Abstract
This study aimed to evaluate the diagnostic performance of arterial spin labelling (ASL) in grading of adult gliomas. Eighteen studies matched the inclusion criteria and were included after systematic searches through EMBASE and MEDLINE databases. The quality of the included studies was assessed utilizing Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2). The quantitative values were extracted and a meta-analysis was subsequently based on a random-effect model with forest plot and joint sensitivity and specificity modelling. Hierarchical summary receiver operating characteristic (HROC) curve analysis was also conducted. The absolute tumour blood flow (TBF) values can differentiate high-grade gliomas (HGGs) from low-grade gliomas (LGGs) and grade II from grade IV tumours. However, it lacked the capacity to differentiate grade II from grade III tumours and grade III from grade IV tumours. In contrast, the relative TBF (rTBF) is effective in differentiating HGG from LGG and in glioma grading. The maximum rTBF (rTBFmax) demonstrated the best results in glioma grading. These results were also reflected in the sensitivity/specificity analysis in which the rTBFmax showed the highest discrimination performance in glioma grading. The estimated effect size for the rTBF was approximately similar between HGGs and LGGs, and grade II and grade III tumours, (–1.46 (–2.00, –0.91), p-value < 0.001), (–1.39 (–1.89, –0.89), p-value < 0.001), respectively; while it exhibited smaller effect size between grade III and grade IV (–1.05 (–1.82, –0.27)), p < 0.05). Sensitivity and specificity analysis replicate these results as well. This meta-analysis suggests that ASL is useful for glioma grading, especially when considering the rTBFmax parameter.
Highlights
WHO grade staging of gliomas has implications for prognosis and choice of therapy and MRI plays a leading role in all phases of tumour management, including diagnosis, therapy, and follow-up
T1-weighted post contrast MRI allows identification regions of blood brain barrier (BBB) disruption [1, 2] which are usually associated with higher WHO grades but presence of contrast enhancement can be misleading as some lowgrade gliomas (LGGs) demonstrate contrast uptake, with lack of enhancement being observed in some high-grade gliomas (HGGs) [3]
Quantitative Arterial spin labelling (ASL) measurements have introduced as output relative tumour blood flow and/or absolute tumour blood flow (TBF) values, which have been reported as useful in distinguishing between HGGs and LGGs [5,6,7] and in glioma grading [8] with some studies reporting negative results [9,10,11]
Summary
WHO grade staging of gliomas has implications for prognosis and choice of therapy and MRI plays a leading role in all phases of tumour management, including diagnosis, therapy, and follow-up. Arterial spin labelling (ASL), which uses magnetically labelled blood water as an inherently diffusible tracer, is performed in clinical settings as, unlike contrast-enhanced perfusion MRI techniques, it can www.oncotarget.com provide absolute cerebral blood flow (CBF) quantification, eliminates the need for contrast agent, and can be repeated for therapy monitoring. ASL is less sensitive to vessels permeability changes, which suggests that it provides tumour perfusion information that reflects vascular density [4]. Quantitative ASL measurements have introduced as output relative (or normalised) tumour blood flow (rTBF) and/or absolute tumour blood flow (TBF) values, which have been reported as useful in distinguishing between HGGs and LGGs [5,6,7] and in glioma grading [8] with some studies reporting negative results [9,10,11].
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