- Cerebral Angiogram
- Imaging Techniques (MRI, CT)
- Petrosal Sinus Sampling
- Spinal Angiogram
- WADA Testing
Cerebral angiograms provide a roadmap of the blood vessels of the brain. Physicians use this blood vessel roadmap to determine how a particular patient’s brain is supplied with blood and how to best proceed with the course of treatment.
Cerebral Angiogram – The procedure for a cerebral angiogram requires that a small tubed catheter, similar to a long piece of spaghetti, be placed in an artery in the groin area. Prior to catheter placement, patients can be given local anesthesia with sedation medication to keep them comfortable. After anesthesia has been taken care of and the catheter is inside the artery; the catheter is navigated under image guidance up to the vessels of the head and neck. Once the catheter has been stabilized then contrast dye is allowed to flow through the catheter for a short period. While the dye is moving through the blood vessels a special x-ray camera or fluoroscope takes pictures of the blood vessels.
Some patients may require additional imaging techniques such as an MRI (magnetic resonance imaging) or a CT ( computerized tomography or CAT scan) to confirm their diagnosis.
- Magnetic resonance imaging (MRI) — is a technique that uses a magnetic field and radio waves to create cross-sectional images of your head and body. These detailed images can be used to diagnose a wide range of conditions.
- A CT scan — also called CT, computerized tomography, or CAT scan — is an X-ray that produces images of your internal organs that are more detailed than regular X-rays. CT scanning involves a device that rotates around your body to create cross-sectional images of the inside of the body.
Magnetic Resonance Imaging (MRI)
The MRI exam is painless. You don't feel the magnetic field or radio waves. Most MRI machines consist of a large magnet shaped like a tunnel. You lie on a table that slides into the tunnel. The magnetic field aligns atomic particles in your cells. When radio waves are broadcast toward these aligned particles, they produce signals that vary according to the type of tissue they are. A computer then creates a composite, three-dimensional representation of your body from the collected signals. Two-dimensional slices can be electronically created from this representation and displayed on a monitor for examination. These images can be then be converted into photographic film for further viewing and analysis.
You should not receive an MRI scan if you have an implantable cardioverter defibrillator or a pacemaker. Its strong magnetic field may interfere with these devices. You should also mention if you think you may be pregnant, because the effects of MRIs on fetuses are not yet understood. Your doctor may recommend an alternative exam.
It's important that you remove any electronic devices and metal objects before your exam. The magnetic field may damage electronic items and metal can interfere with the magnetic field, affecting the quality of images.
CT, Computerized Tomography, or CAT Scan
Some CT scans require that you to ingest a contrast medium before the scan. A contrast medium blocks X-rays and appears white on images. This can help emphasize blood vessels or other structures that need to be examined. Contrast mediums can be taken by mouth, enema, or an injection into a vein (intravenously).
During a CT scan, you lie on a table inside a round machine called a gantry. An X-ray tube inside the machine rotates around your body and sends small doses of radiation through it at various angles. As the X-rays pass through your body, different tissues absorb different amounts. Sensors inside the gantry measure the radiation leaving your body and convert it into electrical signals. A computer then gathers these signals and assigns them a color ranging from black to white depending on signal intensity. CT images are sent to an electronic data file and then reviewed on a computer. A radiologist than interprets these images and sends a report to your doctor.
Unlike MRI, CT scans can be done even if you have an internal cardioverter defibrillator or a pacemaker. However, if you're pregnant your doctor may suggest postponing the procedure or choosing an exam that doesn't involve radiation, such as an ultrasound or MRI.
As with an MRI exam, you will be asked to remove metal objects that might interfere with image results prior to your CT scan.
Petrosal sinus sampling is a diagnostic test performed in patients with a Cushing's syndrome to distinguish between a pituitary or ectopic source of cortisol stimulation. Normally, cortisol production is the end result of a precise biochemical pathway.
The most common cause of Cushing's syndrome is Cushing's disease, where the pituitary gland excretes an excess of a stimulating hormone for the adrenal gland. The over-stimulated adrenal gland then releases excessive levels of cortisol. In approximately 15% of all patients with Cushing’s syndrome there is an ectopic or other source of cortisol production, i.e. excess cortisol is not produced within the pituitary gland. One example of an ectopic source for adrenal gland stimulation is small cell lung carcinoma, where the lung tumor produces excessive stimulation of the adrenal gland. Results from a petrosal sinus sampling compliment other testing strategies and help in planning appropriate surgical or medical management.
The Hypothalamus stimulates the Pituitary gland which stimulates Adrenal gland = CORTISOL.
Prior to undergoing petrosal sinus sampling it is necessary to perform a cerebral venogram. A venogram provides a roadmap of the blood vessels of the brain. Physicians use this blood vessel roadmap to correctly locate the precise area of the brain where samples are to be drawn. ( In a small percentage of cases it is not possible to visualize the petrosal sinus via a venous route and a supplemental arterial route is used. Placement of a catheter in an artery is similar to that of placement in a vein.) The catheter is then advanced to the petrosal sinus and sampling begins. Typically samples are drawn at 5-, 10-, and 15- minute intervals after the catheter is in place. Next a small dose of stimulating hormone is given and further samples are taken at 1-, 3-, 5-, and 10-minute intervals. Samples are then sent to the laboratory for analysis. At the end of sampling all catheters are removed and direct pressure is held over the groin punctures until bleeding has stopped. Patients are then taken to our recovery area where they are closely monitored for 4-6 hours.
Spinal angiograms are the pictures obtained when performing spinal angiography. Pictures obtained with conventional spinal angiography differ from those obtained from a CT angiogram of the spine or an MR angiogram of the spine. CT and MR modalities can often be used as screening tools for blood vessel disease but spinal angiography is usually the procedure of choice because MR angiography cannot detect aneurysms below 2-3 mm in size. Angiograms are performed emergently for patients with bleeding from vessels within the spinal area, e.g. sub-arachnoid hemorrhage. Routine angiograms are performed in the work up of spinal aneurysms, arteriovenous-malformations, or fistulae and vascular tumors of the spine.
A spinal angiogram provides a roadmap of the blood vessels of the spine. A small tubed catheter, similar to a long piece of spaghetti, is placed in through an artery in the groin area. During the process of catheter placement patients will be given local anesthesia and sedation medication to keep them comfortable. If patients are unable to co-operate with the study then it may be necessary to have a general anesthetic. From the groin the catheter is navigated under image guidance up to the vessels of the spine. Once the catheter has been stabilized then contrast dye is allowed to flow through the catheter for a short period. While the dye is moving through the blood vessels a special x-ray camera or fluoroscope takes pictures of the blood vessels. As necessary, smaller micro-catheters can be introduced co-axially through the larger catheter if more detailed pictures are needed.
Spinal angiography is a fairly lengthy procedure due to the number of vessels that need to be injected. A typical procedure time is 3-4 hours. At the end of the angiogram all catheters are removed and direct pressure is held over the groin puncture until bleeding has stopped. Patients are then closely monitored in a recovery area for 4-6 hours.
The Wada test is named after neurologist, Juhn A. Wada. Wada testing is performed prior to epilepsy surgery and provides specific location information about centers within the brain for language, comprehension, recognition, and short-term memory. Knowing where these critical centers are located helps the surgeon plan the safest approach to dealing with the epileptic focus or foci.
Prior to undergoing Wada testing it is necessary to perform a cerebral angiogram. A cerebral angiogram provides a roadmap of the blood vessels of the brain. Physicians use this blood vessel roadmap to correctly locate the appropriate area of the brain to be tested.
Testing then begins with a baseline assessment of behavior. Object recognition, word recognition, speech, language, muscle strength, and short-term memory are all tested. Under image guidance, a short-term local anesthetic, usually sodium amobarbital or sodium methohexital, is injected from the pre-placed catheter into the area being tested. Another series of tests are then performed and compared with the baseline assessment.
At the end of testing all catheters are removed and direct pressure is held over the groin puncture until bleeding has stopped. Patients are then taken to our recovery area where they are closely monitored for 4-6 hours.