Neuroradiology physics review – 1 – Computed Tomography

It’s important for the neuroradiologist to have a basic grasp of physics, particularly in the ways that it may affect image quality. In this video, Dr. Michael Hoch goes through a series of 12 CT cases on physics. Each case is followed by multiple choice questions about that physics principle.

There are a number of ways that physics principles affect images, causing various types of suboptimal images, such as:

  • partial volume averaging – when an object only takes up part of a voxel and the resulting output
  • patient motion – when patient moves during imaging, degrading image quality and causing image blurring
  • streak artifact – when high density material adversely affects CT reconstruction, causing lines across an image
  • ring artifact – when a detector fails and causes rings through the image
  • contrast staining – when breakdown of the blood brain barrier allows leakage of contrast into the brain

Other key principles discussed include:

  • pitch
  • computed tomography dose index (CTDI)
  • dose length product (DLP)
  • pre- and post-patient collimation
  • image filtration

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties who would like to review radiology physics. This may be particularly useful when preparing for the American Board of Radiology (ABR) core and certifying exams.

https://youtu.be/OeP88BJ5Ec4

Neuroradiology Review – Brain Gyral Anatomy

Neuroradiology board review. This lecture is geared towards the ABR core exam for residents, but it would be useful for review for the ABR certifying exam or certificate of added qualification (CAQ) exam for neuroradiology.

In this video, we review gyral anatomy of the brain for some of the more common gyri, including the frontal lobe, temporal lobe, and midline/paramedian gyri.

The ABR board exams, both core and certifying exams, contain some basic anatomy and all of the structures here are fair game. You should be able to pick them out of a list of options as well as put an arrow on them if necessary.

This is the final video of board review 2. Tune in for more videos later!

https://youtu.be/d4GWL1KybJI

Board Review 2 – Case 19

Neuroradiology board review. This lecture is geared towards the ABR core exam for residents, but it would be useful for review for the ABR certifying exam or certificate of added qualification (CAQ) exam for neuroradiology.

More description and the answer (spoiler!) are seen below the video.

This case shows a trauma patient with disruption of the arch of C1 on a CT of the cervical spine. There are injuries to both the anterior and posterior arch.

After presentation, the patient developed posterior fossa symptoms such as nausea and vertigo

The diagnosis is: Jefferson fracture with vertebral artery injury

A number of fractures in the neck have eponyms, and the Jefferson fracture is when the arch of C1 is fractured. It commonly involves injury to both the anterior and posterior arch, although this isn’t a requirement.

After high energy trauma, it is common to have injury to arteries in the neck, so it is important to consider this if a patient develops new symptoms. This patient had a traumatic wall injury of the left vertebral artery which is demonstrated on a T1 weighted fat saturated image of the neck, which showed T1 hyperintense methemoglobin in the wall.

Traumatic arterial injury is often graded using the Denver grading scale, which is as follows:

  • Grade I – < 25% narrowing
  • Grade II – > 25% narrowing or dissection flap
  • Grade III – pseudoaneurysm
  • Grade IV – occlusion
  • Grade V – transection/active extravasation

Injury can be evaluated with either CTA (more common) or MRA.

Board Review 2 – Case 18

Neuroradiology board review. This lecture is geared towards the ABR core exam for residents, but it would be useful for review for the ABR certifying exam or certificate of added qualification (CAQ) exam for neuroradiology.

More description and the answer (spoiler!) are seen below the video.

This case shows a patient with cerebellar tonsils which extend below the foramen magnum. They have a “peglike” or triangular configuration, and extend well below the foramen magnum. The differential for this finding includes Chiari malformation, cerebellar tonsillar ectopia, idiopathic intracranial hypertension (IIH), and spontaneous intracranial hypotension (SIH).

The diagnosis is: Chiari malformation

Chiari malformation is a congenital abnormality in which the cerebellar tonsils extend below the foramen magnum and the posterior fossa is small. Patients can have chronic headaches. CSF flow studies of the foramen magnum can be useful to determine if patients are likely to benefit from surgical decompression with suboccipital craniectomy.

When combined with other abnormalities, there are specific diagnoses, which are:

  • Chiari II – cerebellar tonsillar abnormality + lumbar meningocele/myelomeningocele
  • Chiari III – cerebellar tonsillar abnormality + occipital meningocele

Board Review 2 – Case 17

Neuroradiology board review. This lecture is geared towards the ABR core exam for residents, but it would be useful for review for the ABR certifying exam or certificate of added qualification (CAQ) exam for neuroradiology.

More description and the answer (spoiler!) are seen below the video.

This case shows a CT with hyperdensity ventral to the pons and midbrain consistent with hemorrhage. Further imaging, including MRI and CT angiogram, were normal

The diagnosis is: benign perimesencephalic hemorrhage

This is a relatively benign form of subarachnoid hemorrhage of unknown etiology. The blood products are seen ventral to the pons, and are more common in younger patients. No vascular abnormality or tumor is found, and it is thought to be a result of disrupted veins, although the real cause is unknown. Outcomes are better compared to aneurysmal or traumatic subarachnoid hemorrhage.

Board Review 2 – Case 16

Neuroradiology board review. This lecture is geared towards the ABR core exam for residents, but it would be useful for review for the ABR certifying exam or certificate of added qualification (CAQ) exam for neuroradiology.

More description and the answer (spoiler!) are seen below the video.

This case shows a mass within the spinal canal of the upper thoracic spine. For any spinal canal mass, your first step is to determine if it is:

  • intramedullary (in the spinal cord)
  • intradural extramedullary (inside the dura, but outside the spinal cord)
  • extradural

This mass appears to be extramedullary but intradural. The main differential considerations are meningioma, nerve sheath tumor/schwannoma, or metastasis. This mass has a relatively benign appearance and enhances avidly and homogenously.

The diagnosis is: meningioma

Spinal meningiomas are extramedullary masses that share an imaging appearance with intracranial meningiomas. They are often homogenous and enhance avidly. They can have calcification. The treatment, if symptomatic, is surgical resection.

Board Review 2 – Case 15

Neuroradiology board review. This lecture is geared towards the ABR core exam for residents, but it would be useful for review for the ABR certifying exam or certificate of added qualification (CAQ) exam for neuroradiology.

More description and the answer (spoiler!) are seen below the video.

This case shows a trauma patient who had a significant fall and now has lower extremity symptoms. On the MRI, there are a few compression fractures that you can see, but in addition there is T1 hyperintense fluid in the dorsal epidural space. In the setting of trauma, this is likely to be an epidural hematoma.

The diagnosis is: fracture with spinal epidural hematoma

Epidural hematoma is a dreaded complication of spine trauma that can cause worsening cord injury. It requires close monitoring and possibly surgical drainage if this may improve the symptoms. Look for intraspinal fluid collections after trauma, as they can be hard to identify.

Board Review 2 – Case 14

Neuroradiology board review. This lecture is geared towards the ABR core exam for residents, but it would be useful for review for the ABR certifying exam or certificate of added qualification (CAQ) exam for neuroradiology.

More description and the answer (spoiler!) are seen below the video.

This case shows a patient with a new neurologic deficit and a relatively normal noncontrast head CT. Perfusion, on the other hand, shows an area of decreased CBV, increased MTT, and increased Tmax in the posterior aspect of the left middle cerebral artery (MCA) distribution. There is an associated vessel occlusion on CT angiogram.

The diagnosis is: cerebral ischemia (stroke)

This patient has an area of ischemia in the left MCA territory. Because the CBV is relatively maintained, this tissue is mostly considered penumbra. When there is a significant decrease in volume and flow, it is considered core infarct that is not likely to recover.

Board Review 2 – Case 13

Neuroradiology board review. This lecture is geared towards the ABR core exam for residents, but it would be useful for review for the ABR certifying exam or certificate of added qualification (CAQ) exam for neuroradiology.

More description and the answer (spoiler!) are seen below the video.

This case shows an aggressive lesion of the upper thoracic spine in a relatively young patient. It appears to be centered in the posterior elements of the upper thoracic spine. There is central osseous matrix formation as well as a surrounding soft tissue mass with adjacent bone destruction. This is causing significant narrowing of the spinal canal.

The diagnosis is: osteosarcoma

In this case, you know you are dealing with an aggressive mass because of the soft tissue component and bone destruction. The differential includes primary bone lesions, metastatic disease, and lymphoma, but because of the new bone formation (osteoid matrix), it suggests osteosarcoma.

Board Review Cases – Head and Neck

This playlist is a collection of only the head and neck imaging board review cases on this site. This includes pathologies such as head and neck cancer and skull base abnormalities.

These cases are geared towards preparation for the radiology resident ABR core exam, although similar material is used for the ABR certifying exam general and neuroradiology sections as well as neuroradiology CAQ. The format of this playlist is case-based. Each case consists of a series of images followed by 1 or 2 questions. The first question is usually to name the diagnosis, while the second is a multiple choice question to test deeper understanding of the specific condition. Try to get the diagnosis before you see the second questions.