Ultrasound Probe
We decided to find a commercially-available phased array probe that would satisfy our specifications and be optimal for use in transcranial studies. Rather than design our own transducer, which would be costly given the intricate nature of manufacturing ultrasound probes with multiple piezoelectric crystals and corresponding composite backing and matching layers, we decided that incorporating a commercially-available probe would bypass incompatibility issues with Pulse’s ultrasound system as well as avoid the high costs of the design process. Because Pulse Therapeutics uses the Sonosite M-Turbo ultrasound system, we looked for a phased array probe that would be compatible with the Sonosite M-Turbo.
The probe we found is the Sonosite M-Turbo P21x transducer. Its center frequencies range from 1 to 5 MHz, which includes our optimal frequencies of 2-4MHz for insonation of the MCA. The P21x scan range of 35cm is more than enough for our desired scan range of 30-65mm. The transducer face measures 24mm x 17mm, and the probe is 120mm long.
The P21x is characterized as a broadband transducer so it is capable of operating at a wide range of frequencies without a loss in sensitivity. The increased bandwidth may improve the resolution along the range axis and provide better image quality. Moreover, transducers with a broad bandwidth are used for pulsed-wave ultrasound since they generate short pulses after excitation, as most of its energy is lost from the crystal and converted to sound during the first few vibrations.
A couple of factors must still be taken into consideration. Most importantly, the price of one P21x probe is $11,500, which is almost double our targeted cost of $6,000. If we purchased two probes, as needed in our headset design, we would be over our budget of $20,000. Thus, we will proceed with this setback by only initially purchasing only one probe to design our prototype of the headset. Another factor in buying an externally-designed probe is the customization of the external casing of the probe. To be compatible with our headset design, we need a probe that is cylindrical in shape and threaded to allow the pedestal to be wound up and down the probe. The current design of the P21x is geared towards a handheld approach, where the body of the probe is curved to fit the palm of the user’s hand. We will customize the casing of the P21x probe to fit our parameters by manufacturing the casing using plastic injection molding.