Pressure distribution analysis of X-Ray table mattresses.

BACKGROUND: There is a risk of developing pressure ulcers from lying on an X-ray table mattress, if the mattress pressure redistribution properties are poor. AIM: To assess the pressure redistribution properties of 'new' and 'in current clinical use' X-ray table mattresses. METHODS AND MATERIALS: Twenty one X-ray table mattresses, each of 2.5 cm thickness, were evaluated. An anthropomorphic human phantom of adult stature with five different weights (minimum, first quartile, mean, third quartile and maximum) was used to simulate human head, pelvis and heels (pressure ulcer jeopardy areas). Using Xsensor technology, peak pressure was measured and Interface Pressure Ratio was calculated for the three pressure ulcer jeopardy areas 'with' and 'without' an X-ray table mattress. RESULTS: For all mattresses, statistically significant differences (p < 0.05) were found between the peak pressure values with and without using an X-ray table mattress for the three pressure ulcer jeopardy areas; similarly, for all mattresses, statistically significant differences (p < 0.05) were found between the Interface Pressure Ratio values with and without using x-ray table mattress. The type and age of the mattress was observed to have an impact on peak pressure values and Interface Pressure Ratios, with older mattresses performing worse. CONCLUSION: Peak pressure values and Interface Pressure Ratios are reduced significantly when using newer X-ray table mattresses. This could be because newer mattresses use more appropriate materials in their construction and/or older mattresses have lost their pressure redistribution properties. Radiology departments should consider assessing mattresses pressure redistribution properties, perhaps on an annual basis.

Radiation dose from digital breast tomosynthesis screening - A comparison with full field digital mammography.

OBJECTIVES: To compare Mean Glandular Dose (MGD) and effective dose from digital breast tomosynthesis (DBT) screening with that from full field digital mammography (FFDM) screening. METHOD: To simulate compressed breasts, two Perspex-polyethylene breast phantoms were used, one phantom for compressed breast in craniocaudal and the other for compressed breast in mediolateral oblique. An adult ATOM dosimetry phantom was loaded with high sensitivity thermoluminescence dosimeters; the phantom was then positioned on Hologic Selenia Dimensions mammographic machine to imitate DBT and 4-view FFDM screening. Organ radiation doses were measured from 4-view DBT and 4-view FFDM (craniocaudal and mediolateral oblique views for each breast). Organ radiation doses were used to calculate effective dose from one screening session. RESULTS: MGD for DBT was 3.6 mGy; MGD for FFDM was 2.8 mGy. For DBT, other organs (e.g. thymus, lungs, salivary glands, thyroid, contralateral breast and bone marrow) radiation dose was also higher than for FFDM. The use of DBT for breast cancer screening increases the effective dose (E) of one screening session by 22%. E for DBT was 0.44 mSv; E for FFDM was 0.34 mSv. CONCLUSION: The use of DBT for breast cancer screening increases the radiation dose to screening clients.

A Phantom-Based Method to Assess X-Ray Table Mattress Interface Pressures.

BACKGROUND: Pressure redistribution performance of x-ray table mattresses can influence the development of pressure ulcers in at-risk populations. Interface pressure analysis, with human participants, is a common method to assess mattresses. This approach has limitations that relate to the lack of standardisation between and within humans. AIM: This study aimed to develop and validate an anthropomorphic phantom-based method to assess x-ray table mattress interface pressures as an index of mattress performance. METHODS: A three dimensional phantom simulating an adult's head, pelvis, and heels was printed from x-ray computed tomography image data and attached to a metal frame 175 cm in length. Dry sand was added to the phantom head, pelvis, and heels to represent a range of human weights. Pressure distribution was assessed using XSensor. Phantom validation was achieved by comparing phantom mattress interface pressure characteristics, for five human equivalent weights, against 27 sets of human mattress interface pressure data. RESULTS: Using the correlation coefficient R, phantom and human pressure data showed good correlation for the five phantom weights (R values: head = 0.993, pelvis = 0.997, and heels = 0.996). CONCLUSION: A novel method to test x-ray mattresses for interface pressure was developed and validated. The method could have utility in the testing of x-ray mattresses that are in routine use and for new mattress development. Phantom interface pressure data could be provided by manufacturers to help inform procurement decisions when matching mattress characteristics to medical imaging demands and the underlying patient populations.

Impact of Contralateral Breast Shielding on the Risk of Developing Radiation-induced Cancer from Full-field Digital Mammography Screening.

OBJECTIVE: The objective of this study was to investigate the impact of contralateral breast shielding on the risk of developing radiation-induced cancer from four-view full-field digital mammography (FFDM) screening. METHODS: A poly methyl methacrylate-polyethylene breast phantom and adult ATOM dosimetry phantom were used to measure organ dose on four FFDM machines using craniocaudal and mediolateral oblique projections for each breast. A lead rubber shield of 0.25 mm equivalent lead thickness was used to protect the contralateral breast. Organs dose, effective dose, and effective risk were calculated. For effective risk estimations, the impact of the shield was considered for the routine screening views. RESULTS: The contralateral breast dose was reduced by more than 95%. For each FFDM machine, contralateral breast dose reduction in µGy were 35.20 reduced to 1.93, 41.40 reduced to 0.01, 22.85 reduced to 1.24, and 22.76 reduced to 1.66. Effective risk reduction was significant (P < .05). For all FFDM machines, a small reduction was identified in sternum bone marrow dose due to the use of contralateral breast shield. CONCLUSIONS: The results of the study demonstrate the value of a contralateral breast shield. More research is required to determine whether such a shield has clinical utility.

Calculating Individual Lifetime Effective Risk from Initial Mean Glandular Dose Arising from the First Screening Mammogram.

OBJECTIVES: The objective of the study was to use the initial mean glandular dose (MGD) arising from the first screening mammogram to estimate the individual total screening lifetime effective risk. METHODS: Organ doses from full-field digital mammography (FFDM) screening exposures (craniocaudal and mediolateral oblique for each breast) were measured using a simulated approach, with average breast thickness and adult ATOM phantoms, on 16 FFDM machines. Doses were measured using thermoluminescent dosimeters accommodated inside the ATOM phantom; examined breast MGD was calculated. Total effective risk during a client's lifetime was calculated for 150 screening scenarios of different screening commencement ages and frequencies. For each scenario, a set of conversion factors were obtained to convert MGD values into total effective risk. RESULTS: For the 16 FFDM machines, MGD contributes approximately 98% of total effective risk. This contribution is approximately constant for different screening regimes of different screening commencement ages. MGD contribution remains constant, but the risk reduced because the radiosensitivity of all body tissues, including breast tissue, reduces with age. Three sets of conversion factors were obtained for three screening frequencies (annual, biennial, triennial). Three relationship graphs between screening commencement age and total effective risk, as percentages of MGD, were created. CONCLUSIONS: Graphical representation of total risk could be an easy way to illustrate the total effective risk during a client's lifetime. Screening frequency, commencement age, and MGD are good predictors for total effective risk, generating more understandable data for clients than MGD.

Mathematical modelling of radiation-induced cancer risk from breast screening by mammography.

OBJECTIVES: Establish a method to determine and convey lifetime radiation risk from FFDM screening. METHODS: Radiation risk from screening mammography was quantified using effective risk (number of radiation-induced cancer cases/million). For effective risk calculations, organ doses and examined breast MGD were used. Screening mammography was simulated by exposing a breast phantom for cranio-caudal and medio-lateral oblique for each breast using 16 FFDM machines. An ATOM phantom loaded with TLD dosimeters was positioned in contact with the breast phantom to simulate the client's body. Effective risk data were analysed using SPSS software to establish a regression model to predict the effective risk of any screening programme. Graphs were generated to extrapolate the effective risk of all screening programmes for a range of commencement ages and time intervals between screens. RESULTS: The most important parameters controlling clients' total effective risk within breast screening are the screening commencement age and number of screens (correlation coefficients were -0.865 and 0.714, respectively). Since the tissue radio-sensitivity reduces with age, the end age of screening does not result in noteworthy effect on total effective risk. CONCLUSIONS: The regression model can be used to predict the total effective risk for clients within breast screening but it cannot be used for exact assessment of total effective risk. Graphical representation of risk could be an easy way to represent risk in a fashion which might be helpful to clients and clinicians.

Effective Dose and Effective Risk from Post-Single Photon Emission Computed Tomography Imaging of the Lumbar Spine.

PURPOSE: Planar bone scans play an important role in the staging and monitoring of malignancy and metastases. Metastases in the lumbar spine are associated with significant morbidity; therefore, accurate diagnosis is essential. Supplementary imaging after planar bone scans is often required to characterize lesions; however, this is associated with additional radiation dose. This article provides information on the comparative effective dose and effective risk from supplementary lumbar spine radiographs, low-dose computed tomography (LDCT), and diagnostic CT (DCT). METHOD: Organ dose was measured in a phantom using thermoluminescent dosimeters. Effective dose and effective risk were calculated for radiographs, LDCT, and DCT imaging of the lumbar spine. RESULTS: Radiation dose was 0.56 mSv for the anteroposterior and lateral lumbar spine radiographs, 0.80 mSv for LDCT, and 3.78 mSv for DCT. Additional imaging resulted in an increase in effective dose of 12.28%, 17.54%, and 82.89% for radiographs, LDCT, and DCT, respectively. Risk of cancer induction decreased as age increased. The difference in risk between the modalities also decreased. Males had a statistically significant higher risk than female patients (P = .023), attributed to the sensitive organs being closer to the exposed area. CONCLUSIONS: Effective dose for LDCT is comparable with radiographs of the lumbar spine. With the known benefits of image fusion, it is recommended that LDCT replace radiograph imaging for characterization of lumbar spine lesions identified on planar bone scans. DCT is associated with significantly higher effective dose than LDCT. Effective risk is also higher, and the difference is more marked in younger female patients.

Clinical evaluation of the computed tomography attenuation correction map for myocardial perfusion imaging: the potential for incidental pathology detection.

The benefits of hybrid imaging in nuclear medicine have been proven to increase the diagnostic accuracy and sensitivity of many procedures by localizing or characterizing lesions or by correcting emission data to more accurately represent radiopharmaceutical distribution. Single-photon emission computed tomography/computed tomography (SPECT/CT) has a significant role in the diagnosis and follow-up of ischaemic heart disease with attenuation correction data being obtained on an integrated CT scanner. Initially, the CT component of hybrid SPECT/CT systems was what could be described as low specification utilizing fixed output parameters. As technology has progressed, the CT component of newer systems has specifications that are identical to that of stand-alone diagnostic systems. Irrespective of the type of scanner used, the computed tomography attenuation correction (CTAC) for myocardial perfusion imaging produces low-quality, limited-range CT images of the chest that include the mediastinum, lung fields and surrounding soft tissues. The diagnostic potential of this data set is unclear; yet, examples exist whereby significant pathology can be identified and investigated further. Despite guidance from a number of professional bodies suggesting that evaluation of the resulting images for every medical exposure be carried out, there is no indication as to whether this should include the evaluation of CTAC images. This review aims to initiate discussion by examining the ethical, legal, financial and practical issues (e.g. CT specification and image quality) surrounding the clinical evaluation of the CTAC for myocardial perfusion imaging images. Reference to discussions that have taken place, and continue to take place, in other modalities, current European and UK legislations, and guidelines and research in the field will be made.