No, because the exposure is not always harmless; besides, the repetition of certain examinations or treatments might have adverse effects on someone's health. An example: a CT-scan of the thorax involves an exposure that is several hundreds of times higher than a dental radiography.
It is therefore advisable to keep, together with the doctor in attendance, an overview of the frequency and the number of scanners/radiography that one undergoes.
The equipment used in nuclear medicine is authorized by the authorities and calibrated according to standards that are defined by the manufacturer in consultation with the medical sector. The functioning of the equipment is regularly audited by the FANC or by delegation by Bel V.
In nuclear medicine and imaging, each patient is considered individually; the global approach for his treatment depends on his general health. Up to now, the legislator sets no limits concerning the number of radiographies and CT-scans. However, the use of ionizing radiation for diagnostic and therapeutic purposes should in any case always be justified.