Dept. Of Medical Equipment Huriamila Community College King Saud University 1428 / 1429 Introduction to Medical Equipment (MED 201)

Introduction Lecture 2

Work Fields Bioinstrumentation Bioinstrumentation Biomaterials Biomaterials Biomechanics Biomechanics Biosignals Biosignals Biosystems Biosystems Biotransport Biotransport Clinical engineering Clinical engineering Rehabilitation engineering Rehabilitation engineering

Work Fields (cont.) Bioinstrumentation: Bioinstrumentation: –Deals with principles and problems associated with making measurements in living systems. Biomaterials: Biomaterials: –Design and development of new materials (natural and/or synthetic) to be used as tissue, organ, drug delivery,….etc

Work Fields (cont.) Biomechanics: Biomechanics: –Includes biofluid and biosolid mechanics at molecular, cellular and organ-system levels. (Example: ergonomics: design of chairs and desks to reduce stress and injury.) Biosignals: Biosignals: –Use of data to uncover the mechanisms of biomedical signals origin (Transform and statistical techniques, chaotic analysis….

Work Fields (cont.) Biosystems: Biosystems: –Identify and characterise molecules and cells and understand their function in tissues. Biotransport: Biotransport: –Covers transport processes from organ to subcellular level (transport of ions, proteins, viruses,….)

Work Fields (cont.) Clinical Engineering: Clinical Engineering: –Deals with managing diagnostic and lab equipment in hospitals. Rehabilitation Engineering: Rehabilitation Engineering: –Deals with disabled individuals to achieve better standard of life by designing or modifying new equipment (e.g. prosthetic limb) for them.

Work Environment Industry Industry Government Government Clinical Institution Clinical Institution Academic Research Academic Research

In the scientific method, a hypothesis is tested by experiment to determine its validity. The Need for bioinstrumentation 1. Scientific Method

The physician obtains the history, examines the patient, performs tests to determine the diagnosis and prescribes treatment. The Need for bioinstrumentation The Need for bioinstrumentation : 2- Clinical Diagnosis

A typical measurement system uses sensors to measure the variable, has signal processing and display, and may provide feedback. The Need for bioinstrumentation The Need for bioinstrumentation : 3- Feedback

(a)Without the clinician, the patient may be operating in an ineffective closed loop system. (b)The clinician provides knowledge to provide an effective closed loop system. (a)(b)

In some situations, a patient may monitor vital signs and notify a clinician if abnormalities occur.

Instrument Characteristics Specific Ch/s Specific Ch/s General Ch/s General Ch/s

(a)An input signal which exceeds the dynamic range. (b)The resulting amplified signal is saturated at  1 V. Specific Characteristics: Input Signal Dynamic range

(a)An input signal without dc offset. (b)(b) An input signal with dc offset. Specific Characteristics: DC Offset Voltage

Frequency response of the electrocardiograph. Specific Characteristics: Frequency Response

SpecificationValue Input signal dynamic range ±5 mV Dc offset voltage ±300 mV Slew rate 320 mV/s Frequency response 0.05 to 150 Hz Input impedance at 10 Hz 2.5 M  Dc lead current 0.1  Return time after lead switch 1 s Overload voltage without damage 5000 V Risk current at 120 V 10  Specific Characteristics: An Example ECG Instrument:

(a)(b) (a)A linear system fits the equation y = mx + b. (b)A nonlinear system does not fit a straight line. General Characteristics : Linearity

(a)(b) (a)Continuous signals have values at every instant of time. (b)Discrete-time signals are sampled periodically and do not provide values between these sampling times. General Characteristics : Digital or Analogue

(a) (a)Original waveform. (b)An interfering input may shift the baseline. (c)A modifying input may change the gain. Sources of Errors example: Drift (Thermal voltage)

(a)(b) Data points with (a) low precision and (b) high precision. Precision

Data points with (a) low accuracy and (b) high accuracy. (a)(b) Accuracy

(a)(b) (a)The one-point calibration may miss nonlinearity. (b)The two-point calibration may also miss nonlinearity. Calibration

A hysteresis loop. The output curve obtained when increasing the measurand is different from the output obtained when decreasing the measurand. Sensors: Hysteresis

(a)A low-sensitivity sensor has low gain. (b)A high sensitivity sensor has high gain. (a)(b) Sensors: Sensitivity

(a)(b) (a)Analog signals can have any amplitude value. (b)Digital signals have a limited number of amplitude values. Sensors: Analogue Versus Digital

MeasurementRangeMethod Blood flow 1 to 300 mL/s Electromagnetic or ultrasonic Blood pressure 0 to 400 mmHg Cuff or strain gage Cardiac output 4 to 25 L/min Fick, dye dilution Electrocardiography 0.5 to 4 mV Skin electrodes Electroencephalography 5 to 300  V Scalp electrodes Electromyography 0.1 to 5 mV Needle electrodes Electroretinography 0 to 900  V Contact lens electrodes pH 3 to 13 pH units pH electrode pCO 2 40 to 100 mmHg pCO 2 electrode pO2pO2pO2pO2 30 to 100 mmHg pO 2 electrode Pneumotachography 0 to 600 L/min Pneumotachometer Respiratory rate 2 to 50 breaths/min Impedance Temperature 32 to 40 °C Thermistor Common Medical Measurands

SpecificationValue Pressure range –30 to +300 mmHg Overpressure without damage –400 to mmHg Maximum unbalance ±75 mmHg Linearity and hysteresis ± 2% of reading or ± 1 mmHg Risk current at 120 V 10  A Defibrillator withstand 360 J into 50  Sensor specifications for a blood pressure sensor are determined by a committee composed of individuals from academia, industry, hospitals, and government. Sensors Example: Blood pressure sensor