RR The estimation of the mean glandular dose to the breast MGD for x-ray based imaging modalities forms an essential part of quality control and is needed for risk estimation and for system design and optimisation. Almost all of the methodology used employs Monte Carlo calculated conversion factors to relate the measurable quantity, generally the incident air kerma, to the MGD. After a review of the size and composition of the female breast, the various mathematical models used are discussed, with particular emphasis on models for mammography.
Breast Tomosynthesis Better Than Mammography? Posted on Oct 18, in Radiology http: Tomosynthesis had a higher sensitivity, although slightly lower specificity, than mammography for detecting breast cancer. Overall, the more modern technique detected a significantly higher proportion of cancers than standard mammography, at a lower overall radiation dose than the older approach.
The research was published online October 12 in Lancet Oncology. In an accompanying commentMartin J. This trial includes systems from all manufacturers and takes into account the nature of the cancers detected.
Improvements in Screening Standard digital mammography is hampered by suboptimal sensitivity and specificity, particularly for women who have radiographically dense breasts. This is not least in part due to the overlapping of breast tissue when generating the images. This can hide tumor tissue and thus lead to a false negative result, or healthy tissue can have the appearance of a tumor, creating a false positive result.
Digital breast tomosynthesis improves on standard mammography by obtaining multiple low-dose X-ray projection images at a range of angles by passing the X-ray tube over the breast in an arc.
These projection images are used to create a quasi—three dimensional set of thin image slices of the breast, reducing the overlapping effect seen in standard mammography. Indeed, two previous prospective, population-based screening trials indicated that two-view tomosynthesis combined with two-view digital mammography increased cancer detection in comparison with digital mammography alone.
A further study in which tomosynthesis was combined with simulated mammography had promising results. Every third woman aged 40 to 74 years who was invited to undergo regular national breast cancer screening at a single hospital was invited to take part. The pressure on the breast for digital tomosynthesis was approximately half that used in the mammography examinations.
The images were read and scored by two groups of radiologists, one for each screening method; there were seven radiologists in total. At those meetings, it was decided whether or not to recall the patient.
Three women withdrew consent during follow-up and were excluded. The mean age at baseline was 57 years, and all participants were followed up until their next screening in 1. The mean glandular radiation dose was lower with tomosynthesis than mammography, at 2. The team reports that cancers were detected in of 14, women; cancers were detected in women in the tomosynthesis group, and 97 cancers were detected in 96 women in the mammography group.
The sensitivity was higher for tomosynthesis than for mammography, at The cancer detection rate per women screened was significantly higher for digital tomosynthesis than digital mammography, at 8.
Overall, the positive predictive value for screen recalls was slightly lower with tomosynthesis than mammography, at The negative predictive value was similar, at Twenty-two cancers were detected during the follow-up screening interval, giving an interval cancer incidence of 1.
Of these cancers, two were high-grade octal carcinomas in situ, and two were invasive. Several study authors have disclosed relevant financial relationships, which are listed in the original article. Published online October 12, For this purpose, the American Association of Physicists in Medicine Task Group on Dosimetry in Tomosynthesis Imaging has prepared this report that discusses dosimetry in breast imaging in general, and describes a methodology and provides the data necessary to estimate mean breast glandular dose from a tomosynthesis acquisition.
small fraction of dose deposited in the thyroid when compared to the mean glandular dose to the breast, a collar is not mandatory in general.
Not being associated with the risk of obscuring parts of mammograms, such a collar may be used for young women considering their higher radio sensitivity.
Breast Density Issues Tomosynthesis Differences between tomo and mammo Summary 2.
Basic Concepts of Breast Dosimetry (how) Mean Glandular Dose (MGD) (what) DgN coefficients Current DgN tables may slightly under-estimate dose due to % glandular fraction and skin thickness issues. Most mammography manufacturers estimate a mean glandular dose (MGD) for each exposure taken and insert that value into a DICOM tag for the image.
However, there are many different algorithms for estimating MGD and it is not clear which manufacturers use which algorithm. Further factors for the estimation of mean glandular dose using the United Kingdom, European and IAEA breast dosimetry protocols.
Phys Med Biol ; ; 41 Dance DR, Young KC, van Engen RE. Estimation of mean glandular dose for breast tomosynthesis: factors for use with the UK, European and IAEA breast dosimetry protocols. Phys Med. Mean glandular dose of radiation from a breast CT scan is comparable to that from one screen-film mammogram A single digital breast tomosynthesis view involves a mean glandular dose comparable to that of a digital mammogram.