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A fast intracerebral hemorrhage volume estimation tool based on the ABC/2 formula to assist clinical decision-making.
Approximate ABC/2 arithmetic. Slice mode requires a positive integer and contiguous equally thick slices. Not precise segmentation or a clinical/surgical decision. Reference
Enter CT measurement data to calculate volume.
Tada Formula: V = 0.5 × L × S × H. L represents the maximum length, S the maximum width, and H the height (calculated as slice count × slice thickness). This formula is widely used clinically to estimate intracerebral hemorrhage volume.
Overview
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This calculator applies the ABC/2 approximation to measurements supplied by the user. A is the longest diameter of the hematoma on its largest CT slice; B is the perpendicular diameter on that same slice; C is the head-to-foot extent. The result is an estimated volume in milliliters, not a traced volume from every image slice.
In slice-count mode, C is calculated as the number of contiguous, equally thick slices containing hemorrhage multiplied by slice thickness in centimeters. In direct-height mode, enter C itself in centimeters. The calculator shows one decimal place.
The original ABC/2 method was described for estimating intracerebral hemorrhage volume on CT, using the largest diameter, a perpendicular diameter, and an approximate slice count times slice thickness. The 2022 American Heart Association/American Stroke Association guideline notes that ICH volume is often estimated in practice with ABC/2. These sources describe clinical use of an approximation; they do not make this calculator a diagnostic or treatment system.
Guide
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Use the slice where the hematoma appears largest. Enter its greatest diameter and the diameter perpendicular to it, both in centimeters. Do not pair measurements taken from different slices.
For slice count, enter a positive whole-number count of contiguous slices and the actual slice thickness in centimeters. For direct input, enter the measured head-to-foot height in centimeters; do not multiply it by thickness again.
The result updates when valid positive measurements are present and is rounded to one decimal place. For a quick arithmetic check, multiply A × B × C and divide by 2.
Example: with A = 4 cm, B = 3 cm, and direct C = 5 cm, the estimate is 4 × 3 × 5 ÷ 2 = 30.0 mL. With five slices at 0.5 cm each, C is 2.5 cm and the same A and B produce 15.0 mL.
Use cases
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A trained reader who has already measured a CT hematoma can enter the values to verify the ABC/2 multiplication and compare it with a documented estimate.
In a classroom or case discussion, use the direct-height and slice-count examples to show why slice thickness and the meaning of C must be clear before comparing results.
Q&A
Find concise answers to common questions and confusing cases.
Use slice count only when counting contiguous slices of equal thickness and entering their actual thickness. If the head-to-foot height is already measured, use direct input and enter that height in centimeters.
Slice-count mode requires a positive whole number because it represents a count of slices. Check that you selected the intended mode; direct-height mode accepts a positive height in centimeters.
No. ABC/2 is an approximation. Research reports lower accuracy for large, irregular, or lobar clots, so a numeric output should not be treated as precise segmentation.
Notes
Review scope, result limitations, and important precautions before use.
This page performs arithmetic on entered measurements. It does not interpret imaging, diagnose a condition, grade severity, predict an outcome, or determine surgery or treatment.
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