The Royal Marsden Hospital Manual of Clinical Nursing Procedures - Lisa Dougherty [447]
Indications
Scanning of the brain to assess stroke, tumour, meningeal disease.
Spinal pathology is particularly well demonstrated, including intervertebral disc pathology, tumour, infarction, spinal dysraphism, infection and degenerative diseases.
Differentiation and characterization of benign versus malignant pathology in the liver.
MRI is highly sensitive for imaging of the breast.
MRI is the gold standard for assessment of pelvic malignancy and pelvic anatomy.
(Royal College of Radiologists 2006, 2007)
Contraindications
Patients with non-MRI compatible implanted devices, such as cardiac pacemakers and cochlear implants, must not be scanned. Other implanted devices, for example stents, must be confirmed as MR safe prior to scanning.
Magnetic resonance imaging tends not to be used for acute trauma or for primary whole-body staging of malignancies, for which CT is the preferred imaging modality.
Preprocedural considerations
Assessment and recording tools
A pre-MRI checklist is undertaken for all patients to identify risks from implanted devices which may be harmful to the patient or may severely degrade the image quality (Shellock and Spinazzi 2008).
Pharmacological support
The patient may require intravenous access for contrast injection, most often of a gadolinium-based contrast agent. This is used to enhance areas of suspected pathology, to define tumour bulk or to improve the efficacy of the scan by delineation or characterization of a pathological process (Runge et al. 2009). Claustrophobia can also be an issue and in some cases patients may require an oral sedative to relax them during the procedure. In severe claustrophobia or when scanning young children or individuals with learning difficulties, general anaesthetic may be necessary.
Non-pharmacological support
The scanner is very noisy so it is mandatory that patients are given ear protection during the scan. If the patient feels claustrophobia there are strategies to manage this such as:
adapting the patient’s position
changing the scanning technique
using blindfolds or mirrors
relaxation therapy.
Specific patient preparations
Apart from safety checking, for most scans there is no preparation but for certain body scans the patient may have to abstain from food, but may drink clear (non-caffeine) fluids to ensure their bladder does not fill too quickly, resulting in movement artefacts.
Patients must be able to lie very still, usually lying on their back for significant time periods. Patient comfort is paramount so patients requiring pain relief should continue with pain medication as normal.
Computed tomography (CT)
Definition
Computed tomography images are created when radiation passes through a patient and is absorbed in varying degrees by the body tissue. Multislice data are acquired as a three-dimensional block in a matter of seconds and digitally displayed in coronal, sagittal or axial planes (Fishman and Jeffrey 2004).
Evidence-based approaches
Rationale
Multislice CT has excellent image resolution and is used for diagnosis, staging and monitoring treatment response in the oncology setting, as well as being a research tool. Soft tissues as well as bone and lung anatomy are all seen well on CT scans. Routinely patients are given intravenous contrast medium which perfuses the body tissues and enhances the blood vessels and lesions (Husband and Reznek 2010).
Computed tomography does use radiation but protocols are optimized to give the best image with the lowest dose. Also, the number of body areas scanned and the intervals between scans are closely monitored in accordance with IR(ME)R regulations.
Indications
Computed tomography can image all parts of the body and is used for:
pretreatment staging
interval scans to monitor treatment
follow-up post treatment
diagnosis and assessment of complications:
— bowel obstructions and perforation