The package dcmtk provides CMake targets:

    find_package(DCMTK CONFIG REQUIRED)
    # Note: 23 target(s) were omitted.
    target_link_libraries(main PRIVATE cmr i2d ijg8 dcmfg)

Add the following cmake code to your CMakeLists.txt to create definitions for DCMTK
    if ("${VCPKG_INSTALLED_DIR}/${VCPKG_TARGET_TRIPLET}" STREQUAL "/")
        message(WARNING "No vcpkg install dir found, DCMTK definitions are not set")
    else()
        target_compile_definitions(main
            PUBLIC
                "DCMTK_PREFIX=${VCPKG_INSTALLED_DIR}/${VCPKG_TARGET_TRIPLET}"
                "DCM_DICT_DEFAULT_PATH=${VCPKG_INSTALLED_DIR}/${VCPKG_TARGET_TRIPLET}/share/dcmtk/dicom.dic:${VCPKG_INSTALLED_DIR}/${VCPKG_TARGET_TRIPLET}/share/dcmtk/private.dic"
                "DEFAULT_CONFIGURATION_DIR=${VCPKG_INSTALLED_DIR}/${VCPKG_TARGET_TRIPLET}/etc/dcmtk/"
                "DEFAULT_SUPPORT_DATA_DIR=${VCPKG_INSTALLED_DIR}/${VCPKG_TARGET_TRIPLET}/share/dcmtk/"
        )
    endif()