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Your search keyword '"Muinck Keizer, D.M."' showing total 5 results
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5 results on '"Muinck Keizer, D.M."'

3. Dosimetric impact of soft-tissue based intrafraction motion from 3D cine-MR in prostate SBRT

Author

Muinck-Keizer, D.M. de, Kontaxis, C., Kerkmeijer, L.G.W., Voorst-van Zyp, J.R.N. van der, Berg, C.A.T. van den, Raaymakers, B.W., Lagendijk, J.J., Boer, J.C. den, Muinck-Keizer, D.M. de, Kontaxis, C., Kerkmeijer, L.G.W., Voorst-van Zyp, J.R.N. van der, Berg, C.A.T. van den, Raaymakers, B.W., Lagendijk, J.J., and Boer, J.C. den

Abstract

Item does not contain fulltext, To investigate the dosimetric impact of intrafraction translation and rotation motion of the prostate, as extracted from daily acquired post-treatment 3D cine-MR based on soft-tissue contrast, in extremely hypofractionated (SBRT) prostate patients. Accurate dose reconstruction is performed by using a prostate intrafraction motion trace which is obtained with a soft-tissue based rigid registration method on 3D cine-MR dynamics with a temporal resolution of 11 s. The recorded motion of each time-point was applied to the planning CT, resulting in the respective dynamic volume used for dose calculation. For each treatment fraction, the treatment delivery record was generated by proportionally splitting the plan into 11 s intervals based on the delivered monitor units. For each fraction the doses of all partial plan/dynamic volume combinations were calculated and were summed to lead to the motion-affected fraction dose. Finally, for each patient the five fraction doses were summed, yielding the total treatment dose. Both daily and total doses were compared to the original reference dose of the respective patient to assess the impact of the intrafraction motion. Depending on the underlying motion of the prostate, different types of motion-affected dose distributions were observed. The planning target volumes (PTVs) ensured CTV_30 (seminal vesicles) D99% coverage for all patients, CTV_35 (prostate corpus) coverage for 97% of the patients and GTV_50 (local boost) for 83% of the patients when compared against the strict planning target D99% value. The dosimetric impact due to prostate intrafraction motion in extremely hypofractionated treatments was determined. The presented study is an essential step towards establishing the actual delivered dose to the patient during radiotherapy fractions.

Published
2020

5. Segmentation and determination of joint space width in foot radiographs

Author

Schenk, O., de Muinck Keizer, D.M., Bernelot Moens, H.J., Slump, C.H., Tourassi, Georgia D., and Armato, Samuel G.

Subjects
030203 arthritis & rheumatology, Orthodontics, AAM, JSW, business.industry, Computer science, Radiography, Image segmentation, medicine.disease, 030218 nuclear medicine & medical imaging, Active appearance model, 03 medical and health sciences, 0302 clinical medicine, Segmentation, Rheumatoid arthritis, medicine, Rheumatology department, business, Joint (geology), RA, Foot (unit)
Abstract

Joint damage in rheumatoid arthritis is frequently assessed using radiographs of hands and feet. Evaluation includes measurements of the joint space width (JSW) and detection of erosions. Current visual scoring methods are timeconsuming and subject to inter- and intra-observer variability. Automated measurement methods avoid these limitations and have been fairly successful in hand radiographs. This contribution aims at foot radiographs. Starting from an earlier proposed automated segmentation method we have developed a novel model based image analysis algorithm for JSW measurements. This method uses active appearance and active shape models to identify individual bones. The model compiles ten submodels, each representing a specific bone of the foot (metatarsals 1-5, proximal phalanges 1-5). We have performed segmentation experiments using 24 foot radiographs, randomly selected from a large database from the rheumatology department of a local hospital: 10 for training and 14 for testing. Segmentation was considered successful if the joint locations are correctly determined. Segmentation was successful in only 14%. To improve results a step-by-step analysis will be performed. We performed JSW measurements on 14 randomly selected radiographs. JSW was successfully measured in 75%, mean and standard deviation are 2.30±0.36mm. This is a first step towards automated determination of progression of RA and therapy response in feet using radiographs.

Published
2016

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