Objectives
To assess the combined role of tumor vascularity, estimated from perfusion MRI, and
MGMT
methylation status on overall survival (OS) in patients with glioblastoma.
Methods
A multicentric ...international dataset including 96 patients from NCT03439332 clinical study were used to study the prognostic relationships between
MGMT
and perfusion markers. Relative cerebral blood volume (rCBV) in the most vascularized tumor regions was automatically obtained from preoperative MRIs using ONCOhabitats online analysis service. Cox survival regression models and stratification strategies were conducted to define a subpopulation that is particularly favored by
MGMT
methylation in terms of OS.
Results
rCBV distributions did not differ significantly (
p
> 0.05) in the methylated and the non-methylated subpopulations. In patients with moderately vascularized tumors (rCBV < 10.73),
MGMT
methylation was a positive predictive factor for OS (HR = 2.73,
p
= 0.003, AUC = 0.70). In patients with highly vascularized tumors (rCBV > 10.73), however, there was no significant effect of
MGMT
methylation (HR = 1.72,
p
= 0.10, AUC = 0.56).
Conclusions
Our results indicate the existence of complementary prognostic information provided by
MGMT
methylation and rCBV. Perfusion markers could identify a subpopulation of patients who will benefit the most from
MGMT
methylation. Not considering this information may lead to bias in the interpretation of clinical studies.
Key Points
• MRI perfusion provides complementary prognostic information to MGMT methylation.
• MGMT methylation improves prognosis in glioblastoma patients with moderate vascular profile.
• Failure to consider these relations may lead to bias in the interpretation of clinical studies.
Purpose
To propose a magnetic resonance imaging (MRI) quality assurance procedure that can be used for multicenter comparison of different MR scanners for quantitative diffusion‐weighted imaging ...(DWI).
Materials and Methods
Twenty‐six centers (35 MR scanners with field strengths: 1T, 1.5T, and 3T) were enrolled in the study. Two different DWI acquisition series (b‐value ranges 0–1000 and 0–3000 s/mm2, respectively) were performed for each MR scanner. All DWI acquisitions were performed by using a cylindrical doped water phantom. Mean apparent diffusion coefficient (ADC) values as well as ADC values along each of the three main orthogonal directions of the diffusion gradients (x, y, and z) were calculated. Short‐term repeatability of ADC measurement was evaluated for 26 MR scanners.
Results
A good agreement was found between the nominal and measured mean ADC over all the centers. More than 80% of mean ADC measurements were within 5% from the nominal value, and the highest deviation and overall standard deviation were 9.3% and 3.5%, respectively. Short‐term repeatability of ADC measurement was found <2.5% for all MR scanners.
Conclusion
A specific and widely accepted protocol for quality controls in DWI is still lacking. The DWI quality assurance protocol proposed in this study can be applied in order to assess the reliability of DWI‐derived indices before tackling single‐ as well as multicenter studies. J. MAGN. RESON. IMAGING 2016;43:213–219.
This study aims to investigate whether radiomic quantitative image features (IFs) from perfusion dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) retain sufficient strength to ...predict O6-methylguanine-DNA methyltransferase promoter methylation (MGMT_pm) in newly diagnosed glioblastoma (GB) patients.
We retrospectively reviewed the perfusion DSC-MRI of 59 patients with GB. Patients were classified into three groups: (1) unmethylated if MGMT_pm ≤ 9% (UM); (2) intermediate-methylated if MGMT_pm ranged between 10% and 29% (IM); (3) methylated if MGMT_pm ≥ 30% (M). A total of 92 quantitative IFs were obtained from relative cerebral blood volume and relative cerebral blood flow maps. The Mann-Whitney U-test was applied to assess whether there were statistical differences in IFs between patient groups. Those IFs showing significant difference between two patient groups were termed relevant IFs (rIFs). rIFs were uploaded to a machine learning model to predict the MGMT_pm.
No rIFs were found between UM and IM groups. Fourteen rIFs were found among UM-M, IM-M, and (UM + IM)-M groups. We built a multilayer perceptron deep learning model that classified patients as belonging to UM + IM and M group. The model performed well with 75% sensitivity, 85% specificity, and an area under the receiver-operating curve of .84.
rIFs from perfusion DSC-MRI are potential biomarkers in GBs with a ≥30% MGMT_pm. Otherwise, unmethylated and intermediate-methylated GBs lack of rIFs. Five of 14 rIFs show sufficient strength to build an accurate prediction model of MGMT_pm.
Background
Quantification of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) kinetic parameters (KPs) requires a determination of native tissue T1. Two approaches are adopted: (i) ...tissue T1-maps are acquired; and (ii) an a priori T1 value (fT1) is fixed for all patients (fT1-approach). Although it is more attractive, the fT1-approach might bias the results of KP calculations due to tissue T1 variability.
Purpose
To quantify the tissue T1 variability of recurrent high-grade glioma (HGG) and the error in KP estimation when the fT1-approach is adopted.
Material and Methods
We reviewed the postoperative MRI scans of 28 patients with recurrent HGG after radiochemotherapy. MRI study included T1-maps from multiple-dynamic multiple-echo imaging, DCE-MRI, and contrast enhanced T1-weighted images. KPs were calculated using T1-map and fT1-approach.
Results
The tissue T1 variability of recurrent HGG was relevant. The absolute error in KP estimation, as a function of the deviation of fT1 from the true value, was 8% every 100 ms. The difference between the KPs obtained with fT1-approach from fT1 values of 1300, 1390, and 1500 ms and their reference values were mostly within the 95% confidence interval (± 1.96 standard deviation). Conversely, using fT1 values of 900, 1200, 1600, and 1900 ms causes a significant error in KP estimation (P<0.05).
Conclusion
Recurrent HGG is characterized by a substantial T1 variability. Although the fT1-approach does not account for this variability, it results in a minor effect on the KP estimations provided the fT1 value is in the range of 1300–1500 ms.
The aim of this study was to evaluate the differences in dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) perfusion estimates of high-grade brain gliomas (HGG) due to the use of an ...input function (IF) obtained respectively from arterial (AIF) and venous (VIF) approaches by two different commercially available software applications.
This prospective study includes 20 patients with pathologically confirmed diagnosis of high-grade gliomas. The data source was processed by using two DCE dedicated commercial packages, both based on the extended Toft model, but the first customized to obtain input function from arterial measurement and the second from sagittal sinus sampling. The quantitative parametric perfusion maps estimated from the two software packages were compared by means of a region of interest (ROI) analysis. The resulting input functions from venous and arterial data were also compared.
No significant difference has been found between the perfusion parameters obtained with the two different software packages (P-value < .05). The comparison of the VIFs and AIFs obtained by the two packages showed no statistical differences.
Direct comparison of DCE-MRI measurements with IF generated by means of arterial or venous waveform led to no statistical difference in quantitative metrics for evaluating HGG. However, additional research involving DCE-MRI acquisition protocols and post-processing would be beneficial to further substantiate the effectiveness of venous approach as the IF method compared with arterial-based IF measurement.
This study aims to investigate the feasibility of a "real-time" estimate of the optimal CT perfusion (CTP) acquisition time (T
) in ischemic stroke patients.
The arterial input function, the venous ...output function (VOF), and the time-attenuation curves of ischemic core and ischemic penumbra of 51 patients with acute ischemic stroke in anterior circulation were obtained. The curves were analyzed to determine for each patient the T
value; additionally, several time parameters were derived from each waveform. The relationship between each of these parameters and T
was investigated.
We found a strong linear correlation between each time parameter derived from VOF curve and T
, suggesting that the VOF waveform is rescaled from patient to patient without significant change in shape.
The linear correlation between T
and the VOF time to peak is well suited to implement a new technique to automatically customize the patient's CTP acquisition time. The method does not require an additional dose of contrast medium and does not increase the overall study time, so its use would be desirable to decrease the average radiation dose.
This study aims to investigate the significance of regional hyperperfusion (RH) detected by arterial spin labeling (ASL) in a group of untreated stroke patients, within 24-36 hours after symptom ...onset. The relationship between RH volume and infarcted volume (DIV) as defined on diffusion weighted images (DWIs) was evaluated.
Of the 346 consecutive acute stroke patients who attended our center, we retrospectively reviewed MRI studies of 47 patients who were ineligible for standard treatment with intravenous tissue plasminogen activator. The MRI study included ASL and DWI. The ASL-derived cerebral blood flow (CBF) maps were coregistered on the DWI images. RH volume and DIV were calculated and compared. Patient NIHSS scores were also evaluated at admission, discharge, and after 1 and 6-month follow-up.
Twenty-two patients showed RH with CBF twice than baseline. In all 22 patients, RH overlaps with DWI infarcted area. No significant difference (P = .94) between RH volume and DIV was found (7.2 ± 9.6 and 9.0 ± 11.9 cm
). The Pearson's correlation coefficient between RH and DIV was .93. On univariate analysis, a significant difference was found between patient's groups on NIHSS at any time points, after covariates adjustment NIHSS difference was significant only at admission.
The study showed that ASL perfusion could be an integral part of the MRI examination in the assessment of 24-36 hours not-treated stroke patients as sustained RH group had improved outcomes. More importantly, ASL perfusion may provide evidence of beneficial effects of reperfusion induced by recanalization treatment.
Abstract
The purpose of this study was to describe a simple procedure to assess head exposure of MRI workers to time-varying magnetic field, due to their movements in the static magnetic field of a ...3T MRI scanner. A group of MRI workers were provided with a commercial portable meter that stored in its internal memory the instantaneous B values. The dB/dt was obtained by the post hoc processing of measured data. The movement-induced time-varying electric field (TVEF) was calculated from dB/dt. The weighted peak index was evaluated in the frequency domain, by first computing the spectrum of dB/dt waveform, to verify the compliance with the exposure limits. The portable magnetometer may be useful to locally explore the MRI workers exposure to time-varying magnetic field and perform the local risk assessments in order to carry out the obligations laid down by Directive 2013/35/EU.
The aim of this study was to evaluate the arterial input function (AIF) and tissue enhancement time curve (tissue function TF) obtained after the administration of a half-dose gadobenate dimeglumine ...(0.05-mmol/kg body weight bw) compared with a full dose (0.1-mmol/kg bw) of a standard-relaxivity contrast agent.
We enrolled 40 adult patients with glioblastoma in an interindividual comparative study. Patients were randomized to 1 of the 2 study arms: 20 patients received 0.1-mmol/kg bw of gadoterate; the other 20 patients received 0.05-mmol/kg bw of gadobenate. The patients underwent dynamic contrast-enhanced magnetic resonance imaging examinations. Arterial input function, tissue enhancement time curve (TF), tumor transfer rate (K), and tumor extracellular-extravascular volume fraction (Ve) were calculated for each patients. Averaged AIF, TF, K, and Ve of both groups were compared.
A significant difference (P = 0.001) between the peak AIF values obtained with the 2 different gadolinium-based contrast agents was observed. No difference was found between TFs (P = 0.35). Comparison on kinetic parameters revealed a significant difference for K (P = 0.047) but no difference for Ve (P = 0.74).
The administration of half dose of the high-relaxivity contrast agent gadobenate is effective in improving AIF by reducing T2*-shortening effects on dynamic contrast-enhanced magnetic resonance imaging and ensuring at the same time an adequate signal enhancement in tumor tissue. The use of 0.05-mmol/kg bw of gadobenate not only is feasible but also can lead to a better estimation of K based on a more accurate AIF assessment.
The objective of this study was to assess the effective performance of short echo time magnetic resonance spectroscopy (short TE MRS) for 2HG detection as biomarker of isocitrate dehydrogenase (IDH) ...status in all grade glioma (GL).
A total of 82 GL patients were prospectively investigated by short TE MRS at 3.0 T as part of a multimodal magnetic resonance imaging study protocol. Spectral analysis was performed using linear combination model. Tumor specimens were diagnosed as IDH mutant or wild type according to the 2016 World Health Organization (WHO) classification of brain tumors. Spectra were analyzed for the presence of 2HG. The performance of short TE MRS was evaluated in terms of sensitivity, specificity, and positive and negative likelihood ratio on the overall sample and on GL WHO grades II and III and glioblastoma separately.
The specificity and sensitivity estimated on the overall sample were 88% and 77%, respectively. In GL WHO grades II and III, 100% specificity and 75% sensitivity were estimated.
We reiterate the feasibility to identify IDH status of brain GL using short TE MRS at 3.0 T. The method can correctly detect 2HG as expression of IDH mutation in WHO grades II and III GL with a 100% specificity but a 75% sensitivity. In the evaluation of glioblastoma, short TE MRS performs poorly having a 17% false positive rate.
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