure and focused on treatment of vessel occlusions. Automatic detection holds potential to improve rapid identification of intracranial vessel perforation. In this work, we present the first study on automated perforation detection and localization on X-ray digital subtraction angiography (DSA) image series. We adapt several state-of-the-art single-frame detectors and further propose temporal modules to learn the progressive dynamics of contrast extravasation. Application-tailored loss function and post-processing techniques are designed. We train and validate various automated methods using two national multi-center datasets (i.e., MR CLEAN Registry and MR CLEAN-NoIV Trial), and one international multi-trial dataset (i.e., the HERMES collaboration). With ten-fold cross-validation, the proposed methods achieve an area under the curve (AUC) of the receiver operating characteristic of 0.93 in terms of series level perforation classification. Perforation localization precision and recall reach 0.83 and 0.70 respectively. Furthermore, we demonstrate that the proposed automatic solutions perform at similar level as an expert radiologist.
A Dual-Energy CT (DECT) with a spectral detector greatly extends the capabilities of CT by incorp... more A Dual-Energy CT (DECT) with a spectral detector greatly extends the capabilities of CT by incorporating energy-dependent information of the X-ray attenuation. In order to fully exploit DECT capabilities, it is required to perform a process known as spectral decomposition. However, this process is sensitive to noise, suffers from reduced photon count per layer in DECT scans and generates anti-correlated noise in the estimated material specific images. In order to overcome these problems, the Anti-Correlated Rudin, Osher and Fatemi (AC-ROF) model is applied for noise reduction, exploiting the relationship between the material-specific images. However, this model deteriorates the structural information with intense noise. In this paper we propose to extend this method by integrating it into an iterative reconstruction procedure to improve the noise reduction performance. The resulting algorithm is called Iterative Reconstruction AC-ROF, or IR-AC-ROF. We have tested AC-ROF and IR-AC-RO...
In this study, a novel anthropomorphic head phantom for quantitative image quality assessment in ... more In this study, a novel anthropomorphic head phantom for quantitative image quality assessment in cone beam computed tomography (CBCT) is proposed. The phantom is composed of tissue equivalent materials (TEMs) which are suitable for cost-efficient fabrication methods such as silicone casting and 3D printing. A monocalcium phosphate/gypsum mixture (MCPHG), nylon and a silyl modified polymer gel (SMP) are proposed as bone, muscle and brain equivalent materials respectively. The TEMs were evaluated for their radiodensity in terms of Hounsfield Units (HU) and their X-ray scatter characteristics. The median radiodensity and inter quartile range (IQR) of the MCPHG and SMP were found to be within the range of the theoretical radiodensity for bone and brain tissue: 922 (IQR = 156) and 47 (IQR = 7) HU respectively. The median radiodensity of nylon was slightly outside of the HU range of muscle tissue, but within the HU range of a combination of muscle and adipose tissue: -18 (IQR = 40) HU. Th...
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Papers by Daniel Ruijters