**3. History of dosimetry audit**

The concept of verifying the realized dose in the medical applications of ionizing radiation was introduced in the early 20th century shortly after the first application of X-rays for the treatment of cancer.

Initially, in order to adequately assess the daily fraction that would be prescribed to patients, doctors irradiated their own hands to observe a skin reaction - "dose of erythema".

In 1925, the Swedish physicist R. Sievert [10] created a circulating physical department to standardize the Roentgen radiation (X-rays) used in oncology therapy in his country. The department found some unreliable dosimeters and identified the need for better protective equipment for X-ray personnel. At the same time, the data collected from the measurements of the dosimetric value - Percent Depth Dose (PDD) were used as reference values for the technical equipment used for clinical purposes at that time.

Another documented example of an early dosimetry audit was found in Poland, following Marie Curie's idea that a Laboratory for measuring the dose of X-rays and the radioactive isotope radium used in hospitals at the time should be opened. The laboratory for dosimetry measurements was founded in 1936 [10].

The dosimety laboratory in the International Atomic Energy Agency (IAEA) was established in the early 1960s to organize and conduct dosimetry audits for radiotherapy centers worldwide and to ensure international consistency in radiation dosimetry. The first pilot postal comparison of the radiation dose between different radiotherapy centers was organized by the IAEA in the period 1965–1966 as a joint project with the World Health Organization (WHO).

### **4. The essence of dosimetry audit**

Dosimetry audit (DA) is a tool for quality improvement. It can be defined as a systematic and critical analysis of the quality of the dosimetry activities performed in specific radiotherapy center. The dosimetry audit includes an assessment of data, documents and resources in order to verify the performed clinical dosimetry activity against the adopted international standards of good practice. The essence of the dosimetry audit can be summarized as:


The results of the dosimetry audit inform the staff about the main elements of the quality and the weaknesses of the dosimetry activities carried out, comparing the audited dosimetric practice with the standards for good clinical radiation dosimetry. Dosimetry audit identify areas for improvement and provide confidence in safety and efficacy, which are essential to creating a clinical environment of continuous development and improvement.

One of the main risks for patients undergoing radiation therapy is the delivery of a dosimetry inaccurate therapeutic dose during radiation therapy sessions. Dosimetry inaccuracies directly reflect on tumor control, cancer treatment and toxicity affected the survival, and quality of life of cancer patients. The differences between the prescribed and delivered dose directly affect the clinical outcomes. The precision of the therapeutic method of radiation therapy is mainly related to the high degree of accuracy of the radiation dose applied during the treatment of patients.

Dosimetry audit is a partial audit and related to the quality assurance procedures in the field of the performed dosimetry activities in a specific radiotherapy center and namely [11–13]:


*Dosimetry Audit in Modern Radiotherapy DOI: http://dx.doi.org/10.5772/intechopen.100941*

Dosimetry audit is proactive, ie. consists in reviewing the current clinical dosimetry in order to improve its quality. It is organized and conducted remotely, ie. It is (remote audit).

Dosimetry audit worldwide are organized in different ways, often for geographical, economic or political reasons, but mainly check the fundamental value - the absorbed dose in reference conditions, ie. so-called - beam output [12]. The measurement of the value of the absorbed dose in the so-called reference conditions i.e. beam output is the most fundamental measurement that confirms whether the therapeutic system generating ionizing radiation and used for radiotherapy is properly calibrated [14].

The existence of an error in the calibration of the radiation beams leads to the creation of a systemic error in the treatment of each individual patient, which in turn leads to systemic differences in the results of the conducted radiation therapy.

DA is a key component in quality management in radiotherapy and plays an important role in the safe application and use of new methods and techniques of radiotherapy [15, 16].

### **5. Types of dosimetry audit**

The International Atomic Energy Agency (IAEA) as the founder of the idea of dosimetry audit and main organizator of the program for postal dosimetryc audit with thermoluminescent dosimeters (TLDs) and radiophotoluminescent dosimeters (RPLDs) for nearly fifty years has identified the following types [17] (See **Figure 1**).


**Figure 1.**

*IAEA classification of different types dosimetry audits [17].*
