MRI in obstetric practice part 2
- 1. MRI in Obstetrics PART II BASIC PHYSICS ( ALSO PL SEE PART 1 which contains BASIC PHYSICS OF MRI FOR COMPLETION ) Dr Shivamurthy H M Prof Dr Ayesha Sultana Rajgoli, Resident Dept of OBG SNMC , Bagalkot Karnataka , India .
- 2. What is Resonance ? Also called REVERBERANCE The reinforcement or propagation of sound from an object to a neighbouring object in air media The same applys to Magnetic field also The sound waves sent from TF1 will cause TF2 to vibrate with same frequency
- 3. Definition - MRI It is an imaging modality A procedure that uses Magnetism, Radio waves, and a Computer , to create pictures of areas inside the body on a Monitor screen.
- 4. Dr. Raymond Damadian with his MRI system
- 5. Principles in M R I Four basic steps are involved 1) Placing the patient in the magnetic field. 2) Transmitting Radio frequency pulse by coil on to the subject. 3) Receiving signals from the patient by coil. 4) Transformation of signals into image by complex processing in the computers
- 6. (1) Placing the patient in the magnetic core
- 7. (2) Propagation MRI Pulse (produced by the external magnetic Source) which delivered to pt body • These Pulses from external magnetic coil are also called Resonance Frequency (R F) Pulses • The Protons in pts body will pick up energy in stepwise manner from RF source and precess and they upgrade in their own energy also.
- 8. • The movement of protons in the patients body are under the influence of external magnetic field . • Under this external magnetic influence , all randomly moving protons in patients body will align and precess along the external magnetic field.(z axis)
- 9. • The magnetic field in the patient body will process and generates current . • This current is received as signal by Radio frequency-coil. (3) MR Signals are received
- 10. (4) Formationof image from the signlas MR signals which are received by the coil which is below the patient , are transformed into image by computers by complex processing.
- 11. Comparison of MRI with USG USG MRI Less soft tissue resolution Superior spatial and soft tissue resolution Small field of view Large field of view Multiplanar view difficult Multiplanar view achieved Poor quality image in oligohydramnios and obesity Better visualization Polyhydramnios better image Problem due to excessive fetal movement Cheaper Costly Widely available Limited availability No claustrophobia Claustrophobia Less time required Time consuming
- 12. (a) High cost (b) Maternal obesity (c) Polyhydromnios (d) Claustrophobia- It is a form of anxiety disorder, in which an Irrational fear of having no escape or being closed in can lead to panic attack. Limitations OF MRI
- 13. Indications MATERNAL a) Cerebral vascular flow study and detection of thrombosis. b) Assessment of CPD during third trimester and in labour ( ? ) c) placenta previa work up d) Evaluation of maternal tumours e) Evaluation of placenta previa and accreta f) Evaluation of intra-abdominal malignancies like lymphoma and renal cell carcinoma.
- 14. Evaluation of retroperitoneal space, for eg: detection of adrenal tumours like pheochromocytoma. It is also used for the characterisation of uterine and ovarian masses.
- 15. Ventriculomegaly Agenesis of corpus callosum Cavum septum pellucidum abnormalities Holoprosencephaly Posterior fossa abnormalities Cerebral cortical malformation Cephalocoele Hydranencephaly Monochorionic twin pregnancy complications Fetal indications (1) BRAIN AND SPINE
- 16. • Fetal brain is well observed on T2 weighted sequences because of contrast between CSF and brain tissue. • After 17wks advantages of MRI in diagnosis of both developmental and acquired intracranial abnormalities have been well established, however diagnosis of some abnormalities may not be possible until after 24wks. • Additional sequences such as T1 weighted and diffusion weighted imaging provide information about brain development, cell density,myelination. • In case of septo - optic dysplasia, MR imaging may confirm absence of cavum septum pellucidum BASIC MRI KNOWLADGE OF CENTRAL NERVOUS SYSTEM
- 17. • Neural tube defects • Sacrococcygeal teratoma • Sacral agenesis • Sirenomelia • Vertebral anamolies (1) BRAIN AND SPINE contd......
- 18. (2) SKULL FACE AND NECK Venolymphatic malformations Hemangiomas Goitre Facial clefts Teratomas Other abnormalities with potential airway obstruction
- 19. Congenital cystic adenomatoid malformation Extralobar pulmonary sequestration Bronchogenic cyst congenital lobar overinflation Diaphragmatic hernia Effusions Mediastinal masses Assessment for esophageal atresia Evaluation of pulmonary hypoplasia secondary to diaphragmatic hernia oligohydromnios, chest mass, or skeletal dysplasia (3) THORAX
- 20. a) Abdomino pelvic cystic mass evaluation b) Tumour evaluation(Sacrococcygeal teratoma,suprarenal or renal masses) c) Complex genitourinary anamolies (bladder outlet obstruction syndromes d) Bladder exstrophy, cloacal exstrophy) 5) RETROPERITONEUM Diagnose Anamolies(Anorectal malformations,complex obstructions) 6) COMPLICATIONS OF MONOCHORIONIC TWINS Determine vascular anatomy prior to laser treatment Evaluate co-joined twins 4) ABDOMEN AND PELVIS
- 21. • Fetal brain anatomy before and after surgical intervention • Anamolies for which fetal surgery is planned • FETAL SURGERY ASSESSMENT
- 22. (a) MRI during an early viable pregnancy first trimester (b) Internal cardiac pacemaker (c) Implanted defibrillator (d) Implants or other metals in the body. (e) Renal failure. (f) skin patches and tattoos. Contraindications for Obstetric MRI study
- 23. MRI is a 2D plane in the body is excited and imaged. Each RF pulse excites a narrow slice. Each RF pulse excites the entire imaging volume and encoding is used to discriminate spatially. How 2DMRI is different from 3D MRI ? In 3D MRI, a whole slab is excited and encoded. Each RF pulse excites the entire imaging volume and encoding is used to discriminate spatially. 3D imaging takes longer time due to the need for slice direction encoding but has a higher signal to noise ratio since all the spins inside the slab are contributing to signal 2D MRI 3D MRI
- 24. Effects of gestational age and radiation dose on radiation induced teratogenesis Gestational period Effects Estimated threshold dose Before implantation ( 0-2 wks after fertilization) Death of embryo or no consequence 50-100mgy Organogenesis ( 2-8 wks after fertilization) CONGENITAL anomalies (skeletal,eyes,genitalia) 200mgy Fetal period Effects Estimated threshold dose 8-15 wks Intellectual disability microcephaly(high risk) 60-310mgy 200mgy 16-25 wks Intellectual disability (Low risk) 250-280mgy S, patel S J , Reedee D L , Katz D et al Radigraphics 2007,27:1705 -22
- 25. ACOG Recommendations 2017 regarding diagnostic imaging procedures during pregnancy and lactation: USG and MRI are not associated with risk and are the imaging techniques of choice for the pregnancy. They should be used prudently and only when it provides medical benefit to the patient. With few exceptions, radiation exposure through Xry CT scan, or Nuclear medicine imaging is at a dose much lower than the exposure associated with fetal harm. If these techniques are necessary in addition to USG or MRI or are more readily available for the diagnosis , they should not be withheld in pregnancy. The use of gadolinium contrast with MRI may be used as a contrast agent in a pregnant woman only if it significantly improves diagnostic performance and is expected to improve fetal or maternal outcome. Breastfeeding should not be interrupted after Gadolinium administration.
- 26. some examples of obstetric MRI Images
- 27. Coronal section of brain shows (a) Cavum septum pellucidum (b) Anterior horn of lateral ventricle (c) communicating the dilated lateral ventricles (a) Gross dilatation of lateral and third ventricles (b) Septum pelluicidum is absent (c) The optic chiasma and proximal portion of optic nerves are small Cavum Septum Pellucidum MRI DIAGRAM 1 Contrast image 2 Axial and coronal T1weighted images at
- 28. AGENESIS OF CORPUS CALLOSUM Absence of corpus callosum Poorly formed corpus callosum Axial T2 Image
- 29. A) lateral ventricle B)Interventricular foramen C)Third ventricle D)Fourth ventricle T1 and T2 image Enlarged lateral ventricle VENTRICULOMEGALY
- 30. Absence brain and skull T2W1 axial and saggital view Absence of cranial vault and herniation of cerebral hemisphere ANENCEPHALY
- 31. Big teratoma developed from coccyx T2 W image Large mass containing well defined areas of varying signal intensity
- 32. Microphthalmia T2 w image Malformation of left eye Microphthalmia associated with PHPV
- 33. Bilateral cleft lip and palate Coronal T2W image Face shows a broad fluid(hyperintense) connection b/w the naso and oropharynx on both sides
- 34. MICROGNATHIA
- 35. Hyperintense lesions with septations Hyperintense lesion with septation inside CYSTIC HYGROMA Parasagittal T2 weighted sequence
- 36. Coronal T2W image CERVICAL TERATOMA Mass involving the anterior neck with hyperextension of the head Large mixed signal intensity mass within the soft tissue of the fetal neck. The head is being deviated to the side
- 37. Congenital diaphragmatic hernia It shows the stomach bowel loops and liver A hole in the diaphragm allows abdominal organs to move into the chest Saggital view non contrast
- 38. Saggital and coronal PULMONARY ADENOMATOID MALFORMATION Cyst or mass in the lung Complex hyperintense lesion with cyst nside in the right lungs
- 39. Polycystic Kidneys with Oligohydramnios Coronal T2 image Coronal T2 showing the enlarged kidneys
- 41. Placenta deeply in the uterine wallPLACENTA ACCRETA Thin strips of tissue that is slightly hyperintense. Thinned myometrium in LUS
- 42. Placenta invades the uterine wall. T2 w a)Abnormal f placental tissue abutting the bladder wall b)Appears less conspicuous in the same area
- 43. The main role of MRI is to confirm or exclude lesions suspected on routine USG as well as to define their extent and demonstrate associated abnormalities if any. Fetal MRI Scores over USG due to its higher spatial resolution, Larger field of view, and ability to visualize fetal anatomy well, despite scanty liquor or maternal obesity. Conclusion
- 44. Fetal MRI is now increasingly used in clinical practice, partly because of the increasing interest in fetal medicine and fetal surgery. With accurate diagnosis of abnormality fetal MRI helps in facilitating surgical planning and intervention. It also helps in predicting postnatal outcome as well as management and genetic counselling.
- 45. Sequences such as DWI, apparent diffusion coefficient, MRI spectroscopy,Functional imaging and volumetric data acquisition are under research. Although US remains the primary and predominant modality for disorders related to pregnancy, MRI is now being increasingly used for specific obstetric indications.
- 46. Wider the bandwidth thicker is the slice. (2) Phase encoding( X axis) These gradient are used to localize the point in a slice from where signal is coming. They are applied perpendicular to each other and perpendicular to the slice selection gradient. Typically, for transverse or axial sections following are axes and gradients applied even though X and Y axes are varied
- 47. In a usual sequence, slice selection gradient is turned on at the time of RF pulse. Phase coding gradient is turned on for a short time after slice selection gradient. Frequency encoding(y axis) or read out gradient is on in the end at the time of signal reception. Information from all three axes is sent to the computers to get the particular point in that slice from which the signal is coming
- 48. Short TR and short TE gives T1 weighted images. Long TR and short TE gives T2 weighted images.
- 49. THE END of part II