Bilateral variation in radial bone speed of sound.

The aims of this study were to: (a) examine differences in speed of sound (SOS) between the right (SOS(R)) and left (SOS(L)) radius; (b) detect bone loss following proximal forearm fracture by SOS measurement at the radius; and (c) compare SOS(L) and bone mineral density (BMD) of one-third, mid-distal, ultra-distal and total region of the left radius. Two hundred eighty-seven Caucasian women (mean age 60.4+/-6.7 years) participated in this study. All subjects were right-handed. Twenty-seven women (mean age 63.6+/-8.0 years) had suffered a high-energy fracture of the right or left forearm. The SOS was assessed using a quantitative ultrasound device, whereas BMD was measured by dual energy X-ray absorptiometry (DXA). The SOS(R) was significantly higher than SOS(L) (4047.5+/-121.0 vs 4026.3+/-113.4 m/s; p<0.001). The contralateral absolute difference was 1.94% (95% confidence intervals: 1.73-2.15%). In women who had suffered a fracture of their right forearm, SOS(R) was not significantly higher than SOS(L )(3989.9+/-141.8 vs 3985.0+/-151.1 m/s), whereas the bilateral difference was reduced to 1.45%. In women with a previous fracture of the left forearm, SOS(R) was significantly higher than SOS(L) (4076.9+/-92.8 vs 3992.6+/-124.0 m/s; p<0.01) and the bilateral difference was increased to 2.61%. Of the 260 subjects without fracture, 155 had greater SOS in the right radius, 102 had greater SOS in the left radius and 3 patients had equal values of SOS in both bones. Calculated correlations between SOS and BMD were weak to moderate ( r=0.27-0.41; p<0.0001 for all comparisons). The SOS measurements should be performed on both radial bones. A high-energy forearm fracture results in a decrease in SOS measured at the radius. Radial-bone SOS measurements cannot predict forearm BMD.

Embryo/fetus radiation dose and risk from dual X-ray absorptiometry examinations.

The aim of the current study was to estimate the embryo/fetus radiation doses and risks associated with spinal and hip dual X-ray absorptiometry (DXA) scans performed on the pregnant mother. The results were compared with the embryo/fetus dose from a thoracolumbar radiograph and pelvic radiograph. Posteroanterior (PA) lumbar spine and proximal femur scans during the first, second and third trimesters were performed on a phantom simulating pregnancy at the three trimesters of gestation. All scans were carried out using a Hologic 1000/W pencil beam DXA unit. Moreover, embryo/fetus doses from a (a) thoracolumbar radiograph and (b) pelvic radiograph were estimated for all periods of gestation using the same phantom. Radiation doses were measured using thermoluminescent dosimeters. The dose reduction achievable by shielding the embryo/fetus with a protective apron during DXA scans was studied for all trimesters of gestation. The embryo/fetus doses during the first trimester were measured to be 1.7 mGy and 2.7 mGy for the PA spine and femur DXA scan, respectively, for an embryo/fetus located 8.5 cm from the anterior maternal surface. The risk of excess fatal cancer was 0.2 per million unborn children irradiated in utero for measurements of the spine and 0.3 per million unborn children for measurements of the femur. The embryo/fetus doses during the second and third trimesters were 2.7 mGy and 4.9 mGy respectively for the scans of the lumbar spine. The risk of childhood fatal cancer was 0.3 per million for the second trimester and 0.5 per million for the third trimester. The embryo/fetus radiation doses during the second and third trimesters were estimated as 1.4 mGy and 1.0 mGy respectively for the examinations of the proximal femur. The risk of childhood fatal cancer was 0.1 per million for both trimesters. The use of the apron resulted in a very small change in the dose absorbed by the embryo/fetus. The embryo/fetus dose associated with both DXA modes investigated in the current study is at least 700 times lower in comparison with embryo/fetus dose from a thoracolumbar or pelvic radiograph in all periods of gestation. In conclusion, the embryo/fetus dose in bone density measurements of spine and femur using pencil beam DXA is lower than the average daily natural background in the United States of 8 mGy. The health provider can decide whether a DXA scanning is beneficial to a pregnant woman, taking into account the potential radiation risks to the embryo/fetus presented in the current study.