Dataset Information

Assessment of MRI contrast agent concentration by quantitative susceptibility mapping (QSM): application to estimation of cerebral blood volume during steady state.

ABSTRACT:

Objective

One major issue in dynamic susceptibility contrast MRI (DSC-MRI) is to accurately determine contrast agent (CA) concentration, since T2* relaxivity in vivo is generally unknown and varies between blood and tissue. In this study, quantitative susceptibility mapping (QSM) was used for quantification of CA concentration.

Materials and methods

A DSC-MRI protocol, including phase data acquisition, was applied to 20 healthy volunteers in a test-retest study. By selecting a CSF reference region of interest (ROI), the values of all QSM images were shifted to show no CA-induced change in CSF. CA concentration and cerebral blood volume (CBV) were estimated using shifted QSM data. CSF reference ROI optimization was evaluated by investigation of CBV repeatability. The CBV age dependence was analysed and tissue T2* relaxivity was estimated.

Results

The best repeatability of CBV, using an optimal CSF reference ROI, showed test-versus-retest correlations of r = 0.81 and r = 0.91 for white and grey matter, respectively. A slight CBV decrease with age was observed, and the estimated in vivo T2* relaxivity was 85 mM^-1s^-1.

Conclusion

Provided that a carefully selected CSF reference ROI is used to shift QSM image values, susceptibility information can be used to estimate concentration of contrast agent and to calculate CBV.

SUBMITTER: Lind E

PROVIDER: S-EPMC5701959 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:BackgroundCerebral blood volume (CBV) mapping with a dynamic susceptibility contrast (DSC) perfusion technique has become a clinical tool in diagnosing and follow-up of brain tumors. Ferumoxytol, a long-circulating iron oxide nanoparticle, has been tested for CBV mapping, but the optimal dose has not been established.PurposeTo compare ferumoxytol DSC of two different doses to standard of care gadoteridol by analyzing time-intensity curves and CBV maps in normal-appearing brain regions.Study typeRetrospective.SubjectsFifty-four patients with various brain disorders.Field strength/sequence3T MRI. DSC-MRI was performed with 0.1 mmol/kg gadoteridol and 1 day later with ferumoxytol in doses of 1 or 2 mg/kg.AssessmentSignal changes during first pass, relative CBV (rCBV) in normal-appearing thalamus, putamen, and globus pallidus, and contrast-to-noise ratio (CNR) of the CBV maps were compared between gadoteridol and various doses of ferumoxytol using an automated method. To subjectively assess the quality of the CBV maps, two blinded readers also assessed visual conspicuity of the putamen.Statistical testsLinear mixed effect model was used for statistical comparison.ResultsCompared to gadoteridol, 1 mg/kg ferumoxytol showed no difference in CNR (P = 0.6505), peak ΔR2*, and rCBV in the putamen (P = 0.2669, 0.0871) or in the thalamus (P = 0.517, 0.9787); 2 mg/kg ferumoxytol increased peak ΔR2* as well as the CNR (P < 0.0001), but also mildly increased rCBV in putamen and globus pallidus (P = 0.0005, 0.0012). Signal intensities during first pass remained highly above the noise level, with overlapping of 95% confidence intervals with noise only in 3 out of 162 tested regions. Compared to gadoteridol, the visual image quality showed mild improvement with 1 mg/kg (P = 0.02) and marked improvement with 2 mg/kg ferumoxytol (P < 0.0001).Data conclusion1 mg/kg ferumoxytol provides similar imaging results to standard gadoteridol for DSC-MRI, and 2 mg/kg has a benefit of increased CNR, but may also result in mildly increased rCBV values.Level of evidence3 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2018;48:441-448.

Project description:BACKGROUND:Quantitative susceptibility mapping (QSM) offers a consistent hemorrhage volume measurement independent of imaging parameters. PURPOSE:To investigate the magnetic susceptibility of intracerebral hemorrhage (ICH) as a quantitative measurement for monitoring treatment in hematoma patients. STUDY TYPE:Prospective. POPULATION:Twenty-six patients with acute ICH were recruited and enrolled in treatment including surgery or medication (mannitol) for 1 week. FIELD STRENGTH/SEQUENCE:A 3D gradient echo sequence at 3.0T. ASSESSMENT:The hematoma volumes on computed tomography (CT) and QSM were calculated and used for correlation analysis. Magnetic susceptibility changes from pre- to posttreatment were calculated and compared to the National Institutes of Health stroke scale (NIHSS) measure of neurological deficit for each patient. STATISTICAL TESTS:Mean susceptibility values were calculated over each region of interest (ROI). A one-sample t-test was used to assess the changes of total volumes and mean magnetic susceptibility of ICH identified between pre- and posttreatment images (P < 0.05 was considered significant) and the Bland-Altman analysis with 95% limits of agreement (average difference, ±1.96 SD of the difference). Regression of volume measurements on QSM vs. CT and fitted linear regression of mean susceptibility vs. CT signal intensity for hematoma regions were conducted in all patients. RESULTS:Good correlation was found between hemorrhage volumes calculated from CT and QSM (CT volume = 0.94*QSM volume, r = 0.98). Comparison of QSM pre- and posttreatment showed that the mean ICH volume was reduced by a statistically insignificant amount from 5.74 cm3 to 5.45 cm3 (P = 0.21), while mean magnetic susceptibility was reduced significantly from 0.48 ppm to 0.38 ppm (P = 0.004). A significant positive association was found between changes in magnetic susceptibility values and NIHSS following hematoma treatment (P < 0.01). DATA CONCLUSIONS:QSM in hematoma assessment, as compared with CT, offers a comparably accurate volume measurement; however, susceptibility measurements may enable improved monitoring of ICH treatment compared to volume measurements alone. LEVEL OF EVIDENCE:2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:907-915.