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Quantitative renal cortical perfusion in human subjects with magnetic resonance imaging using iron-oxide nanoparticles: influence of T1 shortening
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Radiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Radiology.
University of Heidelberg, Institute of Clinical Radiology and Nuclear Medicine.
Rikshospitalet University Hospital, Department of Radiology.
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2008 (English)In: Acta radiologica (Stockholm, Sweden : 1987), ISSN 1600-0455, Vol. 49, no 8, 955-62 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Using conventional contrast agents, the technique of quantitative perfusion by observing the transport of a bolus with magnetic resonance imaging (MRI) is limited to the brain due to extravascular leakage. PURPOSE: To perform quantitative perfusion measurements in humans with an intravascular contrast agent, and to estimate the influence of the T1 relaxivity of the contrast agent on the first-pass response. MATERIAL AND METHODS: Renal cortical perfusion was measured quantitatively in six patients with unilateral renal artery stenosis using a rapid gradient double-echo sequence in combination with an intravenous bolus injection of NC100150 Injection, an intravascular contrast agent based on iron-oxide nanoparticles. The influence of T1 relaxivity was measured by comparing perfusion results based on single- and double-echo data. RESULTS: The mean values of cortical blood flow, cortical blood volume, and mean transit time in the normal kidneys were measured to 339+/-60 ml/min/100 g, 41+/-8 ml/100 g, and 7.3+/-1.0 s, respectively, based on double-echo data. The corresponding results based on single-echo data, which are not compensated for the T1 relaxivity, were 254+/-47 ml/min/100 g, 27+/-3 ml/100 g, and 6+/-1.2 s, respectively. CONCLUSION: The use of a double-echo sequence enabled elimination of confounding T1 effects and consequent systematic underestimation of the perfusion.

Place, publisher, year, edition, pages
2008. Vol. 49, no 8, 955-62 p.
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Radiology
Identifiers
URN: urn:nbn:se:uu:diva-103263DOI: 10.1080/02841850802227139ISI: 000260046200017PubMedID: 18615336OAI: oai:DiVA.org:uu-103263DiVA: diva2:217901
Available from: 2009-05-18 Created: 2009-05-18 Last updated: 2012-08-01Bibliographically approved
In thesis
1. Perfusion measurements by dynamic susceptibility MRI
Open this publication in new window or tab >>Perfusion measurements by dynamic susceptibility MRI
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Uppsala: Institutionen för onkologi, radiologi och klinisk immunologi, Uppsala universitet, 2010. 51 p.
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Radiology
Identifiers
urn:nbn:se:uu:diva-143053 (URN)
Presentation
2010-12-10, Föreläsningssalen BFC, Akademiska sjukhuset, Uppsala, 13:00 (Swedish)
Supervisors
Available from: 2011-02-21 Created: 2011-01-19 Last updated: 2011-02-21Bibliographically approved
2. Quantitative Tracer Based MRI Perfusion: Potentials and Limitations
Open this publication in new window or tab >>Quantitative Tracer Based MRI Perfusion: Potentials and Limitations
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Tracer based MRI perfusion measurements is a clinically useful tool to assess regional distributions of tissue blood flow and volume. The method may be based on any of the three relaxation mechanisms T1, T1 and T2*, the latter denoted DSC-MRI being the most common. The primary aim of this work was to study the feasibility of obtaining quantitative estimates using these methods.

1) Feasibility of DSC-MRI for kidneys using an iron oxide based contrast agent and the influence of secondary relaxation effects on the results, part of a clinical phase II trial: The method proved feasible and the underestimation induced by secondary relaxation can be corrected for by using a double echo sequence.

2) Influence of blood flow rate on risk factors for developing cerebral ischemia during cardio pulmonary bypass, measurements in pig with gadolinium based DSC-MRI: The results indicated an ischemic threshold level at a blood flow rate of approximately 6 ml/kg/min.

3) The ability of gadolinium based DSC-MRI to detect changes in global blood flow, experimental measurements in pig and numerical simulations: The results support that DSC-MRI can discriminate between global flow levels in the same subject given that all other parameters are kept constant. The results also indicate that calculated perfusion values are highly sensitive to the arterial deconvolution procedure.

4) Influence of differences in blood/tissue relaxivity and secondary relaxation for a gadolinium based contrast agent, measurements in pig and numerical simulations: The blood/tissue relaxivity ratio is not unity and the situation is complicated by secondary relaxation effects. Deconvolution regularization appears to partly counteract the overestimation induced by difference in blood/tissue relaxivity for DSC-MRI.

In summary, the fundamental assumption of equal blood and tissue relaxivity is experimentally shown to be invalid and the influence of this discrepancy is substantial. Several factors contribute to measurement errors, a combination of these factors can incidentally lead to additive errors or error cancellation based on a variety of experimental and analysis conditions. Given that the differences in blood/tissue relaxivity cannot readily be accounted for in a clinical setting, absolute perfusion quantification by tracer based MRI remains challenging if not impossible.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 67 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 761
Keyword
MRI, Perfusion, Contrast agent, Relaxivity
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Radiology
Identifiers
urn:nbn:se:uu:diva-171901 (URN)978-91-554-8330-2 (ISBN)
Public defence
2012-05-16, Auditorium Minus, Museum Gustavianum, Akademigatan 3, Uppsala, 09:15 (Swedish)
Opponent
Supervisors
Available from: 2012-04-25 Created: 2012-03-29 Last updated: 2012-08-01Bibliographically approved

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Morell, ArvidAhlström, HåkanBjørnerud, Atle

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