Biological Measurement 1 BIOE 571

History of ultrasound and importance to medicine Basic imaging modes I. Topics Covered Today History of ultrasound and importance to medicine Basic imaging modes Ultrasound Propagation Reflection and Transmission Generation of ultrasound

Bioeffects of Ultrasound and HIFU My Research Interests Bioeffects of Ultrasound and HIFU

Bioeffects of Ultrasound and HIFU My Research Interests Bioeffects of Ultrasound and HIFU Cancer detection using spectral imaging techniques Ultrasound computed tomography for characterizing soft tissues Coded excitation to improve ultrasound image quality HIFU therapy and therapy monitoring using ultrasound

Homework – 1-2 per lecture (not too difficult)… Grading Homework – 1-2 per lecture (not too difficult)… Homework may include a small amount of coding, so need to know a little Matlab.

History of Ultrasound First of all: what is ultrasound?

History of Ultrasound First of all: what is ultrasound? Pressure waves at frequencies higher than audible range (> 20 kHz) Compared to X-Rays (and CT) ultrasound is safe and does not produce harmful bioeffects unless used at very high intensity The safety of ultrasound makes it desirable as an imaging modality

History of Ultrasound Initially used as a surgical device and studied for its bioeffects (much of this groundbreaking work was conducted at the Bioacoustics Research Laboratory at the U of I). High intensity ultrasound waves were used in water (SONAR) to detect submarines during world war II This led to the idea of using ultrasound as an imaging device

History of Ultrasound First ultrasound systems for imaging humans was developed in 1950s by Howry and Wild

History of Ultrasound Imaging device of Howry and Wild. The water filled gun turret came from a World War II B29-Bomber. Boy have we come a long way!!!

History of Ultrasound Tomographic image of neck from Howry and Wild. The image showed details not visible with X-ray scanners of the day.

History of Ultrasound First ultrasound systems for imaging humans was developed in 1950s by Howry and Wild The main problem with US scanning was consistent contact. Water was the medium used initially to match into tissue but it was not feasible to put people in tanks of water to image. Late 1950s Dr. Wild developed the first hand held 15 MHz transducer contacting skin directly.

History of Ultrasound As early as 1957, blood velocity was estimated using the Doppler effect by Japanese researcher, Dr. Satomura. In 1965 the first real-time scanner was invented with the advent of improved signal processing and transducers. In 1971, the first arrays were introduced allowing improved real-time scanning of patients. From that point on, US begin to gain prevelance in clinical applications.

History of Ultrasound In 1981, color flow mapping images were first created with a US image of tissue superimposed with blood velocity images. In the 1990s, high-end scanners became digital. And 3-D imaging began to emerge.

Ultrasound Compared to Other Modalities:

Ultrasound Compared to Other Modalities Modality US X-Ray CT MRI Imaged Mechanical properties Tissue absorption Biochemistry Resolution 0.3-3 mm ~ 1mm Penetration 3-25 cm through Safety Safe Ionizing radiation

Ultrasound Compared to Other Modalities Modality US X-Ray CT MRI Speed 100 f/s Minutes 30 s to minutes 10 f/s Portability Excellent Good Poor Cost Low High Very high

Ultrasound

Imaging Modes of Ultrasound B-mode: Brightness-mode M-Mode: Motion mode C-mode: Coronal mode Doppler imaging modes (color flow, power Doppler) Contrast and Tissue Harmonic Imaging Strain Imaging Shear Wave Imaging Future Modes

B-Mode Image

B-Mode Image

M-Mode Image

C-Mode Image A C-Mode ultrasound image of a uterus with a submucus fibroid taken from a 3-D ultrasound image of the uterus.

Doppler

Color Flow Imaging

Harmonic Imaging: Pulse Inversion Harmonic image using pulse inversion, image by Sonoace.

Strain image (left) and B-mode image (right) of lymph node. Strain Imaging Strain image (left) and B-mode image (right) of lymph node.

Shear Wave Imaging

Ultrasonic Attenuation in Tissues Tissue dB/MHzy/cm y Blood 0.14 1.21 Liver 0.45 1.05 Muscle 0.57 1.0 Brain 0.58 1.3 Fat 0.6 1 Breast 0.75 1.5 Bone 3.54 0.4-2.2

Sound Speed in Tissues Measurements of speed of sound in biological media Media Sound speed (m/s) Skin 1500-1750 Muscle 1550-1600 Breast 1430-1550 Brain 1520-1550 Blood 1540-1600 Fat 1350-1470 Bone 2500-4200 Spleen 1520-1570 Cartilage 1660-1670

Example Problem a) b) c) d) None of the above A source (which also acts as a receiver) propagates a delta function through a medium with two layers spaced a distance L apart. What might the return signal look like? a) b) c) d) None of the above ρ c ρ c ρ 2c ρ ρ c 2 2 2 2 L L

Example Problem a) b) c) d) None of the above A source (which also acts as a receiver) propagates a delta function through a medium with two layers spaced a distance L apart. What might the return signal look like? a) b) c) d) None of the above ρ c ρ c ρ 2c ρ ρ c 2 2 2 2 L L WHY???

Example Problem A source (which also acts as a receiver) propagates a delta function through a medium with two layers spaced a distance L apart. What might the return signal look like? Have to take speed of sound into account ρ c ρ c ρ 2c ρ ρ c 2 2 2 2 L L