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Transcript of FYS4250Fysisk institutt - Rikshospitalet FYS 4250.
FYS4250 Fysisk institutt - Rikshospitalet
FYS 4250
FYS4250 Fysisk institutt - Rikshospitalet
Medical instrumentation, intensive care unit
FYS4250 Fysisk institutt - Rikshospitalet
Operating room
FYS4250 Fysisk institutt - Rikshospitalet
Approaches
• Physicians• Physicists, engineers• Researcher• Patients• Functions: diagnostic, therapeutic, support• Invasive / non-invasive• Technology: electromagnetic, optical,
mecanical
FYS4250 Fysisk institutt - Rikshospitalet
FYS4250 Fysisk institutt - Rikshospitalet
Unit of measurement, SI system
U = 5 volt
U is the quantity
5 is the dimension figure
[volt] is the unit
Examples of non SI-units: bar, psi, inch, yard, degrees Fahrenheit, miles, gallon
FYS4250 Fysisk institutt - Rikshospitalet
Interfering modifying desired
FYS4250 Fysisk institutt - Rikshospitalet
Example: modifying,
interfering input
FYS4250 Fysisk institutt - Rikshospitalet
Regulation systems of the body
FYS4250 Fysisk institutt - Rikshospitalet
Servo loop
FYS4250 Fysisk institutt - Rikshospitalet
Servo (negative feedback)
ddf
d xGH
Gy
+=
1Eq.1.3
y = output xd = desired input Gd = gain Hf = part of y back to input
d
dd H
xyG →∞→ ,
FYS4250 Fysisk institutt - Rikshospitalet
Biostatistics
• Sensitivity high → high true positive
• Specificity high → high true negative
FYS4250 Fysisk institutt - Rikshospitalet
Output
Input
Output
Input
(a) (b)
(a) Linear system fits the equation y = mx + b. (b) Nonlinear system does not fit the straight line.
FYS4250 Fysisk institutt - Rikshospitalet
Output
Input
Output
Input
(a) (b)
(a)The one-point calibration may miss nonlinearity. (b)The two-point calibration may also miss nonlinearity.
FYS4250 Fysisk institutt - Rikshospitalet
Sensorsignal
Measurand
A hysteresis loop The output curve obtained when increasing the measurand is different
from the output obtained when decreasing the measurand.
FYS4250 Fysisk institutt - Rikshospitalet
(a) (b)
Precision, (a) low, (b) high
FYS4250 Fysisk institutt - Rikshospitalet
Accuracy: (a) low, (b) high
(a) (b)
FYS4250 Fysisk institutt - Rikshospitalet
Sensitivity
Drifting
FYS4250 Fysisk institutt - Rikshospitalet
Linearity
FYS4250 Fysisk institutt - Rikshospitalet
Dynamic systems
The medical variable to be measured will normally vary as a function of time
The statical and dynamical properties of a measurement instrument can be described with a differeintial equation, usually limited to a 2. order like:
a2d2y/dt2 + a1dy/dt + a0y(t) = b2d2x/dt2 +b1dx/dt + b0x(t)
input x(t), output y(t)
FYS4250 Fysisk institutt - Rikshospitalet
0. order system, static, no energy
storing
FYS4250 Fysisk institutt - Rikshospitalet
1.order system, one energy
storing element, relaxation
FYS4250 Fysisk institutt - Rikshospitalet
2.order system,two energy
storing elements, swinging system
FYS4250 Fysisk institutt - Rikshospitalet
2.order system, blood pressure monitoring
FYS4250 Fysisk institutt - Rikshospitalet
Teknology:How to Design, constructProduce, marketMedical equipment