MRI KNEE OF ORTHOPEDIC IMPORTANCE

PRESENTED BY: Dr. BEN

MRI KNEE OF ORTHOPEDIC IMPORTANCE

MRI is based on the principle of nuclear magnetic resonance (NMR)

Two basic principles of NMR1.Atoms with an odd number of protons or neutrons have spin

2.A moving electric charge, be it positive or negative, produces a magnetic field

Body has many such atoms that can act as good MR nuclei (1H, 13C, 19F, 23Na)

Hydrogen nuclei is one of them which is not only positively charged, but also has magnetic spin

MRI utilizes this magnetic spin property of protons of hydrogen to elicit images

BASICS AND PRINCIPLES OF MRI

Hydrogen nucleus has an unpaired proton which is positively charged

Every hydrogen nucleus is a tiny magnet which produces small but noticeable magnetic field

Hydrogen atom is the only major species in the body that is MR sensitive

Hydrogen is abundant in the body in the form of water and fat

Essentially all MRI is hydrogen (proton) imaging

•In our natural state Hydrogen ions in body are spinning in a haphazard fashion, and cancel all the magnetism.

•When an external magnetic field is applied protons in the body align in one direction. (As the compass aligns in the presence of earth’s magnetic field)

SIGNIFICANCE OF HYDROGEN IN MRI

When RF pulse is stopped higher energy gained by proton is retransmitted and hydrogen nuclei relax by two mechanisms

T1 or spin lattice relaxation- by which original magnetization (Mz) begins to recover.

T2 relaxation or spin spin relaxation - by which magnetization in X-Y plane decays towards zero in an exponential fashion. It is due to incoherence of H nuclei.

T2 values of CNS tissues are shorter than T1 values

CONCEPT OF T1 AND T2 IMAGING

TE (echo time) : time interval in which signals are measured after RF excitation

TR (repetition time) : the time between two excitations is called repetition time

By varying the TR and TE one can obtain T1WI and T2WI

In general a short TR (<1000ms) and short TE (<45 ms) scan is T1WI

Long TR (>2000ms) and long TE (>45ms) scan is T2WI

Long TR (>2000ms) and short TE (<45ms) scan is proton density image

HOW TO OBTAIN T1 AND T2 IMAGES?

Liquids: long T1 and T2 valuesFat: short T1 and T2 values

HYALINE CARTILAGE

ARTICULAR CARTILAGE

SAGITTALCORONAL

AXIAL

SEQUENCE OF EVALUATION

SAGITTAL VIEW

Vastus medialis

Medial gastrocnemius

Sartorius

Vastus medialis

Medial femoral condyle

Medial meniscus

Tibia

Medialgastrocnemius

Gracilis tendon

Sartorius muscle

Vastus medialis


Medial meniscus

Tibia

Semitendinosus tendon

Medialgastrocnemiusmuscle

Gracilis tendon

Medial gastrocnemiustendon

Posterior horn of medial meniscus

Joint capsule

Anterior horn of medial meniscusSemimembranosustendon

Semitendinosustendon

Semimembranosusmuscle

Shaft of the tibia

Shaft of the femur

Infrapatellar fat pad

Patella

Oblique poplitealligament

Posterior cruciate ligament

Popliteus muscle

Posterior cruciateligament

Popliteal artery

Anterior cruciate ligament

Patellard tendon

Quadriceps tendon

Tibial nerve

Popliteal vein


Popliteal artery

Popliteus muscle

Posterior horn oflateral meniscus

Quadriceps tendon

Patella

Patellar tendon

Tibia

Femur

Popliteus muscle

Popliteus tendon

Posterior horn oflateral meniscus

Head of fibula

Anterior horn of lateral meniscus

Lateral femoral condyle

Commonperoneal nerve

Lateral head ofgastrocnemius muscle

Biceps femoris muscle

Tendon of the lateralhead of gastrocnemius

Common peronealnerve

Lateral meniscus

Vastus lateralis muscle

Superior tibiofibularjoint

Tibialis anterior muscle

CORONAL VIEW

Biceps femoris tendon

Biceps femoris

Popliteal artery

Lateral head of gastrocnemius muscle

Head of fibula

Semimembranosusmuscle

Gracilis tendon

Semimembranosustendon

Medial head ofgastrocnemius muscle

Semitendinosustendon

Lateral superior geniculate artery

Sartoriusmuscle

Medial inferior geniculateartery

Popliteal artery

Popliteus muscle

Biceps femoris tendon

Lateral femoral condyleGreatsaphenousvein

Popliteus muscle

Lateral gastrocnemius tendon

Medial gastrocnemius tendon


Sartorius tendon

Gracilistendon

Posterior cruciate ligament

Lateral tibial plateau

Semimembranosus tendon

Medial tibial plateau

Great saphenous vein

Lateral meniscus

Head of the fibula


Lateral collateral ligament Medial collateralligament



Popliteus tendon

Lateral intermuscularseptum


Lateral meniscus

Lateral intercondylar tubercleMedial intercondylar tubercle

Posteriorcruciate ligament

Vastus medialis muscle


Iliotibial band

Iliotibial band

Anterior horn ofmedial meniscus


Vastus lateralis tendon

Lateral retinaculum

Patella

Lateral retinaculum


Patellar tendon

Medial retinaculum

Quadriceps tendon

AXIAL VIEWS

Tibial tuberosity

Saphenous nerve

Great saphenous vein

Medial gastrocnemiusLateral gastrocnemius

Soleus

TibiaTibialis anterior

Fibula

Patellar tendon

Lateral tibial condyleIliotibial tract

Medial tibial condyle

Sartorius tendon

Gracilis tendon

Semitendinosus tendonSemimembranosus tendon



Infrapatellar fat pad Patellar tendon

Popliteus tendon

Sartorius muscle

Semimembranosus tendon

Semitendinosus tendon

Tibial nervePopliteal vein

Popliteal artery

Lateral gastrocnemius

Joint capsule

Superior medial geniculate arterySuperior lateral geniculate artery

PatellaSynovial fluid

Quadriceps tendon

Semitendinosus tendonSemimembranosus muscle

Popliteal artery and vein

Biceps femoris

Femur Vastus medialis

Sartorius muscle

Suprapatellar bursa

BASIC SEQUENCES IN MSK MRI

Proton-density-weighted sequences: they produce images with the highest signal-to-noise ratio and, therefore, provide better resolution than T2-weighted FSE images. USEFUL FOR MENISCI, CARTILAGE

T1-weighted images: produce high a signal-to-noise ratio, useful in showing musculoskeletal anatomy. WORKHOUSE FOR ANATOMY. Fat appear bright signal/white.Gadolinium enhanced T1 with STIR determine presence of abscess

T2-weighted sequences: have the poorest signal-to-noise ratio, and therefore the poorest resolution, but they are used primarily for their fluid sensitivity and their ability to detect pathology that has a high fluid content (e.g., tendon or ligament tears, tumors).

SIGNIFICANCE OF THE DIFFERENT SEQUENCES OF MRI

The ability to depict anatomic detail, bone marrow abnormalities (including marrow infiltrating processes and fractures), meniscal pathology, blood products, melanin, and enhancement after the administration of gadolinium are the strengths of T1- weighted SE sequences.For the assessment of tumors or musculoskeletal infection, fat-suppressed T1-weighted imaging after gadolinium contrast administration represents the sequence of choice because the high signal from fat is suppressed, making enhancement of abnormal tissue more conspicuous .Advantages: Short scan times.

excellent spatial resolution and depiction of anatomic detailDisadvantage: lower sensitivity for detecting soft-tissue edema compared with fluid-sensitive sequences such as fat-suppressed T2-weighted and STIR sequences.

T1 WEIGHTED IMAGING

GADOLINIUM ENHANCED T1 IMAGING

Advantages: excellent for detecting edema/fl uid, which appears bright and is often associated with pathologic processes such as tumors, infection, fractures, tenosynovitis, and bone contusions

good for evaluating ligaments and tendons, cartilage and fluid-filled structures such as cysts.Disadvantage:Long imaging time

inability to detect marrow pathology when not combined with fat-suppression techniques

T2 WEIGHTED IMAGING

are excellent for depicting anatomic detail because of the high signal-to-noise ratio of proton-density–weighted images. used to evaluate regions obscured by high signal on T2-weighted images.

Fat-suppressed proton-density imaging is often used for the MRI evaluation of meniscal and articular cartilage.

Disadvantage: not sensitive for the detection of fl uid and marrow pathology.

PROTON-DENSITY SE AND PROTON-DENSITY FSE

like T2-weighted sequences with fat suppression, is excellent for detecting fluid and edema when administered with a long TE.

STIR can be used as an alternative to T2-weighted imaging. Change the appearance of white to black; highlighting liquids.

On fluid-sensitive-images such as STIR, fluid appears bright and makes the edema and fluid associated with certain types of pathology more conspicuous than they are on non–fluid-sensitive sequences.

Such pathology includes osteomyelitis, fasciitis, abscesses, metastases, primary bone tumors, fractures, tenosynovitis, tendon tears, and bone contusions.

STIR(SHORT TAU INVERSION RECOVERY)

Fat remain bright and hence difficult to differentiate it from liquid.

Hence fat suppression is required and can be performed using STIR

CAN REDUCE METAL ARTEFACT

SPIN ECHO

1. determination of pulse sequence for review

2. evaluation of T2 weighted images

3. evaluation of T1 weighted images

4. evaluation of specialised pulse sequenes

5. correlation of imaging findings with clinical history and examination findings

EVALUATION OF MRI

T1-weighted image

T2-weighted image

Intermediate-weighted or proton-density–weighted image

Fluid-sensitive sequence, such as STIR or fat-suppressed T2-weighted image

Gradient-echo image

Postgadolinium T1-weighted image

SEQUENCE OF MRI USED MOSTLY FOR MUSCULOSKELETAL SYSTEM

On T1 image, fluid(as in joint, bladder, CSF) will appear dark.

In T2 image, fluid will appear bright/white

Recognition of the TR and TE values, which are often printed on the film can give idea regarding image sequence.(TR value is usually 300 to 800 ms for T1-weighted images and 2000 to 5000 ms for T2-weighted images)

HOW TO RECOGNISE T1 VS T2 IMAGE?

Suppression of signal from fat.

Images appear darker than conventional T2help accentuate the increase in T2-weighted signal (relative to the adjacent tissues)

In evaluation of bone marrow edema and edema secondary to other pathologic processes.

FAT-SUPPRESSED T2-WEIGHTED IMAGES ORSTIR IMAGES

STIR

STIR

Postgadolinium T1-weighted images and fat-suppressed postgadolinium T1-weighted images are typically obtained for the evaluation of infection, tumor, and postsurgical changes or scar.

fluid seems to be dark, and the pathology seems to be bright,in postgadolinium T1-weighted image

POSTGADOLINIUM T1-WEIGHTED IMAGES

POST GADOLINIUM ENHANCEMENT

Trauma( hemarthrosis, meniscal tears, ACL tear, PCL tear, MCL and LCL tear, quadeiceps and patellar tendon rupture, etc)

Degenerative conditions

Infection

Inflammatory

Tumors

Miscellaneous

MRI FINDINGS IN SOME COMMON KNEE CONDITIONS

T1 VS T2 IMAGES: SAGITTAL(LATERAL TO MEDIAL)

T1 VS T2 IMAGES: CORONAL(ANTERIOR TO POSTERIOR)

T1 VS T2: AXIAL VIEWS(CEPHALO-CAUDAL)

TraumaticDegenerative knee conditionsInflammatory knee conditions

Infective knee conditionsTumors

MRI FINDINGS IN COMMON ORTHOPEDIC KNEE CONDITIONS

MRI is commonly used to discern the etiology of an acute hemarthrosis,especially when the knee is too tender or the patientis too anxious for a thorough physical examination. MRI is especially helpful when conventional radiographs are negative.Typically, acute hemarthrosis appears as fluid within the joint with high signal intensity on T2-weighted imagesand intermediate signal intensity on T1-weighted images

HEMARTHORIS

BONE MARROW CONTUSIONS

MARROW EDEMA

Meniscal tears are graded according to how they appear on MRI and are best seen on T1-weighted, gradient-echo, and proton-density images.

Menisci show low intensity on all sequences.uses MRI findings to categorize tears as follows• Horizontal• Vertical radial• Vertical longitudinal with/without flap displacement• Complex

MENISCAL TEARS

HORIZONTAL TEAR OF POST. HORN OF MED. MENISCUS

GRADING OF MENISCAL TEARS

MENISCAL TEAR WITH CYST

DOUBLE PCL SIGN

ACL TEARS

CHRONIC ACL TEAR

PCL TEARS

PARTIAL PCL TEAR

MCL TEAR

PATELLAR TENDON RUPTURE

PATELLA ALTA

PATELLA BAJA

CHONDROMALACIAE PATALLAE

QUADRICEPS TENDON RUPTURE

LOOSE BODIES

MEDIAL RETINACULUM TEAR

SYNOVIAL CHONDROMATOSIS

OSTEOARTHRITIS

STRESS FRACTURE

JUMPER’S KNEE

OSGOOD’S SCHLATTER DISEASE

DISCOID MENISCUS

PLICAE

SUPRA PATELLAR PLICA

PES ANSERINUS BURSITIS

PRE PATELLAR BURSITIS

OSTEONECROSIS

BAKER CYST

CHONDRAL DELAMINATION

OSTEOCHONDRAL FRACTURE

OSTEOCHONDRITIS DESSICANS

SYNOVIAL CYST

CHONDROBLASTOMA

CHONDROBLASTOMA

ENCHONDROMA

NON OSSIFYING FIBROMA

CHONDROMYXOID FIBROMA

OSTEOCHONDROMA

GIANT CELL TUMOR

ANEURSYMAL BONE CYST

OSTEOSARCOMA

OSTEOSARCOMA

SEPTIC ARTHRITIS

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MRI KNEE OF ORTHOPEDIC IMPORTANCE