Table 3 Main metabolites studied in 1H-MRS and their biological significances
Metabolite | Biological meaning | ppm | Decreased values | Increased values |
|---|---|---|---|---|
Cho (total Cho-containing compounds) | A metabolic marker cell membrane synthesis and repair. Related to cell density and membrane integrity | 3.22 | Due to cell proliferation and to breakdown of cell membranes. Higher Cho levels are shown in higher grade tumors compared with lower-grade tumors | |
Cr (from both creatine and phosphocreatine, often called referred to as total creatine peak) | Reflects “cellular energetics” | 3.02 | Decreased phospocreatine (PCr) is an inconstant finding in tumors. Represents a low- energy status of glycolisis in primary tumors (high grade gliomas) and in metastatic tumors is the effect of the lack of PCr in most tissues. | |
Lac | Glycolysis Usually lactate is present only in minimun amounts (i.e., in the brain) and is not depicted using the normal spectroscopic techniques. | Doublet peak at 1.33 ppm | Increased Lac is the effect of the high rate of glycolisis. Lac is an end product of glycolysis and increases rapidly during hypoxia It accumulates in necrotic or cystic areas | |
Lip | May indicated tumor necrosis or voxel contamination by diploic space fat, scalp and subcutaneous tissue | 0.9 and 1.3ppm | The rise of Lip is detected in various cellular processes such as necrosis, growth arrest, inflammation, malignancy and apoptosis. | |
Specific metabolites in brain H-MRS | ||||
NAA | A marker of neuronal and axonal density and viability The exact role of NAA in human brain metabolism is uncertain. It is postulated to be involved in lipogenesis pathways Largest peak in a “normal” H- MRS brain spectrum. | 2.02 | Absence of neurons and axons in most tumors but also in white matter diseases (i.e., multiple sclerosis) | |
mI | A glial marker located in astrocytes Involved in osmoregulation and volume regulation | 3.56 | It is a relative marker for low-grade gliomas. Reduced in high-grade tumors | |
Specific metabolites in Prostate H-MRS | ||||
Ci | Normal human prostate gland accumulates and secretes extraordinarily high Ci levels | 2.6 | In prostate cancer Ci levels fall due to consumption of Ci to supply energy to proliferating cells) | |