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1.  Clinical implementation of kV Cone-beam CT for the verification of sequential and integrated photon boost treatments for breast cancer patients 
The British journal of radiology  2012;85(1019):e1051-e1057.
Objective
To formulate a practical method for the use of cone beam CT (CBCT) for the verification of sequential and integrated tumour bed boosts for early breast cancer patients.
Methods
Partial arc scan geometries were assessed on a treatment unit. Imaging dose measurements on an Elekta Synergy cone beam CT system were made in a CT dose phantom for scan parameters 100kV, 25 mA, 40ms with a S20 collimator. The protocol was used to verify the set up of a cohort of 38 patients, all of whom had surgical clips inserted in the tumour bed. Set up errors with, and without, an extended No Action Level (eNAL) protocol were calculated.
Results
Arcs from 260° to 85° (left breast) and 185° to 15°(right breast) were found sufficient to image fiducial markers and anatomy whilst accounting for the physical limits of the equipment. A single treatment and imaging isocentre was found by applying simple constraints: isocentre < 8 cm from midline and isocentre-couch distance < 30 cm. Contra-lateral breast doses were ~2mGy per scan (right breast) and ~12 mGy (left breast). Both mean population systematic error and mean population random error were 3mm prior to correction. The systematic error reduced to 1.5 mm using an eNAL correction protocol, implying a 5 mm set up margin could be achieved.
Conclusion
An image guided verification protocol using CBCT for breast cancer boost plans was implemented successfully. Set up errors were reduced and an acceptable imaging dose to the contra-lateral breast achieved.
doi:10.1259/bjr/28845176
PMCID: PMC3477491  PMID: 22553296
radiotherapy; breast boost; image-guided radiotherapy; cone beam CT; verification
2.  Dose reduction and its influence on diagnostic accuracy and radiation risk in digital mammography: an observer performance study using an anthropomorphic breast phantom 
The British journal of radiology  2007;80(955):557-562.
This study aimed to investigate the effect of dose reduction on diagnostic accuracy and radiation risk in digital mammography. Simulated masses and microcalcifications were positioned in an anthropomorphic breast phantom. Thirty digital images, 14 with lesions, 16 without, were acquired of the phantom using a Mammomat Novation (Siemens, Erlangen, Germany) at each of three dose levels. These corresponded to 100%, 50% and 30% of the normally used average glandular dose (AGD; 1.3 mGy for a standard breast). Eight observers interpreted the 90 unprocessed images in a free-response study and the data was analyzed with the jackknife free-response receiver operating characteristic (JAFROC) method. Observer performance was assessed using the JAFROC figure of merit (FOM). The benefit of radiation risk reduction was estimated based on several risk models. There was no statistically significant difference in performance, as described by the FOM, between the 100% and the 50% dose levels. However, the FOMs for both the 100% and the 50% dose were significantly different from the corresponding quantity for the 30% dose level (F-statistic = 4.95, p-value = 0.01).
A dose reduction of 50% would result in 3-9 fewer breast cancer fatalities per 100,000 women undergoing annual screening from the age of 40 to 49 years. The results of the study indicate a possibility of reducing the dose to the breast to half of the dose level currently used. This has to be confirmed in clinical studies and possible differences depending on lesion type should be further examined.
doi:10.1259/bjr/29933797
PMCID: PMC2253655  PMID: 17704316
Digital mammography; Average glandular dose; Dose reduction; Diagnostic accuracy; Anthropomorphic phantom; JAFROC

Results 1-2 (2)