Question

Describe three modes of ventilation and difference between them

1. Exlplain the concept of a Line Isolation Monitor and why it may be needed in an Operating room 2. List the four major Imaging modalities and differentiate between them as to the pros and cons of each system 3. Explain the components of a general x-ray machine 4. What are the three variables that impact x-ray?

Answer 1

1

.Line isolation monitor is a power panel  that monitor the hazard current of an isolated power system.It is designed to protect the patients,health care professionals and care givers from electric shock.If the electrical current reach dangerous level the power panel alarms.

The LIM is used in operation theaters,icu and other critical areas in a hospital.In an operating room LIM constantly monitor the electric current flowing through it.In operation theater if any line get shorted to earth,it will not cause any earth leakage of current so a surgen can continue the procedures with out any delay.

2

1. .Xay
2. CT scan
3. Ultra sonography
4. MRI

X ray

X ray is a form of electomagnetic radiation.It was discovered by Rontgen.It is a2 dimensional representation of a 3 dimensional object.Height and width are maintained but depth is lost.Air appears black , fat appears grey,Soft tissue appears light shades of grey,and bone appears white.

CT scan

Computed axial tomography is a medical imaging method employing tomography where digital geometry processing is used to generate a three dimensional image of the internals of an object from a large series of two dimensional X ray images taken around a single axis rotation.

MRI

MRI is a spectroscopic imaging technique used in medical setting to produce images of the inside of te human being.It is based on the principles of nuclear magnetic resonance , which is spectroscopic technique used to obtain microscopic chemical ,physical data about the molecules.

Comparison between Ct and MRI

CT scan	MRI scan
Suited for hard tissue evaluation	Suited for soft tissue evaluation
Uses X ray for imaging	Uses large external magnetic field
Usually completed with in 5 minutes	It will take 45 minutes
CT scan pause the risk of radiation	No biological hazards
Patient with any metallic implants get the CT scan	Never do Ct for patients with metallic implants
Iodine based contrast shows more incidence of allergic reaction	Contrast shows less incidence of allergic reaction
Comparatively less cheaper	more expensive
only axial plane images are possible	MRI can be done at any plane

pros-no biological hazards reported,MRI can be done at any palne

Cones-

• It causes clustrophobea,
• limitaions to how big a patient can be
• The scanner is very noisy
• medical contraindications-pacemakers,metallic objects
• more expensive
• Can not be used in temporal lobe epilepsy and pregnancy.

Ultrasonography

Diagnostic medical ultrasound is the use of high frequency sound to aid in diagnosis and treatment of patient.Frequency range is 2-15 MH z.The transducer contains piezoelectric elements/crystals which produce the ultrasound pulses.No reflection in ultrasound indicated as black dots which means fluid with in the cyst,urine , blood.Strong reflections by white dots means diaphragm ,tendon,or bone.

• Inflammed organs can be detected
• Safely used in pregnancy
• No radiation produced

4.Components of general X ray machine

1. Operating console-It help the technician  to control the X ray tube current and voltage
2. High frequency generator-They operate on single phase and gives less voltage ripples
3. Collimator and gird-used to avoid unnecessray exposure to X ray using lead plates,lead shutter is used to restrict the beam.Gird is made up of lead strips,which is used to eliminated scattered light.

5.Three variables that impact X ray

Quality of primary radiation

Voltage,current and duration of exposure

Tube film distance