Power Doppler USG
What is Musculoskeletal (MSK) Ultrasound?
Ultrasound imaging uses high frequency sound waves transmitted through a handheld device (transducer) to examine organs, tissues and blood vessels.
A Musculoskeletal (MSK) Ultrasound is a specialized exam that looks specifically at your muscles and joints. MSK ultrasound technologists have special training in looking at joints, muscles, ligaments, nerves, and tendons. A MSK ultrasound is a specialized technique which uses sound waves above 20 kHz to examine muscles and joints.
It is a safe, non-invasive, inexpensive, sensitive, quick procedure with no radiation hazards. Images are acquired in real time.
This procedure can even be performed in children.
Performing MSK ultrasound need special training to identify abnormality in muscles, ligaments, nerves, tendons and joints(both large and small).
What is Doppler ultrasound?
A transducer is passed lightly over the skin above a blood vessel. It sends and receives sound waves that are amplified through a microphone. The sound waves bounce off solid objects, including blood cells. The movement of blood cells causes a change in the pitch of the reflected sound waves. This is called the Doppler effect. If there is no blood flow, the pitch does not change.
Information from the reflected sound waves can be used to make graphs or pictures that show the flow of blood through the blood vessels.
What are the types of Doppler ultrasound?
The three basic types of Doppler ultrasound are:
- “Bedside” or continuous wave Doppler
This type uses the change in pitch of the sound waves to provide information about blood flow through a blood vessel. The doctor listens to the sounds made by the transducer to assess the blood flow through an area that may be blocked or narrowed. This type of ultrasound can be done at the bedside in the hospital. It uses a portable machine that can quickly check the extent of blood vessel damage or disease.
- Duplex Doppler
This test uses standard ultrasound methods to make a picture of a blood vessel and the organs around it. A computer turns the Doppler sounds into a graph. This graph helps to show the speed and direction of blood flow through the blood vessel.
- Colour Doppler
Colour Doppler uses standard ultrasound methods to make a picture of a blood vessel. A computer changes the Doppler sounds into colours that are overlaid on the image of the blood vessel. These colours show the speed and direction of blood flow through the vessel.
Power Doppler is a special type of colour Doppler.
What is power Doppler used for?
Power Doppler ultrasound (PDS) is used to obtain images that are difficult or impossible to obtain using standard color Doppler.
It provides information about the blood flow in vessels that are located inside organs in detail and also helps in assessing low velocity flow in small vessels like in the synovium. Thus, it is very important tool in the diagnosis and the evaluation of early arthritis.
Increased PDS signals indicate active disease in rheumatoid arthritis, while absence of synovitis by PDS signal is considered ass criterion for remission.
What is musculoskeletal ultrasound with power Doppler used for?
1. Diagnosis of synovitis, joint effusion in early arthritis
2. Bone erosions in Rheumatoid Arthritis
3. Osteoarthritis: cartilage thickness measurement, osteophytes, effusion, synovial proliferation, popliteal cysts, meniscal protrusion.
4. Bursitis: Baker’s cyst
5. Tendon diseases: Tendinosis, rotator cuff tear, plantar fasciitis, tendon rupture, Achilles tendonitis
8. Crystal arthopathy : uric acid crystals deposition in cartilage
9. Muscle disease, localization of abscess, muscle tear
10. Nerve entrapments: Carpel tunnel syndrome and to find cause like tenosynovitis, tendon effusion, increased fatty tissue, ganglion cyst.
11. Systemic Sclerosis: evaluation of skin thickness in scleroderma, assess the severity of skin diseases and response to treatment.
1. Beside procedure in aspiration of joint fluids and intra-articular injections.
2. Cyst decompression ( Baker’s cyst)
3. Direct needles into the joint space to deliver local therapy, biopsy and/or to aspirate fluid
How should I prepare?
Wear comfortable, loose-fitting clothing. One may need to remove all clothing and jewelry in the area to be examined and might need to wear a gown during the procedure.
There is usually no restriction on diet. One need not to be on empty stomach or avoid water before procedure. However, smoking should be avoided for minimum of half an hour and one should rest for some time before the procedure.
How is the procedure done?
The patient may be seated on an examination table, a chair or positioned lying face-up or face-down on an examination table depending on the site to be examined.
The rheumatologist himself/herself may move the extremity of interest or may askthe patient to do so to evaluate the anatomy and function of the joint, muscle, ligament or tendon of interest. After fixing the position, a warm water-based gel is applied to the area in order to help the transducer to make secure contact with the body and eliminate air pockets between the transducer and the skin. This will block the sound waves from passing into the body. The transducer is placed on the body and moved back and forth over the area of interest until the desired images are captured.
There is usually no discomfort during the procedure. However, if scanning is performed over an area of tenderness, one may feel slight pain from the transducer.
Once the imaging is complete, the clear ultrasound gel will be wiped off the skin. Any portions that are not wiped off will dry quickly. The ultrasound gel does not usually stain or discolor clothing.
What are the benefits vs. risks?
Benefits- early diagnosis of arthritis
confirmation of subclinical synovitis
Noninvasive (no needles or injections).
– Temporarily uncomfortable, but not painful
-Easy-to-use and less expensive than most other imaging methods.
– Extremely safe and without radiation.
– Provides a clear picture of soft tissues that do not show up well on x-ray images.
– Provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies and fluid aspiration.
– No safety issues for patients with cardiac pacemakers and certain types of metallic implants or fragments in the body since the procedure does not use strong magnetic field like magnetic resonance imaging (MRI).
– An excellent alternative to MRI for claustrophobic patients.
– Real time capture of images showing the movement of a soft tissue structure such as a tendon, joint or an extremity.
– Faster than MRI and does not require the patient to remain completely still, allowing infants to be imaged without sedation.
– Able to clearly see the hip joints of infants, unlike those of adults, whichare largely made of cartilage.
-Can resume daily activity immediately after the procedure.
Standard diagnostic ultrasound has no known harmful effects on humans.
Who are the candidates for MSK USG?
1. patients with mild joint pain/ stiffness for confirmation of subclinical synovitis
2. patients with joint pain less than 3 months duration for diagnosis of early arthritis (< 3months)
3. patients with undifferentiated arthritis
4. patients with known rheumatic diseases for quantification of synovitis/ inflammation
5. patients with known rheumatic diseases for detection of damage (erosion, joint space reduction, degenerative changes)
6. patients with gout for detection of crystal deposition in joints and damage (erosion)
7. patients with osteoarthritis for measurement of cartilage thickness and degenerative changes
8. patients with shoulder problems (frozen shoulder or rotator cuff tendonitis)
9. patients with bursitis to locate the bursa and record the measurements
10. for injections: intra articular injection (joint injection), injection in tendonitis, bursa aspiration, injection for carpal tunnel syndrome, or frozen shoulder