CT Brain Without Contrast — Dictation, Appropriateness, and Dose for Residents
Stat from the ED. 78-year-old on Eliquis, found down, GCS 13. The ER doc wants to rule out a bleed before you can even finish your last case. You know the attending is going to want a clear, structured report that checks every box: blood, mass effect, hydro, early infarct signs. It’s the bread-and-butter scan of any call shift, but getting it right and getting it fast sets the tone for the whole night. When I was a resident, this was the scan where you proved you could be trusted. For more tips and tools, we’ve also put together a free residents and fellows resource hub with calculators and other high-yield guides.
What a CT Brain Without Contrast Covers and What Attendings Look For
A non-contrast head CT is the workhorse for acute intracranial pathology. It’s fast, widely available, and excellent for identifying acute hemorrhage, which appears hyperdense (bright white) against the brain parenchyma. The entire scan takes less than a minute, providing a rapid assessment of life-threatening conditions.
Your attending expects you to systematically evaluate for a few key things on every single study:
- Acute Blood: Is there epidural, subdural, subarachnoid, or intraparenchymal hemorrhage?
- Mass Effect: Look for midline shift, sulcal effacement, and compression of the basal cisterns. Measure the shift in millimeters.
- Hydrocephalus: Are the ventricles enlarged, especially the temporal horns? Is there evidence of transependymal flow?
- Infarct: Can you see a hyperdense MCA sign (the earliest sign of a large vessel occlusion)? Is there any loss of grey-white differentiation or insular ribbon sign suggesting early cytotoxic edema?
- Fracture: Always scroll through the bone windows. Don’t miss a subtle temporal bone fracture or skull base fracture that could explain pneumocephalus.
This study is the first step for indications like acute head trauma, sudden severe headache (the “worst headache of life”), acute neurologic deficits concerning for stroke, and altered mental status.
Radiology Report Template for CT Brain Without Contrast
This is a solid, defensible template you can use as a macro in your dictation system. It covers the critical areas and provides a consistent structure that attendings appreciate.
Technique
Non-contrast computed tomography images of the brain were acquired in the axial plane and reconstructed in the sagittal and coronal planes. Images were reviewed in both soft tissue and bone windows.
Findings
Hemorrhage: No evidence of acute intracranial, subdural, epidural, or subarachnoid hemorrhage.
Midline Shift: No midline shift.
Ventricles and Cisterns: The ventricular system is normal in size and configuration. The basal cisterns are patent.
Parenchyma: No acute territorial infarct or mass lesion. Grey-white matter differentiation is preserved.
Posterior Fossa: The posterior fossa structures are unremarkable.
Skull and Soft Tissues: No acute fracture is identified. The calvarium and skull base are intact. The visualized soft tissues of the scalp are unremarkable.
Other: The visualized portions of the orbits, paranasal sinuses, and mastoid air cells are clear.
Impression
No acute intracranial hemorrhage, mass effect, or hydrocephalus.
Free Template Sources
Building a personal library of macros is a rite of passage in residency. But you don’t have to start from scratch. If you’re looking for more templates covering different modalities and subspecialties, two great free repositories exist:
- RadReport.org: This is the RSNA’s official library of templates. They are peer-reviewed, standardized, and cover a huge range of common studies.
- Radiology Templates (AU): Maintained by Australian radiologists, this site offers a fantastic collection of practical, user-submitted templates that are easy to adapt.
The Next-Level Move: AI-Assisted Structured Reporting
The problem with templates is that they’re built for negative studies. The moment you see a finding, you have to break the template, describe the pathology, and then restructure your impression. This is where modern tools can streamline your workflow. Instead of clicking through a rigid template, you can dictate your positive findings in free form—”acute 8 mm right-sided subdural hematoma over the convexity with 3 mm of leftward midline shift”—and the AI will generate a perfectly structured report. GigHz Precision AI is designed to do exactly this, using pre-loaded ACR and SIR templates to ensure your report is clean and comprehensive. It also helps surface the appropriate Clinical Decision Support (CDS) frameworks, like LI-RADS or Bosniak, when they’re needed for a specific finding.
When Should You Order a CT Brain Without Contrast? ACR Appropriateness Criteria
The American College of Radiology (ACR) provides evidence-based guidelines on when a study is indicated. For a non-contrast head CT, the key is assessing the pre-test probability of a significant finding.
For acute head trauma, the decision to image is guided by clinical rules. For mild trauma (GCS 13-15), a CT is “Usually Appropriate” if indicated by a validated clinical decision rule like the Canadian CT Head Rule. However, if the patient has mild trauma and the decision rule says imaging isn’t needed, a CT is rated “Usually Not Appropriate.” For moderate (GCS 9-12) or severe (GCS 3-8) head trauma, a non-contrast CT is always the “Usually Appropriate” first step.
In the context of headache, a non-contrast CT is “Usually Appropriate” for a sudden, severe “thunderclap” headache to rule out a subarachnoid hemorrhage. Conversely, for a patient with a history of primary migraine or tension-type headaches and a normal neurologic exam, imaging is “Usually Not Appropriate.”
For suspected acute stroke, a non-contrast head CT is the essential first-line imaging test. Its primary role is to rule out hemorrhage before thrombolytic therapy (like tPA) or mechanical thrombectomy can be considered. It’s almost always paired with a CTA of the head and neck to evaluate for large vessel occlusion.
How Much Radiation Does a CT Brain Without Contrast Deliver?
Patients and referring clinicians often ask about radiation dose. A non-contrast head CT delivers an effective dose of approximately 1.5-2.5 mSv. This is a relatively low dose, comparable to what a person receives from natural background radiation over several months to a few years. The benefit of rapidly diagnosing a life-threatening condition like an intracranial hemorrhage far outweighs the small radiation risk.
Modern scanners use automated dose modulation to minimize radiation while maintaining diagnostic quality. For pediatric patients, protocols are weight-based and use lower kVp settings to keep the dose as low as reasonably achievable (ALARA).
| Exposure Source | Estimated Effective Dose (mSv) |
|---|---|
| CT Brain Without Contrast | 1.5 – 2.5 mSv |
| Natural Background Radiation (1 year) | ~3 mSv |
| Chest X-ray (2 views) | ~0.1 mSv |
CT Brain Without Contrast Imaging Protocol — Phases, Contrast, and Reconstructions
The non-contrast head CT protocol is standardized and designed for speed and diagnostic accuracy. The process begins with a lateral topogram (scout image) to plan the helical acquisition, which runs from below the foramen magnum to the vertex of the skull. The patient’s chin is tucked to minimize radiation dose to the lenses of the eyes.
The raw data is then used to create several different image series that are sent to PACS for review. This includes thicker 5 mm axial slices for primary review and thin-slice (1-1.5 mm) reconstructions that allow for high-quality multiplanar reformats (MPRs) in the coronal and sagittal planes. A dedicated bone kernel is always used to create bone-window images for fracture evaluation.
| Phase / Reconstruction | Key Parameters | Purpose |
|---|---|---|
| Topogram (Scout) | Lateral view, low dose | Scan planning |
| Axial Helical Acquisition | kVp: 120-130; mAs: Auto-modulated (~200-250) | Primary raw data acquisition |
| Axial Review (Soft Tissue) | 5 mm slice thickness | Primary review for hemorrhage, infarct, mass |
| MPR (Coronal/Sagittal) | 1-1.5 mm thin reconstruction source | Anatomic localization, assessing for herniation |
| Bone Windows | 1-1.5 mm thin recon, bone kernel | Fracture detection |
Common protocol pitfalls: The most common issue is patient motion, which can obscure subtle findings. Another pitfall is beam-hardening artifact in the posterior fossa, which can mimic or hide pathology; this is an inherent limitation of CT, and MRI is superior for evaluating this region if clinically indicated. Finally, ensure the field of view (FOV) is appropriately sized to the patient’s head to maximize spatial resolution.
3+ months free for radiology residents and fellows
Look like a rockstar on your reports. With the GigHz Radiology Report Assistant, you can dictate your positive findings in free form, and our AI will generate a clean, structured report using ACR and SIR templates, firing the appropriate clinical decision support automatically. We’re offering extended free access to trainees because we need your feedback to keep improving the product for the next generation of radiologists.
To apply, all we ask for are three items:
- Your PGY year (e.g., PGY-2, PGY-4)
- Your training type (radiology residency or fellowship specialty)
- Your training program / hospital name
The process is simple. No credit card, no long forms. Just reply to the application with those three details, and we’ll get you set up. You can apply for the residents free-access program here.
Free GigHz Tools That Pair With This Article
Three free tools that complement the material above:
- ACR Appropriateness Criteria Lookup — Type an indication or clinical scenario in plain language and get the imaging studies the ACR rates for it, with adult and pediatric radiation levels. Built directly from 297 ACR topics, 1,336 clinical variants, and 15,823 procedure ratings.
- GigHz Imaging Protocol Library — A searchable library of 131 imaging protocols with the physics specs surfaced and the matching ACR Appropriateness Criteria alongside. Plain-English narratives readable in 60 seconds, organized by modality.
- GigHz Radiation Dose Calculator — Pick the imaging studies a patient has had and see total dose in millisieverts (mSv) with comparisons to natural background radiation, transatlantic flights, and chest X-rays. Useful for shared decision-making.
Frequently Asked Questions
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Does it work with PowerScribe or other dictation systems?
Yes. It works alongside your existing dictation system. You can dictate your findings, use the tool to structure your report, and then copy-paste the final, clean text directly into your PACS/RIS.
Can I use this on my phone or iPad?
Absolutely. The tool is fully responsive and designed to work on desktops, tablets, and mobile devices, so you can use it wherever you’re reading.
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Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 7, 2026
