11/22/2023 0 Comments Calcium fragment 3![]() ![]() ![]() 19 However, the sensitivity and specificity of MRI in characterizing and detecting breast cancers associated with microcalcifications are lower (45%–100% and 37%–95%, respectively). 18,19 MRI provides multiplanar sectioning, 3D views, and superior soft tissue contrast contrast-enhanced breast MRI provides a sensitivity between 71% and 100% and specificity of 81%–99% in the detection of breast cancer. In fact, the American Cancer Society has issued guidelines that include annual breast MRI screening for high risk subjects: women with familial or genetic predisposition for breast cancer, dense breast tissue, and/or lifetime risk greater than 20%–25% based on family and/or clinical history. 15–17ĭue to these well-recognized limitations of mammography, MRI has become increasingly important for the detection and delineation of breast cancer. 14 In addition, there are increased adverse consequences from the cumulative effects of ionizing radiation to breast tissue in women who start screening at a younger age, such as women with a BRCA mutation. 13 The predicted number of cancers induced in 100 000 women who undergo annual screening mammograms from age 40 to 55 yr and biennially from 55 to 74 yr (for a total of 25 examinations, 3.7 mGy to both breasts for each exam) is 86.4. The updated 2007 International Commission on Radiological Protection estimated that the risk of breast cancer death due to exposure of breast tissue to ionizing radiation has approximately doubled compared to 19 estimates. 12 Another potential limitation of mammography is the cumulative effects of exposure of breast tissue to ionizing radiation. 11 Indeed, MRI has higher sensitivity to breast cancer than mammography in women with a 15% or greater lifetime risk of the disease. 11 On the other hand, magnetic resonance imaging (MRI) sensitivity does not seem to be as affected by density as is mammography. ![]() Furthermore, screening mammography has a significantly lower sensitivity in women with extremely dense breasts than in those with almost entirely fatty breasts (62.2% vs 88.2%, respectively) women with breasts in the highest density category have a four- to sixfold greater risk of developing breast cancer compared with those who are least dense. While x-ray mammography can detect calcifications due to the large mass attenuation coefficient differences (a factor of approximately 13) between calcium and surrounding breast tissue, 4 leading to a sensitivity between 74% and 95% and a specificity between 89% and 99%, 5–10 precise localization of calcium deposits is difficult due to the planar nature of mammography. 2 Additionally, high risk lesions such as atypical hyperplasia (which suggest a long-term absolute risk of developing breast cancer of over 25% at 25 yr) can also be associated with microcalcifications. 1 In fact, 86% of ductal carcinoma in situ (DCIS), which is an early form of noninvasive breast cancer, is detected by microcalcifications on mammograms. Although calcifications are common and frequently associated with benign changes, between 48% and 63% of malignant breast cancers contain microcalcifications and are often the sole mammographic feature indicating malignancy. There continue to be major efforts to develop new methods to detect early breast cancers that present as microcalcifications. For both assessments of calcium fragments in phantoms and biopsy-based simulated microcalcifications in breast MRIs, receiver operator characteristic curve analyses were performed to determine the cross-correlation index cutoff, for achieving optimal sensitivity and specificity, and the area under the curve (AUC), for measuring the method’s performance. The method was also evaluated for detection of simulated microcalcifications, modeled from biopsy samples of malignant breast cancer, inserted in silico into breast magnetic resonance imaging (MRIs) of healthy subjects at 7 T. The method was tested experimentally for detection of calcium fragments within gel phantoms and calcium-like inhomogeneities within chicken tissue at 7 T with optimized MR acquisition parameters. The influence of signal-to-noise ratio and various other MR parameters on the results were assessed using simulations and validated experimentally. Characteristic dipole signatures of calcium deposits were detected in magnetic resonance phase images by computing the cross-correlation between the acquired data and a library of templates containing simulated phase patterns of spherical deposits. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |