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HAZARDS OF IONISING RADIATION

HAZARDS OF IONISING RADIATION

The majority of ionising radiation comes from natural sources on Earth and cosmic rays, and this makes up the background radiation. However, medical exposure accounts for around 15% of the total received by humans. The e ff ects of ionising radiation can be broadly divided into two groups. The first group comprises predictable, dose-dependent tissue e ff ects and includes, for example, the development of cataracts in the lens of the eye. These e ff ects are important for those chronically exposed to radiation, including those using image intensifiers regularly . The second group comprises the all-or-nothing e ff ects such as the development of cancer (termed stochastic). These e ff ects are not dose dependent, but increase in likelihood with increased radiation dose. The risk of radiation-induced cancer for plain films of the chest or extremities is very small, of the order of 1:1 /uni00A0 000 /uni00A0 000. However, that risk rises considerably for high-dose examina - tions such as CT of the abdomen or pelvis, where the estimated lifetime excess risk of cancer increases to the order of 1:1000. Use of CT has increased dramatically in the last 20 years, with 2 a 12-fold increase in the UK, and it has been estimated that up m ) to 30% of these e xaminations may be unnecessary . Obviously , the risk of such examinations has to be balanced against the benefit to the patient in terms of increased diagnostic yield, and must also be viewed in the context that the lifetime risk of cancer for people generally is about 1:3. Nevertheless, the - increased risk is important since it is iatrogenic and applied to a large population. Therefore, techniques that do not use ionis - ing radiation, such as ultrasound and MRI, should be carefully - considered as alternatives, particularly in children and young people. In the UK, the Ionising Radiation (Medical Exposure) Regu lations (IR(ME)R) introduced in 2000, and amended in 2006, impose on the radiologist the duty to the patient to make sure that all studies involving radiation (plain radiographs, CT and nuclear medicine) are performed appropriately and to the highest standards. Inappropria te use of radiation is a criminal o ff ence, so investigations involving radiation need careful consideration in order to prevent wasteful use of radiology . Summary box 8.2 Criteria for useful investigations There are special considerations for portable and fluoros copy units. The longer an operator keeps the fluoroscopy unit running, the higher the dose of radiation to all in the vicinity . Portable x-ray machines and fluoroscopic imaging equipment use much more radiation to achieve the same result. T and patients in the next bed, are at risk when portable equip ment is used. The result is also of lower quality , so portable x-ray machines should not be used unless absolutely necessary . When using the image intensifier, lead aprons, thyroid shields, lead glasses and radiation badges should always be worn. Preg nancy in the female patient or sta ff must be excluded. Wilhelm Conrad Roentgen , 1845–1923, Professor of Physics, Würzburg (1888–1900), and then at Munich, Germany . He was awarded the Nobel Prize in Physics in 1901 for his work on x-rays. - Responsibilities of the radiologist and referrer /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF The UK’s Royal College of Radiologists produces an evidence-based guidance tool, called iRefer, which is widely available on line and shows radiation doses for common procedures ( Table 8.1 ). -

A useful investigation is one in which the result – positive or negative – will inform clinical management and/or add con /f_i dence to the clinician’s diagnosis. A signi /f_i cant number of radiological investigations do not ful /f_i l these aims and may add unnecessarily to irradiation of patients. To avoid the wasteful use of radiology, the important questions to be asked are as follows.

  1. Has it been done already ? Repeating investigations that have already been done: such as at another hospital, in an outpatient department or in an emergency department. Every attempt should be made to obtain previous images and reports. Transfer of digital data through electronic links will assist in this respect. Although guidelines may not directly address this question, there are other initiatives that do
  2. Is it needed ? Undertaking investigations when results are unlikely to affect patient management or over-investigating: because the anticipated positive /f_i nding is usually irrelevant – for example, degenerative spinal disease – or because a positive /f_i nding is unlikely. Some clinicians and patients tend to rely on investigations more than others for reassurance
  3. Is it needed now ? Investigating too early: for example, before the disease could have progressed or resolved, or before the results could in /f_l uence treatment. The need for investigation and treatment should be reviewed at a more appropriate time
  4. Is this the best investigation ? Doing the wrong investigation: imaging techniques undergo rapid change. It is often helpful to discuss an investigation with a specialist in clinical radiology or nuclear medicine before it is requested
  5. Has the problem been properly explained ? Failing to provide appropriate clinical information and questions that the imaging investigation should answer: de /f_i ciencies here may lead to the use of the wrong technique, or the report being poorly focused on the clinical problem. In some clinical situations /f_i rm guidelines have been established Radiologists have a legal responsibility to keep imaging as safe as possible The referrer has a duty to balance risk against bene /f_i t The referrer must provide adequate clinical details to allow justi /f_i cation of the examination Avoid using portable (mobile) x-ray machines whenever practical Take all precautions when using an image intensi /f_i er The gonads, eyes and thyroid are especially vulnerable to radiation and should be protected TABLE 8.1 Band classi /f_i cation of the typical doses of ionising radiation from common imaging procedures. Examples Lifetime Symbol Typical additional effective risk of cancer dose (mSv) induction /exam None 0 US; MRI 0 <1:20 /uni00A0 000 <1 CXR; XR limb, pelvis, lumbar spine; mammography 1:20 /uni00A0 000–1:4000 1–5 IVU; NM (e.g. bone); CT head and neck 5.1–10 CT KUB; NM 1:4000–1:2000 (e.g. cardiac)

1:2000 10 Extensive CT studies, some NM studies (e.g. some PET/CT) CT, computed tomography; CXR, chest x-ray; IVU, intravenous urog

raphy; KUB, kidneys, ureters and bladder; MRI, magnetic resonance imaging; NM, nuclear medicine; PET, positron emission tomography; US, ultrasound; XR, x-ray. Source: https://www.rcr.ac.uk/sites/default/ /f_i les/documents/irefer_ introductoryiaea.pdf.

HAZARDS OF IONISING RADIATION

The majority of ionising radiation comes from natural sources on Earth and cosmic rays, and this makes up the background radiation. However, medical exposure accounts for around 15% of the total received by humans. The e ff ects of ionising radiation can be broadly divided into two groups. The first group comprises predictable, dose-dependent tissue e ff ects and includes, for example, the development of cataracts in the lens of the eye. These e ff ects are important for those chronically exposed to radiation, including those using image intensifiers regularly . The second group comprises the all-or-nothing e ff ects such as the development of cancer (termed stochastic). These e ff ects are not dose dependent, but increase in likelihood with increased radiation dose. The risk of radiation-induced cancer for plain films of the chest or extremities is very small, of the order of 1:1 /uni00A0 000 /uni00A0 000. However, that risk rises considerably for high-dose examina - tions such as CT of the abdomen or pelvis, where the estimated lifetime excess risk of cancer increases to the order of 1:1000. Use of CT has increased dramatically in the last 20 years, with 2 a 12-fold increase in the UK, and it has been estimated that up m ) to 30% of these e xaminations may be unnecessary . Obviously , the risk of such examinations has to be balanced against the benefit to the patient in terms of increased diagnostic yield, and must also be viewed in the context that the lifetime risk of cancer for people generally is about 1:3. Nevertheless, the - increased risk is important since it is iatrogenic and applied to a large population. Therefore, techniques that do not use ionis - ing radiation, such as ultrasound and MRI, should be carefully - considered as alternatives, particularly in children and young people. In the UK, the Ionising Radiation (Medical Exposure) Regu lations (IR(ME)R) introduced in 2000, and amended in 2006, impose on the radiologist the duty to the patient to make sure that all studies involving radiation (plain radiographs, CT and nuclear medicine) are performed appropriately and to the highest standards. Inappropria te use of radiation is a criminal o ff ence, so investigations involving radiation need careful consideration in order to prevent wasteful use of radiology . Summary box 8.2 Criteria for useful investigations There are special considerations for portable and fluoros copy units. The longer an operator keeps the fluoroscopy unit running, the higher the dose of radiation to all in the vicinity . Portable x-ray machines and fluoroscopic imaging equipment use much more radiation to achieve the same result. T and patients in the next bed, are at risk when portable equip ment is used. The result is also of lower quality , so portable x-ray machines should not be used unless absolutely necessary . When using the image intensifier, lead aprons, thyroid shields, lead glasses and radiation badges should always be worn. Preg nancy in the female patient or sta ff must be excluded. Wilhelm Conrad Roentgen , 1845–1923, Professor of Physics, Würzburg (1888–1900), and then at Munich, Germany . He was awarded the Nobel Prize in Physics in 1901 for his work on x-rays. - Responsibilities of the radiologist and referrer /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF The UK’s Royal College of Radiologists produces an evidence-based guidance tool, called iRefer, which is widely available on line and shows radiation doses for common procedures ( Table 8.1 ). -

A useful investigation is one in which the result – positive or negative – will inform clinical management and/or add con /f_i dence to the clinician’s diagnosis. A signi /f_i cant number of radiological investigations do not ful /f_i l these aims and may add unnecessarily to irradiation of patients. To avoid the wasteful use of radiology, the important questions to be asked are as follows.

  1. Has it been done already ? Repeating investigations that have already been done: such as at another hospital, in an outpatient department or in an emergency department. Every attempt should be made to obtain previous images and reports. Transfer of digital data through electronic links will assist in this respect. Although guidelines may not directly address this question, there are other initiatives that do
  2. Is it needed ? Undertaking investigations when results are unlikely to affect patient management or over-investigating: because the anticipated positive /f_i nding is usually irrelevant – for example, degenerative spinal disease – or because a positive /f_i nding is unlikely. Some clinicians and patients tend to rely on investigations more than others for reassurance
  3. Is it needed now ? Investigating too early: for example, before the disease could have progressed or resolved, or before the results could in /f_l uence treatment. The need for investigation and treatment should be reviewed at a more appropriate time
  4. Is this the best investigation ? Doing the wrong investigation: imaging techniques undergo rapid change. It is often helpful to discuss an investigation with a specialist in clinical radiology or nuclear medicine before it is requested
  5. Has the problem been properly explained ? Failing to provide appropriate clinical information and questions that the imaging investigation should answer: de /f_i ciencies here may lead to the use of the wrong technique, or the report being poorly focused on the clinical problem. In some clinical situations /f_i rm guidelines have been established Radiologists have a legal responsibility to keep imaging as safe as possible The referrer has a duty to balance risk against bene /f_i t The referrer must provide adequate clinical details to allow justi /f_i cation of the examination Avoid using portable (mobile) x-ray machines whenever practical Take all precautions when using an image intensi /f_i er The gonads, eyes and thyroid are especially vulnerable to radiation and should be protected TABLE 8.1 Band classi /f_i cation of the typical doses of ionising radiation from common imaging procedures. Examples Lifetime Symbol Typical additional effective risk of cancer dose (mSv) induction /exam None 0 US; MRI 0 <1:20 /uni00A0 000 <1 CXR; XR limb, pelvis, lumbar spine; mammography 1:20 /uni00A0 000–1:4000 1–5 IVU; NM (e.g. bone); CT head and neck 5.1–10 CT KUB; NM 1:4000–1:2000 (e.g. cardiac)

1:2000 10 Extensive CT studies, some NM studies (e.g. some PET/CT) CT, computed tomography; CXR, chest x-ray; IVU, intravenous urog

raphy; KUB, kidneys, ureters and bladder; MRI, magnetic resonance imaging; NM, nuclear medicine; PET, positron emission tomography; US, ultrasound; XR, x-ray. Source: https://www.rcr.ac.uk/sites/default/ /f_i les/documents/irefer_ introductoryiaea.pdf.

HAZARDS OF IONISING RADIATION

The majority of ionising radiation comes from natural sources on Earth and cosmic rays, and this makes up the background radiation. However, medical exposure accounts for around 15% of the total received by humans. The e ff ects of ionising radiation can be broadly divided into two groups. The first group comprises predictable, dose-dependent tissue e ff ects and includes, for example, the development of cataracts in the lens of the eye. These e ff ects are important for those chronically exposed to radiation, including those using image intensifiers regularly . The second group comprises the all-or-nothing e ff ects such as the development of cancer (termed stochastic). These e ff ects are not dose dependent, but increase in likelihood with increased radiation dose. The risk of radiation-induced cancer for plain films of the chest or extremities is very small, of the order of 1:1 /uni00A0 000 /uni00A0 000. However, that risk rises considerably for high-dose examina - tions such as CT of the abdomen or pelvis, where the estimated lifetime excess risk of cancer increases to the order of 1:1000. Use of CT has increased dramatically in the last 20 years, with 2 a 12-fold increase in the UK, and it has been estimated that up m ) to 30% of these e xaminations may be unnecessary . Obviously , the risk of such examinations has to be balanced against the benefit to the patient in terms of increased diagnostic yield, and must also be viewed in the context that the lifetime risk of cancer for people generally is about 1:3. Nevertheless, the - increased risk is important since it is iatrogenic and applied to a large population. Therefore, techniques that do not use ionis - ing radiation, such as ultrasound and MRI, should be carefully - considered as alternatives, particularly in children and young people. In the UK, the Ionising Radiation (Medical Exposure) Regu lations (IR(ME)R) introduced in 2000, and amended in 2006, impose on the radiologist the duty to the patient to make sure that all studies involving radiation (plain radiographs, CT and nuclear medicine) are performed appropriately and to the highest standards. Inappropria te use of radiation is a criminal o ff ence, so investigations involving radiation need careful consideration in order to prevent wasteful use of radiology . Summary box 8.2 Criteria for useful investigations There are special considerations for portable and fluoros copy units. The longer an operator keeps the fluoroscopy unit running, the higher the dose of radiation to all in the vicinity . Portable x-ray machines and fluoroscopic imaging equipment use much more radiation to achieve the same result. T and patients in the next bed, are at risk when portable equip ment is used. The result is also of lower quality , so portable x-ray machines should not be used unless absolutely necessary . When using the image intensifier, lead aprons, thyroid shields, lead glasses and radiation badges should always be worn. Preg nancy in the female patient or sta ff must be excluded. Wilhelm Conrad Roentgen , 1845–1923, Professor of Physics, Würzburg (1888–1900), and then at Munich, Germany . He was awarded the Nobel Prize in Physics in 1901 for his work on x-rays. - Responsibilities of the radiologist and referrer /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF /uni25CF The UK’s Royal College of Radiologists produces an evidence-based guidance tool, called iRefer, which is widely available on line and shows radiation doses for common procedures ( Table 8.1 ). -

A useful investigation is one in which the result – positive or negative – will inform clinical management and/or add con /f_i dence to the clinician’s diagnosis. A signi /f_i cant number of radiological investigations do not ful /f_i l these aims and may add unnecessarily to irradiation of patients. To avoid the wasteful use of radiology, the important questions to be asked are as follows.

  1. Has it been done already ? Repeating investigations that have already been done: such as at another hospital, in an outpatient department or in an emergency department. Every attempt should be made to obtain previous images and reports. Transfer of digital data through electronic links will assist in this respect. Although guidelines may not directly address this question, there are other initiatives that do
  2. Is it needed ? Undertaking investigations when results are unlikely to affect patient management or over-investigating: because the anticipated positive /f_i nding is usually irrelevant – for example, degenerative spinal disease – or because a positive /f_i nding is unlikely. Some clinicians and patients tend to rely on investigations more than others for reassurance
  3. Is it needed now ? Investigating too early: for example, before the disease could have progressed or resolved, or before the results could in /f_l uence treatment. The need for investigation and treatment should be reviewed at a more appropriate time
  4. Is this the best investigation ? Doing the wrong investigation: imaging techniques undergo rapid change. It is often helpful to discuss an investigation with a specialist in clinical radiology or nuclear medicine before it is requested
  5. Has the problem been properly explained ? Failing to provide appropriate clinical information and questions that the imaging investigation should answer: de /f_i ciencies here may lead to the use of the wrong technique, or the report being poorly focused on the clinical problem. In some clinical situations /f_i rm guidelines have been established Radiologists have a legal responsibility to keep imaging as safe as possible The referrer has a duty to balance risk against bene /f_i t The referrer must provide adequate clinical details to allow justi /f_i cation of the examination Avoid using portable (mobile) x-ray machines whenever practical Take all precautions when using an image intensi /f_i er The gonads, eyes and thyroid are especially vulnerable to radiation and should be protected TABLE 8.1 Band classi /f_i cation of the typical doses of ionising radiation from common imaging procedures. Examples Lifetime Symbol Typical additional effective risk of cancer dose (mSv) induction /exam None 0 US; MRI 0 <1:20 /uni00A0 000 <1 CXR; XR limb, pelvis, lumbar spine; mammography 1:20 /uni00A0 000–1:4000 1–5 IVU; NM (e.g. bone); CT head and neck 5.1–10 CT KUB; NM 1:4000–1:2000 (e.g. cardiac)

1:2000 10 Extensive CT studies, some NM studies (e.g. some PET/CT) CT, computed tomography; CXR, chest x-ray; IVU, intravenous urog

raphy; KUB, kidneys, ureters and bladder; MRI, magnetic resonance imaging; NM, nuclear medicine; PET, positron emission tomography; US, ultrasound; XR, x-ray. Source: https://www.rcr.ac.uk/sites/default/ /f_i les/documents/irefer_ introductoryiaea.pdf.

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