Intro to Medical Imaging - Lec

What are the two divisions of medical imaging? What are they used for?

Therapeutic

• Guide procedures such as surgery and rad therapy (Fluoroscopy, angiography, IR)

Diagnostic

• Detect and diagnose disease (XR, CT, MRI, US, nuclear med)

What is the imaging technique with ionizing radiation and what is its principle/key concepts?

XR has a anatomical focus

• Tissues absorb X rays different (attenuated)

Key concepts

• radiodensity, superimposition, and contrast agents (barium/idoninated)

Clinical:

• Skeletal - breaks, arthritis, dislocations

• Chest (CXR) - pneumonia, HF, lung mass, pneumothorax

• Abdomen (KUB) - bowel obs, free air (perforation)

• Screening - mammography

Limits: Poor soft tissue, radiation dose (low),, only 2D

Now describe CT. Key concepts, clinical strengths, limits.

Creates cross sectional slides, computer reconstructs in 3D

Key concepts: Hounsfield units (HU), multiple images, IV contrast (asses vascularity, organ perfusion, inflam), CT angio(CTS) and venography (CTV)

Clinical: Emergency, oncology, vascular, abdomen/pelvis

Limits: sig rad dose, IV contrast (nephropathy allergy), metal artifacts

Now describe a technique that used real time imaging with sound waves.

Ultrasound - non ionizing, used high freq sound waves

Key concepts: Echogenicity (hyper/hypo/an-echoic), acoustic shadowing (gallstones) and enchantment, Doppler (direction/presence/velocity)

Clinical: Ob/Gyn (fetal asses, ovarian/uterine path), cardio (EKG{structure and function}), abdomen, vascular (DVT or carotid stenosis)

Point of care (POCUS): FAST exam (trauma), gunslinging procedures

Limits: Operator dep, bone and gas, obese patients

Now describe MRI. The principle/key concepts/clinical rel/limits.

Non ionizing, uses magnet and radio waves

Key concepts: T1 vs T2 weighting: Contract mechanism (T1: fat is bright, T2: water/pathology is bright), also can used fMRI to monitor blood flow

Clinical: Neurology, MSK, abdomen/pelvis

Limits: Slow, expensive, NSF risk with gadolinium

Describe nuclear medicine. They key concepts, clinical rel, limits and principle.

Pt given radioactive tracer —> emittion detected

• radiopharm accumulates in target organ based on metabolic activity —>decays and emits gamma radiation —→ increased uptake in areas with increased metabolic activity

Key concept:

Clinical (How is it working): Onco(PET/CT), cardio(SPECT), endo, skeletal, neuro(PET)

Limits: High rad dose, low spacial resolution, exp

***”Hot spots” on imaging indicative of infection,, fracture, or malignancy

Compare and contrast MRI/CT/and PET/SPECT. Radiation use, type of tissues they examine, cost, and speed.

What is the principle we use when addressing a susceptible postulation ie pregnant or elderly?

We use the ALARA —> as low as reasonably possible principle

**8However for urgency —> FAST (US), CT or if outpatient MRI, PET/CT