2024-03-29T14:25:48Z
http://eprints.drcmr.dk/cgi/oai2
oai:www.drcmr.dk:10
2008-06-28T18:38:09Z
7374617475733D707562
7375626A656374733D453031:45303178333730:4530317833373078333530:453031783337307833353078353030
7375626A656374733D493032:49303278393033
7375626A656374733D4A3031:4A303178383937:4A30317838393778323830:4A3031783839377832383078353030:4A303178383937783238307835303078343830
74797065733D61727469636C65
http://eprints.drcmr.dk/10/
A graphical simulator for teaching basic and advanced MR imaging techniques.
Hanson, Lars G.
Teaching
Magnetic Resonance Imaging
Medical Illustration
Teaching of magnetic resonance (MR) imaging techniques typically involves considerable handwaving, literally, to explain concepts such as resonance, rotating frames, dephasing, refocusing, sequences, and imaging. A proper understanding of MR contrast and imaging techniques is crucial for radiologists, radiographers, and technical staff alike, but it is notoriously challenging to explain spin dynamics by using traditional teaching tools. The author developed a freely available graphical simulator based on the Bloch equations to aid in the teaching of topics ranging from precession and relaxation to advanced concepts such as stimulated echoes, spin tagging, and k-space-methods. A graphical user interface provides the user with a three-dimensional view of spin isochromates that can be manipulated by selecting radiofrequency pulses and gradient events. Even complicated sequences can be visualized in an intuitive way. The cross-platform software is primarily designed for use in lectures, but is also useful for self studies and student assignments. Movies available at http://radiographics.rsnajnls.org/cgi/content/full/e27/DC1.
Radiological Society of North America, Inc (RSNA)
2007-08-10
Article
PeerReviewed
http://radiographics.rsnajnls.org/cgi/content/abstract/27/6/e27
Hanson, Lars G. (2007) A graphical simulator for teaching basic and advanced MR imaging techniques. Radiographics, 27 (6). e27. ISSN 1527-1323
http://eprints.drcmr.dk/10/
oai:www.drcmr.dk:18
2010-04-02T00:05:21Z
7374617475733D707562
7375626A656374733D453031:45303178333730:4530317833373078333530:453031783337307833353078353030:45303178333730783335307835303078323030
7375626A656374733D453035:45303578303437
7375626A656374733D453031:45303178333730:4530317833373078333736:453031783337307833373678333030
74797065733D61727469636C65
http://eprints.drcmr.dk/18/
Encoding of electrophysiology and other signals in MR images.
Hanson, Lars G
Lund, Torben E
Hanson, Christian G
Electroencephalography
Echo-Planar Imaging
Artifacts
PURPOSE: To develop a gradient insensitive, generic technique for recording of non-MR signals by use of surplus scanner bandwidth. MATERIALS AND METHODS: Relatively simple battery driven hardware is used to transform one or more signals into radio waves detectable by the MR scanner. Similar to the "magstripe" technique used for encoding of soundtracks in motion pictures, the electrical signals are in this way encoded as artifacts appearing in the MR images or spectra outside the region of interest. The encoded signals are subsequently reconstructed from the signal recorded by the scanner. RESULTS: Electrophysiological (EP) eye and heart muscular recording (electrooculography [EOG] and electrocardiography [ECG]) during fast echo planar imaging (EPI) is demonstrated with an expandable, modular 8-channel prototype implementation. The gradient artifacts that would normally be dominating EOG are largely eliminated. CONCLUSION: The method provides relatively inexpensive sampling with inherent microsecond synchronization and it reduces gradient artifacts in physiological recordings significantly. When oversampling is employed, the method is compatible with all MR reconstruction and postprocessing techniques.
Wiley InterScience
2007
Article
PeerReviewed
application/pdf
http://eprints.drcmr.dk/18/1/article.pdf
http://dx.doi.org/10.1002/jmri.20906
Hanson, Lars G and Lund, Torben E and Hanson, Christian G (2007) Encoding of electrophysiology and other signals in MR images. Journal of Magnetic Resonance Imaging : JMRI, 25 (5). pp. 1059-66. ISSN 1053-1807
http://eprints.drcmr.dk/18/http://eprints.drcmr.dk/18/1/
oai:www.drcmr.dk:19
2010-04-02T00:05:23Z
7374617475733D707562
7375626A656374733D473036:47303678353335
7375626A656374733D453031:45303178333730:4530317833373078333530:453031783337307833353078383235:45303178333730783335307838323578353030:4530317833373078333530783832357835303078323030
7375626A656374733D453035:45303578313936:4530357831393678383637:453035783139367838363778353139
74797065733D61727469636C65
http://eprints.drcmr.dk/19/
Reconstruction strategy for echo planar spectroscopy and its application to partially undersampled imaging.
Hanson, L G
Schaumburg, K
Paulson, O B
Metabolism
Magnetic Resonance Spectroscopy
Echo-Planar Imaging
The most commonly encountered form of echo planar spectroscopy involves oscillating gradients in one spatial dimension during readout. Data are consequently not sampled on a Cartesian grid. A fast gridding algorithm applicable to this particular situation is presented. The method is optimal, i.e., it performs as well as the full discrete Fourier transform for band limited signals while allowing for use of the fast Fourier transform. The method is demonstrated for reconstruction of data that are partially undersampled in the time domain. The advantages of undersampling are lower hardware requirements or fewer interleaves per acquisition. The method is of particular interest when large bandwidths are needed (e.g., for high field scanning) and for scanners with limited gradient performance. The unavoidable artifacts resulting from undersampling are demonstrated to be acceptable for spectroscopy with long echo times.
Wiley InterScience
2000
Article
PeerReviewed
application/pdf
http://eprints.drcmr.dk/19/1/article.pdf
http://dx.doi.org/10.1002/1522-2594(200009)44:3%3C412::AID-MRM11%3E3.0.CO;2-P
Hanson, L G and Schaumburg, K and Paulson, O B (2000) Reconstruction strategy for echo planar spectroscopy and its application to partially undersampled imaging. Magnetic Resonance in Medicine, 44 (3). pp. 412-7. ISSN 0740-3194
http://eprints.drcmr.dk/19/http://eprints.drcmr.dk/19/1/
oai:www.drcmr.dk:20
2010-04-02T00:05:24Z
7374617475733D707562
7375626A656374733D473036:47303678353335
7375626A656374733D453031:45303178333730:4530317833373078333530:453031783337307833353078353030
7375626A656374733D453035:45303578313936:4530357831393678383637:453035783139367838363778353139
74797065733D61727469636C65
http://eprints.drcmr.dk/20/
Optimal voxel size for measuring global gray and white matter proton metabolite concentrations using chemical shift imaging.
Hanson, L G
Adalsteinsson, E
Pfefferbaum, A
Spielman, D M
Metabolism
Magnetic Resonance Imaging
Magnetic Resonance Spectroscopy
Quantification of gray and white matter levels of spectroscopically visible metabolites can provide important insights into brain development and pathological conditions. Chemical shift imaging offers a gain in efficiency for estimation of global gray and white matter metabolite concentrations compared to single voxel methods. In the present study, the optimal voxel size is calculated from segmented human brain data and accompanying field maps. The optimal voxel size is found to be approximately 8 cc, but a wide range of values, 4-64 cc, can be chosen with little increase in estimated concentration error (<15%). Magn Reson Med 44:10-18, 2000.
Wiley InterScience
2000
Article
PeerReviewed
application/pdf
http://eprints.drcmr.dk/20/1/article3.pdf
http://dx.doi.org/10.1002/1522-2594(200007)44:1%3C10::AID-MRM3%3E3.0.CO;2-8
Hanson, L G and Adalsteinsson, E and Pfefferbaum, A and Spielman, D M (2000) Optimal voxel size for measuring global gray and white matter proton metabolite concentrations using chemical shift imaging. Magnetic Resonance in Medicine: MRM, 44 (1). pp. 10-8. ISSN 0740-3194
http://eprints.drcmr.dk/20/http://eprints.drcmr.dk/20/1/
oai:www.drcmr.dk:21
2010-04-02T08:24:07Z
7374617475733D707562
7375626A656374733D453031:45303178333730:4530317833373078333530:453031783337307833353078353030
7375626A656374733D483031:48303178363731:4830317836373178353739:483031783637317835373978363331
7375626A656374733D483031:48303178363731:4830317836373178373638:483031783637317837363878363338:48303178363731783736387836333878373231
74797065733D61727469636C65
http://eprints.drcmr.dk/21/
MR-skanning: Billeder fra den forbudte side af bølgelængdegrænsen
Hanson, Lars G.
Magnetic Resonance Imaging
Radio Waves
Magnetic Resonance Spectroscopy
Det er velkendt at almindelige optiske teknikker som mikroskopi og gennemlysning er bølgelængebegrænsede: På grund af lysets diffraktion ses ingen detaljer, der er mindre end bølgeængden af det anvendte lys. Ikke desto mindre er Magnetisk Resonans (MR) billeddannelse nu en udbredt skanningsmetode, der giver yderst detaljerede billeder af kroppens indre trods brug af bølgelængder i størrelsesorden meter. I 2002 blev en Nobelpris for klassisk MR billeddannelse givet til Paul Lauterbur og Sir Peter Mansfield. I de senere år har endnu en metode til at omgå bølgelængde-begrænsningen vundet stor indpas. Artiklen introducerer kernemagnetisk resonans (NMR) og de vigtigste billeddannelsesprincipper.
Niels Bohr Institute, University of Copenhagen
2006
Article
NonPeerReviewed
application/pdf
http://eprints.drcmr.dk/21/1/artikel.pdf
http://www.gamma.nbi.dk/
Hanson, Lars G. (2006) MR-skanning: Billeder fra den forbudte side af bølgelængdegrænsen. Gamma - tidsskrift for fysik (143). pp. 8-26. ISSN 0108-0954
http://eprints.drcmr.dk/21/http://eprints.drcmr.dk/21/1/
oai:www.drcmr.dk:22
2010-04-02T00:05:34Z
7374617475733D707562
7375626A656374733D493032:49303278393033:4930327839303378333032
7375626A656374733D4A3031:4A303178383937:4A30317838393778323830:4A3031783839377832383078353030:4A303178383937783238307835303078343830
7375626A656374733D483031:48303178363731:4830317836373178353739:483031783637317835373978363331
7375626A656374733D453031:45303178333730:4530317833373078333530:453031783337307833353078353030
74797065733D61727469636C65
http://eprints.drcmr.dk/22/
Is Quantum Mechanics necessary for understanding Magnetic Resonance?
Hanson, Lars G.
Models, Educational
Magnetic Resonance Imaging
Medical Illustration
Magnetic Resonance Spectroscopy
Educational material introducing magnetic resonance typically contains sections on the underlying principles. Unfortunately the explanations given are often unnecessarily complicated or even wrong. Magnetic resonance is often presented as a phenomenon that necessitates a quantum mechanical explanation whereas it really is a classical effect, i.e. a consequence of the common sense expressed in classical mechanics. This insight is not new, but there have been few attempts to challenge common misleading explanations, so authors and educators are inadvertently keeping myths alive. As a result, new students' first encounters with magnetic resonance are often obscured by explanations that make the subject difficult to understand. Typical problems are addressed and alternative intuitive
explanations are provided.
Wiley InterScience
2008-09-03
Article
PeerReviewed
application/pdf
http://eprints.drcmr.dk/22/1/article.pdf
image/jpeg
http://eprints.drcmr.dk/22/2/MagSpherical2crop.jpg
image/jpeg
http://eprints.drcmr.dk/22/3/MagPrecession2.jpg
image/jpeg
http://eprints.drcmr.dk/22/4/MagEquilib2.jpg
image/jpeg
http://eprints.drcmr.dk/22/5/MagRotated2.jpg
http://www3.interscience.wiley.com/journal/121394126/abstract
Hanson, Lars G. (2008) Is Quantum Mechanics necessary for understanding Magnetic Resonance? Concepts in Magnetic Resonance Part A, 32A (5). pp. 329-340. ISSN 1546-6086
http://eprints.drcmr.dk/22/http://eprints.drcmr.dk/22/1/http://eprints.drcmr.dk/22/2/http://eprints.drcmr.dk/22/3/http://eprints.drcmr.dk/22/4/http://eprints.drcmr.dk/22/5/
oai:www.drcmr.dk:24
2010-12-09T23:39:08Z
7374617475733D707562
7375626A656374733D463032:46303278343633:4630327834363378313838:463032783436337831383878343039
7375626A656374733D463032:46303278343633:4630327834363378353933:463032783436337835393378393332
7375626A656374733D463032:46303278343633:4630327834363378313838
74797065733D61727469636C65
http://eprints.drcmr.dk/24/
An integration of first-person methodologies in cognitive science
Overgaard, Morten
Gallagher, Shaun
Ramsøy, Thomas Z.
Cognition
Consciousness
Visual Perception
A number of recent publications have argued that a scientific approach to consciousness needs a rigorous approach to first-person data collection. As mainstream experimental psychology has long abandoned such introspective or phenomenological method, there is at present no generally agreed upon method for first-person
data collection in experimental consciousness studies. There are, however, a number of recent articles that all claim to provide a unique contribution to such a methodology. This article reviews these suggestions and extracts their core features. It is argued that the suggested methods are generally overlapping and compatible, and a number of concrete methods that easily are applied to experimental studies are put forward.
2008
Article
PeerReviewed
application/pdf
http://eprints.drcmr.dk/24/1/
Overgaard, Morten and Gallagher, Shaun and Ramsøy, Thomas Z. (2008) An integration of first-person methodologies in cognitive science. Journal of Consciousness Studies, 15 (5). pp. 100-120.
http://eprints.drcmr.dk/24/http://eprints.drcmr.dk/24/1/
oai:www.drcmr.dk:29
2010-04-02T08:37:41Z
7374617475733D707562
7375626A656374733D453035:45303578313332
7375626A656374733D4C3031:4C303178323234:4C30317832323478383030
74797065733D61727469636C65
http://eprints.drcmr.dk/29/
Shift Invariant Multilinear Decomposition of Neuroimaging Data
Mørup, Morten
Hansen, Lars K
Arnfred, Sidse M
Lim, Lek-Heng
Madsen, Kristoffer H
Signal Processing, Computer-Assisted
Brain Mapping
We present an algorithm for multilinear decomposition that allows for arbitrary shifts along one modality. The method is applied to neural activity arranged in the three modalities space, time, and trial. Thus, the algorithm models neural activity as a linear superposition of components with a fixed time course that may vary across either trials or space in its overall intensity and latency. Its utility is demonstrated on simulated data as well as actual EEG, and fMRI data. We show how shift-invariant multilinear decompositions of multiway data can successfully cope with variable latencies in data derived from neural activity--a problem that has caused degenerate solutions especially in modeling neuroimaging data with instantaneous multilinear decompositions. Our algorithm is available for download at www.erpwavelab.org.
Elsevier
2008-10-01
Article
PeerReviewed
application/pdf
http://eprints.drcmr.dk/29/1/Shift_invariant_decomp_2008.pdf
http://dx.doi.org/10.1016/j.neuroimage.2008.05.062
Mørup, Morten and Hansen, Lars K and Arnfred, Sidse M and Lim, Lek-Heng and Madsen, Kristoffer H (2008) Shift Invariant Multilinear Decomposition of Neuroimaging Data. Neuroimage, 42 (4). pp. 1439-1450.
http://eprints.drcmr.dk/29/http://eprints.drcmr.dk/29/1/
oai:www.drcmr.dk:34
2010-04-02T08:36:19Z
7374617475733D707562
7375626A656374733D433130:43313078313134:4331307831313478333735:433130783131347833373578353030
74797065733D61727469636C65
http://eprints.drcmr.dk/34/
NORdic trial of oral Methylprednisolone as add-on therapy
to Interferon beta-1a for treatment of relapsing-remitting
Multiple Sclerosis (NORMIMS study): a randomised,
placebo-controlled trial
Soelberg Sorensen, Per
Mellgren, Svein Ivar
Svenningsson, Anders
Elovaara, Irina
Frederiksen, Jette Lautrup
Beiske, Antonie Giaever
Myhr, Kjell-Morten
Søgaard, Lise Vejby
Olsen, Inge Christoffer
Sandberg-Wollheim, Magnhild
Multiple Sclerosis
Treatment of relapsing-remitting multiple sclerosis with interferon beta is only partly effective, and new more effective and safe strategies are needed. Our aim was to assess the efficacy of oral methylprednisolone as an
add-on therapy to subcutaneous interferon beta-1a to reduce the yearly relapse rate in patients with relapsing-remitting
multiple sclerosis.
Methods: NORMIMS (NORdic trial of oral Methylprednisolone as add-on therapy to Interferon beta-1a for treatment
of relapsing-remitting Multiple Sclerosis) was a randomised, placebo-controlled trial done in 29 neurology departments in Denmark, Norway, Sweden, and Finland. We enrolled outpatients with relapsing-remitting multiple sclerosis who had had at least one relapse within the previous 12 months despite subcutaneous interferon beta-1a treatment (44 microg three times per week). We randomly allocated patients by computer to add-on therapy of either 200 mg
methylprednisolone or matching placebo, both given orally on 5 consecutive days every 4 weeks for at least 96 weeks.
The primary outcome measure was mean yearly relapse rate. Primary analyses were by intention to treat. This trial is
registered, number ISRCTN16202527.
Findings: 66 patients were assigned to interferon beta and oral methylprednisolone and 64 were assigned to interferon
beta and placebo. A high proportion of patients withdrew from the study before week 96 (26% [17 of 66] on
methylprednisolone vs 17% [11 of 64] on placebo). The mean yearly relapse rate was 0.22 for methylprednisolone
compared with 0.59 for placebo (62% reduction, 95% CI 39-77%; p<0.0001). Sleep disturbance and neurological and
psychiatric symptoms were the most frequent adverse events recorded in the methylprednisolone group. Bone mineral density had not changed after 96 weeks.
Interpretation: Oral methylprednisolone given in pulses every 4 weeks as an add-on therapy to subcutaneous interferon beta-1a in patients with relapsing-remitting multiple sclerosis leads to a significant reduction in relapse rate. However, because of the small number of patients and the high dropout rate, these findings need to be corroborated in larger cohorts.
2009-06
Article
PeerReviewed
application/pdf
http://eprints.drcmr.dk/34/1/NORMIMS_Published_article_processed.pdf
Soelberg Sorensen, Per and Mellgren, Svein Ivar and Svenningsson, Anders and Elovaara, Irina and Frederiksen, Jette Lautrup and Beiske, Antonie Giaever and Myhr, Kjell-Morten and Søgaard, Lise Vejby and Olsen, Inge Christoffer and Sandberg-Wollheim, Magnhild (2009) NORdic trial of oral Methylprednisolone as add-on therapy to Interferon beta-1a for treatment of relapsing-remitting Multiple Sclerosis (NORMIMS study): a randomised, placebo-controlled trial. Lancet Neurology, 8 (6). pp. 519-529.
http://eprints.drcmr.dk/34/http://eprints.drcmr.dk/34/1/
oai:www.drcmr.dk:40
2010-04-02T00:05:55Z
7374617475733D707562
7375626A656374733D4D3031:4D303178303630:4D30317830363078373033:4D3031783036307837303378353230
7375626A656374733D453035:45303578313936:4530357831393678383637:453035783139367838363778353139
7375626A656374733D453031:45303178333730
7375626A656374733D483031:48303178363731:4830317836373178353739:483031783637317835373978363331
74797065733D61727469636C65
http://eprints.drcmr.dk/40/
Motion correction of Single Voxel Spectroscopy by Independent Component Analysis applied to spectra from non-anesthetized pediatric subjects
de Nijs, Robin
Miranda, Maria J.
Hansen, Lars K
Hanson, Lars G.
Magnetic Resonance Spectroscopy
Infant, Newborn
Diagnostic Techniques and Procedures
Magnetic Resonance Spectroscopy
For Single Voxel Spectroscopy (SVS), the acquisition of the spectrum is typically repeated n times and then combined with a factor in order to improve the Signal-to-Noise Ratio (SNR). In practice the acquisitions are not only affected by random noise, but also by physiological motion and subject movements. Since the influence of physiological motion such as cardiac and respiratory motion on the data is limited, it can be compensated for without data-loss. Individual acquisitions hampered by subject movements on the other hand need to be rejected, if no correction or compensation is possible. If the individual acquisitions are stored, it is possible to identify and reject the motion-disturbed acquisitions before averaging.
Several automatic algorithms were investigated using a dataset of spectra from non-anesthetized infants with a gestational age of 40 weeks. Median filtering removed most subject movement artifacts, but at the cost of increased sensitivity to random noise. Neither Independent Component Analysis (ICA) nor outlier identification with multiple comparisons has this problem. These two algorithms are novel in this context. The peak height values of the metabolites were increased compared to the mean of all acquisitions for both methods, although primarily for the ICA method.
Wiley InterScience
2009-09-24
Article
PeerReviewed
application/pdf
http://eprints.drcmr.dk/40/1/Motion_rejection_01112009.pdf
de Nijs, Robin and Miranda, Maria J. and Hansen, Lars K and Hanson, Lars G. (2009) Motion correction of Single Voxel Spectroscopy by Independent Component Analysis applied to spectra from non-anesthetized pediatric subjects. Magnetic Resonance in Medicine, 62 (5). pp. 1147-1154. ISSN 0740-3194
http://eprints.drcmr.dk/40/http://eprints.drcmr.dk/40/1/
oai:www.drcmr.dk:41
2010-09-19T08:32:43Z
7374617475733D707562
7375626A656374733D453031:45303178333730:4530317833373078333530:453031783337307833353078353030
7375626A656374733D4A3031:4A303178383937
74797065733D61727469636C65
http://eprints.drcmr.dk/41/
MR-skanning ved 7 tesla feltstyrke etableres i Danmark
Hanson, Lars G.
Magnetic Resonance Imaging
Technology
Igennem længere tid har en bred kreds
af forskere og klinikere på hospitaler
og universiteter [1] forsøgt at rejse de
nødvendige midler til at etablere ultrahøjfelts
MR-skanning i Danmark. I juni
2010 udløstes jubel, da “the John and
Birthe Meyer Foundation” meget generøst
bevilgede 38,6 Mkr til indkøb af en
human MR-skanner med en feltstyrke
på 7 tesla. Dette svarer til cirka 140
tusind gange jordens magnetfelt hvilket
mere end fordobler hospitalernes
hidtil kraftigste felter. Bevillingen supplerede
offentlig støtte på 27,4 Mkr fra
Forsknings- og Innovationsstyrelsens
infrastrukturmidler, og dermed er den
nødvendige kapital til etablering af en
7T facilitet ved MR-forskningscentret på
Hvidovre Hospital tilvejebragt. Ultimo
2011 kan brugere af MR-skanning i
Danmark se frem til væsentligt forbedrede
undersøgelser på en række områder,
og nye typer målinger, som ikke
er mulige ved lavere felt. Med fokus på
tekniske forhold beskrives her de unikke
muligheder og udfordringer, som skanning
ved 7T feltstyrke afstedkommer.
Der tages udgangspunkt i en kort generel
beskrivelse af MR.
Scanpublisher A/S
2010-08
Article
NonPeerReviewed
application/pdf
http://eprints.drcmr.dk/41/1/7T_Hanson_MTI_p20_n4_2010.pdf
http://www.e-pages.dk/scanpub/202/
Hanson, Lars G. (2010) MR-skanning ved 7 tesla feltstyrke etableres i Danmark. MTI - Medicinsk Teknologi & Informatik, 7 (4). pp. 20-22. ISSN 1901-4465
http://eprints.drcmr.dk/41/http://eprints.drcmr.dk/41/1/