Chapter 6 HISTORY WHAT WAS THE NAME OF

Chapter 6

HISTORY WHAT WAS THE NAME OF THE 1 ST X-RAY TUBE? Coolidge �The model for today’s xray tube

TUBE SUPPORTS �Over-head �Floor-to-Ceiling �Floor �Mobile �C-arm

PROTECTIVE HOUSING � LIST PURPOSE � CONSTRUCTION

INSULATING OIL Between envelope & tube housing �Absorbs heat

GLASS/METAL ENVELOPE Maintains vacuum Permits electrons to flow �Window-emits x-rays

CATHODE Negative side of x-ray tube �Filament �Focusing cup

ANODE ASSEMBLY Positive side �Anode �induction motor

TARGET Area where electrons bombard anode Focal spot �Precise point at which x-rays are created Rectangular

FOCAL SPOT Actual focal spot –point of electron interaction Effective Focal Spot -area projected onto patient **Size controlled by Target Angle**

LINE-FOCUS PRINCIPLE Angled anode increases heat capacity & resolution

ANODE-HEEL EFFECT Variation in beam intensity Anode absorbs some x-rays Beam intensity greatest @ cathode side Position thickest part at cathode side of x -ray tube

OFF-FOCUS RADIATION Extra focal �Photons �Causes �May not produced at focal spot “ghosting” contribute 25 -30% of primary beam

TUBE RATING CHARTS Determines maximum technical combinations allowable without exceeding tube heating limits �Technical factors under m. A curve are considered safe

EXTENDING TUBE LIFE �Warm up anode �Do not hold rotor switch unnecessarily �Use lower m. A stations when possible �Do not make repeated exposure near tube loading limits �Do not rotate tube housing rapidly