Fundamentals of CT: Head and Neck Angiography

Fundamentals of CT:  Head and Neck Angiography   Upon completion of this course you should be able to:   • Explain the concept and purpose of computed tomography angiography • Identify pertinent vascular anatomy of the head and neck • Describe the importance of IV contrast in CTA examinations • Explain the workflow of obtaining optimal IV contrast enhancement • Describe image reconstruction and post processing techniques in CTA • Radiology examination of arteries     -  Imaging of vessels throughout the body • Head, neck, chest/lungs, abdomen, and extremities   -  Variety of indications • Vessel patency, aneurysm, injury, and congenital anomalies • Can be performed using different modalities • Special Procedure Suite/Cath Lab • Fluoroscopic evaluation • Sterile technique as in an operating room • Cost, time, radiation are factors • Therapeutic treatment can be delivered • Effective • Non-invasive • No radiation • Not all patients can have MRI • Non-invasive • Fast • Accessible • Lower radiation dose, contrast volume • High quality images • Focus on vessels during peak contrast enhancement • Many factors influence timing • Tools on modern equipment help ensure success • Sever headaches • Memory loss • Slurred speech • Dizziness • Vision changes • Trauma • Weakness/numbness • Loss of coordination or balance                                                    • Right common carotid   -  Arises from first branch of brachiocephalic • Left common carotid   -  Arises from aortic arch • Bifurcate into internal and external Right internal carotid Right external carotid Right common carotid Brachiocephalic   Left internal carotid Left external  carotid Left subclavian Left common carotid University of Wisconsin School of Medicine and Public Health, Department of Radiology. (2010). [Diagram]. Retrieved from https://sites.google.com/a/wisc.edu/neuroradiology/anatomy/under-spin/vascular-anatomy Brachiocephalic Aortic arch • Enter through carotid canals  • Primary anterior circulation   -  Ophthalmic arteries   -  PCA   -  Anterior choroidal artery  • Bifurcate into ACA and MCA Ophthalmic  Artery Cavernous Sinus Anterior Cerebral Artery Middle Cerebral Artery Posterior Communicating Artery (posterior cerebral artery not shown) Internal Carotid Artery Naresh, R. G. (2016, January 23). Cerebral circulation and brainstem syndromes [PowerPoint]. Retrieved from https://www.slideshare.net/DrRudraNaresh/cerebral-circulation-and-brain-stem-syndromes • Anterior to ICA along posterior mandible • Branch into arteries supplying the head and face   -  Thyroid, tongue, pharynx, face, maxilla, and temporal regions   -  Occipital and posterior auricular areas Superficial temporal Maxillary Posterior auricular Occipital Facial Lingual Ascending pharyngeal Superior thyroid Radiopaedia.org, & Jones, M.D., J. (2017). [Illustration]. Retrieved from https://radiopaedia.org/articles/branches-of-the-external-carotid-artery-mnemonic • Internal carotids bifurcate into R/L ACAs, R/L MCAs   -  ACAs connect via ACOM • Vertebral arteries join to form basilar • Basilar bifurcates into R/L PCAs   -  PCAs connect via PCOM PCA ACA MCA Internal Carotid Artery Basilar • Contrast used to visualize soft tissue structures in X-ray • IV contrast injected to visualize blood vessels • Increases attenuation • Filtered by liver and kidneys, excreted in urine • Assess kidney function   -  BUN   -  Creatinine   -  Normal Limits (1) (2) Hosten AO. BUN and Creatinine. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 193.Available from: https://www.ncbi.nlm.nih.gov/books/NBK305/ • Warm feeling throughout the body • Metallic taste • Feel as if urinating • Nausea • Allergic reaction • Itching • Rash • Shock • Shortness of breath • Damage to the kidneys       American Academy of Dermatology. (2017). [Photograph]. Retrieved from https://www.aad.org/public/diseases/itchy-skin/hives 1 Fixed/empiric delay 2 Test Bolus 3 Bolus Tracking/CARE Bolus HU Time(s) Early Late  Optimal Window  • Prescribed contrast volume, set scan delay   -  Based on averages and experience   -  Outcomes can vary • ~ 15 - 20 ml of contrast • Injected at same rate as study • Scan with no table movement • Real-time injection monitoring • Incorporated into scan protocol • Triggers on user-defined HU threshold • Volumes of thin-sliced data in seconds  • Alternate views to axial • MPR, MIP, SSD, and VRT • View 2D axials in any plane   -  Coronal   -  Sagittal   -  Oblique   -  Curved Images:  Siemens Healthineers • Highest density voxels   -  Includes bone • Bone removal tools yield 3D volumes demonstrated vessels Images:  Siemens Healthineers • Oldest type of 3D viewing • Displays anatomy in a specified Hounsfield unit range • Cannot extract vessel from bone • Only displays vascular surfaces     Images:  Siemens Healthineers • Multiple thresholds display different tissue classes simultaneously • Different colors and transparencies impart depth     Images:  Siemens Healthineers • Low dose non-enhanced CT (NECT) for bone mask • Regular dose CTA • Bone removed Images:  Siemens Healthineers • Technological advances only part of the picture • CT technologist ties it all together • Successful, safe, diagnostic CTA angiography You have now completed the course Fundamentals of CT: Head and Neck Angiography.  You should now be able to:   • Explain the concept and purpose of computed tomography angiography • Identify pertinent vascular anatomy of the head and neck • Describe the importance of IV contrast in CTA examinations • Explain the workflow of obtaining optimal IV contrast enhancement • Describe image reconstruction and post processing techniques in CTA