Amide Proton Transfer Contrast Distribution in Different Brain Regions in Young Healthy Subjects

Abstract

Objectives: To define normal signal intensity values of amide proton transfer-weighted (APTw) magnetic resonance (MR) imaging in different brain regions. Materials and Methods: Twenty healthy subjects (9 females, mean age 29 years, range 19-37 years) underwent MR imaging at 3 Tesla. 3D APTw (RF saturation B 1,rms = 2 µT, duration 2 s, 100% duty cycle) and 2D T2-weighted turbo spin echo (TSE) images were acquired. Postprocessing (image fusion, ROI measurements of APTw intensity values in 22 different brain regions) was performed and controlled by two independent neuroradiologists. Values were measured separately for each brain hemisphere. A subject was scanned both in prone and supine position to investigate differences between hemispheres. A mixed model on a 5% significance level was used to assess the effect of gender, brain region and side on APTw intensity values. Results: Mean APTw intensity values in the hippocampus and amygdala varied between 1.13 and 1.57%, in the deep subcortical nuclei (putamen, globus pallidus, head of caudate nucleus, thalamus, red nucleus, substantia nigra) between 0.73 and 1.84%, in the frontal, occipital and parietal cortex between 0.56 and 1.03%; in the insular cortex between 1.11 and 1.15%, in the temporal cortex between 1.22 and 1.37%, in the frontal, occipital and parietal white matter between 0.32 and 0.54% and in the temporal white matter between 0.83 and 0.89%. APTw intensity values were significantly impacted both by brain region (p < 0.001) and by side (p < 0.001), whereby overall values on the left side were higher than on the right side (1.13 vs. 0.9%). Gender did not significantly impact APTw intensity values (p = 0.24). APTw intensity values between the left and the right side were partially reversed after changing the position of one subject from supine to prone. Conclusion: We determined normal baseline APTw intensity values in different anatomical localizations in healthy subjects. APTw intensity values differed both between anatomical regions and between left and right brain hemisphere.

Amide Proton Transfer Weighted Imaging Shows Differences in Multiple Sclerosis Lesions and White Matter Hyperintensities of Presumed Vascular Origin

“…content in the cytoplasm and the base-catalyzed exchange rate at physiological pH range (21). However, it should be acknowledged that the APTw signal may be contaminated by a variety of other technical factors (18,(29)(30)(31)(32)(33)(34). It is known that water longitudinal relaxation time (T 1 ) influences the APTw signal.…”

“…Additionally, semi-solid magnetization transfer (MT) and other nearby CEST and relayed nuclear Overhauser enhancement (rNOE) saturation transfer effects have been shown to affect the APTw signal. Lastly an imperfect distribution of the irradiation power across the brain can trigger B1 effects which may also impact APTw intensity values (34). It has been hypothesized that the increase in APTw signal intensity values in MSL in MS patients may be caused by changes in the intracellular amide proton content.…”

Amide Proton Transfer-Weighted MRI Might Help Distinguish Amnestic Mild Cognitive Impairment From a Normal Elderly Population

“…First, we hypothesized that this might be related to the size of the sample; our sample size was 74, compared with 20 for Sartoretti et al Second, the effect of age on the APTw value cannot be ignored (33). The subjects of our study were middle-aged and elderly healthy people, while the subjects of Sartoretti et al (26) were young healthy volunteers. However, recent studies have shown no significant correlation between APT signals and age in any brain regions (35).…”

Amide proton transfer weighted (APTw) imaging based radiomics allows for the differentiation of gliomas from metastases

“…16 slices with a slice thickness of 3.85 mm were acquired. The first slice was centered at the inferior border connecting the rostrum and the splenium of the corpus callosum 19 , 20 . Details on how APTw imaging contrast was generated can be found in the supplementary material .…”

“…Table 1 shows the sequence parameters for the APTw sequence. We used a clinically approved APTw sequence [18][19][20] acquired in transverse oblique orientation parallel to the intercommissural line. 16 slices with a slice thickness of 3.85 mm were acquired.…”