Exploring MRI

MRI breast with spectroscopy
Magnetic resonance imaging of the breast is best used for patients with known cancer or those at high risk for developing cancer. The criterion for selection of patients is very important and it is necessary to have a clear list of indications so that there is no confusion to the referring clinician. At the same time, it is helpful to have a fixed protocol in terms of the sequences used and technologist training in positioning the patient.
There are various indications/points to be kept in mind while finding out an appropriate case for this technique for patients, like…
? Patient with known cancer for detection of multi focal (same quadrant) and multi centric (different quadrant) disease.
? Picking up incidental synchronous contralateral carcinoma.
? Patient with positive margins following breast conservation surgery as it can detect residual disease.
? Patient with inoperable locally advanced breast carcinoma, it can assess response to neo adjuvant chemotherapy.
? Suspected recurrence can be confirmed with MRI in previously treated breast.
? Axillary node metastases with unknown primary.
? Patients with high risk of breast cancer.
? For pre-operative breast MRI, the following points need to be considered:
? Young patients, patient with dense breasts.
? Patient with difficult tumor histology such as infiltrating lobular carcinoma and tumor with extensive intraductal component.
? Unsuspected DCIS, staging, tumor size and chest wall/pectoralis invasion.

Technique
The patient is made to lie down prone with the breast positioned in the coil. Breast should be centered in the coil to avoid artifacts, have uniform coverage and eliminate redundant tissue. Breast should be pulled away from the chest wall as much
as possible and immobilised. Simultaneous acquisition of images of both breasts is done with an eight-channel coil.

MR Spectroscopy
MR spectroscopy (MRS) offers the capability of using MRI to non-invasively study tissue
bio-chemistry. In the conventional MRI technique, the hydrogen atom in water is the main one that is resonated. In MRS, either 1H atoms or other atoms like 31P, 23Na, K, 19F or Li are resonated within a given region called a voxel. Information on these molecules is presented as a graph with precision frequency on the x-axis revealing the identity of a compound and intensity on the y-axis, which helps quantify the amount of a substance.
The two most widely used MRS techniques involve either viewing 1H atoms in molecules other than water or 31P containing molecules. In 1H MRS, the water signal must first be suppressed as it is much greater than the signal from other IH, containing compounds and has overlapping spectroscopic peaks with these compounds. 

MR spectroscopy in breast
MRI of breast has been shown to be more sensitive than other screening procedures for breast cancer. It has a sensitivity of >90 per cent and specificity of 50-70 per cent. However, it also depicts more abnormal findings. False positive findings occur in fibroadenomas, papillomas, proliferative and non-proliferative changes in the breast. Unexpected enhancing lesions have also been reported in 16-29 per cent of examinations. This leads to breast biopsy, which could be avoided if we know the lesion
is benign.
MRS in breast lesions is a recently described
non-invasive method that has shown promising results in differentiating benign from malignant lesions. It gives information about the chemical contents in the lesions by measuring the choline, which is a tumor marker. High levels of choline are likely to be found in malignant lesions on proton MRS. The specificity of MRS is 85 per cent and sensitivity 100 per cent.
The limitation of MRI breast is the false positives. Proton magnetic