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Amyloid beta (Aβ) is partially cleared from the CSF via skull base perivascular and perineural lymphatic pathways, particularly at the nasal cavity. In vivo differences in Aβ level at the nasal cavity between patients with Alzheimer’s disease (AD), subjects with mild cognitive impairment (MCI) and cognitively normal (CN) individuals have not been previously assessed. This is a retrospective evaluation of subject level data from the ADNI-1/GO database. Standardized uptake value ratio (SUVR) maximum on 11C-Pittsburgh compound-B (PiB)-PET was assessed at the nasal cavity on 223 scans. Exploratory ROI analysis was also performed at other skull base sites. SUVR maximum values and their differences between groups (CN, MCI, AD) were assessed. CSF Aβ levels and CSF Aβ 42/40 ratios were correlated with SUVR maximum values. 103 subjects with 223 PiB-PET scans (47 CN, 32 AD and 144 MCI) were included in the study. The SUVR maxima at the nasal cavity were significantly lower in subjects with AD [1.35 (± 0.31)] compared to CN [1.54 (± 0.30); p = 0.024] and MCI [1.49 (± 0.33); p = 0.049]. At very low CSF Aβ, less than 132 pg/ml, there was significant correlation with nasal cavity SUVR maximum. The summed averaged SUVR maximum values were significantly lower in subjects with AD [1.35 (± 0.16)] compared to CN [1.49 (± 0.17); p = 0.003] and MCI [1.40 (± 0.17); p = 0.017]. Patients with AD demonstrate reduced nasal cavity PiB-PET radiotracer uptake compared to MCI and CN, possibly representing reduced Aβ clearance via perineural/perivascular lymphatic pathway. Further work is necessary to elucidate the true nature of this finding.

Background Stereotactic radiosurgery (SRS) is used to manage intracranial metastases in a significant fraction of patients. Local progression after SRS can often only be detected with increased volume of enhancement on serial MRI scans which may lag true progression by weeks or months. Methods Patients with intracranial metastases (N = 11) were scanned using hyperpolarized $$^{13}$$ 13 C MRI prior to treatment with stereotactic radiosurgery (SRS). The status of each lesion was then recorded at six months post-treatment follow-up (or at the time of death). Results The positive predictive value of $$^{13}$$ 13 C-lactate signal, measured pre-treatment, for prediction of progression of intracranial metastases at six months post-treatment with SRS was 0.8 $$p < 0.05$$ p < 0.05 , and the AUC from an ROC analysis was 0.77 $$p < 0.05$$ p < 0.05 . The distribution of $$^{13}$$ 13 C-lactate z-scores was different for intracranial metastases from different primary cancer types (F = 2.46, $$p = 0.1$$ p = 0.1 ). Conclusions Hyperpolarized $$^{13}$$ 13 C imaging has potential as a method for improving outcomes for patients with intracranial metastases, by identifying patients at high risk of treatment failure with SRS and considering other therapeutic options such as surgery.

The use of MRI with iron-based magnetic nanoparticles for imaging cells is a rapidly growing field of research. We have recently reported that single iron-labeled cells could be detected, as signal voids, in vivo in mouse brains using a balanced steady-state free precession imaging sequence (b-SSFP) and a customized microimaging system at 1.5 T.In the current study we assess the benefits, and challenges, of using a higher magnetic field strength for imaging iron-labeled cells with b-SSFP, using ex vivo mouse brain specimens imaged with near identical systems at 1.5 and 3.0 T.The substantial banding artifact that appears in 3 T b-SSFP images was readily minimized with RF phase cycling, allowing for banding-free b-SSFP images to be compared between the two field strengths. This study revealed that with an optimal 3 T b-SSFP imaging protocol, more than twice as many signal voids were detected as with 1.5 T.There are several factors that contributed to this important result. First, a greater-than-linear SNR gain was achieved in mouse brain images at 3 T. Second, a reduction in the bandwidth, and the associated increase in repetition time and SNR, produced a dramatic increase in the contrast generated by iron-labeled cells.