الفهرس 
Normal Anatomy and MRI Anatomy of the BreastOnly 14 pages are availabe for public view
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Abstract
espite the improvement in the detection of breast cancer with the widespread application of mammography and ultrasound, some breast lesions still remain difficult to diagnose and characterize, especially in dense fibroglandular breasts.
Contrast material–enhanced breast MR imaging is currently accepted as the most sensitive imaging technique for the diagnosis and staging of breast cancer especially in the dense fibroglandular breasts. However, several studies have noted that conventional breast MR imaging, including T2-weighted imaging and contrast-enhanced T1- weighted imaging, is limited in terms of specificity in the assessment of breast tumors. Con¬sequently, there has been considerable interest in the development of adjunct MR imaging methods to improve the specificity of dynamic contrast-enhanced breast MR imaging, and proton MR spectroscopy (¹H MRS) imaging is being investigated for its potential to improve breast disease diagnosis at the cost of a small increase in examination time.
Magnetic resonance spectroscopy (MRS) offers unique possibilities for non-invasive clinical studies of human biochemistry in vivo. Chemical shift, which refers to the variation in the resonance frequency due to the chemical environment, can be explained by the fact that the moving electrons surrounding the protons can generate their own local magnetic field. With its ability to identify different compounds by their chemical shifts, MRS is especially useful in studying metabolism to detect cancer cells.
Rather than generating an image, MRS produces a graph of the resonance amplitudes of various metabolites on the y-axis (in arbitrary units) versus the resonance frequencies on the x-axis (in Hz or ppm). The resonance amplitudes and frequencies are determined by the relative concentrations and the chemical structures of the metabolites respectively.
The markers that are useful in breast diseases are centered at 3.2 ppm and are generally referred to as the choline peak. Choline is considered an important metabolite in proton MR spectroscopy in the mammary gland area because they are precursors of the phospholipids that compose cell membranes, increases in choline signals are thought to reflect increased membrane synthesis. In the mammary gland area, choline shows a promise of enabling differentiation between benign and malignant tumors and of serving as an indicator of tumor activity and viability.
In this study we attempted to investigate the validity of ¹H MRS in evaluation of suspicious breast lesions i.e. the ability of ¹H MRS to detect and characterize lesions in patients referred for MRI with suspicious clinical or sono-mammographic lesions and further correlation of these results with histopathological data and/ or follow up results.
Wide range of size, different types of lesions “including mass and non-mass-like lesions”, different clinical presentations “whether to detect and characterize an overt or occult breast lesions or to differentiate tumor recurrence from post-therapeutic changes” and different pathological entities were included in this study. We found that ¹H MRS measurement increased the specificity of the breast MRI in characterization of different breast lesions especially when its results are combined with the results of conventional dynamic MRI. ¹H MRS was also of great help in differentiating between post-therapeutic changes from recurrent breast cancers.
Although only limited number of the included cases was evaluated for potential of axillary lymph node malignant infiltration by performing ¹H MRS study for the suspicious nodes, we also found that ¹H MRS was helpful to detect lymph nodes’ infiltration by the malignant processes, yet, further studies on larger group of patients are needed to confirm these results.
It should be kept in mind that MRS has a generally low SNR. This fact limits the applicability of MRS in the diagnosis of early breast cancer and generally small lesions. Although breast cancer might be detected by means of spectroscopic imaging only, single-voxel spectroscopy cannot be used for lesion detection. Consequently, MR spectroscopy does depend on further MR imaging–based techniques, limiting its use in the diagnostic setting.
Currently, using a 1.5T MR system, in vivo ¹H MRS can only be performed with confidence on lesions larger than 1 cm3. The introduction of higher field MR systems (i.e. 3.0 T) in clinical centers will have a positive impact on the application of this technique in breast examination. As the magnetic field strength increases from 1.5 T to 3.0 T, chemical shift dispersion is increased and SNR is increased by nearly two-fold implying that smaller breast lesions and axillary nodes may be studied using ¹H MRS.
In conclusion, we can say that ¹H MRS is a short non-invasive scan that can be inserted easily into standard clinical breast MRI protocols as a potential adjunct that can be added routinely to conventional breast MRI. Detection of choline peak with estimation of the choline SNR can accurately differentiate benign from malignant breast lesions with high sensitivity and specificity especially when its results are combined with the results of the standard DCE- MRI scan.