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25 results on '"Bol, G.H."'

8. EP-1624 First clinical experiences with SBRT on the 1.5 T MR-linac for pelvic lymph node oligometastases

Author

Werensteijn-Honingh, A.M., primary, Kroon, P.S., additional, Winkel, D., additional, Aalbers, E.M., additional, Van Asselen, B., additional, Bol, G.H., additional, Brown, K.J., additional, Eppinga, W.S.C., additional, Glitzner, M., additional, Breugel, E.N. De Groot-van, additional, Hackett, S.L., additional, Intven, M., additional, Kok, J.G.M., additional, Kotte, A.N., additional, Lagendijk, J.J.W., additional, Philippens, M.E.P., additional, Tijssen, R.H.N., additional, Wolthaus, J.W.H., additional, Woodings, S.J., additional, Raaymakers, B.W., additional, and Jürgenliemk-Schulz, I.M., additional

Published
2019
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9. Adaptive radiotherapy: The Elekta Unity MR-linac concept

Author

Winkel, D., Bol, G.H., Kroon, P.S., Asselen, B. van, Hackett, S.S., Werensteijn-Honingh, A.M., Intven, M.P.W., Eppinga, W.S.C., Tijssen, R.H.N., Kerkmeijer, L.G.W., Boer, H.C. de, Mook, S., Meijer, G.J, Hes, J., Willemsen-Bosman, M., Breugel, E.N. de Groot-van, Jurgenliemk-Schulz, I.M., Raaymakers, B.W., Winkel, D., Bol, G.H., Kroon, P.S., Asselen, B. van, Hackett, S.S., Werensteijn-Honingh, A.M., Intven, M.P.W., Eppinga, W.S.C., Tijssen, R.H.N., Kerkmeijer, L.G.W., Boer, H.C. de, Mook, S., Meijer, G.J, Hes, J., Willemsen-Bosman, M., Breugel, E.N. de Groot-van, Jurgenliemk-Schulz, I.M., and Raaymakers, B.W.

Abstract

Contains fulltext : 215382.pdf (publisher's version ) (Open Access), Background and purpose: The promise of the MR-linac is that one can visualize all anatomical changes during the course of radiotherapy and hence adapt the treatment plan in order to always have the optimal treatment. Yet, there is a trade-off to be made between the time spent for adapting the treatment plan against the dosimetric gain. In this work, the various daily plan adaptation methods will be presented and applied on a variety of tumour sites. The aim is to provide an insight in the behavior of the state-of-the-art 1.5T MRI guided on-line adaptive radiotherapy methods. Materials and methods: To explore the different available plan adaptation workflows and methods, we have simulated online plan adaptation for five cases with varying levels of inter-fraction motion, regions of interest and target sizes: prostate, rectum, esophagus and lymph node oligometastases (single and multiple target). The plans were evaluated based on the clinical dose constraints and the optimization time was measured. Results: The time needed for plan adaptation ranged between 17 and 485s. More advanced plan adaptation methods generally resulted in more plans that met the clinical dose criteria. Violations were often caused by insufficient PTV coverage or, for the multiple lymph node case, a too high dose to OAR in the vicinity of the PTV. With full online replanning it was possible to create plans that met all clinical dose constraints for all cases. Conclusion: Daily full online replanning is the most robust adaptive planning method for Unity. It is feasible for specific sites in clinically acceptable times. Faster methods are available, but before applying these, the specific use cases should be explored dosimetrically.

Published
2019

10. PO-0863: “First in Man” treatments with the MRI-linac provide clinical proof of the concept

Author

Jürgenliemk-Schulz, I.M., primary, Raaymakers, B.W., additional, Van Asselen, B., additional, Bol, G.H., additional, Brown, K.J., additional, Doornaert, P., additional, De Groot-van Breugel, E.N., additional, Hackett, S.L., additional, Kasperts, N., additional, Kiekebosch, I.H., additional, Kerkmeijer, L.G.W., additional, Kok, J.G.M., additional, Kotte, A.N.T., additional, Meijers, L.T.C., additional, Nomden, C.N., additional, Pais, B.R., additional, Philippens, M.E.P., additional, Sikkes, G.G., additional, Tersteeg, J.H.A., additional, Tijssen, R.H.N., additional, Wolthaus, J.W.H., additional, Woodings, S.J., additional, and Lagendijk, J.J.W., additional

Published
2018
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12. Periprostatic fat correlates with tumour aggressiveness in prostate cancer patients

Author

Roermund, J.G.H. van, Hinnen, K.A., Tolman, C.J., Bol, G.H., Witjes, J.A., Bosch, J.L.H.R., Kiemeney, L.A.L.M., and Vulpen, M. van

Subjects
Aetiology, screening and detection [ONCOL 5], Molecular epidemiology Aetiology, screening and detection [NCEBP 1]
Abstract

Contains fulltext : 97213.pdf (Publisher’s version ) (Closed access) STUDY TYPE: Prognostic (case series). LEVEL OF EVIDENCE: 4. What's known on the subject? and What does the study add? Nowadays more and more publications have been published about the topic prostate cancer aggressiveness and obesity with mixed results. However, most of the publications used the BMI as a marker for obesity, while the most metabolic active fat is the visceral fat. To learn more about these relations we measured and used the visceral fat in our paper. OBJECTIVE: To examine if the periprostatic fat measured on computed tomography (CT) correlates with advanced disease we examined patients who received radiotherapy for localized prostate cancer. Several USA reports found a positive association between obesity and prostate cancer aggressiveness. However, in recent European studies these conclusions were not confirmed. Studies concerning this issue have basically relied on body mass index (BMI), as a marker of general obesity. Visceral fat, however, is the most metabolically active and best measured on CT. PATIENTS AND METHODS: In 932 patients, who were treated with external radiotherapy (N=311) or brachytherapy (N=621) for their T1-3N0M0 prostate cancer, different fat measurements (periprostatic fat, subcutaneous fat thickness) were performed on a CT. Associations between the different fat measurements and risk of having high-risk (according to Ash et al., PSA>20 or Gleason score>/=8 or T3) disease was measured. RESULTS: The median age (IQR) was 67.0 years (62.0-71.0) and median BMI (IQR) was 25.8 (24.2-28.3). Logistic regression analyses, adjusted for age, revealed a significant association between periprostatic fat density (PFD) and risk of having a high risk disease. (Odds ratio [95% CI] 1.06 [1.04-1.08], P

Published
2011
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13. OC-0163: Online workflow for the First-in-Man study on bone metastases at the MRI-linear accelerator

Author

Meijers, L.T.C., primary, Hoogcarspel, S.J., additional, Kotte, A.N.T.J., additional, Nomden, C.N.N., additional, Sikkes, G.G., additional, Kiekebosch, I.H., additional, Groot de, E.N., additional, Bol, G.H., additional, Asselen van, B., additional, Jurgenliemk-Schulz, I.M., additional, Kerkmeijer, L.G.W., additional, and Raaymakers, B.W., additional

Published
2017
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14. PO-0905: (Semi-)Automatic contouring strategies for rectal boost treatment on the MR-Linac

Author

Nomden, C.N., primary, Intven, M.P.W., additional, Kotte, A.N.T.J., additional, Kiekebosch, I.H., additional, Mook, S., additional, Jürgenliemk-Schulz, I.M., additional, Sikkes, G.G., additional, Meijers, L.T.C., additional, De Groot, E.N., additional, Bol, G.H., additional, Van Asselen, B., additional, Kerkmeijer, L.G.W., additional, and Raaymakers, B.W., additional

Published
2017
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15. Towards online MRI-guided radiotherapy

Author

Bol, G.H., Lagendijk, J.J.W., Raaymakers, B.W., and University Utrecht

Subjects
VOI delineation, virtual couch shift, IMRT, Monte-Carlo, ERE, MR-linac, radiotherapy, MRI
Abstract

First, we present two offline position verification methods which can be used in radiotherapy for detecting the position of the bony anatomy of a patient automatically with portal imaging, even if every single portal image of each segment of an (IMRT) treatment beam contains insufficient matching information. Additional position verification fields will no longer be necessary, which speeds up the treatment and reduces the total dose to the patient. Second, a tool is described which enhances the way tumors can be delineated by using multiple imaging modalities. This tool is especially useful when multiple MRI sequences are available as well as the standard planning CT. We also developed a marker which is visible on MRI and on EPID. A separate CT for detecting the markers is no longer needed. The gold marker with steel core can be detected on various MRI sequences, reducing the overall systematic radiotherapy treatment error. The MRI linear accelerator (MRL) facilitates continuous patient anatomy updates regarding translations, rotations and deformations of targets and OAR during a course of radiotherapy. Accounting for this information demands high speed, online IMRT re-optimization. Therefore, we developed a fast IMRT optimization system which combines a GPU based Monte-Carlo dose calculation engine for online beamlet generation (GPUMCD) and a fast inverse dose optimization algorithm (FIDO). We show that for the presented cases the beamlets generation and optimization routines are fast enough for online IMRT planning. Furthermore, there is no influence of the magnetic field on plan quality and complexity, and equal optimization constraints at 0T and 1.5T lead to almost identical dose distributions. One of the most significant effects of the transverse magnetic field on the dose distribution occur around air cavities: the electron return effect (ERE). We investigated the effects of non-stationary spherical air cavities on IMRT dose delivery in 0.35T and 1.5T transverse magnetic fields by using Monte Carlo simulations. Our observations show the intrinsic ERE compensation by equidistant and opposing beam configurations for moving spherical air cavities within the target area. IMRT gives some additional compensation, but only in the case of correct positioning of the air cavity according to the IMRT compensation. For air cavities appearing or disappearing during a fraction this correct positioning is absent and gating or plan re-optimization should be used. Finally, we introduce an online 'virtual couch shift' (VCS): we translate and/or rotate the pre-treatment dose distribution to compensate for the changes in patient anatomy and generate a new plan which delivers the transformed dose distribution automatically. The VCS is the first step towards compensating all anatomical changes (translation, rotations, and deformations) by online re-optimization of the IMRT dose distribution.

Published
2015

20. Periprostatic fat measured on computed tomography as a marker for prostate cancer aggressiveness.

Author

Roermund, J.G.H. van, Bol, G.H., Witjes, J.A., Ruud Bosch, J.L., Kiemeney, L.A.L.M., Vulpen, M. van, Roermund, J.G.H. van, Bol, G.H., Witjes, J.A., Ruud Bosch, J.L., Kiemeney, L.A.L.M., and Vulpen, M. van

Abstract

01 december 2010, Contains fulltext : 89797.pdf (publisher's version ) (Closed access), OBJECTIVE: Several reports found that obesity was associated with prostate cancer (PC) aggressiveness among men treated with radical prostatectomy or radiotherapy. Studies concerning this issue have basically relied on body mass index (BMI), as a marker for general obesity. Because visceral fat is the most metabolic active fat, we sought to evaluate if periprostatic fat measured on a computed tomography (CT) is a better marker than BMI to predict PC aggressiveness in a Dutch population who underwent brachytherapy for localized PC. PATIENTS AND METHODS: Of the 902 patients who underwent brachytherapy, 725 CT scans were available. Subcutaneous fat thickness (CFT), periprostatic fat area (cm(2)) and fat-density (%) were determined on the CT scan. Patients were stratified into three groups: <25, 25-75 and >75 percentile of the fat-density. Associations between the three fat-density subgroups and BMI and PC aggressiveness were examined. RESULTS: 237 patients were classified as having normal weight (37.2%), 320 as overweight (50.2%) and 80 as obese (12.6%). There was a strong significant association between BMI and fat-density and CFT. The strongest correlation was seen between BMI and CFT (Pearson r coefficient = 0.71). Logistic regression analysis revealed no statistically significant association between the different fat measurements and the risk of having a high-risk disease. CONCLUSIONS: Periprostatic fat and fat-density as measured with CT were not correlated with PC aggressiveness in patients receiving brachytherapy. However, 31% of the patients with a normal BMI had a fat-density of >75 percentile of the periprostatic fat-density.

Published
2010

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