RPS 1411a - Arterial spin labeling brain perfusion

Purpose:

To explore the application value of PLD in 3D-pcASL perfusion imaging in normal children and to find the optimal PLD values ​​for children at each age group.

Methods and materials:

5 groups of children, with 50 patients in each group, who underwent routine MRIs with normal results were included. The patients were stratified according to the following ages: <1 month, 1 to 6 months, 6 to 12 months, 1 to 3 years, 3 to 6 years, and 6 to 18 years. All patients received 3D-pcASL scanning. The PLD values were set to 1,025 ms, 1,525 ms, or 2,025 ms. In subjective evaluations, the SNR and CBF of 3D-pcASL perfusion images under different PLD values ​​were compared and analysed.

Results:

For patients in the < 1 month group and 1 to 6 months group, when the PLD value was 1,025 ms, the brain CBF values and SNR values were higher than those of the images with PLD values of 1,525 ms and 2,025 ms. For patients in the 6 to 12 months group, 1 to 3 years group, 3 to 6 years group, and 6 to 18 years group, when the PLD value was 1,525 ms, the brain CBF values and SNR values were higher than those of the images with PLD values ​​of 1,025 ms and 2,025 ms.

Conclusion:

The optimal PLD value for infants who are aged ≤6 months is 1,025 ms. The optimal PLD value for children >6 months to 18 years old is 1,525 ms.

Limitations:

The deficiency of this study is that some children used sedatives during the examination.

Ethics committee approval

Ethics committee approval obtained.

Funding:

No funding was received for this work.

Purpose:

Arterial spin labelling (ASL) is a promising non-invasive MRI perfusion technique but remains challenging to use in sickle cell disease (SCD) cerebral vasculopathy, which results in long arterial transit times (ATT) through collateral pathways. We aimed to validate multi-delay ASL for cerebral blood flow (CBF) measurements in SCD patients with cerebral vasculopathy.

Methods and materials:

We performed single-delay ASL (labelling duration=1,500 milliseconds, post-labelling delay=2,025 milliseconds) and multi-delay ASL (labelling duration=4,000 milliseconds, 7 post-labelling delays: 2,000-5,000 milliseconds) on a 3-Tesla MRI scanner in 21 patients with SCD cerebral vasculopathy. Dynamic susceptibility contrast MRI was used to assess the disease severity and to identify cortical regions with normal (<2 seconds), moderate (2-4 seconds), and severe (>4 seconds) Tmax. Normalised relative CBF (rCBF), ATT, and Tmax values were automatically extracted from 20 cortical regions.

Results:

Single-delay ASL measured lower rCBF that were 93%, 89% (p<0.001), and 84% (p=0.011) of the multi-delay ASL values in cortical regions of normal, moderate, and severe Tmax, respectively. Compared to multi-delay ASL, single-delay ASL underestimated rCBF by 16% in regions with severe Tmax (p=0.014), especially in anterior and middle cerebral artery perfusion territories. ATT was correlated with Tmax in cortical regions with severe Tmax (ρ=0.56, p<0.001). ATT maps were visually comparable to that of Tmax.

Conclusion:

Non-invasive multi-delay ASL improves CBF assessment in SCD cerebral vasculopathy, particularly in cortical regions with long ATT. It could reduce the need for contrast injection in patients difficult to infuse.

Limitations:

No reference standard such as [¹⁵O]-water positron emission tomography was available to validate the accuracy of rCBF measurement from ASL.

Ethics committee approval

The study was approved by the Comité de Protection des Personnes Île-de-France Saint-Louis Ethics Committee.

Funding:

The Agence Régionale de Santé Ile-de-France.

Purpose:

To compare cerebrovascular reserve (CVR) in affected and unaffected vascular territories in patients with Moyamoya disease (MMD) using ASL.

Methods and materials:

9 patients with MMD were included before or after revascularisation surgery of unilaterally or bilaterally affected vascular territories. All patients were examined on a 3T MR scanner. CBF maps, based on 3D-pCASL acquisition, were acquired before and 5, 15, and 25 minutes after an i.v. acetazolamide (ACZ) injection and registered to each patient’s 3D-T1-weighted image. A vascular territory template was spatially normalised to the patient-specific space. CBF values were extracted from regions supplied by the middle and anterior cerebral arteries and categorised as affected or unaffected based on DSA. CVR was calculated as CBF augmentation post-ACZ injection relative to baseline. A post label delay of 2,500 ms and large regions-of-interests were used to account for possible arterial transit time artefacts.

Results:

A total of 19 examinations were analysed, generating 76 vascular territories (12 unaffected and 64 affected). Average CVRs (CI95%) in unaffected vascular territories were 60% (46-73%), 54% (44-64%), and 46% (38-54%) at 5, 15, and 25 minutes after ACZ injection, respectively. Corresponding values in affected vascular territories were 42% (38-47%), 40% (36-45%), and 38% (34-42%). Differences between unaffected and affected vascular territories were significant at 5 minutes (p=0.006) and 15 minutes (p=0.017), but not at 25 minutes (p=0.095).

Conclusion:

CVR derived from ASL can differentiate between unaffected and affected vascular territories. ASL has potential as a non-invasive diagnostic method in patients with MMD.

Limitations:

The small number of unaffected vascular territories is a potential source of bias.

Ethics committee approval

Approved by the regional ethics committee (DNR 2019/01316). Written informed consent was given.

Funding:

No funding was received for this work.

Purpose:

Acute intermittent porphyria (AIP) is a rare inherited disorder presenting with abdominal, neurologic, and psychiatric symptoms.

Several studies documented brain perfusion defects by single-photon emission tomography (SPET) in subjects affected by AIP. PCASL is a non-invasive MRI technique for measuring tissue perfusion with a lot of potential clinical applications. Our purpose is to evaluate the role of pCASL and to compare it with SPET findings in this cohort of patients.

Methods and materials:

50 patients (26 group; 24 control) with AIP were included in the study. All subjects underwent MR examination using a 3T MR scanner with conventional sequences and pCASL, and had been studied by single-photon emission computed tomography. Two blinded neuroradiologists evaluated MR images and two experienced observers (20 years and 25 years) reviewed by consensus all SPECT images.

Results:

Conventional MRI showed no significant findings in all patients. All presented a variable pattern of SPECT including multiple mild to moderate perfusion cortical defects, bilateral or asymmetric. The most involved regions were temporal, frontal, and parietal lobes. We found a similar pattern of hypoperfusion with pCASL in 20 patients. 2 patients were excluded because of movement artefacts. 3 subjects didn’t manifest any significative perfusion alteration.

Conclusion:

pCASL represents an important and reliable alternative to others more expensive or invasive techniques, like PET or SPECT, for measuring cerebral perfusion in AIP patients. It could become a useful tool in research and clinical practice.

Limitations:

The retrospective nature of the study; difficult in the control group.

Ethics committee approval

Patient consent was obtained.

Funding:

No funding was received for this work.

Purpose:

Arterial spin labelling (ASL) is a non-invasive and quantitative imaging method to evaluate brain perfusion and angiography (4D-MRA ASL) using magnetically labelled arterial blood water as an endogenous tracer. The aim of this review is to discuss the applications of ASL in the setting of acute ischaemic stroke (AIS) and transient ischaemic attack (TIA).

Methods and materials:

A literature review was conducted searching the electronic databases PubMed and SCOPUS from inception to May 2019 to identify relevant peer-reviewed English publications. Qualitative and quantitative ASL imaging data were extracted.

Results:

After screening 404 titles and abstracts, and 41 full-text articles, 34 studies were included. ASL is an accurate and fairly versatile technique that provides useful imaging information required by the current AIS treatment guidelines. ASL has a high sensitivity (>85%) and accuracy for the detection of the arterial occlusion site. This technique is successful in depicting the ischaemic penumbra, with a tendency to show larger volumes than dynamic-susceptibility contrast MRI perfusion. ASL can reliably rule-out stroke by recognising its mimics and may even help to sustain the diagnosis of minor stroke/TIA, monitor clinical evolution, and stratify the risk of future stroke. The new 4D-MRA ASL defines the arterial occlusion site and collateral circulation status, which helps to predict the clinical outcome.

Conclusion:

ASL has proven to be an accurate alternative for stroke evaluation, allowing quantitative brain perfusion analysis, the definition of occlusion site, and collateral delineation with 4D-MRA. This technique is especially important when contrast agents are contraindicated, repeated image is needed, or the paediatric population is implicated. It is very effective for TIA/minor stroke evaluation.

Limitations:

Available studies have small sample sizes and use different approaches to evaluate perfusion, limiting the comparability of results.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

Accurate identification of the epileptogenic zone is an important prerequisite in the presurgical evaluation of refractory epilepsy.

The arterial spin labelling (ASL) non-contrast perfusion technique not only provides structural abnormalities but also a functional characterisation of abnormalities, and may play a vital role in structural MRI negative epilepsy.

Methods and materials:

We examined 50 patients with intractable epilepsy. On the basis of their clinical and electrophysiological findings, 32 patients had temporal lobe epilepsy, 3 had post-ischaemic scar lesions, 9 had focal seizures, and 6 had dysplastic lesions.

MRI was performed using a 3.0-T Skyra (Siemens). ASL was performed with a pulsed sequence using a QUIPSII perfusion mode. Relative cerebral blood flow maps for ASL were calculated for contrast-enhanced perfusion-weighted imaging using Syngo perfusion (MR) software.

An epilepsy protocol was used: axial T2W, sagittal T1W and sagittal 3D FLAIR, SWI, and diffusion-weighted imaging with 62-direction scanning. Interictal FDG PET/CT was used for comparison with ASL.

Results:

All cases with temporal lobe epilepsy showed hypoperfusion in the affected temporal lobe on both the interictal PET and ASL maps. In those cases where a cortical lesion was visible on imaging and corresponded with an alteration seen on PET, the same result seen on ASL perfusion.

Conclusion:

The perfusion maps obtained with ASL corresponded well with the PET perfusion and EEG results in patients with intractable epilepsy.

ASL not only allows the localisation of the epileptogenic focus but also provides the functional characterisation of abnormalities identified by MRI. ASL is a non-contrast, non-radiation useful supplementary investigation. It has the potential to make MRI a one-stop-shop in epilepsy evaluation.

Limitations:

Despite a slightly reduced resolution with ASL, we found a correlation between ASL, PET, and electrophysiological data.

Ethics committee approval

n/a

Funding:

No funding was received for this work.