An Overview of Thermal and Mechanical Acoustic Output Indices

Hedrick, W. R.; Hykes, D. L.

doi:10.1177/875647939300900502

Cited by 11 publications

(8 citation statements)

References 3 publications

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“…The theoretical value of heating by ultrasound energy is given by calculating the thermal index (TI) [6, 7]. Consequently, SBIT is 3.57°C (thermal index of the cranium; TIC) and CBTT is 0.04°C (thermal index of soft tissue; TIS), respectively (see Appendix, parts 1, 2).…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, based on the ultrasound absorption specificity of the cranium, TI at the SBI is represented by the TIC (equation 3) [6, 7]:…”

Section: Appendixmentioning

confidence: 99%

“…If the beam is neither focused nor diffuse, we use the following values in the calculation: I = 130.0 mW/cm 2 , f = 2 MHz, a = 30.1 dB/cm/MHz (this value, 30.1 ± 3.92, was estimated by using excised rabbit cranium in our preliminary experiment; it is not so different from that of humans, 23.3 dB/cm/MHz [14]), p = 0.25 cm (measured thickness of rabbit skull), b = 0.3 dB/cm/MHz, q = 0.45 cm and A = 0.7 2 π cm 2 [7]. Therefore, the TIS at the depth of 0.7 cm from the skull surface was 0.04°C.…”

Section: Appendixmentioning

confidence: 99%

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Does Long-Term Continuous Transcranial Doppler Monitoring Require a Pause for Safer Use?

Nakagawa¹,

Ishibashi²,

Matsushima³

et al. 2007

Cerebrovasc Dis

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Background: Transcranial Doppler sonography (TCD) has been used widely for long-term monitoring of cerebral blood flow without adverse reports. However, attention has not been adequately paid to the fact that an increase in the time period of TCD insonation causes brain temperature to rise due to ultrasound absorption by tissue and the skull. We measured the actual temperature rise in local brain tissue induced by TCD insonation over a long time period duringin vivo animal experiments in order to verify whether or not a pause is required in long-term, continuous TCD monitoring. Methods: We inserted thermocouples into the skull-brain interface (SBI) of 15 New Zealand White rabbits (10: TCD application group; 5: control group, TCD non-application group). The TCD probe was placed on the parietal bone, and changes in SBI temperature (SBIT) were measured for 90 min. TCD was set at maximum output level (0.2 W, 2 MHz). Results: SBIT in the TCD group increased rapidly to 3.47°C within 25 min and then reached a plateau. The maximum time for safe continuous TCD application is estimated to be 33 min. Conclusions: Even though there are large differences in factors, such as brain volume and environmental conditions, between rabbits and humans, there is less difference in their cerebral blood flow per brain weight, which is the parameter that is mainly associated with heat reduction. Accordingly, the findings of the present experiment suggest that long-term TCD monitoring in clinical use should include a pause after every 30 min of insonation to avoid thermal damage to the brain surface.

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Section: Discussionmentioning

confidence: 99%

“…Furthermore, based on the ultrasound absorption specificity of the cranium, TI at the SBI is represented by the TIC (equation 3) [6, 7]:…”

Section: Appendixmentioning

confidence: 99%

Section: Appendixmentioning

confidence: 99%

See 1 more Smart Citation

Does Long-Term Continuous Transcranial Doppler Monitoring Require a Pause for Safer Use?

Nakagawa¹,

Ishibashi²,

Matsushima³

et al. 2007

Cerebrovasc Dis

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“…The acoustic output level was assessed according to the mechanical index displayed on the screen. The mechanical index provides an indirect measure of the acoustic intensity 35 and was kept at or less than 0.5 in phases I and II to limit bubble rupture. To minimize bias in the phase II studies, observers (F.F.…”

Section: Methodsmentioning

confidence: 99%

Contrast-Enhanced Transrectal Ultrasonography of a Novel Canine Prostate Cancer Model

Forsberg

Johnson²,

Merton

et al. 2002

Journal of Ultrasound in Medicine

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Objective. This study evaluated the utility of a new animal model for prostate cancer imaging using a new ultrasonographic contrast agent (Sonazoid [NC100100]; Amersham Health, Oslo, Norway), for prostate cancer detection. Methods. Twenty-four dogs had a canine transmissible venereal sarcoma cell line injected (50 million cells/mL) directly into the prostate, producing a neoplasm in 15 to 40 days. Transrectal ultrasonography was performed in power Doppler mode on 8 dogs (phase I) and in gray scale phase inversion harmonic imaging mode on 16 animals (including control animals without tumors; phase II). Evaluations were repeated after intravenous injections of the contrast agent (dose, 0.00625-0.20 µL/kg). Histopathologic examination was performed after each study. For the phase II experiments, sensitivity, specificity, and accuracy were calculated. Results. The contrast agent improved visualization of the prostate cancer vascularity and delineation of tumor size and shape in both power Doppler and phase inversion harmonic imaging modes. Canine transmissible venereal sarcoma tumors ranging from 3 × 5 to 40 × 50 mm were detected. The accuracy for detecting the number of prostate tumors increased (in phase II) from 67% to 87% with the addition of the contrast agent. Histopathologic examination confirmed the ultrasonographic findings and revealed typical canine transmissible venereal sarcoma cells infiltrating the prostate with moderate neovascularity. Conclusions. The novel canine tumor model was useful for evaluating ultrasonographic prostate imaging techniques. Improved detection of prostate tumors in dogs was possible with gray scale phase inversion harmonic imaging of the contrast agent. The accuracy of lesion detection increased from 67% to 87%. Key words: animal model; phase inversion harmonic imaging; prostate cancer; ultrasonographic contrast agent.

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“…The pressure level was assessed using the MI displayed on the screen. The MI provides an indirect measure of the acoustic pressure 19 and was kept above 0.8 at all times to facilitate bubble rupture.…”

Section: Methodsmentioning

confidence: 99%

Gray scale second harmonic imaging of acoustic emission signals improves detection of liver tumors in rabbits.

Forsberg

Liu

Merton

et al. 2000

Journal of Ultrasound in Medicine

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This study evaluates a new reticuloendothelium specific sonographic contrast agent NC100100 (Sonazoid) for detection of liver VX-2 tumors in rabbits. Gray scale imaging of five groups of three rabbits, with hepatic VX-2 tumors implanted 7, 10, 12, 14, and 18 days previously, was performed prior to injection of Sonazoid (dosages, 0.01-0.5 ml/kg). Sonazoid produces induced acoustic emission after uptake in the liver. Therefore, harmonic gray scale images were obtained immediately after injection as well as delayed (by up to 2(1/2) h). Five rabbits (one from each group) also had angiography performed, while all animals were evaluated by pathologic examination. Non-contrast enhanced sonography detected 17 of 61 tumors (29%), as well as three false-positives, while the addition of Sonazoid detected 57 tumors (93%) and one false-positive (P<0.001). Acoustic emission made 2 x 2 mm tumors (invisible in conventional B-mode sonography) clearly perceivable in harmonic gray scale. In the subgroup that received angiography, 12 of 36 tumors (33%) were detected with conventional sonography compared to 22 tumors (61%) seen with angiography (P = 0.002). After injection of Sonazoid the ultrasonographic detection rate increased to 97% (35 of 36 tumors), which was a significant improvement over angiography (P = 0.00024). Improved detection of hepatic VX-2 tumors with second harmonic gray scale imaging of Sonazoid is possible because of this agent's acoustic emission capabilities.

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An Overview of Thermal and Mechanical Acoustic Output Indices

Cited by 11 publications

References 3 publications

Does Long-Term Continuous Transcranial Doppler Monitoring Require a Pause for Safer Use?

Does Long-Term Continuous Transcranial Doppler Monitoring Require a Pause for Safer Use?

Contrast-Enhanced Transrectal Ultrasonography of a Novel Canine Prostate Cancer Model

Gray scale second harmonic imaging of acoustic emission signals improves detection of liver tumors in rabbits.

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