BONE DENSITOMETRY

BONE DENSITOMETRY

• THE ART AND SCIENCE OF MEASURING THE BONE MINERAL CONTENT AND DENSITY OF SPECIFIC SKELETAL SITES OR THE WHOLE BODY.

THE MOST VERSATILE AND WIDELY USED TECHNIQUE

• DUAL X-RAY ABSORPTIOMETRY

DXA

DXA

DXA ADVANTAGES

• LOW RADIATION DOSE

• WIDE AVAILABILITY

• EASE OF USE

• SHORT SCAN TIME

• HIGH RESOLUTION IMAGES

• GOOD PRECISION

• STABLE CALIBRATION

DXA

• IS A SUBTRACTION TECHNIQUE- SOFT TISSUE STRUCTURES ARE ELIMINATED. X-RAY ATTENUATION OF THE BONE IS MEASURED. BONE MINERAL DENSITY IS CALCULATED

(BMD)

BMD

DXA• SCANS PROVIDE IMAGES FOR THE

PURPOSE OF CONFIRMING THE CORRECT POSITIONING OF THE PATIENT AND CORRECT PLACEMENT OF ROI ( REGION OF INTEREST)

• IMAGES ARE NOT USED FOR DIAGNOSIS!!

• THE BONE DENSITY RESULTS ARE COMPUTED AND PRINTED BY SOFTWARE

DXA COMPUTATIONAL SOFTWARE

HISTORY• OSTEOPOROSIS UNDETECTED AND OVERLOOKED

UNTIL 1920s.

• THE FIRST PUBLICATION ABOUT BONE MASS APPEARED IN 1930s.

• RA- RADIOGRAPHIC ABSORPTIOMETRY- X-RAY TAKEN AND COMPARED TO A STANDARD

RADIOGRAPH • RADIOGAMMETRY – INTRODUCED IN THE 1960s

IN RESPONSE TO THE MEASUREMENT OF A BONE LOSS IN ASTRONAUTS.

• IN 1970 CT WAS USED THROUGH THE SPECALIZED SOFTWARE. QUANTITATIVE CT.

• 1970s AND 1980s BROUGHT THE FIRST DEDICATED SCANNERS. FIRST SPA THEN DPA. USED RADIOISOTOPE AS A SOURCE OF RADIATION.

• FIRST COMMERCIAL DXA SCANNER INTRODUCED IN 1987 FIRST USED RADIOISOTOPE AS THE X-RAY SOURCE THEN REPLACED BY THE X-RAY TUBE.

• DXA OF THE HIP AND SPINE IS THE MOST ACCEPTED METHOD FOR MEASURING BONE DENSITY

CT BONE DENSITOMETRY

SPA SCANNER

HIP AND SPINE DXA

BONE BIOLOGY

SKELETON PURPOSES

• BODY SUPPORT

• RED BLOOD CELLS MANUFACTURING

• MINERAL STORAGE

BONE TYPES

• CORTICAL

• TRABECULAR- ( CANCELLOUS)

                                                   

                 

BONE CROSS-SECTION

CORTICAL BONE ACCOUNTS FOR 80% OF SKELETAL MASS

IT SUPPORTS WEIGHT

TRABECULAR BONE IS THE DELICATE LATTICE WITHIN

THE BONE THAT ADDS STRENGTH

SPECIFIC BONE

• 40% ORGANIC MATTER

• 60% BONE MINERAL

DXA MEASURES THE DENSITY OF BONE MINERAL

BONE IS CONSTANTLY GOING HROUGH THE REMODELING

PROCESS

PEAK BONE MASS AT THE AGE OF 30-35

DECREASING BONE MASS STARTING AT THE AGE OF

50

DECREASE IN BONE MASS PRONOUNCED IN WOMEN

AT MENOPAUSE

LOSS OF BONE PRESERVING ESTROGEN!

OSTEOPOROSIS

Osteoporosis, or "thin" bones, is a disease that gradually weakens bones, making them more fragile and likely to break. It is not a form of arthritis. Osteoporosis leads to an increase in certain types of fractures (broken bones), such as hip fractures, wrist fractures, and compression fractures of the spinal vertebrae (back bones)

RISK FACTORS FOR OSTEOPOROSIS IN WOMEN

• MENOPAUSE• SMALL BONE FRAME• FAMILY HISTORY• ADVANCED AGE• LOW CALCIUM DIET• INACTIVE LIFESTYLE• CIGARETTE SMOKING• GI MALABSORPTION PROBLEM• CERTAIN MEDICATION USE-

CORTICOSTEROIDS

MINERAL CONTENT CALCULATION IN BONE

DENSITOMETRY

BMC = BMD X AREA

DXA SYSTEMS

• PENCIL BEAM

• FAN BEAM

PENCIL BEAM SCANNER

FAN BEAM SCANNER