Explore · Seeing a volume
One shape. Many slices.
Slide a plane through the same three-dimensional shape. Watch the cross-section change while the object itself stays exactly the same.
A geometric object, not an organ, tumour or scan. Only the cutting level changes. Shape size, image contrast and treatment response are not being measured.
The same object
The selected cross-section
Slide from one end to the other. Near the middle, the cross-section is larger. Near an end, it is smaller. This ideal shape has circular horizontal sections; real anatomy is more complex.
The cutting plane is near the centre. The shape itself has not changed.
A slice is part of a volume.
Different levels can look different
The same three-dimensional object can produce different two-dimensional outlines at different levels. Here, moving the plane changes the circle even though nothing about the object changes.
The dashed reference, when selected, is the central section of this same shape. It is not a previous scan or a treatment comparison.
The connection with CT
CT uses X-ray measurements from different angles to reconstruct cross-sectional images. The images can also be combined into three-dimensional views. The body is not physically cut into slices.
This diagram does not reproduce CT physics, pixel values, slice thickness, scan quality or disease. It is a way to understand the idea of a cross-section.
One picture is not the whole assessment.
Do not use this shape to interpret a scan or decide whether cancer has changed. Radiologists and oncology teams review the relevant images and comparisons in context. Formal treatment-response assessment has defined methods; this explorer does not implement them.
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Sources & clinical review
Clinically reviewed and approved by Dr AlHilali on 4 November 2026.