4D DYNAMIC MRA – clinical applications

ABSTRACT ID 1116

Thoracic outlet syndrome

Aims and objectives – To demonstrate the role of 4D dynamic MRA( TWIST MRA) in thoracic outlet syndrome

3D CE MRA Vs 4D Dynamic ( TWIST ) MRACE 3D MRA

provides high resolution 3D MRA data set of the vascular target region.

The images are static and does not provide dynamic flow information

4D Dynamic ( Twist ) MRA (Time resolved angiography with stochastic tragectories ) with high temporal resolution offers 3D data set of images along with dynamic flow information.

Techniques of twist-4D TWIST MRA done after injecting 5-7 cc of contrast followed

by application of MRA sequences immediately after the contrast administration with multiple measurments are taken in rapid succession.

Contrast timing is less critical Images are evaluate in MIP format in cine mode to visualized

real time flow TWIST MRA has advantage of answering vascular diagnostic

questions where blood flow dynamics play a role such as atareovenous malformations, venous malformation in the brain.

For the reasons indicated above TWIST MRA is gaining clinical importance.

This novel 4d MRA can be used in studying thoracic outlet syndrome where documentation of subclavian artery compression on arm elevation is must in diagnosing vascular thoracic outlet syndrome

4D DYNAMIC MRATwist MRA 8 measurements Fov – 450 Body matrix coil -- 12 channel Contrast – 7 cc , IV, hand injection Total scan time – 4 minutes

CASE 1 Female 31 yrs presented with pain on arm

elevation with clinical assessment suggestive of arterial thoracic outlet syndrome

Twist MRA done by injecting 5 – 8 cc of gadolinium contrast via the opposite upper limb

It has demonstrated focal severe stenosis of left subclavian artery on arm elevation and normal flow in arm neutral position

3D CE MRA Vs 4D Dynamic ( TWIST ) MRA

4D DYNAMIC MRA – ARM NEUTRAL POSITION (click on the image)

4D DYNAMIC MRA – ARM ELEVATED POSITION( click on the image)

THORACIC OUTLETThree compartments

Interscalene triangle Costo clavicular space Retopectoralis minor space Dynamically induced compression of neural,arterial,venous structures --- thoracic outlet syndrome Age- 20-40 yrs

Female – male ratio- 4:1 Symptoms – elevation of arms Three distinct syndromes – Neurogenic ( 90-95%), arterial (5-10%),venous Provacative clinical tests – Roos test, Adsons test, Wright test, costoclavicular test

THORACIC OUTLET There are three common sites of compression:

scalene triangle- between  scalenus anterior and scalenus medius muscles

costoclavicular space between clavicle and 1st rib

Subpectoral space - between pectoralis minor and coracoid process

The scalene triangle is defined by the first rib and the anterior and middle scalene muscles and is the most medial compartment. The subclavian artery and branches of the brachial plexus pass through the borders of this triangle while the subclavian vein passes anterior to it.

THORACIC OUTLETE SYNDROME-Thoracic outlet syndrome (TOS) refers to a group of clinical syndromes caused by congenital or acquired compression of brachial plexus  (neurogenic TOS) or subclavian artery  or subclavian vein as they pass through the thoracic inlet. NEUROGENIC TOS Sensory/Motor Upper plexus TOS– C5,C6,C7 nerves Lower plexus TOS- common,C8,T1 nerves

ARTERIAL TOS

Weakness, cold and pain Complication – sub clavian artery thrombosis with peripheral embolization

Venous TOS-Pain ,swelling, cyanosis – subclavian vein compression leads to swelling and thrombosis- paget schroetter syndrome TOS - Etiologies Scalenus anticus syndrome-

Bone abnormalities – cervical rib Elongated C7 transverse process First Rib /clavicle (Tumor/Exostosis, excessive callus) Soft tissue abnormalities Poor posture and weak muscular support in thin woman

Cervical rib

Increased incidence in TOS ( 5-9% in TOS ,1% In normal population) COMLETE-INCOMPLETE Clue to tight fibrous band - Elevation of sub clavian artery

CONGENITAL SOFT TISSUE ABNORMALITIES Anterior scalene muscle hypertrophyCommon belly origin of scalene muscles Brachial plexus passing through anterior scalene muscleBroad middle scalene Interdigitations between scalene muscles Supernumery muscles – scalene minimus muscle Anomalous fibrous bands

IMAGING MODALITIES-

PLAIN RADIOGRAPHY – cervical spine and CXR CT ANGIOGRAPHYMRI WITH MRADOPPLER

Ct angiographyUseful to asses vessels and bony relationsFine analysis of brachial plexus not possible

Other applicationsOther conditions TWIST MRA used areLimb vascular malformation- venous

hemangioma,AVMPeripheral  Arterial disease Hand vascularity - small vessel disease of the

hand