MR Basics: Module 11 Pathology Part 1

Transcription

1 Module 11 Transcript For educational and institutional use. This transcript is licensed for noncommercial, educational inhouse or online educational course use only in educational and corporate institutions. Any broadcast, duplication, circulation, public viewing, conference viewing or Internet posting of this product is strictly prohibited. Purchase of the product constitutes an agreement to these terms. In return for the licensed use, the Licensee hereby releases, and waives any and all claims and/or liabilities that may arise against ASRT as a result of the product and its licensing.

2 MR Basics: Module 11 Pathology Part 1 1. MR Basics Pathology Part 1 Welcome to Module 11 of MR Basics Pathology Part 1. This module was written by John Deans. 2. License Agreement and Disclaimer 3. Objectives After completing this module, you will be able to: Differentiate between the axial, coronal and sagittal planes of the body on magnetic resonance (MR) images. Distinguish between normal and pathologic tissues on MR scans. Locate pathology as demonstrated on MR images. Describe the origin of each pathology presented in the module. List symptoms associated with each pathology and condition. Describe the disease progression for specific pathologies. Discuss treatment options for certain pathologic conditions. 4. Introduction According to Taber s medical dictionary, pathology is the study of the nature and cause of disease which involves changes in structure and function. In this module, we discuss pathology of the brain, vascular systems of the head and neck, and the spine. The module covers some of the common pathologic conditions that a technologist might encounter while performing magnetic resonance (MR) imaging. 5. Magnetic Resonance Imaging Before we begin our pathology discussion, let s go over a few MR basics. Play the animation on this slide as we review. MR uses strong magnetic fields, radio-frequency (RF) waves and the hydrogen atoms of the patient s body to create an image. When a patient is placed in the magnetic field of an MR scanner, the body s hydrogen atoms align either parallel or antiparallel to the magnetic field. An RF pulse is applied and turned on and off rapidly. When the RF pulse is on, the hydrogen protons flip away from the parallel axis of the magnetic field. When the RF pulse is turned off, the hydrogen protons start to relax and return to their parallel position. The signals given off during relaxation are received by the RF coils of the MR scanner and sent to a computer where they are reconstructed into an image. This process is repeated many times during the exam. 6. Pulse Sequences A combination of pulse sequences and scan planes are needed to diagnose pathology. MR uses a variety of pulse sequences to emphasize different types of anatomy. The pulse sequences often are referred to as weighting and can be grouped into three general types of scans: T1 relaxation time, T2 relaxation time and proton density ASRT. All rights reserved. 1 MR Basics: Module 11

3 The chart on this slide outlines scan parameters for contrast weighting, although scan parameters may be equipment and facility specific. It is important to remember that fat has a short T1 and T2 time, and water has a long T1 and T2 time. A T1-weighted scan has a short repetition time and a short echo time. Fat and slow-flowing blood have a high signal and appear bright on T1-weighted images. Anatomy or pathology that contains a high concentration of fluid, such as simple cysts or cerebrospinal fluid, has a low signal and appears dark on T1-weighted images. A T2-weighted scan has a long repetition time and a long echo time. Fat and muscle have a low signal and appear dark, while anatomy or pathology with a high concentration of fluid have a high signal and appear bright. A proton density scan has a long repetition time and a short echo time. Cerebrospinal fluid appears gray on a proton density image because it produces an intermediate signal. Lesions often appear white or gray to white, allowing for clear discrimination between anatomy and pathology. 7. Imaging Planes MR images can be obtained in all 3 planes: axial, coronal and sagittal. A structure should be scanned in a minimum of 2 different planes to help distinguish between normal and abnormal anatomy and to verify the location of anatomy and pathology. 8. The Brain Now that we ve done a quick review of MR imaging, let s begin our discussion with brain pathology. It s important to remember the anatomy and function of each part of the brain as you take the patient s history. Compiling a thorough patient history helps the radiologist make an accurate diagnosis, and a visual assessment of the patient is just as important as a verbal assessment. Many times what you see, such as one-sided weakness or facial droop, combined with the patient s history, provides the additional information needed to help both the radiologist and the ordering physician. 9. Brain Anatomy First, let s discuss some basic anatomy of the brain. The brain is one of the largest organs in the human body. An adult brain weighs approximately 3 pounds (1.36 kg). It is made up of 100 billion neurons and is the center for intellect, emotions, behavior and memory. The brain is divided into 4 principle parts: the brain stem, diencephalon, cerebrum and cerebellum. 10. The Brain Stem The brain stem consists of the medulla oblongata, pons and midbrain. The medulla oblongata extends from the pons to the spinal cord and sits anterior to the cerebellum. It contains all the tracts that connect the spinal cord and various parts of the brain. The medulla regulates heart rate, the respiratory centers that control breathing and the diameter of the blood vessels, which regulate blood pressure. The medulla also has reflex centers for coughing, sneezing, swallowing and vomiting. The pons lies directly superior to the medulla oblongata and anterior to the cerebellum. It connects the spinal cord to the brain and, like the medulla, consists of tracts of white matter ASRT. All rights reserved. 2 MR Basics: Module 11

4 The 2 respiratory centers located in the pons work with those in the medulla to help control the breathing rhythm. The midbrain extends from the pons to the lower portion of the diencephalon. The midbrain closes the cerebral aqueduct, the tunnel that connects the third and fourth ventricles. Visual, auditory and equilibrium reflexes are located in the midbrain. 11. The Diencephalon Located superior to the brain stem, the diencephalon consists of the thalamus and hypothalamus. The thalamus is superior to the hypothalamus and forms the lateral wall of the third ventricle. Mostly composed of gray matter, it is a relay station for several sensory impulses. The thalamus groups the impulses and then sends them to the cerebrum where the sensations are felt. The hypothalamus is superior to the pituitary gland and forms the floor and part of the wall of the third ventricle. It controls many bodily functions and is one of the major regulators of homeostasis, that is, the ability to maintain a stable internal environment while adjusting to external environmental changes. The hypothalamus produces a wide range of hormones. It also is responsible for heart rate, the movement of food through the gastrointestinal tract, control of body temperature, regulation of food intake and sleep cycles. 12. The Cerebrum The largest and most superior part of the brain is the cerebrum. It consists of a right and left hemisphere, which are separated by the longitudinal fissure. Within each hemisphere is a lateral ventricle. The surface of the cerebrum, or cerebral cortex, is composed of gray matter. The cerebrum also contains white matter, which is made up of myelinated axons and dendrites. The axons and dendrites connect the 2 cerebral hemispheres to each other and to the other parts of the brain. 13. The Cerebellum The second largest part of the brain, the cerebellum lies inferior to the cerebrum and posterior to the brain stem. It is separated from the medulla and pons by the fourth ventricle. The functions of the cerebellum include coordination, the appropriate trajectory and endpoint of movement and equilibrium. The cerebellum functions below the level of conscious thought. For instance, if you reach for a pitcher of water, the impulse that signals the arm movements comes from your cerebrum. The cerebellum is responsible for adjusting the impulse so your arm and finger movements are coordinated and you don t reach past the pitcher. The cerebellum also is involved in some sensory functions. If you pick up the pitcher of water with your eyes closed, you can tell if the pitcher was full, half full or empty. The cerebellum works with the midbrain and the receptors in the inner ears to regulate equilibrium. 14. Knowledge Check 15. Knowledge Check 2014 ASRT. All rights reserved. 3 MR Basics: Module 11

5 16. Cavernoma Now we ll discuss some pathologies and conditions of the brain that you might see when performing an MR scan. A cavernoma, also known as a cerebral cavernous malformation (CCM), cavernous angioma or cavernous hemangioma, is a benign vascular abnormality of the central nervous system. Mainly found in the brain and spinal cord, it is a cluster of abnormal, dilated vessels covered by a fibrous capsule. The cells that line a cavernoma are similar to the cells lining normal blood vessels; however, in the malformation, they tend to leak and produce small bleeds. Cavernomas are filled with slow-flowing blood and appear similar to a blackberry. They vary in size, are slow-growing and occur more often in women than in men, usually between the ages of 40 and 50. Children of individuals with a cavernoma have a 50% chance of developing this malformation. However, 9 out of 10 patients with a cavernoma diagnosis do not have a family history of the condition. 17. Cavernoma Symptoms vary according to the size and location of the cavernoma. Common symptoms include seizures, stroke due to the bleeding, visual changes and slurred speech. However, approximately half of patients do not experience any symptoms, and the cavernoma appears as an incidental finding during a scan for another condition. 18. Case Study: Cavernoma The patient in the images on this slide is a 1-year-old child with a history of seizures. The mother of this patient also has a known cavernoma. The child s cavernoma is located along the inferior medulla and is more prominent on the right side. The image on the left is an axial gradient-echo scan. In this image, the cavernoma is mostly hypodense with multiple hyperintense signals in the center. Cavernomas contain blood at various stages of breakdown. Hemosiderin, which is an iron pigment byproduct of degraded hemoglobin, appears dark. The image on the right is a coronal T2-weighted scan. The cavernoma appears hyperintense on this image. 19. Neuroglial Cyst A neuroglial cyst is a benign condition that affects the neuroglial cells. Glial cells occupy about half of the space in the central nervous system, guide neural connections and provide nutrients and insulating myelin. In a developed nervous system, glial cells are able to multiply and divide. In the case of a traumatic injury, they multiply and fill the space that was previously occupied by neurons. 20. Neuroglial Cyst There are 4 types of glial cells in the central nervous system: astrocytes, oligodendrocytes, microglia and ependymal. Astrocytes take part in brain development, help create the blood-brain barrier and form the link between neurons and blood vessels. Oligodendrocytes form a supporting network for the neurons. They make up the lipid and protein covering called the myelin sheath. Microglia 2014 ASRT. All rights reserved. 4 MR Basics: Module 11

6 protect the central nervous system. They engulf invading microbes and clear away dead cells. Ependymal cells form the lining for the ventricles and the central canal of the spinal cord. 21. Case Study: Neuroglial Cyst This patient presented with a new onset of facial tics. A tic is a sudden, involuntary contraction of the facial muscle. The diagnosis was a neuroglial cyst of an ependymal cell. The benign ependymal neuroglial cyst in these images is located along the left temporal lobe, medial to the temporal horn of the lateral ventricle. The cyst appears hypointense on the axial T1-weighted image on the left and hyperintense on the axial T2-weighted scan on the right. 22. Meningioma A meningioma is a slow-growing, highly vascular benign tumor that mostly occurs along the meningeal vessels and the superior longitudinal sinus. Because about 90% of these tumors are located above the tentorium cerebelli, it is important to acquire the last slice of a brain scan through the meninges. This intracranial neoplasm invades the dura and skull, resulting in a thinning of the cranium. A meningioma also may occur in the spine. 23. Meningioma Meningiomas are the second most common primary tumor affecting the central nervous system, accounting for approximately 20% of all primary brain tumors. Meningiomas usually occur in adults between the ages of 40 and 60 and are more prevalent in women. Symptoms vary according to the size and location of the tumor. Common symptoms include headaches, nausea, vomiting, seizures and changes in mental status. 24. Case Study: Meningioma The images on this slide are of a patient with a known meningioma; MR imaging was performed to check the meningioma. The tumor was located in the right posterior frontal and parietal lobes and had already started to invade the dura mater. A meningioma can appear isointense to hypointense on T1- and T2-weighted scans. The image on the left is a sagittal T1-weighted scan before contrast; the meningioma appears hypointense. The image on the right is a sagittal T1-weighted postcontrast scan. Because a meningioma is highly vascular, it enhances greatly on the postcontrast scan. Edema surrounds the mass and is more evident on the postcontrast image. 25. Encephalomalacia Encephalomalacia is also known as cerebral softening and is a degeneration of the brain tissue. Caused by an infarct, inflammation or hemorrhage, it can occur in any lobe of the brain and results in the loss of function in that lobe. Encephalomalacia is categorized according to the tissue it affects: leukoencephalomalacia is the softening of the white matter, and polioencephalomalacia is the softening of the gray matter. It also is classified according to the stage of damage and the color: red, yellow or white softening. Symptoms vary greatly according to severity and location of the condition ASRT. All rights reserved. 5 MR Basics: Module 11

7 26. Case Study: Encephalomalacia This small infant was a victim of shaken baby syndrome. The patient suffered an anoxic brain injury, which occurs when there is an oxygen deficiency. The reduced oxygen supply can be the result of respiratory obstruction or reduced respiratory movements. The condition also can be caused by reduced lung surface area, which limits the exchange of gases, as in the case of a patient with pneumonia. The image on the left is an axial gradient-echo scan, and the image on the right is an axial T2- weighted scan. Both images show evidence of cerebral atrophy of the right parietal lobe, extending posteriorly into the temporal and occipital lobes. The lateral ventricles are dilated, with increased dilation of the occipital horn on the right. The encephalomalacia is seen in the right supratentorial, which is the cause of the dilation of the lateral ventricles. 27. Leukoencephalopathy Leukoencephalopathy is a group of diseases affecting the white matter tissue of the brain. These diseases disrupt the myelin sheath, which is the fatty layer that protects the nerve cells. Once the myelin sheath is destroyed, the nerve cells are left unprotected. Symptoms vary depending on the area of the brain that is affected. Leukoencephalopathy is progressive, and although some patients may stabilize, the loss of neurologic function is irreversible. 28. Leukoencephalopathy Leukoencephalopathy in cancer patients is most often related to the use of methotrexate chemotherapy, although there have been some cases related to other chemotherapy drugs. The route of administration of the drug, whether intravenously or directly into the brain through a port, does not seem to have a bearing on the rate of occurrence. The disease may not present until years after the end of methotrexate treatment. The incidence of leukoencephalopathy increases as the strength of the drugs used and the length of survival time increases. A longer survival period allows time for the side effects of chemotherapy to appear. 29. Leukoencephalopathy Multifocal, or disseminated, necrotizing leukoencephalopathy occurs most often when methotrexate or cytarabine therapy is combined with a large cumulative dose of whole-brain irradiation. In this form of the disease, there are multiple sites of destruction of both the myelin sheath and the nerve cells. The deterioration begins with the nerve cell and then spreads to the myelin sheath. Progressive, multifocal leukoencephalopathy occurs in patients with long-term immunosuppression caused by a disease such as leukemia or by immunosuppressive drug therapy. In this disorder, the John Cunningham virus that is commonly found in the kidneys of healthy individuals enters the brain of the immunosuppressed patient. The virus infects and destroys the cells that produce the myelin sheath. The majority of patients with this form of leukoencephalopathy die within 6 months of the onset of the infection ASRT. All rights reserved. 6 MR Basics: Module 11

8 30. Case Study: Leukoencephalopathy The image on the left is a diffusion-weighted scan. Diffusion weighting is an MR technique that shows the diffusion of water molecules through membranes. The image on the right is an apparent diffusion coefficient (ADC) map, which is created by postprocessing the diffusionweighted scan. Abnormal tissue appears darker than normal tissue on the ADC map. The patient in these scans is a toddler who accidently ingested methadone. On the diffusionweighted image, the areas of restricted diffusion in the white matter of the cerebellar lobes appear very bright. The same areas appear dark on the ADC map. There is also a patchy area of restricted diffusion in the cerebrum. The appearance of the white matter is consistent with multifocal necrotizing leukoencephalopathy caused by the methadone. 31. Cerebral Infarction A cerebral infarction is the necrosis of brain tissue due to a lack of blood. It often is caused by stenosis, or occlusion, of an artery that is responsible for supplying blood to an area. Two sets of arteries serve as the main blood supply to the brain: the common carotid arteries and the right and left vertebral arteries. 32. Cerebral Infarction The common carotid arteries divide into the external and internal carotid arteries at approximately the level of the fourth cervical vertebra. The external carotid arteries provide blood to the face and scalp. The internal carotid arteries supply blood to three-fifths of the anterior cerebrum, excluding parts of the temporal lobe and occipital lobe. Reduced blood flow through the internal carotid arteries results in a loss of function in the frontal lobe. The patient can experience weakness or paralysis on the side of the body opposite the affected internal carotid artery. The vertebral arteries merge to form the basilar artery. The vertebrobasilar artery supplies the posterior two-fifths of the cerebrum, part of the cerebellum and the brain stem. An occluded vertebral artery can cause many symptoms including blindness and paralysis. 33. Case Study: Cerebral Infarction The patient shown in these images is a 57-year-old man who presented at the emergency department with a sudden change in mental status. Numerous areas of restricted diffusion were diagnosed, indicating new acute ischemic infarctions and a loss of blood supply to certain areas of the brain. An extensive area of restriction is seen in the posterior left parietal and temporal lobes. The image on the left is an axial diffusion-weighted scan. The area of infarct appears hyperintense in the lower left side of the brain. The image on the right is an axial T2-weighted scan. The same area appears hyperintense compared to the surrounding tissues, but darker than on the diffusion-weighted image. 34. Small Vessel Occlusive Disease Small vessel occlusive disease is the weakening of the arterial vessels of the brain. Stroke is often the first sign of this condition and is most often caused by hemorrhage rather than 2014 ASRT. All rights reserved. 7 MR Basics: Module 11

9 ischemia. Small vessel occlusive disease is more prevalent in women and patients with diabetes. Individuals with this condition are at increased risk of multiple strokes within their lifetime. Patients with small vessel occlusive disease often experience seizures and migraine headaches accompanied by visual changes. Symptoms vary and many patients can be asymptomatic. 35. Case Study: Small Vessel Occlusive Disease These images show a 48-year-old female patient who presented to the emergency department with a severe headache and visual changes that came on suddenly and lasted for several hours. The axial T2-weighted image on the left shows several scattered hyperintense foci within the subcortical white matter of the cerebral hemisphere. These hyperintense areas are due to ischemic change from small vessel occlusive disease. The image on the right is an axial T1- weighted scan in which the same areas appear hypointense. 36. Knowledge Check 37. Knowledge Check 38. Arnold-Chiari Malformation An Arnold-Chiari malformation is characterized by the downward elongation of the medulla oblongata, cerebellum and the fourth ventricle into the cervical portion of the spinal cord. Usually, this condition is the result of a small posterior fossa, which causes a herniation of the brain stem and cerebellar tonsils through the foramen magnum. The malformation constricts the flow of cerebrospinal fluid (CSF). Although the condition generally occurs during fetal development, rare cases are seen into adulthood. Arnold-Chiari malformations that occur later in life are the result of the CSF being drained away because of infection, injury or exposure to toxic substances. 39. Arnold-Chiari Malformation Arnold-Chiari malformations are categorized into 4 types. In type 1, only the lower part of the cerebellum and the cerebellar tonsils extend into the foramen magnum. The protrusion reaches approximately 5 to 6 cm below the base of the skull. No hydrocephalus is involved, and the fourth ventricle remains in its normal location. In some instances, there may be a syrinx in the cervical spine area. A syrinx is a fluid-filled cavity within the spinal cord. Type 1 Arnold-Chiari malformations are often asymptomatic, and the malformation is diagnosed as an incidental finding during diagnostic imaging for another condition. As the malformation starts to progress to type 2, the patient may have pain in the back of the head and neck that increases in intensity with activity. In addition, the patient may experience dizziness, difficulty with swallowing and sleep apnea. 40. Arnold-Chiari Malformation A type 2 Arnold-Chiari malformation is usually only seen in children born with spina bifida. Spina bifida is a congenital defect in which part of the spinal cord and its meninges are exposed through a hole in the spine. In this type of malformation, the cerebellar tonsils, vermis of the 2014 ASRT. All rights reserved. 8 MR Basics: Module 11

10 fourth ventricle, cerebellum and medulla oblongata herniate through the foramen magnum and into the cervical spinal canal. Hydrocephalus occurs when the fourth ventricle is obstructed. This type is also associated with agenesis, or abnormal development, of the corpus callosum. 41. Arnold-Chiari Malformation A type 3 Arnold-Chiari malformation is characterized by the displacement of the cerebellum, meninges and occasionally the brain stem into an encephalocele. An encephalocele is a congenital failure of the skull to close, which results in the herniation of the brain tissue into a sac-like protrusion. A type 4 malformation involves an incomplete or undeveloped cerebellum. It sometimes is associated with exposed parts of the skull and spinal cord. 42. Case Study: Arnold-Chiari Malformation A type 2 Arnold-Chiari malformation was diagnosed at birth in the 5-month-old infant shown in these images. An MR scan was performed to evaluate the surgical repair of a myelomeningocele, a defect in which the exposed spinal cord protrudes posteriorly. The malformation is usually associated with spinal nerve paralysis and is caused by the failure of the neural tube to fuse during early embryogenesis. The image on the left is a sagittal T1-weighted scan that demonstrates the herniation of the cerebellar tonsils through the foramen magnum. The herniation is more pronounced on the left side of the cerebellum. The dilated ventricles, or ventriculomegaly, are due to the Chiari malformation and an obstruction at the level of the Sylvian aqueduct. The obstruction was diagnosed because of the lack of CSF signal within the aqueduct. The ventricles appear hypointense in this image. The image on the right is a coronal T2-weighted scan. The dilated ventricles appear hyperintense on this image. The 4 straight bright lines outside the anatomy are signal from saline bags. When imaging smaller anatomy, placing saline bags within the coil helps increase the signal. 43. Dandy-Walker Syndrome Dandy-Walker syndrome is a congenital malformation of the cerebellum. It is a form of hydrocephalus that causes an enlargement of the fourth ventricle. An increase in the fluid spaces surrounding the brain results in increased pressure within the brain. A cyst that forms at the base of the skull, or the posterior fossa, causes a narrowing or complete absence of the cerebellar vermis. The vermis is located in the middle of the cerebellum; it is associated with posture and movement and receives somatic sensory input. In Dandy-Walker syndrome, there also is abnormal development of the corpus callosum, which is the bundle of nerve fibers that connects the cerebellar hemispheres. 44. Dandy-Walker Syndrome Dandy-Walker syndrome is most often diagnosed within the first year after birth. Symptoms in infants include an enlarged head circumference and slow development of motor skills. Approximately 10% of cases are not diagnosed until late childhood or early adulthood. In older 2014 ASRT. All rights reserved. 9 MR Basics: Module 11

11 individuals, symptoms include headaches, seizures, irritability and vomiting. The pressure on the cerebellum affects the nerves that control the eyes, resulting in jerky eye movements. Because the cerebellum is responsible for skilled movement, coordination, posture and balance, these functions also are affected, and the patient will display a lack of muscle coordination and unsteadiness. Dandy-Walker syndrome is also associated with malformations of the heart, face and limbs. Often, the affected individual has additional toes and fingers or fused fingers and toes. 45. Case Study: Dandy-Walker Syndrome The images on this slide were part of a routine follow-up scan of a 1-year-old child with a diagnosis of congenital Dandy-Walker syndrome. In this study, the cerebellar vermis is completely absent. A flattening along the posterior aspect of the brain stem is caused by the mass effect from the cyst. The cyst takes up the entire area of the posterior fossa, and there is severe ventriculomegaly within the right lateral ventricle. During the follow-up, the radiologist noted that the lateral and third ventricles had doubled in size since an MR scan 9 months earlier. The posterior fossa cyst also had increased in size. On imaging, the cysts appear as a largely dilated fourth ventricle and an expanded posterior fossa. The image on the left is a sagittal T1-weighted scan. The area of hydrocephalus and the posterior fossa cyst appear hypointense, or dark. On the axial T2-weighted image on the right, the same areas appear hyperintense, or bright. 46. Acoustic Neuroma An acoustic neuroma, also known as a vestibular schwannoma, is a benign tumor that develops from the Schwann cells on the eighth cranial nerve. The eighth cranial, or vestibulocochlear, nerve arises from the brain stem and is located in the inner ear. It is responsible for transmitting sound and equilibrium. An acoustic neuroma is the most common cerebellopontine-angle tumor. Patients often present with hearing loss, tinnitus and vertigo. These tumors can be fast or slow growing. In many cases, the tumor is present for a long time, but the patient does not seek treatment until the symptoms become more severe. 47. Case Study: Acoustic Neuroma The patient in these images had a history of a left vestibular schwannoma that had been surgically removed. He presented to the emergency department with severe nausea, vertigo and ringing in the ears. An acoustic neuroma appears dark on a T1-weighted noncontrast scan and bright on a T2- weighted scan. Postcontrast T1-weighted images demonstrate enhancement in the area of the tumor. These images show a large heterogeneously enhancing lesion in the left cerebellopontine angle. There is significant mass effect on the brain stem, left brachium pontis and anterior left cerebellum as well, which results in a deformity of the fourth ventricle. There also is minimal dilation of the third ventricle ASRT. All rights reserved. 10 MR Basics: Module 11

12 The image on the left is an axial T1-weighted postcontrast scan. The area of the acoustic neuroma is greatly enhanced. An axial T2-weighted postcontrast scan is on the right. Normally, MR protocols do not include a T2-weighted postcontrast scan. However, this scan was performed as part of a protocol to plot the landmarks for a patient undergoing brain surgery. This patient also had a pituitary adenoma that we ll discuss next. 48. Pituitary Adenoma A pituitary adenoma is a benign tumor of the pituitary gland, which is located in the hollowedout area of the sphenoid bone called the sella turcica. The pituitary gland is called the master gland because it plays a major role in regulating vital functions of the body. It is responsible for producing 8 different hormones that act as messengers to other glands in the body. Some of the processes the pituitary gland controls include metabolism, growth, sexual maturation, reproduction and blood pressure. 49. Pituitary Adenoma Pituitary adenomas are the most common primary neoplasms found in the sella turcica region and represent approximately 10% of all intracranial neoplasms. The tumors generally occur in adults between 30 and 40 years of age. The most common signs and symptoms are frontal headaches, visual changes, personality changes, seizures, stunted growth and changes in menstrual cycle. 50. Pituitary Adenoma Pituitary adenomas are classified into 2 groups: functioning and nonfunctioning neoplasms. Functioning adenomas can produce hormones. A pituitary adenoma also can be categorized as a microadenoma, which is less than 1 cm in size or a macroadenoma, which measures more than 1 cm. 51. Case Study: Pituitary Adenoma The patient seen in these images is the same patient with the acoustic neuroma we discussed previously. This patient also had a history of pituitary adenoma. Recall that he presented to the emergency department with severe nausea, vertigo and ringing in the ears. The pituitary adenoma appears hypointense, or dark, on the T1-weighted noncontrast scan. Multiple, heterogeneous signals are also common with an adenoma. The axial T1-weighted postcontrast image on the left demonstrates a heterogeneous enhancement within the pituitary fossa. The image on the right is an axial T2-weighted postcontrast scan. You might remember from the previous slide on acoustic neuromas that this protocol is performed to establish landmarks for surgery. 52. Brain Metastasis Metastasis is the spread of cancer cells from another organ. Most metastases to the brain parenchyma spread from the following primary cancers: lung, breast, gastrointestinal tract, kidney and melanoma. Metastases to the calvaria, or skull, are generally from breast or prostate cancer. Metastases to the meninges of the brain spread from bone and breast cancer ASRT. All rights reserved. 11 MR Basics: Module 11

13 53. Brain Metastasis The symptoms of brain metastasis are varied and depend on the extent of disease and the location of the lesions. Symptoms include seizures, loss of motor function, visual changes, headaches and changes in personality. Most often, brain metastases are discovered during a routine work-up for a patient who has been diagnosed with a primary cancer. 54. Case Study: Brain Metastasis This patient is a 47-year-old woman with a history of metastatic melanoma. Melanoma is a form of cancer that begins in the melanocytes, the cells that make pigment. Melanoma can begin in any pigmented skin such as a mole, the eye or the intestines. This patient presented to the oncologist s office with increasing episodes of headaches lasting longer in duration and was immediately referred for MR imaging. An MR scan of the brain had been performed 14 months earlier, and the results were negative. The images on this slide show a new, enhancing intracranial metastasis in the right frontal lobe, with mass effect and edema producing a right-to-left anterior interhemispheric shift. The sagittal T1-weighted precontrast image on the left shows a lesion of heterogeneous signal in the frontal lobe. On the right is an axial T1-weighted postcontrast scan. The lesion in the frontal lobe is hypointense in the center with hyperintense signal surrounding it. The hypointense signal anterior to the lesion in the right hemisphere is edema. There is mass effect on the right frontal horn and anterior corpus callosum, with mild mass effect on the left frontal horn. 55. Subarachnoid Hemorrhage A subarachnoid hemorrhage is the extravasation of blood into the subarachnoid space, especially the basal cisterns and cerebrospinal fluid pathways. The subarachnoid space contains CSF and is located between the arachnoid membrane and the pia mater. A subarachnoid hemorrhage is most often the result of a ruptured aneurysm, intracranial arteriovenous malformation (AVM) or traumatic injury to the head. A subarachnoid hemorrhage due to aneurysm or AVM most often occurs between ages 40 and 50. The most common symptoms of a subarachnoid hemorrhage are headaches, visual changes, motor deficits and loss of consciousness. 56. Case Study: Subarachnoid Hemorrhage This 10-month-old infant was brought to the emergency department after falling from a couch and striking his head. When he arrived, he was unconscious. MR imaging demonstrated a subarachnoid hemorrhage within the sulci both anteriorly and posteriorly. The image on the left is an axial fluid-attenuated inversion recovery (FLAIR) scan. A FLAIR scan is used in brain and spine imaging to visualize periventricular and cord lesions more clearly. Because the high signal of the cerebrospinal fluid is nulled in a FLAIR scan, it is an ideal technique for demonstrating a subarachnoid hemorrhage. In this image, the blood in the subarachnoid space has a hyperintense signal ASRT. All rights reserved. 12 MR Basics: Module 11

14 On the right is an axial T1-weighted scan. There is some hyperintense signal in the area of the subarachnoid hemorrhage on this image; however, the FLAIR scan shows more detail of the pathology. The patient also has a subdural hemorrhage that we ll discuss next. 57. Subdural Hemorrhage A subdural hemorrhage is the result of blood vessels rupturing in the subdural space. The subdural space is located between the arachnoid membrane and the dura mater. A subdural hemorrhage often is caused by trauma to the head, but it also can occur spontaneously, mostly in elderly patients. If the hemorrhage becomes large enough, the increased pressure on the brain can cause a stroke. Like a subarachnoid hemorrhage, symptoms of a subdural hemorrhage include headaches, visual changes, motor deficits and loss of consciousness. 58. Case Study: Subdural Hemorrhage This patient is the same 10-month-old infant with the subarachnoid hemorrhage seen previously. You ll remember that he was brought to the emergency department after falling from a couch and striking his head. When he arrived, he was unconscious. A subdural hemorrhage appears along the right side of the falx and along both sides of the tentorium. There also is evidence of extensive restricted diffusion of the gray and white matter throughout the brain, indicating cerebral ischemia. The image on the left is an axial gradient-echo scan. Gradient-echo pulse sequences use a shorter repetition time and therefore the scan time is shorter, which makes these sequences ideal for imaging children and for breath-hold scans. In this image, the subdural hemorrhage is a hypointense signal in the right frontal lobe. The scan on the right is an axial T1-weighted postcontrast scan that shows the same area has a hyperintense signal. 59. Sinusitis Sinusitis, or rhinosinusitis, is an inflammation of the paranasal sinuses. When the sinuses become inflamed and swollen, the area does not drain properly and there is a buildup of mucus. Sinus inflammation can be caused by nasal polyps, a deviated septum, the common cold or be the result of an allergic reaction. Sinus infections can be bacterial, viral or fungal. Symptoms of sinusitis include facial pain, nasal congestion, loss of smell and nasal discharge. Patients also may complain of a headache, toothache, halitosis or fever. 60. Sinusitis Sinusitis can be classified as acute, subacute or chronic. Acute sinusitis lasts up to a maximum of 4 weeks, subacute sinusitis continues from 4 to 12 weeks, and chronic sinusitis persists a minimum of 12 weeks or continues to be present. Sinusitis also may be identified by the sinus affected: maxillary sinusitis, frontal sinusitis, ethmoid sinusitis or sphenoid sinusitis. The area of pain depends on the sinus cavity that is inflamed ASRT. All rights reserved. 13 MR Basics: Module 11

15 61. Case Study: Sinusitis This patient s diagnosis is acute sinusitis of the right maxillary sinus, thickening of the mucosal lining with restricted diffusion suggesting pus and a possible abscess. There also is a mucus retention cyst in the left maxillary sinus. In the axial T2-weighted image on the left, the cyst in the left maxillary sinus appears hyperintense. The infection in the right maxillary sinus has densities ranging from hyperintense to hypointense, which indicates fluid and infection. The image on the right is an axial T1- weighted scan. In this image, the cyst and the infection in the right maxillary sinus are both hypointense. 62. Knowledge Check 63. Knowledge Check 64. Cranial Vessels Next we ll discuss some pathologies and conditions of the vascular system of the head you might see during MR imaging. But first, we ll start with some basic anatomy. The circle of Willis is a ring of arteries at the base of the brain encircling the stalk of the pituitary gland. It provides communication between the blood supply of the forebrain and the hindbrain, the internal carotid arteries and the vertebrobasilar system. The circle of Willis is formed when the internal carotid arteries (ICA) enter the brain and divide into the anterior cerebral arteries (ACA) and the middle cerebral arteries (MCA). The anterior cerebral arteries join at the anterior communicating artery. This connection forms the anterior portion of the circle and provides the anterior circulation. Posteriorly, the right and left vertebral arteries unite to form the basilar artery. The basilar artery branches into the left and right posterior cerebral arteries (PCA), forming the posterior circulation. The posterior cerebral arteries complete the circle of Willis by joining the internal carotid system at the posterior communicating arteries. Because the network of arteries forms a circle, if 1 of the main arteries becomes occluded other vessels can provide collateral circulation to the smaller distal arteries. 65. Cranial Vessels Now that we ve discussed how the vessels connect, let s look at the individual arteries and their function. The anterior cerebral arteries (ACA) extend upward and forward from the internal carotid arteries. The ACAs supply blood to the frontal lobes. The frontal lobes are responsible for controlling logical thought, personality and voluntary movement, especially of the legs. The middle cerebral arteries (MCA) are the largest branches of the internal carotid arteries and are responsible for blood supply to a portion of the frontal lobe, as well as to the lateral surface of the temporal and parietal lobes. The temporal lobe is responsible for organizing sensory input, auditory perception, speech production and memory formation ASRT. All rights reserved. 14 MR Basics: Module 11

16 The posterior cerebral arteries (PCA) stem from the basilar artery and supply blood to the temporal and occipital lobes. The occipital lobe houses the primary visual cortex and receives visual input from the retina. 66. Magnetic Resonance Angiography Magnetic resonance angiography (MRA) is a technique used to visualize blood flow. MRA uses variations of gradient-echo sequences to produce vascular contrast within a vessel. Gradientecho sequences have short echo times, which minimize the dephasing of the blood signal. MRA images the blood flow within the vessel rather than the vessel itself. The flowing blood provides the primary source of signal intensity in the image. By imaging the blood flow, any disruptions due to pathology such as occlusions, aneurysms and avascular malformations are easily visualized. MRA can be used to image any vessels within the body, but in this module we ll focus on the brain and neck. 67. Cerebral Aneurysm A cerebral aneurysm is a weakened wall of an artery in the brain. Blood collects and fills the weakened area, causing a sac-like protrusion that can eventually rupture and cause a hemorrhage. An aneurysm can be due to a congenital defect or a disease process. For instance, diseases such as hypertension, atherosclerosis or arteriosclerosis can inhibit blood flow, increasing the pressure against the vessel wall and causing it to rupture. 68. Cerebral Aneurysm Let s take a moment to look at the relationship of hypertension, atherosclerosis and arteriosclerosis to cerebral aneurysms. Hypertension, also referred to as high blood pressure, has its greatest effects on the arteries and the heart. Over time, hypertension leads to weakening arterial walls, which then can cause an aneurysm. Atherosclerosis is an accumulation of cholesterol deposits in the lining of the arterial walls. This buildup narrows the lumen of the vessel, increasing the pressure against the artery wall. The increased pressure weakens the vessel walls, potentially leading to an aneurysm. Arteriosclerosis, also known as hardening of the arteries, is the process by which the arteries lose their elasticity, causing the arterial walls to weaken. The pressure of the blood flow against the weakened vessel then can cause a rupture. 69. Cerebral Aneurysm The symptoms experienced by a patient depend on the location of the cerebral aneurysm and whether the aneurysm has ruptured. Some patients are asymptomatic, and the aneurysm might be an incidental finding on an MR scan performed for another reason. If an aneurysm ruptures, the patient will experience a severe headache with a rapid onset. 70. Case Study: Cerebral Aneurysm This 81-year-old woman was referred for MR imaging because of frequent headaches and visual changes. The patient had been in an altercation in which she had received a blow to the head ASRT. All rights reserved. 15 MR Basics: Module 11

17 A basilar aneurysm was diagnosed. Most people with a basilar aneurysm experience transient ischemic attacks (TIAs), or mini strokes. The most common symptoms are weakness on 1 side of the body, difficulty with speech, dizziness, headaches and visual changes. An aneurysm has varied intensities on T1- and T2-weighted images because of a void in blood flow. To rule out an aneurysm, MRA also must be performed. The axial T1-weighted image on the left shows an aneurysm in the midbasilar artery. The image on the right is a coronal maximum intensity projection (MIP). A MIP is a reformatted image that allows the area of interest to be viewed at different angles. During postprocessing, the MR technologist also can remove any overlapping anatomy obscuring the area of interest. In addition to the basilar aneurysm, there is severe narrowing of the left anterior cerebral artery as well. 71. Cervical Arteries Now we ll discuss some pathologies and conditions of the vascular system of the neck. First, let s review some basic anatomy. The aorta has 3 main branches that supply blood to the head and arms: the brachiocephalic artery, left common carotid artery and the left subclavian artery. The brachiocephalic artery divides into the right common carotid artery and right subclavian artery. The right and left common carotid arteries extend into the neck where they each bifurcate into the internal and external carotid arteries. This bifurcation occurs at approximately the level of the fourth cervical vertebra. The external carotid arteries supply blood to the face and scalp, and the internal carotid arteries supply blood to the anterior portion of the cerebrum. The vertebral arteries originate posteriorly from the superior section of the subclavian arteries. They join within the brain to form the basilar artery. They carry blood to the posterior fossa and occipital lobe. 72. Vertebral Artery Stenosis The vertebral arteries supply oxygenated blood to the posterior part of the brain. Stenosis is the constriction or narrowing of the arterial lumen, most often the result of atherosclerosis. Symptoms vary according to the degree of stenosis. Patients may present with stroke or TIA symptoms such as visual changes, dizziness, speech difficulty, or numbness or weakness of an arm or leg. Many patients are asymptomatic, and the diagnosis is an incidental finding on a study performed for another purpose. 73. Case Study: Vertebral Artery Stenosis The 48-year-old woman shown here presented to the emergency department with a sudden onset, severe headache, visual changes and extreme sensitivity to light. The image on the left is a coronal MIP from the MRA scan showing a stenosis of the left vertebral artery. On the right is an axial MIP from the same MRA scan. In this projection, the severity of the stenosis is more visible. 74. Knowledge Check 2014 ASRT. All rights reserved. 16 MR Basics: Module 11

18 75. Knowledge Check 76. The Vertebral Column Next let s discuss the vertebral column, which is second only to the brain as the most-imaged anatomy in the MR department. According to the National Institute for Neurological Disorders and Stroke, Americans spend approximately $50 billion each year on low back pain. Low back pain is the most common job-related disability and leading reason for missed work. 77. Vertebral Column Anatomy The vertebral, or spinal, column represents about two-fifths of the total height of an individual. The spine is made up of vertebrae, which are named according to their location in the vertebral column. There are 7 cervical, 12 thoracic and 5 lumbar vertebrae. The sacrum is formed by 5 fused vertebrae, and the coccyx is fused from 4 to 5 bones. The cervical, thoracic and lumbar vertebrae are separated by intervertebral discs. Each disc has an outer fibrocartilaginous ring and a soft inner portion called the nucleus pulposus. The discs absorb vertical shock and permit movement of the vertebral column. The vertebrae are connected by ligaments and work together to support the head and trunk of the body. They also form the spinal canal, which houses and protects the spinal cord. 78. Vertebral Column Curvatures The spine has 4 natural curves. The cervical and lumbar spine are convex in that they curve anteriorly; the thoracic spine and the sacrum curve posteriorly and are concave. The curves of the vertebral column help increase spinal strength, absorb shock from walking and position the head over the center of the body to allow a person to walk upright. 79. Cervical Vertebrae The 7 cervical vertebrae are located in the neck. The bodies of the cervical vertebrae are smaller than those of the thoracic and lumbar spine, but their posterior elements are larger. The first cervical vertebra is called the atlas. Together with the occipital bone, it supports the skull. The articulation of the atlas and the occipital bone allows the head to move in a forward and backward motion. The second vertebra is known as the axis. A dense bony projection of the axis called the odontoid process extends superiorly through the atlas. The odontoid process and the atlas form a pivot joint that allows side-to-side motion of the head. The remaining cervical vertebrae are simply identified by the letters and numbers C3 through C Thoracic and Lumbar Vertebrae The vertebrae in the thoracic spine are named T1 through T12, moving from superior to inferior. The first 10 thoracic vertebrae form joints with the ribs at the posterior aspect of the trunk. They also serve as an attachment point for the muscles of the back. The 5 lumbar vertebrae are the largest and strongest bones of the spine and are located in the lower back. From superior to inferior, they are identified as L1 through L5. The lumbar spine provides support for the lower back ASRT. All rights reserved. 17 MR Basics: Module 11