Medical diagnostic systems 

(Orvosbiológiai képalkotó rendszerek) 

Ultrasound – its place in medical diagnostics 

(Az ultrahang helye az orvosi diagnosztikában) 
Miklós Gyöngy 



• 
EM attenuation = mass attenuation coefficient × density Magnetic resonance imaging (MRI) 

• 
density, relaxation times T1,T2 of (proton) magnetic dipoles Nuclear medicine (PET) 

• 
emissions from radioisotopes (e.g. fludeoxyglucose 18F) Ultrasound (B-mode, Doppler) 

• 
level of backscatter from different depths (arrival times) 


• 
frequency shift in received signal 








Magnetic resonance imaging (MRI) 
• 
resonance, relaxation, shielding, tumbling Nuclear medicine (PET) 

• 
metabolic uptake of radioisotopes Ultrasound (B-mode, Doppler) 

• 
density, compressibility contrast › scattering 

• 
moving scatterers › Doppler effect 


• 
density and compressibility › speed of sound (SoS) 

• 
absorption and scattering › attenuation 







Magnetic resonance imaging (MRI) 
• 	1.5 T, spin-lattice relaxation time T1 [Nitz and Reimer 1999]: 
normal liver: 493 ms; malignant liver: 905 ms 

Nuclear medicine (PET) 
• 5 	µg/g/min glucose metabolic rate in bone marrow [Yao et al. 1995] 
Ultrasound (B-mode) 
• 
backscatter/stiffness/attenuation/SoS/density/non-linearity... 

• 	
cheap (~$20k machine, personnel, electricity, gel) 

• 	
portable 

• 	
fast (10-100 Hz) 






• relatively safe Disadvantages of ultrasound 
• 	
qualitative 

• 	
poor image quality (speckle) 


• 	
depth/resolution trade-off 







Medical diagnostic systems – The place of ultrasound 

Applications of ultrasound 

Application  Example  Why ultrasound?  
Abdominal organs  Cysts  Water-filled cysts very hypoechoic;  
speckle indicates pus  
Cancer diagnosis  Hard lumps  Ultrasound elastography for  
detecting stiff inclusions  
Cardiovascular system  Heart motion  High frame rate;  
Doppler effect  
Eye  Biometry  Strong echoes from boundaries;  
accurate distance measurement  

Foetus Measure size 	Safety; easy delineation of baby from hypoechoic amniotic fluid 


Medical diagnostic systems – The place of ultrasound 

Abscess (pus) in the spleen 


Courtesy of Zonare Medical Systems http://www.zonare.com/products/clinical-images/id_2/ 


Medical diagnostic systems – The place of ultrasound 

Cancerous (malignant) breast tumour 


Courtesy of Zonare Medical Systems http://www.zonare.com/products/clinical-images/id_4/ 


Medical diagnostic systems – The place of ultrasound 

Benign breast tumour 


Courtesy of Zonare Medical Systems http://www.zonare.com/products/clinical-images/id_4/ 


Medical diagnostic systems – The place of ultrasound 

Internal carotid artery blood flow 

pulsed wave 
(PW) Doppler 
gives spatial map 
of blood flow 
Region of 
interest (ROI) 
selected for 
continuous 
wave (CW) 
Doppler 


CW Doppler gives accurate distribution 
of velocities over time for one ROI 


Courtesy of Zonare Medical Systems http://www.zonare.com/products/clinical-images/id_10/ 


Medical diagnostic systems – The place of ultrasound 

Eye biometry 
aqueous vitreous [Thijssen1993] cornea humour lens humour retina sclera speed of sound (m/s) 1620 



transducer 
Example: 
difference in return time 
between front and back of lens 
(c=1.647 mm/µs) is t=4.86 µs. 
Lens thickness is ct/2 = 4 mm. 


simulated echoes from eye based on image above 



Medical diagnostic systems – The place of ultrasound 

Foetus 


Courtesy of Zonare Medical Systems http://www.zonare.com/products/clinical-images/id_7/ 



[Akar et al. 2006] Measurement of attenuation coefficents for bone, muscle, fat and water at 140, 364 and 662 keV .-ray energies. 
http://enformatik.ktu.edu.tr/eakademik/1703/articles/makale_25.pdf 
[Nitz and Reimer 1999] Contrast mechanisms in MR imaging [Thijssen 1993] The history of ultrasound techniques in ophthalmology [Yao et al. 1995] Quantitative PET imaging of bone marrow glucose metabolic response to 
hematopoietic cytokines