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Dual energy CT: Physics and applications
K. Perisinakis / Physica Medica 32 (2016) 194–195
RADIATION INCIDENTS AND ACCIDENTS IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY. WHAT TO DO NEXT IN INTERVENTIONAL RADIOLOGY Virginia Tsapaki. Konstantopoulio General Hospital, Athens, Greece The International Commission on Radiological Protection (ICRP) defines interventional Radiology (IR) procedures as the techniques that encompass guided diagnostic and therapeutic interventions either by percutaneous or other access under local anaesthesia and/or sedation. Fluoroscopic imaging is applied to best localise the lesion or the treatment site as well as to continuously monitor and record the procedure. Whereas diagnostic radiology is generally safe for patients and staff, these techniques involve high risk of skin injuries of patients and occupational overexposure of staff involved. IR skin injuries are termed as fluoroscopy-induced radiation dermatitis. They usually appear within 7–14 days of exposure and may be acute or chronic. A certain threshold is required, reached either at once or in cumulative radiation doses. It causes inflammation of the skin, presenting as erythema, pain, and pruritus that may later transform into ulceration, atrophy, telangiectasia, sclerosis, discoloration, and malignancy, such as invasive basal cell or squamous cell carcinoma. A number of cases are reported in the literature in order to emphasize the importance of recognizing fluoroscopy as a cause of radiation dermatitis among other skin injuries. Interventionalists are often unaware of the high radiation doses to which a patient’s skin may be subjected, even with the use of modern, state of the art equipment. This paper will consider the knowledge, techniques and possible regulatory requirements necessary to prevent radiological incidents and accidents and provide recommendations in the case such events occur. http://dx.doi.org/10.1016/j.ejmp.2016.07.348
RADIATION INCIDENTS AND ACCIDENTS IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY. WHAT TO DO NEXT IN PREGNANT PATIENTS John Damilakis. University of Crete, Greece Despite precautions, pregnant patients occasionally are exposed accidentally to X-rays. Accidental irradiation of pregnant patients occurs during the first postconception weeks. During the first 2 weeks postconception, the embryo will either recover completely or not survive. This is known as ‘all or nothing effect’. From the 3rd to 8th week postconception, malformation of body organs is the most possible form of damage. Therefore, after accidental examination of pregnant patients, the gestational age should be known. Accurate estimation of embryo/fetus radiation dose is needed when the mother is after the 2nd week of gestation and the embryo has been exposed primarily to X-ray beam. CODE (COnceptus Dose Estimation) is a free web-based software tool (uploaded on embryodose. med.uoc.gr) that can be used for estimation of embryo dose from radiography, diagnostic fluoroscopy, CT and fluoroscopically-guided procedures. It is important to avoid accidental irradiation during pregnancy. Careful screening is needed to identify pregnant patients before X-ray examinations. According to ICRP publication 84, ‘investigation of the reproductive status of a female of childbearing age prior to X-ray imaging’ is needed. Also, ‘it is prudent to consider as pregnant any woman of reproductive age presenting herself for an X-ray examination at a time when a menstrual period is overdue, or
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missed, unless there is information that precludes a pregnancy’. X-ray departments must have posters in the waiting area asking female patients to inform the radiographer or radiologist about a possible pregnancy. http://dx.doi.org/10.1016/j.ejmp.2016.07.349
X-RAY COMPUTED TOMOGRAPHY DEDICATED TO THE BREAST Paolo Russo. University of Naples Federico II, Dept. of Physics ‘‘Ettore Pancini” & INFN Sect. of Naples, Naples, Italy Planar digital mammography is the gold standard for breast cancer screening; also available in conjunction with mammography is Digital Breast Tomosynthesis, as a pseudo-tomographic imaging modality of the compressed breast in clinical diagnosis. However, fully 3D X-ray computed tomography of the uncompressed pendant breast is now available both experimentally and commercially, using cone-beam dedicated scanners. They provide excellent-contrast views of the 3D anatomy of the breast, based on X-ray attenuation in breast tissues. Significant advancements are expected from different phase contrast techniques, now being explored experimentally for both 2D and 3D X-ray imaging of the breast, for their potential to provide improved visibility of soft masses. Both laboratory setups using X-ray tubes, and synchrotron radiation based CT setups will be described. http://dx.doi.org/10.1016/j.ejmp.2016.07.350
DUAL ENERGY CT: PHYSICS AND APPLICATIONS Kostas Perisinakis. University of Crete, Medical School, Greece Despite material differentiation through CT scans acquired with X-ray beams of different spectra had been conceived soon after the emergence of single energy CT in early 70 s, the clinical endorsement of the method and its widespread application was only initiated after the introduction of the first dual source CT systems in 2006. Ever since dual energy CT (DECT) technology has rapidly progressed and several clinical applications have emerged. Apart from enhancing image quality through artifact suppression, DECT imaging was found to provide unique data on tissue composition and function, and therefore it was enthusiastically welcomed by clinicians. Nowadays, most modern commercially available CT scanners provide the ability for dual energy CT imaging. Although the underlying basic principles of dual-energy CT are the same regardless of scanner type, there are different technical implementation approaches adopted by different vendors. Currently, there are four different DECT imaging methods available i.e. the dual CT scan, the dual source, the fast kV switching and the two-layer detector approach with considerable differences regarding both image data acquisition and processing. Understanding of these differences may help optimization of DECT imaging protocols and identify pros and cons for each technical implementation of DECT imaging. Renal stone differentiation, pulmonary perfusion and metallic implant imaging are well established clinical applications of DECT imaging, while there are several promising applications under investigation in musculoskeletal, liver, genitourinary and heart imaging. http://dx.doi.org/10.1016/j.ejmp.2016.07.351
RADIATION INCIDENTS AND ACCIDENTS IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY. WHAT TO DO NEXT IN INTERVENTIONAL RADIOLOGY Virginia Tsapaki. Konstantopoulio General Hospital, Athens, Greece The International Commission on Radiological Protection (ICRP) defines interventional Radiology (IR) procedures as the techniques that encompass guided diagnostic and therapeutic interventions either by percutaneous or other access under local anaesthesia and/or sedation. Fluoroscopic imaging is applied to best localise the lesion or the treatment site as well as to continuously monitor and record the procedure. Whereas diagnostic radiology is generally safe for patients and staff, these techniques involve high risk of skin injuries of patients and occupational overexposure of staff involved. IR skin injuries are termed as fluoroscopy-induced radiation dermatitis. They usually appear within 7–14 days of exposure and may be acute or chronic. A certain threshold is required, reached either at once or in cumulative radiation doses. It causes inflammation of the skin, presenting as erythema, pain, and pruritus that may later transform into ulceration, atrophy, telangiectasia, sclerosis, discoloration, and malignancy, such as invasive basal cell or squamous cell carcinoma. A number of cases are reported in the literature in order to emphasize the importance of recognizing fluoroscopy as a cause of radiation dermatitis among other skin injuries. Interventionalists are often unaware of the high radiation doses to which a patient’s skin may be subjected, even with the use of modern, state of the art equipment. This paper will consider the knowledge, techniques and possible regulatory requirements necessary to prevent radiological incidents and accidents and provide recommendations in the case such events occur. http://dx.doi.org/10.1016/j.ejmp.2016.07.348
RADIATION INCIDENTS AND ACCIDENTS IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY. WHAT TO DO NEXT IN PREGNANT PATIENTS John Damilakis. University of Crete, Greece Despite precautions, pregnant patients occasionally are exposed accidentally to X-rays. Accidental irradiation of pregnant patients occurs during the first postconception weeks. During the first 2 weeks postconception, the embryo will either recover completely or not survive. This is known as ‘all or nothing effect’. From the 3rd to 8th week postconception, malformation of body organs is the most possible form of damage. Therefore, after accidental examination of pregnant patients, the gestational age should be known. Accurate estimation of embryo/fetus radiation dose is needed when the mother is after the 2nd week of gestation and the embryo has been exposed primarily to X-ray beam. CODE (COnceptus Dose Estimation) is a free web-based software tool (uploaded on embryodose. med.uoc.gr) that can be used for estimation of embryo dose from radiography, diagnostic fluoroscopy, CT and fluoroscopically-guided procedures. It is important to avoid accidental irradiation during pregnancy. Careful screening is needed to identify pregnant patients before X-ray examinations. According to ICRP publication 84, ‘investigation of the reproductive status of a female of childbearing age prior to X-ray imaging’ is needed. Also, ‘it is prudent to consider as pregnant any woman of reproductive age presenting herself for an X-ray examination at a time when a menstrual period is overdue, or
195
missed, unless there is information that precludes a pregnancy’. X-ray departments must have posters in the waiting area asking female patients to inform the radiographer or radiologist about a possible pregnancy. http://dx.doi.org/10.1016/j.ejmp.2016.07.349
X-RAY COMPUTED TOMOGRAPHY DEDICATED TO THE BREAST Paolo Russo. University of Naples Federico II, Dept. of Physics ‘‘Ettore Pancini” & INFN Sect. of Naples, Naples, Italy Planar digital mammography is the gold standard for breast cancer screening; also available in conjunction with mammography is Digital Breast Tomosynthesis, as a pseudo-tomographic imaging modality of the compressed breast in clinical diagnosis. However, fully 3D X-ray computed tomography of the uncompressed pendant breast is now available both experimentally and commercially, using cone-beam dedicated scanners. They provide excellent-contrast views of the 3D anatomy of the breast, based on X-ray attenuation in breast tissues. Significant advancements are expected from different phase contrast techniques, now being explored experimentally for both 2D and 3D X-ray imaging of the breast, for their potential to provide improved visibility of soft masses. Both laboratory setups using X-ray tubes, and synchrotron radiation based CT setups will be described. http://dx.doi.org/10.1016/j.ejmp.2016.07.350
DUAL ENERGY CT: PHYSICS AND APPLICATIONS Kostas Perisinakis. University of Crete, Medical School, Greece Despite material differentiation through CT scans acquired with X-ray beams of different spectra had been conceived soon after the emergence of single energy CT in early 70 s, the clinical endorsement of the method and its widespread application was only initiated after the introduction of the first dual source CT systems in 2006. Ever since dual energy CT (DECT) technology has rapidly progressed and several clinical applications have emerged. Apart from enhancing image quality through artifact suppression, DECT imaging was found to provide unique data on tissue composition and function, and therefore it was enthusiastically welcomed by clinicians. Nowadays, most modern commercially available CT scanners provide the ability for dual energy CT imaging. Although the underlying basic principles of dual-energy CT are the same regardless of scanner type, there are different technical implementation approaches adopted by different vendors. Currently, there are four different DECT imaging methods available i.e. the dual CT scan, the dual source, the fast kV switching and the two-layer detector approach with considerable differences regarding both image data acquisition and processing. Understanding of these differences may help optimization of DECT imaging protocols and identify pros and cons for each technical implementation of DECT imaging. Renal stone differentiation, pulmonary perfusion and metallic implant imaging are well established clinical applications of DECT imaging, while there are several promising applications under investigation in musculoskeletal, liver, genitourinary and heart imaging. http://dx.doi.org/10.1016/j.ejmp.2016.07.351