Quantitative T2-mapping using MRI for detection of prostate malignancy: a systematic review of the literature

Quantitative T2-mapping using magnetic resonance imaging (MRI) allows measurement of tissue T2-relaxation times to complement anatomical and spatial information derived from T2-weighted imaging. Studies have shown varying T2-relaxation times between prostate malignancy and non-malignant prostatic tissue. This paper aims to critically review the literature in a systematic review, to determine the usefulness of T2-mapping in the evaluation of prostate malignancy. A literature search of PubMed and Embase databases was performed. There were 17 studies, up to 31 June 2018, that measured T2-relaxation times of prostate cancer and non-malignant prostatic tissue. Data reviewed from each study included: number of patients and regions of interest evaluated; patient age; study design; T2-mapping technique utilized; reported T2-relaxation values; method of data analysis; method of “ground-truth” assessment; and reported limitations. The T2-relaxation times of prostate cancer and non-malignant prostatic tissue were compared. The T2-relaxation times in the transition zone (TZ) are generally lower than the peripheral zone (PZ). The T2-relaxation times in prostate malignancy are significantly lower than normal PZ in all the studies that performed a statistical comparison. In three out of four studies that performed a statistical comparison, there was no significant difference in the T2-relaxation times between prostate malignancy and non-malignant TZ. T2-mapping appears useful in identifying prostate malignancy in the peripheral zone but is unable to reliably distinguish prostate malignancy and non-malignant transition zone. Further studies are recommended to determine if T2-mapping can improve diagnostic accuracy when used in conjunction with multiparametric MRI for detection of prostate malignancy.