Volume 68, Issue 6 Louisville Medicine | Page 11

es continue to grow . Deep brain stimulators ( DBS ), vagal nerve stimulators ( VNS ) and spinal cord stimulators are now common . Fortunately , many pacemakers are now MRI compatible . Even if MRI compatible , there may still be restrictions on the scanning time and types of sequences utilized .
Finally , most new MRI scanners have shorter gantry length and wider bores to better accommodate the claustrophobic and obese patients .
Nuclear medicine neuroimaging studies continue to evolve . Radionuclide cisternography can be used to evaluate potential CSF leaks ( trauma , post-operative , spontaneous intracranial hypotension ) and communicating hydrocephalus , i . e . NPH . Brain single-photon emission computed tomography ( SPECT ) is utilized to evaluate some forms of dementia , epilepsy patients pre and post ictal , and to evaluate vascular reserve in intracranial vascular disorders ( such as Moya-Moya disease ) before and after challenge with Diamox administration . The dopamine transporter ( DAT ) brain SPECT scan was FDA approved in 2011 to help diagnose Parkinson ’ s disease and Parkinson syndromes from other causes of tremor ( Image 6 ). Positron Emission Tomography ( PET ) can also be used to evaluate dementia and epilepsy patients . Cerebral blood flow studies are still performed to corroborate clinically suspected brain death .
The first contrast medium used for ventriculography and pneumoencephalography was air . In the 1980s , CT air cisternography was still performed to evaluate the IACs . Iophendylate , an oil-based iodine containing intrathecal contrast , was the first myelography contrast . However , it had to be removed at the end of the myelogram via an L5-S1 puncture , but any remaining droplets could cause arachnoiditis . It was discontinued in 1988 . Current non-ionic and low-osmolar ( LOCM ) myelography contrast is very safe .
The addition of intravenous ( IV ) contrast to CT and MRI examinations improves lesion detection and characterization because of increased vascularity and / or blood brain barrier ( BBB ) breakdown . Iodinated contrast safety has improved significantly over the past four decades . Ionic hyper-osmolar contrast media ( HOCM ) is painful during angiography , had more adverse allergic reactions , was more toxic to the kidneys and caused local tissue damage when extravasated . The current generation of intra-arterial , IV and intrathecal contrast media are lower-osmolar agents with a smaller incidence of adverse reactions . In the early 1990s , because of significantly greater expense , LOCM was only used for select patients , such as with a previous contrast reaction history . Now , the LOCM are exclusively used .
ALL IN THE HEAD spine . In 2006 , the association of GBCA and nephrogenic systemic fibrosis ( NSF ) was discovered in patients with end-stage chronic kidney disease ( CKD ), usually on dialysis , who had undergone several MRI exams with contrast . Rigid screening procedures for CKD and use of safer GBCA have nearly eliminated NSF associated with MRI contrast . GBCA are safe and have a lower incidence of adverse reactions compared to iodinated contrast . 3
Because of CTA and MRA of the head and neck , conventional cerebral-cervical catheter angiography with greater inherent risks has decreased significantly . CTA and MRA can be used to diagnose and follow patients with cerebrovascular disease . MRA of the head without contrast can be performed in a few minutes to screen for aneurysms , and to follow post-coil treated aneurysm patients . MRA of the neck with contrast can evaluate the carotid and vertebral arteries from the aortic arch to the skull base ( Image 7 ). CTA of the head and neck is immediately performed after CTP in stroke protocol patients in the ER . CTA head is used to follow patients after cerebral aneurysm clipping . Conventional catheter angiography , now digital subtraction angiography ( DSA ), is still used for specific diagnostic and therapeutic indications . Currently , most cerebral angiography is performed by interventional neuroradiologists or endovascular neurosurgeons .
Although I have witnessed significant advancements the past three plus decades , neuroimaging will continue to evolve with further development of higher resolution 3D anatomic imaging , more functional and physiologic applications and imaging targeting specific tumors or disease biomarkers . The future is bright .
References :
1
Hoeffner EG , Mukherji SK , et al Neuroradiology Back to the Future : Brain Imaging AJNR Am J Neuroradiol 2012 ; 33:5-11
2
Powers WJ , Rubinstein AA , et al 2018 Guidelines for the Early Management of Patients With Acute Ischemic Stroke . Stroke 2018 ; 49 : e46-e99 .
3
ACR Committee on Drugs and Contrast Media ACR Manual on Contrast Media 2020 American College of Radiology 2020 ; 1-131 .
Dr . Burger is a practicing neuroradiologist at Diagnostic Imaging Alliance of Louisville .
In 1988 , the FDA approved gadolinium based contrast agents ( GBCA ) for IV use with MRI examinations . Thousands of doses have been injected to improve lesion detection in the brain and
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