Computed tomography perfusion measurements for definition of lesions in early acute stroke

Background: Perfusion computed tomography (CT) is an evolving technique in the diagnosis of acute stroke. After complex deconvolution algorithms, perfusion color maps-cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT)— are produced, they give visual confirmation of perfusion deficit in ischemic area, but some discrepancies exist regarding this technique in reliability of quantitative detection of tissue viability: penumbra (tissue at risk) that surrounds core (necrosis). Purpose: The purpose of this prospective study was to define brain tissue viability grade on the basis of the perfusion CT parameters in acute stroke patients. Material and Methods: Multimodal CT imaging protocol (unenhanced CT of the brain, CT angiography of head and neck blood vessels, followed by brain perfusion CT and 24 hours follow-up brain CT) was performed. Perfusion deficit was detected first visually, with subsequent manual quantitative and relative measurements in affected and contra-lateral hemisphere in 87 patients. Results: Visual perfusion deficit on perfusion CT images was found in 78 cases (38 female, 40 male;mean age 30 - 84 years): penumbra lesion (n = 49) and core lesion (n = 42). Both lesion types were detected by increased MTT on perfusion CT map, penumbra area showed mean values 202.40% (113% - 345% ± 57.17) and core (41% - 320% ± 64.53) in comparison to contra-lateral hemisphere. CBV mean values in penumbra group were increased up to 113.10% (45% - 276% ± 36.29) and in core decreased till 41.82% (3% - 107% ± 27.09). CBF values were decreased up to 65.63% (31% - 137% ± 22) in penumbra lesion and markedly decreased till 25.94% (4% - 79% ± 17.35) in core. Conclusion: Our study shows that perfusion CT measurements relative threshold values are recommended in definition of penumbra and core lesions in acute stroke patients.

The value of magnetic resonance spectroscopy and diffusion tensor imaging in characterization of gliomas growth patterns and treatment efficiency

The objective of the study was to assess the usefulness of magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) in detection of vital tumor cell infiltration presence in peritumoral brain areas and determination of biochemical changes in the brain parenchyma after received treatment. 73 patients with present, morphologically conformed brain gliomas and 77 gliomas patients in remission stage after combined therapy underwent magnetic resonance imaging (MRI) including MRS and DTI. Fractional anisotropy (FA) and metabolite ratios—choline/creatine (Cho/Cr), myoinositol/creatine (MI/Cr), lactate-lipid/creatine (LL/Cr), N-acetyl aspartate/creatine (NAA/Cr)—were measured in the tumor, perifocal edema zone, distant and contra-lateral normal appearing white matter. We observed gradual reduction of Cho/Cr, MI/Cr, LL/Cr mean ratios and step-by-step increase of NAA/Cr, FA mean values in the direction from the tumor to the distant and contra-lateral normal-appearing white matter. LL/Cr ratios within distal normal appearing white matter decreased in patients after radiotherapy/chemotherapy. Our study suggests that MRS and DTI in combination with structural MRI sequences enhance vital glial tumor cells areas and possible infiltration border. MRS and DTI quantitative measurements in the glioma peritumoral area reveal pathological changes, despite the normal signal intensity in structural MRI. We suggest that increased LL/Cr ratios and decreased FA values may have the superior implications in the detecting of glial tumors extent along the white matter tracts. NAA/Cr reduction and Cho/Cr increase may provide additional diagnostic value. LL/Cr ratio in distal normal signal intensity area could be used as radiation/chemotherapy effectiveness criteria, as this will reduce after the received treatment and in remission period.