Domain: Healthcare — Imaging Medicine
Target concept: Ultrasound Manifestations of Cholelithiasis

Video generation prompt: Perform ultrasound examination on patients with gallstone, and observe the presence of echogenic foci within the gallbladder and their posterior acoustic shadowing.

Evaluation guide:
(i) Target concept: Ultrasound detection of gallstones via intrinsic echogenicity and resultant posterior acoustic shadowing.
Minimum mechanism: A calcified or highly reflective spherical/ovoid object suspended in anechoic fluid must generate a collinear, distally extending zone of signal dropout along the ultrasound beam path.
(ii)Storyline: 1. Probe placed in stable contact with skin over right upper quadrant → 2. Gallbladder lumen emerges as uniform anechoic space bounded by hyperechoic walls → 3. At least one discrete echogenic focus appears intraluminally (not wall-attached) → 4. Immediately distal to each focus, a vertically oriented, featureless dark band (posterior acoustic shadow) appears and persists → 5. Shadow remains fixed in alignment with focus across time, with no lateral deviation or premature termination. Perspective: Fixed transverse abdominal view; visibility constraint: Gallbladder must be fully contained in frame, unobscured by rib shadow or bowel gas.

Manual:
Experimental Procedure
1. Position ultrasound probe transversely over right upper quadrant, applying gentle pressure to achieve optimal gallbladder visualization.
2. Identify gallbladder lumen as anechoic (dark) oval structure bounded by smooth hyperechoic (bright) walls.
3. Scan slowly to detect intraluminal echogenic foci that do not move with patient position change.
Observation of Experimental Phenomena
- One or more discrete, bright, non-shadowing echogenic foci within gallbladder lumen.
- Each echogenic focus casts a well-defined, vertically oriented posterior acoustic shadow extending distally.
- No internal echoes within shadow; shadow terminates cleanly at depth limit of field.
Summary of Experimental Principles
Cholelithiasis appears on ultrasound as intraluminal echogenic foci due to acoustic impedance mismatch between calcified stone and bile. Posterior acoustic shadowing results from near-complete sound wave attenuation and reflection at the stone-bile interface.

Prompt Grounding rubric:
level_1: No gallbladder anatomy visible; no ultrasound probe or transducer shown; no echogenic foci present; no posterior acoustic shadowing; no gallbladder lumen or wall structure identifiable.
level_2: Gallbladder anatomy partially visible (e.g., only wall or only lumen), but no probe in contact with skin; echogenic foci absent; posterior acoustic shadowing absent; sequence of probe placement → scanning → observation not represented.
level_3: Gallbladder anatomy clearly visible (lumen, wall, and fluid-filled space); ultrasound probe is visibly in contact with skin surface over right upper quadrant; at least one echogenic focus appears within gallbladder lumen; posterior acoustic shadowing is present behind at least one echogenic focus; all elements appear in same scene with fixed viewpoint.
level_4: All 3-point criteria satisfied, AND echogenic foci are multiple or clearly clustered within gallbladder lumen (not attached to wall), AND posterior acoustic shadowing extends continuously from each echogenic focus without interruption, AND probe remains in stable contact throughout the entire 10-second duration (no lifting, repositioning, or removal).
level_5: All 4-point criteria satisfied, AND echogenic foci are exclusively intraluminal (no wall-attached or mural calcifications), AND posterior acoustic shadowing is uniformly dark and sharply demarcated behind every echogenic focus, AND gallbladder lumen maintains homogeneous anechoic appearance surrounding all foci, AND no extraneous objects (e.g., bowel gas, liver parenchyma artifacts) obscure the gallbladder region.

Scientific and Causal Correctness rubric:
level_1: Echogenic foci appear hypoechoic or isoechoic relative to gallbladder lumen; posterior acoustic shadowing is absent or appears as bright enhancement instead of shadow; echogenic foci are embedded in gallbladder wall or liver tissue; no causal link between echogenic focus and shadow visible.
level_2: Echogenic foci are present but incorrectly located (e.g., outside gallbladder lumen, within liver, or floating in air); posterior acoustic shadowing appears in wrong location (e.g., anterior to focus, lateral to focus, or disconnected); shadowing is fragmented and inconsistent across foci; causal relationship (focus → shadow) is visually broken.
level_3: Echogenic foci are hyper-reflective (bright white) relative to anechoic gallbladder lumen; posterior acoustic shadowing appears directly behind each echogenic focus as a vertically oriented dark zone; shadowing begins immediately distal to the focus and extends downward; spatial alignment between focus and shadow is consistent with ultrasound physics.
level_4: All 3-point criteria satisfied, AND no false shadowing (e.g., no shadow behind non-echogenic structures); no reverberation artifacts misinterpreted as shadowing; echogenic foci do not exhibit comet-tail artifact (which would indicate cholesterol polyp, not stone); shadowing does not fade or widen abnormally with depth.
level_5: All 4-point criteria satisfied, AND echogenic foci show clean, sharp margins (no halo or rim sign); shadowing is uniform in darkness and shape across all foci; no competing acoustic phenomena (e.g., edge artifact, mirror image, or beam distortion) interfere with focus-shadow pairing; causal chain is unambiguous: each discrete echogenic focus produces one contiguous posterior acoustic shadow aligned along the ultrasound beam path.

Spatiotemporal Consistency rubric:
level_1: Gallbladder disappears/reappears abruptly; probe jumps between locations; echogenic foci teleport across frame; shadowing flickers on/off discontinuously; major structural breaks (e.g., gallbladder wall splits, lumen collapses then re-expands).
level_2: Gallbladder remains visible but undergoes unnatural deformation (e.g., pulsating lumen size, wobbling wall contour); probe contact is intermittent (visible lift-and-replace motion); echogenic foci blink or change position mid-sequence; shadowing appears/disappears inconsistently across frames.
level_3: Gallbladder maintains stable anatomical shape and position; probe remains in continuous contact with skin surface; echogenic foci remain stationary within lumen; posterior acoustic shadowing remains fixed in vertical alignment behind each focus; no abrupt lighting changes, no frame skips, no object warping.
level_4: All 3-point criteria satisfied, AND gallbladder wall thickness and curvature remain constant; probe pressure does not cause visible indentation or displacement of underlying tissue; echogenic foci do not drift, rotate, or change brightness; shadowing maintains consistent vertical orientation and length across time.
level_5: All 4-point criteria satisfied, AND inter-frame motion is smooth and natural (no stutter, no interpolation artifacts); no parallax shift between probe, skin surface, and gallbladder; no temporal mismatch (e.g., shadow appearing before focus or lagging after focus); no spatial disjunction (e.g., focus and shadow occupying different depth planes due to perspective error).