Physics Flashcards

Question

Outline the role an Indigenous Health Worker may have in the care of an Indigenous patient undergoing a radiological procedure. (3-4 marks)

Answer 1

Indigenous Health Workers provide cultural support, facilitate communication, and ensure culturally safe care, particularly for Aboriginal and Torres Strait Islander patients undergoing medical imaging.

Answer 2

Discreetly discuss the error directly with the radiologist to verify and correct it. If appropriate, escalate to a supervisor if correction is not pursued, prioritizing patient safety and maintaining professionalism.

Answer 3

Explain that a CTPA requires contrast for diagnostic accuracy. Offer to discuss alternative imaging with the senior clinician and educate the junior doctor on appropriate imaging protocols.

Answer 4

Seek assistance from a colleague with prostate MRI expertise or suggest transferring the case to ensure accurate reporting and patient care.

Answer 5

MDTs improve diagnostic accuracy, facilitate comprehensive treatment planning, and enhance patient outcomes by integrating expert opinions across specialties.

Answer 6

Ensure all images are de-identified, follow privacy protocols, and confirm that viewing and discussing them complies with institutional policies.

Answer 7

communicate findings, potential complications, and follow-up requirements clearly to the clinical team, ensuring a structured and documented handover.

Answer 8

Ensure direct communication of critical findings to the responsible clinical team, confirming understanding and documenting the handover to guarantee timely follow-up.

Answer 9

GBCAs carry a risk of nephrogenic systemic fibrosis (NSF) in patients with severe renal impairment and a very low risk of allergic reactions. Gadolinium deposition has also been observed in the brain, but no adverse effects have been conclusively linked to this.

Answer 10

Screen patients for renal impairment (e.g., eGFR <30 mL/min/1.73m²) before administering GBCAs, avoid using GBCAs in high-risk patients, and use lower-risk agents like macrocyclic GBCAs if necessary.

Answer 11

Assess the severity and type of past reaction, consult an allergist if needed, and consider premedication with corticosteroids and antihistamines for mild reactions. For severe allergies, avoid GBCAs unless absolutely necessary.

Answer 12

Macrocyclic GBCAs have a more stable structure that traps gadolinium ions, reducing the risk of dissociation and tissue deposition compared to linear agents. Macrocyclic agents are generally considered safer, particularly in patients needing multiple scans.

Answer 13

BCAs are generally avoided during pregnancy due to limited safety data and theoretical risks to the fetus. Use of contrast is only considered if the potential benefits outweigh the risks, such as in critical clinical situations.

Answer 14

1. Dual-Source Dual-Energy CT: - This type uses two X-ray tubes and two detectors mounted at 90 degrees from each other. Each tube operates at a different energy level, allowing simultaneous data acquisition. This setup is highly effective for rapid imaging, such as cardiac scans. 2. Single-Source Dual-Energy with Fast kVp Switching: - In this type, a single X-ray tube alternates between high and low kilovoltage (kVp) settings very rapidly during each rotation. It’s commonly used for high temporal resolution applications and is efficient as it requires only one X-ray tube and detector. 3. Dual-Layer Detector Dual-Energy CT: - This scanner has a single X-ray tube but uses a specialized detector with two layers. The top layer detects lower-energy photons, while the bottom layer detects higher-energy photons from the same X-ray beam. It allows simultaneous energy separation and is effective for routine clinical applications. 4. Sequential Dual-Energy CT (Dual kVp): - This method involves taking two consecutive scans of the same area at different kVp settings. Though less efficient and potentially more prone to motion artifacts, it is an option for scanners that lack simultaneous dual-energy capabilities. 5. Dual-Spiral or Dual-Phase Acquisition: - In this approach, two helical scans are performed at different energy levels with a single X-ray tube, which is adjusted between scans. It is generally used less frequently due to the longer scan times and higher radiation dose.

Answer 15

Answer: For low-risk procedures (e.g., diagnostic angiography or non-vascular biopsies), an INR threshold of ≤1.8 is generally acceptable. Often, anticoagulants may not need to be withheld, but this depends on institutional guidelines and patient-specific factors. Consultation with the referring team may be warranted.

Answer 16

Answer: For intermediate-risk procedures (e.g., tunneled central venous catheter placement, lung biopsy), an INR ≤1.5 is typically recommended. Warfarin is usually withheld 3–5 days prior, allowing INR to fall to the acceptable level, with bridging therapy considered based on patient risk factors.

Answer 17

Answer: High-risk procedures (e.g., transjugular liver biopsy, renal biopsy) generally require an INR ≤1.5. Warfarin should be withheld for about 5 days, and bridging with low molecular weight heparin (LMWH) may be needed in high-thrombotic-risk patients. INR should be checked pre-procedure to confirm it is within the safe range.

Answer 18

Answer: For low-risk procedures, aspirin is usually not withheld, as the bleeding risk is minimal. However, if there is a specific contraindication or institutional preference, holding aspirin for about 5-7 days may be considered.

Answer 19

Answer: Yes, for intermediate-risk procedures, clopidogrel is typically withheld for 5 days to reduce bleeding risk. Consultation with the referring physician is advisable to assess thrombotic risk and to determine if bridging therapy is required.

Answer 20

Answer: In emergency situations, reversing anticoagulation with agents such as vitamin K or prothrombin complex concentrates (PCC) may be considered. The decision should weigh the urgency of the procedure against the bleeding risk, and consultation with hematology may be appropriate.

Answer 21

Answer: Posterior acoustic enhancement is an increased echo brightness seen distal to a fluid-filled structure, such as a cyst or bladder. It occurs because fluid allows sound waves to pass with minimal attenuation, resulting in stronger echoes from tissues behind it. This is often used as a diagnostic feature to differentiate cystic from solid structures.

Answer 22

Answer: Higher frequency transducers provide better resolution but have limited penetration, making them suitable for superficial structures (e.g., thyroid, breast). Lower frequencies penetrate deeper but offer lower resolution, which is more appropriate for abdominal or pelvic imaging.

Answer 23

Cause: Caused by sound waves bouncing back and forth between two strong reflectors, such as the transducer and the tissue surface. It results in multiple equally spaced echoes, often seen with air or metallic objects.

Answer 24

Cause: Similar to reverberation, but usually due to a small, highly reflective object like a metallic clip or tiny calcifications. It appears as a series of closely spaced echoes extending from the reflector.

Answer 25

a map of proton energy within fat and water based tissues of the body

Answer 26

Anything with no fat or no water will be low on T2 - Hemosiderin - Flow void - Cortical bone - Densely fibrotic tissue - Calcium

Answer 27

The rationale behind a two-stage revision for prosthetic joint infection (PJI) is to effectively eradicate the infection before implanting a new prosthesis, thus reducing the risk of recurrence. The procedure involves two stages: First Stage: Removal of the infected prosthesis and placement of an antibiotic-loaded cement spacer. The removal of the infected hardware and thorough debridement helps eliminate biofilm and infected tissue, while the spacer maintains joint space and releases high local concentrations of antibiotics to treat the infection. Second Stage: After confirming the infection has resolved (usually through negative cultures and clinical markers like CRP and ESR), a new prosthesis is implanted. This staged approach allows better control over infection, increasing the chances of a successful long-term outcome compared to single-stage revision.

Answer 28

MRI has several limitations in assessing possible infection in a joint replacement due to the presence of metal, which can cause artifacts that obscure surrounding soft tissue and bone detail. Here are the main limitations and strategies to minimize them: Metal Artifacts: Metal in joint replacements causes signal voids, image distortion, and susceptibility artifacts that obscure adjacent tissues. Solution: Use metal artifact reduction sequences (MARS), optimized MRI sequences (e.g., STIR or View Angle Tilting), and advanced techniques like MAVRIC or SEMAC to reduce artifact and improve visualization of the periprosthetic region. Limited Sensitivity for Detecting Infection: MRI has reduced sensitivity for differentiating between inflammation due to infection versus other causes (e.g., aseptic loosening). Solution: Complement MRI with clinical markers (e.g., CRP, ESR) and other imaging modalities such as nuclear medicine scans (e.g., white blood cell scintigraphy) or PET-CT to enhance diagnostic accuracy. Challenges with Soft Tissue Visualization: Artifact may obscure important soft tissue details, such as abscesses or sinus tracts around the implant. Solution: Position the patient to minimize artifact direction and select sequences that provide better contrast for soft tissues around the implant.

Answer 29

Bone Scan (typically a 3-phase bone scan): Appearance: Increased uptake in all three phases (blood flow, blood pool, and delayed phase) Distinguishing Features: While increased uptake is common in both infection and aseptic loosening, infection tends to show more intense and diffuse uptake in the delayed phase. However, bone scans alone cannot reliably differentiate infection from aseptic loosening. Labeled White Cell Scan (e.g., with Indium-111 or Technetium-99m HMPAO): Appearance: Increased uptake of labeled white cells around the prosthesis, particularly if the uptake persists or increases on delayed images (e.g., 24-hour images). Distinguishing Features: In cases of infection, labeled white cell uptake will typically localize to areas of infection, while aseptic loosening usually shows little to no white cell uptake. A combined labeled white cell and bone marrow scan can improve specificity, as matching uptake on both indicates aseptic loosening, whereas discordant uptake suggests infection.

Answer 30

Diffusion restriction in MRI refers to the limited movement of water molecules in tissues, which can be visualized using diffusion-weighted imaging (DWI). It works based on the principle that water molecules naturally move, or "diffuse," in tissues. In healthy tissues, water molecules can move more freely. However, in areas where cells are densely packed or there is cellular swelling, such as in tumors, abscesses, or acute ischemic strokes, water movement is restricted.

Answer 31

Verify Device Compatibility Consult with Cardiology and Obtain Clearance For MRI-conditional devices, follow the manufacturer’s guidelines and ensure all MRI conditions (e.g., specific field strength, limited body part) are met. A qualified cardiology or EP professional should reprogram the pacemaker to MRI-safe mode Implement Safety Monitoring Use the lowest feasible MRI field strength (often 1.5T), minimize scan time, and apply MRI sequences that limit radiofrequency (RF) exposure and heating. Post-Scan Evaluation by Cardiology.

Physics Flashcards

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