AIDT 온디바이스 STEM 고강도 집속 초음파(HIFU) 비선형 베스터벨트(Westervelt) 캐비테이션 서보 엔진

using System;
using System.Runtime.CompilerServices;

namespace ZeliDesk.Stem.BiomedicalAcoustics
{
    public readonly ref struct HifuAcousticState
    {
        public readonly float FocalPeakPressureMpa;
        public readonly float FocalTemperatureC;
        public readonly float ThermalDoseCEM43;
        public readonly bool IsCavitationActive;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public HifuAcousticState(float pressure, float tempC, float cem43, bool cav)
        {
            FocalPeakPressureMpa = pressure;
            FocalTemperatureC = tempC;
            ThermalDoseCEM43 = cem43;
            IsCavitationActive = cav;
        }
    }

    public ref struct HifuWesterveltServo
    {
        private const float SpeedOfSound = 1540.0f; // m/s in tissue
        private const float Density = 1050.0f;       // kg/m^3
        private const float BetaNonlinear = 4.2f;    // B/A tissue parameter
        private const float SpecificHeatC = 3700.0f; // J/(kg*K)

        private float _focalTempC;
        private float _accumulatedCEM43;

        public HifuWesterveltServo(float initialTempC = 37.0f)
        {
            _focalTempC = initialTempC;
            _accumulatedCEM43 = 0.0f;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public HifuAcousticState UpdateServo(float acousticPowerWatts, float pulseDutyCycle, float dt = 0.0001f)
        {
            // Non-linear shock wave pressure gain at geometric focus
            float nominalLinearP = MathF.Sqrt(acousticPowerWatts * 8.5e11f) * 1e-6f; // MPa scale
            float shockGain = 1.0f + 0.15f * nominalLinearP; // Westervelt steepening
            float peakPressureMpa = nominalLinearP * shockGain;

            // Thermal deposition Q = 2 * alpha * I
            float intensityWM2 = (peakPressureMpa * 1e6f) * (peakPressureMpa * 1e6f) / (2.0f * Density * SpeedOfSound);
            float qHeatPerVol = 2.0f * 15.0f * intensityWM2 * pulseDutyCycle; // 15 Np/m absorption
            float tempRiseRate = qHeatPerVol / (Density * SpecificHeatC);

            _focalTempC += (tempRiseRate - (_focalTempC - 37.0f) * 0.4f) * dt;

            // Sapareto-Dewey Cumulative Equivalent Minutes (CEM43)
            float rFactor = _focalTempC >= 43.0f ? 0.5f : 0.25f;
            float dtMinutes = dt / 60.0f;
            _accumulatedCEM43 += MathF.Pow(rFactor, 43.0f - _focalTempC) * dtMinutes;

            bool cavitation = peakPressureMpa > 4.5f;

            return new HifuAcousticState(peakPressureMpa, _focalTempC, _accumulatedCEM43, cavitation);
        }
    }
}