|Overview||Using an ex-vivo model (porcine lens) this study showed that at ISPTA.3= 50 mW/cm2 (FDA maximum exposure level for ophthalmic exams) the maximum and average temperature rises were 0.23°C and 0.09°C, respectively. Tis study also determined that a 1.5°C temperature rise was not obtained until ISPTA.3 ≈ 435 mW/cm2.
|Authors||Randy L King, Yunbo Liu, Gerald R Harris
|Journal||Ultrasound in Medicine and Biology, February 2017, Volume 43, Issue 2, Pages 476-481|
|Recommendation/Comment||Relevant for ophthalmological ultrasound.|
|Clinical implication||Operating below the FDA maximum exposure (ISPTA.3= 50 mW/cm2) should result in relatively low heating in ophthalmic exposures.|
|Ultrasound speciality||Quality and safety Issues, physics and US equipment|
Randy L King, Yunbo Liu, Gerald R Harris
Ultrasound in Medicine and Biology, February 2017, Volume 43, Issue 2, Pages 476-481
The soft tissue thermal index defined in the Output Display Standard is not applicable to eye exposures because of unique eye properties such as high ultrasound absorption in the lens and orbital fat. To address this potential safety issue, the U.S. Food and Drug Administration has recommended a maximum exposure level for ophthalmic exams of 50 mW/cm2 (derated spatial-peak temporal-average intensity, ISPTA.3) based on a model of ultrasound propagation in the eye. To gain a better understanding of actual temperature rise as a function of ISPTA.3, an ex vivo experimental study within the porcine lens was performed. Both temperature and acoustic pressure were measured simultaneously in the lens using a fiberoptic probe. At ISPTA.3= 50 mW/cm2, the maximum and average temperature rises over 133 measurements were 0.23°C and 0.09°C, respectively. A 1.5°C temperature rise was not obtained until ISPTA.3 ≈ 435 mW/cm2. The data indicate that operating below the Food and Drug Administration guidance level should result in relatively low heating in ophthalmic exposures.
Eye; Lens; Ophthalmic; Porcine; Safety; Temperature rise; Ultrasound.