A clinic compares two flat-panel detectors with identical 35-cm field of view for extremity work. Detector A uses a 2000 x 2000 matrix and Detector B uses a 3000 x 3000 matrix with smaller detector elements and tighter pitch. The supervisor asks which property sets the limiting spatial resolution for fine bone detail. Which detector characteristic determines the Nyquist frequency and MTF cutoff described?

Nyquist frequency equals 1/(2 x pixel pitch), so smaller detector elements sampled more densely across the same field raise the maximum spatial frequency that can be represented without aliasing, and the modulation transfer function extends to higher frequencies before falling to zero. Detector A with larger pitch therefore has a lower Nyquist limit and earlier MTF roll-off despite identical coverage, while Detector B preserves fine trabecular and cortical detail because its sampling interval is finer. The distractor about larger elements improving high-frequency MTF reverses the relationship because larger pitch increases blur and lowers cutoff; the distractor about increased matrix lowering Nyquist confuses matrix with pitch since more pixels over the same field means smaller pixels and higher Nyquist; the distractor about wider pitch increasing Nyquist also inverts the formula and would actually promote aliasing. Exam caveat: distinguish sampling-limited resolution from contrast or noise, which depend on dose and DQE. Practical check: compare stated pixel pitch in millimeters and compute Nyquist to verify which detector truly resolves finer line pairs.