BREAST-TUMOR IMAGING WITH ULTRA-LOW FIELD MRI

Ultra low field MRI was evaluated for breast tumor imaging. Twenty-seven patients with a known or suspected breast malignancy were imaged preoperatively with a T-2-weighted gradient-echo sequence. Additional IR- and gradient-echo sequences were used for measurements of T-1 and T-2 relaxation times. Seventeen resected specimens were also imaged within four hours after removal. Nineteen of 23 carcinomas detected at mammography were also detected with MRI (sensitivity 83%), and one of four benign cases was evaluated as pathologic (specificity 75%). Most of the tumors had T-1 and T-2 relaxation times longer than those of normal breast parenchyma. The T-1 values of the tumors were significantly different from the T-1 values of fat (p =.0002) and breast parenchyma (p =.0151). The tumor T-2 values differed significantly from the T-2 of breast parenchyma (p =.0223) but not from that of fat (p =.1475). In vitro tumor measurements were similar to the in vivo measurements. Despite these statistically significant findings, the calculated relaxation times were not considered sufficiently reliable for the clinical evaluation of breast tumors.