The Qualifier None is identified by letter "Z" and occupies the 6th position in the ICD10-PCS procedure code structure.
Below a selection of ICD 10 PCS codes related to CG21YZ
Tomo Nucl Med Imag Parathyroid Gland w Oth Radionuclide
Tomo Nucl Med Imag of Parathyroid Gland using Technetium 99m
Tomo Nucl Med Imag of Parathyroid Gland using Thallium 201