Domain: Healthcare — Imaging Medicine
Target concept: Normal CT findings of the brain without contrast enhancement

Video generation prompt: Perform CT plain scan of the brain in normal adults with a slice thickness of 5 mm, and observe the morphology of the cerebral hemispheres, cerebellum, brainstem, and ventricles.

Evaluation guide:
(i) Target concept: A static, diagnostic-quality axial CT image of a normal adult brain, acquired without intravenous contrast, at 5 mm slice thickness, enabling identification of four key neuroanatomical regions.
Minimum mechanism: The image must originate from X-ray transmission through tissue, producing differential attenuation represented as grayscale; no optical photography, MRI signal, or synthetic rendering logic may underlie the appearance.
(ii)Storyline: Frame 1–3: Stable view of axial brain slice entering full visibility (no pan/zoom required if already centered). Frames 4–10: Static display of the slice with uninterrupted visibility of all four structures (cerebral hemispheres, ventricles, cerebellum, brainstem) in correct spatial relationships; grayscale remains stable; no motion, flicker, or structural change. Perspective is fixed axial plane; no oblique tilt, no rotation, no multiplanar reformats: only one true axial slice, fully in-frame, no occlusion.

Manual:
Experimental Procedure
1. Position supine adult head in CT gantry.
2. Acquire axial non-contrast CT scan at 5 mm slice thickness.
3. Display single representative axial slice at level of basal ganglia and lateral ventricles.
Observation of Experimental Phenomena
- Symmetric cerebral hemispheres with distinct gray-white differentiation.
- Clearly defined lateral ventricles with atria, bodies, and frontal horns.
- Cerebellum visible inferiorly with characteristic foliated surface.
- Brainstem visible as continuous structure connecting midbrain, pons, and medulla.
Summary of Experimental Principles
Normal CT findings of the brain without contrast enhancement require uniform grayscale attenuation: CSF is hypodense (dark), white matter is isodense-to-slightly-hyperdense (lighter gray), gray matter is intermediate. Anatomy must be symmetric, unremarkable, and conform to standard axial landmarks.

Prompt Grounding rubric:
level_1: No CT scanner or head/brain imagery appears; no axial cross-section is shown; none of the four structures (cerebral hemispheres, cerebellum, brainstem, ventricles) can be identified; nothing about the video resembles a brain CT scan.
level_2: Some kind of medical-imaging or head-shaped image appears, but it isn't presented as an axial cross-section (e.g., it's a 3D rendering, a photo of a head, or a different scan plane); at least one of the four required structures (hemispheres, cerebellum, brainstem, ventricles) cannot be identified at all.
level_3: A single axial cross-section of a human head is shown; the cerebral hemispheres, cerebellum, brainstem, and ventricles are all visually identifiable within it; however, at least one of the following is off: the video shows more than one slice, a scrolling stack, or a reformatted (non-axial) view instead of one steady axial image; or the relative arrangement of the structures is wrong (e.g., the cerebellum appears above rather than below the cerebral hemispheres).
level_4: Everything at the 3-point level is present, and in addition, all four structures sit in their correct relative positions (the cerebellum below the cerebral hemispheres, the brainstem connecting the cerebrum and cerebellum, the ventricles centered within the hemispheres); the video presents exactly one continuous axial slice, not a scroll through multiple levels, not a 3D reconstruction, not a coronal or sagittal reformat; no extra objects or overlays appear in the frame.
level_5: Everything at the 4-point level is present, and in addition, every structure looks equally sharp and in focus, with no blurring or smearing in one area but not another; there are no text labels, arrows, or annotations drawn over the image; the full head is framed in view with no cropping, zooming, or panning partway through.

Scientific and Causal Correctness rubric:
level_1: The structures are shown in ways that contradict basic anatomy (e.g., the ventricles look like solid lumps rather than fluid-filled spaces, or the cerebellum and brainstem appear fused into one blob); the grayscale doesn't reflect real CT physics at all (e.g., the whole image is one flat shade, or colors other than gray dominate).
level_2: At least two of the four structures are clearly misshapen or misplaced (e.g., the cerebellum sits above the cerebral hemispheres, or the ventricles appear only on one side with no explanation); the grayscale is backwards or implausible (e.g., the fluid in the ventricles looks bright white instead of dark, or gray matter and white matter look identical with no visible contrast).
level_3: All four structures are present and recognizable; the general grayscale ordering is right: the fluid-filled ventricles read darker than brain tissue, and there is some visible contrast between gray matter and white matter; however, at least one structure's shape departs from normal anatomy (e.g., the ventricles look unusually large or slit-like, the cerebellar folia are smoothed away, or the brainstem doesn't read as a continuous stalk between the cerebrum and cerebellum).
level_4: Everything at the 3-point level is present, and in addition, the ventricles look symmetric and appropriately sized; the cerebellum's fine folded surface (folia) is visible; the brainstem reads as one continuous structure; the cortical folding pattern of the cerebral hemispheres looks normal; the gray-white contrast and the darkness of the CSF-filled spaces look internally consistent across the whole image, matching what non-contrast CT is expected to show, without any bright enhancement-like patches that would suggest contrast dye was given.
level_5: Everything at the 4-point level is present, and in addition, no structure shows an unexpected bright or dark patch within it; there are no streaky or blocky artifacts running across the image; every fluid-filled space (ventricles, basal cisterns) reads at the same uniformly dark shade; the boundary between gray matter and white matter stays crisp everywhere; the two hemispheres look essentially mirror-symmetric, aside from the small natural variation seen in real brains.

Spatiotemporal Consistency rubric:
level_1: The video cuts abruptly between unrelated views (e.g., an axial slice suddenly becomes a 3D render or a photograph); the brain appears split or cut off at the frame's edge; the overall brightness of the image changes suddenly partway through; a structure jumps to a different position or size with no transition.
level_2: At least one clear glitch occurs: the brainstem or another structure briefly vanishes and reappears somewhere else; the ventricles change shape suddenly between two moments; the slice appears to rotate or tilt visibly; the image brightens or dims suddenly with nothing shown to explain it, like an exposure change.
level_3: Every structure stays in the same place and at the same size relative to the others for the whole video; nothing tears, warps, or jumps; the overall brightness and contrast of the image stay the same throughout; there may be a brief, minor flicker or a slight shimmer along an edge, or one instance of the image briefly settling before holding steady, but nothing more disruptive than that.
level_4: No flicker, shimmer, or wavering is visible anywhere; every structure keeps the exact same size, shape, and position across the entire video; the overall brightness and contrast never waver; there are no skipped or frozen frames; if there's any slow zoom, it moves at an even, steady pace throughout.
level_5: Everything at the 4-point level is present, and in addition, the image looks like a single unchanging, steadily held scan for its entire duration: no patch of the image looks noticeably grainier, smoother, or differently textured than the rest, as if assembled from different sources; the viewing angle never appears to tilt or shift even slightly; the slice reads as a genuinely static, held CT image rather than something subtly animating.