Phosphorus‐31 MR spectroscopy of normal adult human brain and brain tumours

Abstract

Localized phosphorus-31 MR spectra were obtained in vivo in a large series of normal human brain tissue specimens of healthy volunteers (n=36) and various brain tumours (n=52). Tumour types examined included grade II and grade III gliomas (n=15 and n=1, respectively), glioblastomas (n=16) and meningeomas (n=12). An additional eight tumours were analysed during chemo- or radiotherapy. Spectra were acquired using a modified ISIS pulse sequence with a repetition time of 3 s. Voxel sizes ranged from 56 to 129 ml. The spectra were evaluated using a least-square variable projection (VARPRO) fitting procedure in the time domain, which allows semi-quantitative determination of relative metabolite concentrations. The measurements in normal cerebrum of healthy volunteers revealed the following results of metabolite signal intensity ratios: pH 7.04 (+/- 0.01), PCr/alpha-ATP 0.51 (+/- 0.03), P(i)/alpha-ATP 0.17 (+/-0.02), PCr/P(i) 2.09 (+/-0.12), PDE/alpha-ATP 3.65 (+/-0.13) and PME/alpha-ATP 0.41 (+/-0.04). Meningiomas showed the most obvious changes when compared with normal brain tissue. They are characterized by an alkaline environment (pH 7.16 +/- 0.03; p<0.005), a decrease in the phosphocreatine peak (p<0.0001) and significantly decreased phosphodiesters (p<0.0001). Glioblastomas also showed alkalization (pH 7.12 +/- 0.02; p<0.001) and a decrease in PDE/alpha-NTP (p<0.05), but no significant changes in PCr/alpha-NTP or PCr/Pi. In gliomas with low malignancy, less distinct changes could be detected with slight alkalization (pH 7.09 +/- 0.02; p<0.05) and more than a two-fold reduction in the PDE/alpha-NTP ratio (p<0.05). The spectra of brain tumours during chemo- and radiotherapy indicated clear but inconsistent influence of the therapy.

Energy Status And Metabolism in Intracranial Space Occupying Lesions: A Prospective 31p Spectroscopic Study

“…Previous studies have found significantly high PME/PDE ratio in astrocytoma, metastases and lymphoma compared to controls [13]. But these findings are variable and have limitations as previous studies had also shown increase in both PME and PDE in most tumours , proliferating tissues like regenerating liver, benign tumours and embryo [5].…”

“…It detects various metabolites like Phosphomonoesterase (PME), Phosphodiesterase (PDE), inorganic phosphates (Pi), Phosphocreatine (PCr), adenosine triphosphate (ATP) and their ratios like PME/PDE, PME/PCr etc which can be used to characterise tumours. These values may be potentially useful by complimenting the findings of other diagnostic modalities like proton spectroscopy [3][4][5].…”

“…P MRS is an established technique for evaluating tumours of extremity, head, neck and liver [5][6][7][8][9]. It allows non invasive characterization of phosphate containing compounds within tumour cells and determination of energy status and pH [9][10][11].…”

“…The phosphate metabolites imaged are probably intracellular as the extra cellular concentration of these metabolites is negligible [12]. The integral values obtained of each metabolites are not absolute but relative [4] and thus various metabolite ratios are used like PME/ PDE, PDE/ATP, PCr/ATP etc in various studies [5,13].…”

Beyi̇n Tümörleri̇ni̇n 3t Manyeti̇k Alanda i̇n Vi̇vo Fosfor Manyeti̇k Rezonans Spektroskopi̇k Görüntüleme Pi̇kleri̇ni̇n Z-Skorlarina Dayali İncelenmesi̇

“…β-ATP piki içerisinde adenozinmonofosfat (AMP) ve adenozindifosfat (ADP) kontaminasyonu olmadığı için, ATP düzeyini tahmin etmekte kullanılır. Metabolik bilgilere ek olarak, 31 P-MRSG'de inorganik fosfat (Pi) ve PCr piklerinin arasındaki frekans farkı kullanılarak hücre içi pH düzeyi hesaplanabilir (6). Proton MR spektroskopisi ile oksijen yetersizliğini ölçmede kullanılan laktat pikinin tespiti aynı frekansta görünen lipid pikleri nedeniyle özel spektral düzenleme planları gerektirirken (7), 31 P MR spektrumu PCr, Pi ve β-ATP piklerinin ölçümü sayesinde iskemik durum hakkında kolayca bir değerlendirme verebilir.…”