Open access Original research BMJ Open: first published as 10.1136/bmjopen-2020-036785 on 11 June 2020. Downloaded from Addition of arterial spin- labelled MR perfusion to conventional brain MRI: clinical experience in a retrospective cohort study Puneet Belani,1 Shingo Kihira ,1 Felipe Pacheco,1 Puneet Pawha,1 Giuseppe Cruciata,1 Kambiz Nael2 To cite: Belani P, Kihira S, ABSTRACT Strengths and limitations of this study Pacheco F, et al. Addition Objective The usage of arterial spin labelling (ASL) of arterial spin- labelled MR perfusion has exponentially increased due to improved ► To our knowledge, this is the first study to assess perfusion to conventional and faster acquisition time and ease of postprocessing. We brain MRI: clinical additional findings from arterial spin labelling (ASL) aimed to report potential additional findings obtained by experience in a retrospective MRI compared with conventional MRI for a variety adding ASL to routine unenhanced brain MRI for patients cohort study. BMJ Open of neurological pathology seen in routine clinical being scanned in a hospital setting for various neurological 2020;10:e036785. doi:10.1136/ practice. bmjopen-2020-036785 indications. ► The study consists of a relatively large patient co- Design Retrospective. hort, which strengthens the validity of the study. ► Prepublication history for Setting Large tertiary hospital. this paper is available online. ► There was only one observer in the study, which lim- Participants 676 patients. To view these files, please visit its the assessment of reproducibility. Primary outcome Additional findings fromASL sequence the journal online (http:// dx. doi. ► This is a retrospective cohort study, which limits the compared with conventional MRI. org/ 10. 1136/ bmjopen- 2020- determination of the effect of ASL images on clinical Results Our patient cohorts consisted of 676 patients 036785). management. with 257 with acute infarcts and 419 without an infarct. ► The 1.5 T is not a preferred magnetic field for ASL, Received 06 January 2020 Additional findings from ASL were observed in 13.9% which may suggest that additional findings may be Revised 21 April 2020 (94/676) of patients. In the non- infarct group, additional Accepted 06 May 2020 underestimated in this study. findings from ASL were observed in 7.4% (31/419) http://bmjopen.bmj.com/ of patients, whereas in patients with an acute infarct, supplemental information was obtained in 24.5% (63/257) of patients. with at least five sequences including T1, T2, Conclusion The addition of an ASL sequence to routine Fluid- attenuted inversion recovery (FLAIR), brain MRI in a hospital setting provides additional findings gradient- recalled- echo (GRE) and diffusion- compared with conventional brain MRI in about 7.4% of 5 6 patients with additional supplementary information in weighted imaging (DWI). 24.5% of patients with acute infarct. Arterial spin labelling (ASL) is a contrast- free MR perfusion technique that uses on September 28, 2021 by guest. Protected copyright. magnetically labelled water as a freely diffus- INTRODUCTION ible tracer to measure cerebral blood flow Neuroimaging constitutes a significant (CBF).7–9 Twenty- five years after its intro- © Author(s) (or their portion of hospital-based imaging both duction and with significant advances in employer(s)) 2020. Re- use for CT and MRI.1–3 Although most acute permitted under CC BY-NC. No sequence design, hardware technology and hospital- based neurological encounters can commercial re- use. See rights postprocessing techniques, ASL has become and permissions. Published by be assessed with CT, MRI offers an attractive BMJ. readily available for routine clinical prac- alternative due to the lack of ionising radia- 10 11 1Department of Radiology, Icahn tion and superior soft tissue contrast that is tice in recent years. In particular, ASL School of Medicine at Mount extremely useful for a detailed evaluation has shown promising results in the assess- Sinai, New York, New York, USA ment of acute neurological disorders such 2 of brain tissue. In fact, the Appropriateness Department of Radiological 12–16 Criteria of the American College of Radiology as stroke, transient ischaemic attack Sciences, David Geffen School 17 18 19 20 21 of Medicine, University of list MRI as the desired imaging modality (TIA), seizure, migraine headaches, California Los Angeles, Los for most neurological symptoms, including as well as various neuropsychiatric diseases 22 23 Angeles, California, USA headache, focal neurological deficits, altered such as major depressive disorder, Alzheimer’s dementia24–26 and Parkinson’s Correspondence to mental status, ataxia, seizure and vision 4 27–30 Dr Kambiz Nael; loss. A conventional brain MRI consists of disease. In this study, we aimed to inves- kambiznael@ gmail. com several weightings and is often constructed tigate additional findings from ASL imaging Belani P, et al. BMJ Open 2020;10:e036785. doi:10.1136/bmjopen-2020-036785 1 Open access BMJ Open: first published as 10.1136/bmjopen-2020-036785 on 11 June 2020. Downloaded from compared with routine unenhanced brain MRI scan in a imaging and communications in medicine (DICOM) CBF hospital setting. maps along with all other anatomical imaging were sent to picture archiving and communication system (PACS) and were available for interpretation. MatERIALS AND METHODS Study population Image analysis This is a single- centre retrospective study. Patients who For the purpose of this study, ASL images were retrospec- presented to our inpatient and emergency department tively evaluated by one board-certified neuroradiologist from January 2015 to September 2018 were included if for the detection of regional hypoperfusion or hyperper- they had concurrent ASL imaging obtained with a routine fusion. The observer was blinded to the final diagnosis to unenhanced brain MRI scan. A total of 5676 brain MRIs avoid bias. ‘Additional diagnostic findings’ were noted in were performed in our hospital (inpatient and emer- the context of conventional images and final diagnosis. gency department) of which 700 patients had MRI with For example, in a patient with a diagnosis of TIA, for addi- concurrent ASL imaging that met our inclusion and tional findings to be counted, initial ASL analysis (blinded exclusion criteria. Contrast- enhanced brain MRIs did not to TIA diagnosis) must have been recorded as regional have ASL and therefore were not included in this study. hypoperfusion. In a review of conventional imaging for Indications for these studies included a variety of neuro- this case, there should be no evidence of acute infarction. logical indications seen in routine clinical settings such Image analysis was performed on a PACS (Centricity, as headaches, altered mental status, neurological deficits GE Healthcare, Chicago, Illinois, USA) station without and seizures. Specific protocols, for example, epilepsy any additional software. Additional findings were noted protocol, multiple- sclerosis protocol, internal auditory if the ASL finding (1) suggested a new diagnosis, (2) canal protocol and brain tumour protocol, did not have helped narrow the differential or (3) prompted further ASL imaging routinely included and were excluded from imaging/workup, which would not have been considered the study. Paediatric patients were excluded. Patients with conventional imaging only. were excluded if the ASL images were severely limited In patients with acute infarct, the diagnosis was made by motion artefact or insufficient tagging. This yielded a by DWI and therefore ASL findings if any were consid- total of 700 cases with concurrent ASL imaging. Of which, ered supplementary and not as an ‘additional finding’. 24 were excluded due to various reasons: motion artefact In patients who had multiple regions of perfusion abnor- and insufficient tagging (n=14), inability of the patient mality or a mixture of hypoperfusion and hyperperfu- to complete the ASL sequence (n=6) and susceptibility sion, the most acutely relevant ASL finding was regarded artefacts (n=4). This resulted in the inclusion of a total of as the predominant perfusion pattern. For example, in a patient with an acute infarct with associated luxury hyper- 676 patients in our study. http://bmjopen.bmj.com/ perfusion and a chronic infarct elsewhere with corre- Image acquisition sponding hypoperfusion, the hyperperfusion related to Imaging protocol for brain MRI included the acquisi- acute infarction was included in the data analysis. tion of sagittal T1, axial T2, axial GRE, axial FLAIR, axial Final diagnoses were extracted from patients’ discharge DWI and axial ASL. Image acquisition was performed summary and patients were categorised into two groups: using two 1.5 T clinical MRI units (GE Optima MR450w; acute infarction and non- infarction. Percentages of ASL GE Medical Systems, Milwaukee) with an eight-channel abnormalities were calculated and subdivided in each category. head coil for signal reception. Three-dimensional (3D) on September 28, 2021 by guest. Protected copyright. pseudocontinuous ASL with a fast spin-echo stack- of- spiral readout with eight interleaves was used with each Patient and public involvement spiral arm including 512 sampling points. The following Patients and/or the public were not involved in the parameters were applied: repetition time (TR)/echo time design, or conduct, or reporting, or dissemination plans (TE): 4525/11 ms; field- of- view (FOV): 24×24 cm, matrix of this research. size: 64×64 mm, 30 slices each 4 mm thick; and number of excitation (NEX)=3. Pseudocontinuous spin labelling was performed for 1.5 s before postlabelling delay of 2 s. RESULTS Background suppression was achieved by applying inver- Patient cohort sion pulses on the volume to be imaged, allowing for Our final cohort included 676 patients. The mean±SD of the increase in the sharpness of the bolus.31 This setting age (years) was 62±18 with a median of 64. Among our resulted in the acquisition of a 3D voxel size of 3.8×3.8 cohort, 312 were men and 364 were women. CBF analysis × 4 mm3 during 4:30 min. Scanner software was used of the cohort revealed 79 patients with hyperperfusion, for online image reconstruction.