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RC 113 - Patient-specific dosimetry
Physics in Medical Imaging EuroSafe Imaging Education Interventional Radiology
Wednesday, February 27, 08:30 - 10:00
Room: G
Type of session: Refresher Course
Topic: Physics in Medical Imaging, EuroSafe Imaging, Education, Interventional Radiology
Moderator: E. Samara (Sion/CH)

Chairperson's introduction
E. Samara; Sion/CH
Learning Objectives

1. To understand the needs for personalised dosimetry.
2. To learn about existing and new methodologies used for patient dosimetry.
3. To understand the challenges for the implementation of patient-specific dosimetry.


The use of ionising radiation in medical imaging offers substantial benefits for the diagnosis and treatment of numerous medical conditions in children and adults. However, exposure to ionising radiation may be associated with harmful risks. Justification and optimisation as principles of radiation protection make radiation dosimetry fundamental. Physicians need to know the levels of exposure, and hence the risks from imaging examinations that they have to justify and operators of X-ray cases such as examinations of children and pregnant patients or screening examinations require specific organ dose estimations. Moreover, to prevent tissue reactions patient skin dose needs to be estimated during radiological interventional procedures. Patient characteristics, such as age, sex and size, should be taken into consideration for specific patient dose assessments. Each modality (radiography, fluoroscopy, mammography, computed tomography, etc.) has its specificities and demands different methods to calculate the dose. Modern imaging modalities usually display conventional dosimetry metrics, such as dose-area product, incident air-kerma or computed tomography dose index that do not represent individual patient dose. Thus, numerous sophisticated concepts and methods have been proposed to estimate patient radiation dose that includes either physical measurements with dosimeters and anthropomorphic phantoms or computational measurements using Monte Carlo simulations. All these methods progressively allow to more accurate estimations of individual patient doses.

A. Breast imaging dosimetry
I. Sechopoulos; Nijmegen/NL
Learning Objectives

1. To understand the current method to estimate organ dose in mammography and its limitations.
2. To understand breast dosimetry in emerging modalities.
3. To learn about upcoming approaches in breast dosimetry.


Mammographic dosimetry is a subject of intense interest due to the use of this imaging modality for population-based screening. However, established breast dosimetry methods do not result in patient-specific dose estimates. Rather, our current methods provide estimates of dose to a model breast, even if the actual technique used for a specific acquisition is taken into account. New insights into breast anatomy have provided us, for the first time, with estimates of how current dose predictions can differ from actual patient-specific doses. During this talk, the current method and model for breast dosimetry in mammography and digital breast tomosynthesis will be reviewed, and its capabilities and limitations discussed. How patient-specific breast dosimetry could be achieved and the current progress towards this goal will be presented, and what its potential applications could be will be discussed.

B. Patient dosimetry in CT and CBCT
S. Edyvean; London/GB
Learning Objectives

1. To understand what is estimated.
2. To learn how to measure it.


Conventional CT is a complex imaging device which can utilise narrow or wide beams, helical scanning, varying tube current, varying kV, and operating with various and dynamic collimations - all of which can affect patient dose. Cone beam CT (or flat panel CT) uses different technology, referring to cross-sectional imaging with digital x-ray systems used in dental, digital radiography or radiotherapy. Many of the challenges are similar for both conventional CT and cone-beam CT; however, there has been substantially more research, and literature available, for the former. The dose distribution for both can be complex, due to the geometry of irradiation. When considering patient-specific dosimetry, the technology, exposure settings, and the patient, all need to be considered. As with other modalities, the scope to directly measure doses using physical dosimeters is limited. Therefore, doses need to be estimated using regular-shaped, or anthropomorphic, phantoms, or calculated using mathematical modelling techniques. The appropriate application, and the limitations, of standard dose indices (such as the computed tomography dose index, the size-specific dose index, the cone beam dose index), together with their associated methodologies and phantoms, will be addressed. Monte Carlo calculations from a modelled scanner and patient characteristics give more precise organ dose information, and there are a number of applied software packages developed to utilise these data. The advantages and limitations of these will be discussed.

C. Patient dose in fluoroscopy and interventional
A. Trianni; Udine/IT
Learning Objectives

1. To review the fundamental patient dosimetry quantities.
2. To learn about calculation of patient dose for interventional procedures.
3. To learn about real time patient dose monitoring strategies.


Biological effects induced by exposure to radiation made evident the need for accurate dosimetry from the early days of X-ray use in medicine. Later the scientific interest turned also to the estimation of risks of radiation-induced cancer and genetic effects. Various dosimetric quantities have been used in diagnostic radiology and sometimes confusion is caused because the same name is used for different quantities. The question arises: what is patient dose and what is not? It’s common practice to indicate the dose received by a patient in radiology using the dosimetric indexes defined for the different imaging modalities. However, dosimetric indexes are a useful tool for practices optimisation and comparison, but certainly, they don’t describe patient dose. To accurately estimate patient dose there is the need to collect a lot of information concerning patient characteristics and irradiation events in order to obtain organ or tissue dose. Nowadays, thanks to the digital technology used in medical imaging, various ways of collecting these data are available. The information is communicated using specific standards (i.e. DICOM), such as the non-image information object definitions. These objects are carrying information about equipment output and other dose-related information which allow the user to provide a more accurate estimate of patient dose. This talk will review the basic concepts of patient dosimetry as well as the existing DICOM objects and IHE profiles used to monitor patient exposure, highlighting the pros and cons and introducing to future developments.

Panel discussion: The future of patient-specific dosimetry
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