Imaging of the Respiratory System Flashcards

Question

V/Q scans: indications and contraindications

Answer 1

Indications: ? PE; to assess pulmonary abnormalities such as stenosis; to look for causes of pulmonary hypertension. Contraindications: Caution taken if… there are documented hypersensitivity reactions, patient pregnant/lactating, recent nuclear medicine studies performed, established pulmonary hypertension; right to left cardiac shunt

Answer 2

V = ventilation demonstrates airflow Q = perfusion for flow of blood Then reviewed for mismatch (matched=low probability of PE.) Ventilation deficiency-? Airway obstruction Perfusion deficiency- ? vascular obstruction. Filling defect in perfusion phase requires mismatch in V phase (no defect) to indicate P.E. Patient breathes in gaseous isotope (e.g., Krypton: 81mKr gas) assess ventilation. Has IV administration of radioisotope such as technetium labelled with macro aggregated albumin (Tc99m MAA) – assess perfusion Imaged using a gamma camera Breathing kit for the gas Current chest radiograph to correlate Perfusion and ventilation positioning must be reproduced exactly

Answer 3

Advantages: Useful for chest wall investigations e.g. effusions, pleural masses, some mediastinal masses. Used as guidance for needle biopsies/aspirations e.g. of a mass Limitations: Of no use for demonstrating lungs-ultrasound absorbed by air therefore aerated tissue not suitable for US imaging

Answer 4

Indications: To demonstrate PEs, arteriovenous malformations-where CT/RNI have not yielded results. Can also be performed as a therapeutic procedure e.g. thrombolysis. Contraindications: contrast allergy, renal failure/impairment. poor clotting-tendency to bleed; raised pulmonary pressure

Answer 5

MRI of the chest gives detailed pictures of structures within the chest cavity, including the mediastinum, chest wall, pleura, heart and vessels, from almost any angle. MRI also provides sequential imaging of the cardiovascular system that is important to assess the health and function of these structures (heart, valves, great vessels, etc.) Advantages: Increasing role for cardiac and aortic imaging. Can be used for assessing or staging tumours - provides excellent tissue differentiation. Good for Pancoast’s Tumours Can show chest with patient breathing hyperpolarised Helium 3 (3He)-for air flow. Can be used to assess structures as well as functionality. Can be used if patient cannot have contrast Use with patients where ? mass involving spinal cord canal Considered safe (no radiation) – Patients with non MRI safe metal in body cannot undergo scans. MRI is also better than CT at distinguishing the lung mass from the adjacent atelectasis or consolidation.

Answer 6

Issue with air in the lung creating artefact + long acquisition time. Does not work well to take pictures of parts of the body that are moving, like your lungs, which move with breathing. For that reason, MRI is rarely used to look at the lungs.

Answer 7

Gadolinium-based contrast agents are often mild. Symptoms include: pain in bones and joints Burning or pins and needles sensation in the skin. Brain fog Headache Vision or hearing changes skin thickening, or discolouration Nausea, vomiting or diarrhoea Difficulty breathing Flu-like symptoms Metallic taste People who have multiple MRIs with GBCAs potentially increase the risk for toxicity. pregnant women, people who have kidney problems & people with inflammatory conditions, or children, are at higher risk of adverse reactions.

Answer 8

can visualize and quantify both microstructure and key functional parameters at the alveolar-capillary interface where gas exchange occurs. Such gas-phase MRI readouts have the potential of detecting the earliest signs of impairment in lung disease. Xenon gas MRI offers unique advantages for longitudinal studies, especially those involving children and pregnant women (very safe). Absence of ionizing radiation. Hyperpolarized129Xe MRI is a rapid and well-tolerated exam. Provides region-specific quantification of interstitial barrier thickness and Red Blood Cell transfer efficiency. Potential as robust tool for measuring disease progression and therapeutic response in patients with IPF, sensitively and non-invasively. A technique that is emerging as a means of monitoring the lung function of discharged COVID19 patients… aiding in understanding of long term effects.

Answer 9

Nuclear Medicine imaging techniques; often combined with CT and MRI. PET: positron emission tomography; established in many RNI departments now. May be combined with a CT system to combine anatomical with functional detail. PET-CT: hybrid imaging – single system with 2 imaging platforms (PET & CT.) SPECT-CT: Single Photon Emission CT uses CT as integrated part of the system

Answer 10

PET scans use radiopharmaceuticals to create three-dimensional images. The main difference between SPECT and PET scans is the type of radiotracers used. SPECT measures gamma rays emitted from radioisotope (e.g. technetium-99m). PET scans use positron emitting radioisotopes - the decay of the radiotracers produce small particles called positrons. A positron is a particle with roughly the same mass as an electron but oppositely charged. These react with electrons in the body and when these two particles combine they annihilate each other. This annihilation produces a small amount of energy in the form of two gamma photons that shoot off in opposite directions. The detectors in the PET scanner measure these photons and use this information to create images of internal organs. Increasing mode of choice for Ca lung & staging/metastases; also lymphatic activity. Gives functional (metabolic) info along with anatomical visualisation; recommended for tumours > 1cm FDG-PET: fluorodeoxy-glucose taken up by tumours, especially lung.

Answer 11

Inflammation also increases uptake of FDG so not without limitations Can have poor spatial and temporal resolution: PET gives better contrast & resolution than SPECT. SPECT is lower cost PET is very expensive. PET has shorter scan times SPECT has much longer scan times

Answer 12

Use of water soluble contrast-reactions are rare and usually low risk. But things to be aware of-need to monitor patients for signs of reaction. May be mild, moderate or severe. Can include nausea, feeling of urinary urgency (mild) to bronchospasm/arrest/LOC (severe) May have reaction at injection/cannulation site-pain, extravasation, irritation. Need to establish patient history with reference to allergies (? previous contrast reactions) Proximity of the crash trolley-know where in case asked to bring. Crash call number Patient reassurance in event of mild reaction (metallic taste, rash, nausea.) Raise the alarm if patient struggles to breathe, become non responsive. A radiologist should be within shouting distance

Answer 13

Electromagnetic Navigational Bronchoscopy: Minimally invasive approach that uses navigation technology to access peripheral areas of the lung. Viable option for diagnostic investigation when the location of the pulmonary nodule means alternative diagnostic investigations would result in low diagnostic yield (conventional bronchoscopy) or pose a high risk of complications. Can be used as an alternative to CT guided biopsy of suspected lung cancer. Less invasive and reduced risk of pneumothorax (1.5 % compared with up to 24% with CT guided biopsy) & pulmonary haemorrhage. Utilises cutting edge technology – only a few Trusts in the country can perform them (LTHT included!)

Answer 14

Within the team: Communication with helpers/radiographers/radiologists etc Liaison with wards/porters Room preparation (Check drug stores & crash trolleys Use of equipment Record dose/drugs (Batch number, strength, expiry date, person who administered) Radiation Protection Infection Control For the Patient: Dignity & respect Preparation Physical support Psychological support

Answer 15

PREPARATION ID LMP Justification Previous images Explanation of procedure Previous medical history Previous contrast reactions Consent Equipment Radiolucent gown Removal of artefacts Medication Smoking Diabetic patients

Answer 16

Physical care: EG, back to changing cubicles, getting dressed. Information regarding diet & possible side effects. Results Drug effects If had isotope-info regarding how long to keep distance from family.