====== Head computed tomography ====== {{ ::right_hemisphere.jpg?400|}} ====== ๐Ÿง  Head CT Modalities ====== This page outlines the main types of head CT imaging, classified by contrast use, protocol, and clinical application. ===== โœ… 1. Non-Contrast CT (NCCT) ===== **Uses:** * Head trauma. * Stroke (ischemic or hemorrhagic). * Hydrocephalus. * Seizures. * Pre-contrast baseline. **Advantages:** * Fast and widely available. * Excellent for detecting: * Acute hemorrhage. * Skull fractures. * Midline shift or mass effect. ----- ===== โœ… 2. Contrast-Enhanced CT (CECT) ===== **Uses:** * Tumor evaluation. * Abscess or infectious processes. * Suspected dural sinus thrombosis. * Postoperative assessment. **Considerations:** * Avoid in contrast allergy or renal impairment. * Enhances vascular and soft tissue detail. ----- ===== โœ… 3. CT Angiography (CTA) ===== **Uses:** * Aneurysms. * AVMs (arteriovenous malformations). * Intracranial stenosis or occlusion. * Vessel dissection. * Preoperative vascular mapping. **Technique:** * IV contrast + timed arterial phase acquisition. ----- ===== โœ… 4. CT Venography (CTV) ===== **Uses:** * Cerebral venous sinus thrombosis (CVST). * Preoperative venous evaluation. **Notes:** * Venous phase acquisition after contrast injection. ----- ===== โœ… 5. CT Perfusion (CTP) ===== **Uses:** * Acute ischemic stroke workup. * Guides thrombolysis or thrombectomy decision-making. **Parameters analyzed:** * Cerebral blood flow (CBF). * Cerebral blood volume (CBV). * Mean transit time (MTT). * Time to peak (TTP). ----- ===== โœ… 6. 3D Reconstruction CT ===== **Uses:** * Neurosurgical planning. * Skull fractures. * Craniofacial deformities or trauma. * Shunt/catheter evaluation. **Tools:** * Multiplanar and volumetric reconstruction software. ----- ===== โœ… 7. Cone-Beam CT (CBCT) ===== **Uses:** * Sinus imaging. * Skull base evaluation. * Dental/maxillofacial surgery planning. **Notes:** * Superior bony detail with lower radiation dose. * Limited soft tissue contrast. ----- ===== ๐Ÿงพ Summary Table ===== ^ Modality ^ Contrast Used? ^ Clinical Applications ^ | Non-Contrast CT (NCCT) | No | Trauma, stroke, hydrocephalus, hemorrhage | | Contrast-Enhanced CT | Yes | Tumors, infections, postop evaluation | | CT Angiography (CTA) | Yes | Aneurysms, AVMs, stenosis, stroke | | CT Venography (CTV) | Yes | Sinus thrombosis, venous anatomy | | CT Perfusion (CTP) | Yes | Stroke: core vs penumbra assessment | | 3D Reconstruction CT | Optional | Planning, fractures, catheter visualization | | Cone-Beam CT (CBCT) | No | ENT, dental, sinus, skull base imaging | ===== Indications ===== Non[[contrast]] [[CT scan]]s are often employed in [[emergency]] situations (to quickly rule out most acute abnormalities), to evaluate bone in great detail, or as a screening test. It excels in demonstrating acute blood (EDH, SDH, IPH, SAH), fractures, foreign bodies, [[pneumocephalus]], and [[hydrocephalus]]. It is weak in demonstrating acute [[stroke]] ([[DWI]] [[MRI]] is preferred), and often has poor signal quality in the [[posterior fossa]] (due to bone artifact). IV enhanced CT scans are used primarily for imaging [[neoplasm]]s or [[vascular malformation]]s, especially in patients with contraindications to MRI. All CT contrast agents contain iodine. A typical IV dose of contrast: 60โ€“65 ml o fe.g.Isovue3 00ยฎ which delivers 18โ€“19.5 grams of iodine. [[Cranial CT]] (CCT) scans and hospital admission are increasingly performed to rule out [[intracranial hemorrhage]] in patients after [[minor head injury]] (MHI), particularly in older patients and in those receiving [[antiplatelet]] therapy. This leads to high radiation exposure and a growing financial burden see [[Canadian CT Head Rule]]. see [[Postoperative computerized tomography]]. see [[Computed Tomography for chronic subdural hematoma]]. ---- Before a [[biopsy]], detailed imaging studies are conducted, typically using techniques such as [[computed tomography]] (CT) or [[magnetic resonance imaging]] (MRI). These images help identify the location and dimensions of the abnormality. ====Repeat head computed tomography==== A definitive consensus on the standardization of practice of a routine repeat [[head]] [[CT]] (RHCT) scan in patients with [[traumatic intracranial hemorrhage]] is lacking. After mTBI, worsening of repeat head CT finding is seen in a third of patients and is associated with worse outcomes. A substantial fraction of patients who require operative intervention will have no clinical changes in the first 8 hours, supporting the value of repeat head CT within this time frame ((Thorson CM, Van Haren RM, Otero CA, Guarch GA, Curia E, Barrera JM, Busko AM, Namias N, Bullock MR, Livingstone AS, Proctor KG. Repeat head computed tomography after minimal brain injury identifies the need for craniotomy in the absence of neurologic change. J Trauma Acute Care Surg. 2013 Apr;74(4):967-73 ; discussion 973-5. doi: 10.1097/TA.0b013e3182877fed. PubMed PMID: 23511133. )). Neurologic examination can be trusted and is reliable in pediatric blunt TBI patients in determining when an RHCT scan is necessary. Aziz et al. recommend that RHCT is required routinely in patients with intracranial hemorrhage with GCS score of 8 or less and in patients with GCS greater than 8 and that RHCT be performed only when there are clinical indications ((Aziz H, Rhee P, Pandit V, Ibrahim-Zada I, Kulvatunyou N, Wynne J, Zangbar B, O'Keeffe T, Tang A, Friese RS, Joseph B. Mild and moderate pediatric traumatic brain injury: replace routine repeat head computed tomography with neurologic examination. J Trauma Acute Care Surg. 2013 Oct;75(4):550-4. doi: 10.1097/TA.0b013e3182a53a77. PubMed PMID: 24064865.)). Routine repeat head CT scan is not warranted in patients with normal [[neurologic examination]]. Routine repeat head CT scan does not supplement the need for [[neurologic examination]] for determining management in patients with [[traumatic brain injury]] ((Joseph B, Aziz H, Pandit V, Kulvatunyou N, Hashmi A, Tang A, Sadoun M, O'Keeffe T, Vercruysse G, Green DJ, Friese RS, Rhee P. A three-year prospective study of repeat head computed tomography in patients with traumatic brain injury. J Am Coll Surg. 2014 Jul;219(1):45-51. doi: 10.1016/j.jamcollsurg.2013.12.062. Epub 2014 Mar 1. PubMed PMID: 24745622.)). [[Emergency department]] (ED) [[management]] of [[mild traumatic brain injury]] (TBI) with any form of [[traumatic intracranial hemorrhage]] (ICH) is variable. Since 2000, The Department of Emergency Medicine, University of Cincinnati, Cincinnati, OH, standard practice has been to obtain a repeat [[head computed tomography]] (CT) at least 6 hours after initial imaging. Patients are eligible for discharge if clinical and CT findings are stable. Whether this practice is safe is unknown. Discharge after a repeat head CT and brief period of observation in the ED allowed early discharge of a cohort of mild TBI patients with traumatic ICH without delayed adverse outcomes. Whether this justifies the cost and radiation exposure involved with this pattern of practice requires further study ((Kreitzer N, Lyons MS, Hart K, Lindsell CJ, Chung S, Yick A, Bonomo J. Repeat neuroimaging of mild traumatic brain-injured patients with acute traumatic intracranial hemorrhage: clinical outcomes and radiographic features. Acad Emerg Med. 2014 Oct;21(10):1083-91. doi: 10.1111/acem.12479. PubMed PMID: 25308130.)). ====Hemorrhagic stroke==== High rates of head CT use for patients with hemorrhagic stroke are frequently observed, without an association with decreased mortality. A higher number of physicians consulted was associated with high-intensity use of head CT ((Bekelis K, Fisher ES, Labropoulos N, Zhou W, Skinner J. Variations in the intensive use of head CT for elderly patients with hemorrhagic stroke. Radiology. 2015 Apr;275(1):188-95. doi: 10.1148/radiol.14141362. Epub 2014 Oct 29. PubMed PMID: 25353250. )). ==== Time to CT scan ==== Emergent brain computed tomography (CT) scan allows for the identification of patients presenting with acute severe [[neurological symptoms]] in whom medical and surgical [[intervention]]s may be lifesaving. The aim of the study was to evaluate if the time to CT from arrival at the [[emergency department]] exceeded 30 min in patients admitted with acute severe neurological symptoms. This was a retrospective register-based [[quality assurance]] study. We identified patients admitted to the emergency department with acute severe neurological symptoms between April 1st, 2016, and September 30th, 2020. Data were retrieved from the registry of acute medical team activations. We considered that time to CT from arrival at the emergency department should not exceed 30 min in more than 10% of patients. A total of 559 patients were included. Median time from arrival at the emergency department until CT scan was 24 min (IQR 16-35) in children (< 18 years), 10 min (IQR 7-17) for adults (18-59 years), and 11 min (IQR 7-16) for elders (> 60 years). This time interval exceeded 30 min for 8.2% (95% CI 6.1-10.9) of all included patients, 35.3% of children, 5.9% of adults, and 8.6% of elders. No children died within 30 days. The 30-day mortality was 21.3% (95% CI 16.4-27) in adults and 43.9% (95% CI 38.2-49.8) in elders. Time from arrival at our emergency department until brain CT scan exceeded 30 min in 8.2% of all included patients but exceeded the defined quality aim in children and could be improved ((Pape P, Jensen AH, Bergdal O, Munch TN, Rudolph SS, Rasmussen LS. Time to CT scan for patients with acute severe neurological symptoms: a quality assurance study. Sci Rep. 2022 Sep 10;12(1):15269. doi: 10.1038/s41598-022-19512-x. PMID: 36088471.)).