midterm revision w1-6
imaging modalities
X-ray
CT
MRI
Ultrasound
Dexa
Nuclear Medicine
PETCT
PETMRI
Mammography
Fluoroscopy
Angiography / Interventional Radiology (Cath lab)
key hospital personnel
Director of Nursing (DON)
Assistant director of nursing (ADON)
Clinical Nurse Manager (CNM)
Bed Manager
Chief Executive Officer
Chaplin
HCA
Porters
Support staff
Catering Consultant
Registrar
Senior House Officer (SHO)
Interns
key hospital departments
A&E
Outpatient Department (OPD)
Wards and units (Medical / Surgical/
Day wards / Oncology / Medical
Assessment Unit MAU)
Intensive Care Unit
Stroke Unit
High Dependency Unit (HDU)
Coronary Care Unit (CCU)
Speech and Language Therapy (SLT)
Medical Physics / Clinical Engineering
Occupational Health
Endoscopy
NICU
Paediatrics
Theatre
Anaesthetics
Pathology
Technical Services / Maintenance
radiograph formation
Beam of xray photons generated by the xray tube, is directed at an object/person
A detector/receiver is placed behind the object & receives the transmitted xray photons.
The transmitted/received xray photons not absorbed/attenuated form the image.
The xray photon beam is attenuated (loses intensity) as it passes through the object – some photons are absorbed while others may be deflected or scattered.
This is dependent on the object's density, thickness and structural composition in addition to the original power or energy level of the photon beam.
Computer algorithm constructs the image & displays it
radiopacity
White/bright regions on the radiograph. Structures not easily penetrated by xrays. Structures which have attenuated the xray photons.
radiopaque tissue have a high density, high atomic number (Z) and are thick.
eg; bone, metal
Image Density / Brightness
Image Density / Brightness
image density / brightness
High image brightness = low image density = radiopaque objects
Low image brightness = high image density = radiolucent objects
contrast
Low-contrast image - show little difference in density between structures
-contrast image - how a larger difference in density between structures
magnification and distortion
affected by SID - source to image distance
to reduce magnification as much as possible we make the affected body part parallel to the detector, make the SID as small as possible.
however for larger and thicker body parts - chest, abdomen, hips-, we need to increase the SID so as a result we need to also increase the exposure factors to make up for the extra distance.
when body part is not parallel, joint spaces will appear narrow leading to an incorrect osteoarthritis diagnosis (OA)
spatial resolution
we need fine detail to be able to see abnormalities in the bone and tissue
to reduce geometric unsharpness we make sure that we are using the right focal spot size (FSS) for the affected body part.
to reduce motion unsharpness we make sure that the patient keeps still for the duration of the xray - we do this by practicing breathing and using radiolucent foam pads and explaining to them the importance of keeping still in order to gain cooperation. we also try to reduce the exposure time as much as possible.
inherent unsharpness is unavoidable because the body outline is naturally curved, but we can try to limit it as much as possible.
noise
a grainy appearance on the radiograph that reduces image quality- usually caused cause by under/overexposure or motion during the exposure.
it can make the image undiagnostic
it can be avoided by increasing the mAs
legalities
people who can legally request xray examinations
doctors - registered medical practitioners
nurses with the correct qualifications
physiotherapists (soon)
dentists
radiographers
justification and principles
SI 256 and SI
for any radiological procedure undertaken, the radiation dose should be ALARA - as low as reasonably achievable
for an examination to be carried out, it must be justified- meaning a) that the benefit of receiving the procedure (the clinical information it will provide) must be greater than the risk of getting the procedure and b) the requested exam should be the most appropriate for the patients clinical indication as different exams, projections and modalities all have different benefits and risks.
iRefer Guidelines are used to make sure that all exams carried out fit these requirements
pre xray considerations
complete and correct referral card
the referral card should have the patient’s name, date of birth and address.
it should also have the region to be examined and the correct side.
it must have a justified clinical indication and/or relevant patient history
it has to have the referrer signature and their contact details
correct patient
to identify a patient we ask open ended questions about their NAME, DATE OF BIRTH AND ADDRESS, making sure not to violate the patient
10 step image appraisal - VERY IMPORTANT
ID AND ANATOMICAL MARKERS
the patient’s name and id number should be present