{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T01:42:21Z","timestamp":1760060541498,"version":"build-2065373602"},"reference-count":46,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2025,9,9]],"date-time":"2025-09-09T00:00:00Z","timestamp":1757376000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Applied Sciences"],"abstract":"<jats:p>To directly address the important issue of MRI geometric distortions in stereotactic radiosurgery (SRS) planning, we performed a phantom study of sequence acquisition optimization. This study analyzed, in particular, the effects of clinically relevant gadolinium (Gd) concentration as filling solution for the phantom, as well as phase encoding reversal direction and flip angle on distortion. We created a rigid geometric grid phantom with 840 fiducial markers for distortion quantification on a 3T MRI scanner. To choose the optimal filling solution, an anthropomorphic RANDO phantom was employed, and 1 mmol\/L gadolinium was chosen due to clinical relevance. An automated Python-based software (version 3.7.1) was developed for efficient detection and matching of phantom inserts between MRI and CT scans. A series of MRI acquisition parameter optimizations were systematically evaluated. The standard SRS protocol exhibited the highest average distortion of 1.301 mm. Notably, reversing the phase-encoding direction to anterior\u2013posterior (AP) reduced the mean distortion to 0.725 mm, a 44.27% decrease, while the maximum distortion was reduced by 15.65%. The AP phase sequence maintained acquisition time, SAR, SNR, and CNR within acceptable limits. Additional distortion reduction was achieved by increasing the flip angle from 12\u00b0 to 18\u00b0. In this work, we succeeded in significantly reducing the mean distortion observed in phantom images. As the gadolinium concentration used in the phantom is clinically similar to the gadolinium concentration observed in patients undergoing MRI scans with contrast agents, the achieved distortion reduction is prospectively reproducible in patients.<\/jats:p>","DOI":"10.3390\/app15189864","type":"journal-article","created":{"date-parts":[[2025,9,10]],"date-time":"2025-09-10T12:27:41Z","timestamp":1757507261000},"page":"9864","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Minimizing 3T MRI Geometric Distortions for Stereotactic Radiosurgery via Anterior\u2013Posterior Phase Encoding\u2013A Phantom Study"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6122-3238","authenticated-orcid":false,"given":"Bernardo","family":"Campilho","sequence":"first","affiliation":[{"name":"Department of Physics and Astronomy, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal"},{"name":"High-Field MR Center, Center for Medical Physics and BME, Medical University of Vienna, 1009 Vienna, Austria"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0056-6034","authenticated-orcid":false,"given":"Sofia","family":"Silva","sequence":"additional","affiliation":[{"name":"Medical Physics, Radiobiology and Radiation Protection Group, IPO Porto Research Center (CI-IPO), Portuguese Oncology Institute of Porto (IPO\/Porto), 4200-072 Porto, Portugal"},{"name":"Medical Physics Department, Portuguese Oncology Institute of Coimbra, 3000-075 Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9863-2078","authenticated-orcid":false,"given":"Sara","family":"Pinto","sequence":"additional","affiliation":[{"name":"Medical Physics, Radiobiology and Radiation Protection Group, IPO Porto Research Center (CI-IPO), Portuguese Oncology Institute of Porto (IPO\/Porto), 4200-072 Porto, Portugal"},{"name":"Medical Physics Department, Portuguese Oncology Institute of Porto (IPO\/Porto), 4200-072 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3962-4040","authenticated-orcid":false,"given":"Pedro","family":"Conde","sequence":"additional","affiliation":[{"name":"Medical Physics, Radiobiology and Radiation Protection Group, IPO Porto Research Center (CI-IPO), Portuguese Oncology Institute of Porto (IPO\/Porto), 4200-072 Porto, Portugal"},{"name":"Radiotherapy Department, Portuguese Oncology Institute of Porto (IPO\/Porto), 4200-072 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7078-7257","authenticated-orcid":false,"given":"Joana","family":"Lencart","sequence":"additional","affiliation":[{"name":"Medical Physics, Radiobiology and Radiation Protection Group, IPO Porto Research Center (CI-IPO), Portuguese Oncology Institute of Porto (IPO\/Porto), 4200-072 Porto, Portugal"},{"name":"Medical Physics Department, Portuguese Oncology Institute of Porto (IPO\/Porto), 4200-072 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7574-7630","authenticated-orcid":false,"given":"Bruno","family":"Mendes","sequence":"additional","affiliation":[{"name":"Medical Physics, Radiobiology and Radiation Protection Group, IPO Porto Research Center (CI-IPO), Portuguese Oncology Institute of Porto (IPO\/Porto), 4200-072 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2465-5143","authenticated-orcid":false,"given":"Jo\u00e3o","family":"Santos","sequence":"additional","affiliation":[{"name":"Medical Physics, Radiobiology and Radiation Protection Group, IPO Porto Research Center (CI-IPO), Portuguese Oncology Institute of Porto (IPO\/Porto), 4200-072 Porto, Portugal"},{"name":"Medical Physics Department, Portuguese Oncology Institute of Porto (IPO\/Porto), 4200-072 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,9,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"S2","DOI":"10.1259\/bjr\/41321492","article-title":"New developments in mri for target volume delineation in radiotherapy","volume":"79","author":"Khoo","year":"2006","journal-title":"Br. J. Radiol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1016\/j.radonc.2016.09.018","article-title":"Consensus opinion on mri simulation for external beam radiation treatment planning","volume":"121","author":"Paulson","year":"2016","journal-title":"Radiother. Oncol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"388","DOI":"10.1118\/1.2402331","article-title":"Characterization, prediction, and correction of geometric distortion in mr images","volume":"34","author":"Baldwin","year":"2007","journal-title":"Med. Phys."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"6601","DOI":"10.1088\/0031-9155\/55\/22\/002","article-title":"Development of a geometrically accurate imaging protocol at 3 tesla mri for stereotactic radiosurgery treatment planning","volume":"55","author":"Zhang","year":"2010","journal-title":"Phys. Med. Biol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"277","DOI":"10.1016\/j.mric.2007.06.002","article-title":"A review of mr physics: 3t versus 1.5 t","volume":"15","author":"Soher","year":"2007","journal-title":"Magn. Reson. Imaging Clin. N. Am."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"136","DOI":"10.3340\/jkns.2014.55.3.136","article-title":"Reliability of stereotactic coordinates of 1.5-tesla and 3-tesla mri in radiosurgery and functional neurosurgery","volume":"55","author":"Kim","year":"2014","journal-title":"J. Korean Neurosurg. Soc."},{"key":"ref_7","unstructured":"Lavrador, R.F.D. (2010). Correction of Image Distortions in Magnetic Resonance Imaging: Intensity Inhomogeneities Correction and Evaluation. [PhD Thesis, Universidade de Coimbra]."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"278","DOI":"10.1002\/mrm.1910350221","article-title":"Inhomogeneity correction using an estimated linear field map","volume":"35","author":"Irarrazabal","year":"1996","journal-title":"Magn. Reson. Med."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1007\/PL00002385","article-title":"Aspects of mr image distortions in radiotherapy treatment planning","volume":"177","author":"Fransson","year":"2001","journal-title":"Strahlenther. Onkol."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Simpson, J.H. (2012). Simpson. Chapter 2-instrumental considerations. Organic Structure Determination Using 2-D NMR Spectroscopy, Academic Press. [2nd ed.].","DOI":"10.1016\/B978-0-12-384970-0.00002-8"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1016\/j.ab.2016.06.003","article-title":"B0 magnetic field homogeneity and shimming for in vivo magnetic resonance spectroscopy","volume":"529","author":"Juchem","year":"2017","journal-title":"Anal. Biochem."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"952","DOI":"10.1002\/(SICI)1522-2594(199911)42:5<952::AID-MRM16>3.0.CO;2-S","article-title":"Sense: Sensitivity encoding for fast mri","volume":"42","author":"Pruessmann","year":"1999","journal-title":"Magn. Reson. Med. Off. J. Int. Soc. Magn. Reson. Med."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Liu, X., Li, Z., Rong, Y., Cao, M., Li, H., Jia, C., Shi, L., Lu, W., Gong, G., and Yin, Y. (2021). A comparison of the distortion in the same field mri and mr-linac system with a 3d printed phantom. Front. Oncol., 11.","DOI":"10.3389\/fonc.2021.579451"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"103","DOI":"10.1007\/s13246-014-0252-2","article-title":"Mri distortion: Considerations for mri based radiotherapy treatment planning","volume":"37","author":"Walker","year":"2014","journal-title":"Australas. Phys. Eng. Sci. Med."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"80","DOI":"10.1016\/j.phro.2020.07.004","article-title":"Audit feasibility for geometric distortion in magnetic resonance imaging for radiotherapy","volume":"15","author":"Alzahrani","year":"2020","journal-title":"Phys. Imaging Radiat. Oncol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"5357","DOI":"10.1002\/mp.12465","article-title":"Distortion-free diffusion mri using an mri-guided tri-cobalt 60 radiotherapy system: Sequence verification and preliminary clinical experience","volume":"44","author":"Gao","year":"2017","journal-title":"Med. Phys."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1234","DOI":"10.1016\/j.ijrobp.2014.08.349","article-title":"A simple and efficient methodology to improve geometric accuracy in gamma knife radiation surgery: Implementation in multiple brain metastases","volume":"90","author":"Karaiskos","year":"2014","journal-title":"Int. J. Radiat. Oncol."},{"key":"ref_18","first-page":"E636","article-title":"Task group 284 report: Magnetic resonance imaging simulation in radiotherapy: Considerations for clinical implementation, optimization, and quality assurance","volume":"48","author":"Paulson","year":"2021","journal-title":"Med. Phys."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"49","DOI":"10.2174\/1573405052953029","article-title":"Geometric distortion in structural magnetic resonance imaging","volume":"1","author":"Wang","year":"2005","journal-title":"Curr. Med. Imaging Rev."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1638","DOI":"10.1002\/mp.12150","article-title":"Fully-automated analysis of jaszczak phantom measurements as part of routine spect quality control","volume":"44","author":"Hirtl","year":"2017","journal-title":"Med. Phys."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1137","DOI":"10.1109\/TNS.1980.4330986","article-title":"Spect: Single photon emission computed tomography","volume":"27","author":"Jaszczak","year":"1980","journal-title":"IEEE Trans. Nucl. Sci."},{"key":"ref_22","unstructured":"MODUS (2025, August 29). Measuring Geometric Distortion with Sub-Millimeter Accuracy in Mrgrt qa. White Paper, 2021. Available online: https:\/\/modusqa.com\/wp-content\/uploads\/2020\/02\/MRID3D_WhitePaper-v3_PRINT.pdf."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"561","DOI":"10.34067\/KID.0000272019","article-title":"Gadolinium-based contrast agent use, their safety, and practice evolution","volume":"1","author":"Do","year":"2020","journal-title":"Kidney360"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"625","DOI":"10.1016\/j.mric.2012.08.004","article-title":"Gadolinium-based magnetic resonance contrast agents for neuroradiology: An overview","volume":"20","author":"Kanal","year":"2012","journal-title":"Magn. Reson. Imaging Clin. N. Am."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1002\/cmmi.100","article-title":"Comparative study of the physicochemical properties of six clinical low molecular weight gadolinium contrast agents","volume":"1","author":"Laurent","year":"2006","journal-title":"Contrast Media Mol. Imaging"},{"key":"ref_26","unstructured":"Bettiol, M., Aragno, D., and Bencivenghi, A. (2013, January 16\u201319). RM phantom preparation with CuSO4 and NiCl2 water solutions. Proceedings of the Congresso Nazionale AIFM, Torino, Italy."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2108","DOI":"10.3906\/elk-1602-123","article-title":"Aqueous paramagnetic solutions for mri phantoms at 3 t:A detailed study on relaxivities","volume":"25","author":"Thangavel","year":"2017","journal-title":"Turk. J. Electr. Eng. Comput. Sci."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"242","DOI":"10.1017\/S1460396919000591","article-title":"Fabrication of anthropomorphic phantoms for use in total body irradiations studies","volume":"19","author":"Monzari","year":"2020","journal-title":"J. Radiother. Pract."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"800","DOI":"10.1118\/1.596552","article-title":"Anthropomorphic radiation therapy phantoms: A quantitative assessment of tissue substitutes","volume":"17","author":"Kleck","year":"1990","journal-title":"Med. Phys."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"DeWerd, L.A., and Kissick, M. (2014). The Phantoms of Medical and Health Physics, Springer.","DOI":"10.1007\/978-1-4614-8304-5"},{"key":"ref_31","unstructured":"Silva, S., Pinto, S., Conde, P., Lencart, J., Machado, E., and Santos, J.A.M. (2022, January 7\u201310). Optimization of the 3t mri acquisition for radiosurgery patients using a customized head phantom. Proceedings of the F\u00cdSICA 2022\u201323\u00aa Confer\u00eancia Nacional de F\u00edsica e 32\u00ba Encontro Ib\u00e9rico para o Ensino da F\u00edsica, Porto, Portugal."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"375","DOI":"10.1002\/jmri.20969","article-title":"Measurement of signal-to-noise ratios in mr images: Influence of multichannel coils, parallel imaging, and reconstruction filters","volume":"26","author":"Dietrich","year":"2007","journal-title":"J. Magn. Reson. Imaging"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Seo, Y., and Wang, Z.J. (2021). Measurement and evaluation of specific absorption rate and temperature elevation caused by an artificial hip joint during mri scanning. Sci. Rep., 11.","DOI":"10.1038\/s41598-020-80828-7"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1097\/RLI.0000000000000374","article-title":"Critical questions regarding gadolinium deposition in the brain and body after injections of the gadolinium-based contrast agents, safety, and clinical recommendations in consideration of the ema\u2019s pharmacovigilance and risk assessment committee recommendation for suspension of the marketing authorizations for 4 linear agents","volume":"52","author":"Runge","year":"2017","journal-title":"Investig. Radiol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"154","DOI":"10.1097\/MNH.0000000000000475","article-title":"Gadolinium-based contrast agents: Why nephrologists need to be concerned","volume":"28","author":"Leyba","year":"2019","journal-title":"Curr. Opin. Nephrol. Hypertens."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"3009","DOI":"10.18632\/aging.101108","article-title":"Nickel chloride (nicl2) in hepatic toxicity: Apoptosis, g2\/m cell cycle arrest and inflammatory response","volume":"8","author":"Guo","year":"2016","journal-title":"Aging"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"219","DOI":"10.1016\/j.toxlet.2005.05.019","article-title":"Toxic effect of nickel in an in vitro model of human oral epithelium","volume":"159","author":"Trombetta","year":"2005","journal-title":"Toxicol. Lett."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"100457","DOI":"10.1016\/j.focha.2023.100457","article-title":"Natural blue colourant preparations from blue pea flower and spirulina: A comparison stability study","volume":"3","author":"Gamage","year":"2023","journal-title":"Food Chem. Adv."},{"key":"ref_39","unstructured":"FDA (2013). Dotarem\u00ae (Gadoterate Meglumine) Injection for Intravenous Use."},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Schilling, K.G., Blaber, J., Hansen, C., Cai, L., Rogers, B., Anderson, A.W., Smith, S., Kanakaraj, P., Rex, T., and Resnick, S.M. (2020). Distortion correction of diffusion weighted MRI without reverse phase-encoding scans or field-maps. PLoS ONE, 15.","DOI":"10.1101\/2020.01.19.911784"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"539","DOI":"10.1016\/j.nicl.2016.03.022","article-title":"Choosing the polarity of the phase-encoding direction in diffusion MRI: Does it matter for group analysis?","volume":"11","author":"Kennis","year":"2016","journal-title":"NeuroImage Clin."},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Zhao, Y., Li, Y., Jiang, L., Fu, K., Xie, H., and Ran, Q. (2023). Effect of the phase encoding direction on the image quality of breast diffusion-weighted magnetic resonance images. Preprint.","DOI":"10.21203\/rs.3.rs-2758615\/v1"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"329","DOI":"10.1016\/0730-725X(85)90397-2","article-title":"Susceptibility artefacts in NMR imaging","volume":"3","author":"Tischler","year":"1985","journal-title":"Magn. Reson. Imaging"},{"key":"ref_44","first-page":"130","article-title":"Magnetic susceptibility of the elements and inorganic compounds","volume":"Volume 81","author":"Lide","year":"2005","journal-title":"Handbook of Chemistry and Physics"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"547","DOI":"10.2214\/AJR.11.7364","article-title":"Metal-Induced Artifacts in MRI","volume":"197","author":"Hargreaves","year":"2011","journal-title":"Am. J. Roentgenol."},{"key":"ref_46","first-page":"20200346","article-title":"Geometric uncertainties in daily online IGRT: Refining the CTV-PTV margin for contemporary photon radiotherapy","volume":"93","author":"Tudor","year":"2020","journal-title":"Br. Inst. Radiol."}],"container-title":["Applied Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-3417\/15\/18\/9864\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T18:42:35Z","timestamp":1760035355000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-3417\/15\/18\/9864"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,9,9]]},"references-count":46,"journal-issue":{"issue":"18","published-online":{"date-parts":[[2025,9]]}},"alternative-id":["app15189864"],"URL":"https:\/\/doi.org\/10.3390\/app15189864","relation":{},"ISSN":["2076-3417"],"issn-type":[{"type":"electronic","value":"2076-3417"}],"subject":[],"published":{"date-parts":[[2025,9,9]]}}}