Intro to Patient Diagnostics

Wilhelm Conrad Roentgen

discovered x-rays in 1895

• first used dignostically in 1896

Attenuation

the reduction in the intensity of the X-ray beam as it passes through matter, caused by absorption or scattering of photons

more dense structures attenuate __________ meaning _______

less dense structures attenuate ___________ meaning ________

more meaning less blackening of the film

less meaning more blackening of the film

X-Ray (XR)

form of electromagnetic radiation or energy of extremely short wavelength

• shorter wavelength = more penetration (energy) through tissue providing a better image

Radiolucent vs Radiopaque

Radiolucent

• less dense objects

• appears black on x-ray

• ex: air in the lungs

Radiopaque

• more dense

• appears white on x-ray

• ex: bones

Radiographic Densities (least to most)

gas (air), fat, soft tissue (water), bone (metal)

Identify what each of the colored stars indicate:

Green

Pink

Blue

Green: kidney stones - appear radiopaque because Ca+ presents that way

Pink: phleoboliths - Ca+ appears radiopaque

Blue: air bubbles

Identify the radiolucent and radiopaque figures in the X-ray image

Radiolucent (less dense, translucent)

• air in the lungs

Radiopaque (more dense)

• clavicle, heart, diaphragm, blood vessels (from density of blood)

What factors affect Image Quality in x-rays

• thickness of part being examined - obese pt

• motion

  • shorten exposure time to overcome

• scatter

  • causes fog as the beam scatters

• magnification

  • have the part of interest closest to the film

  • AP: anterior posterior where anterior side is to the film

  • PA: posterior anterior where the posterior side is to the film

• distortion - object is not perfectly perpendicular to the beam

AP Film

Anterior-posterior

-where the film is placed behind the pt's back with the x-ray unit in front

-typically captured with portable x-ray when pt is incapacitated

PA Film

posterior-anterior

-pt stands or sits upright with the chest against the film holder

-heart and lungs (normal chest x-ray)

Plain Film

no contrast

-skeletal

Contrast Studies and Examples

radiopaque contrast media administered

-GI tract (via swallow or enema)

-Urinary tract (urography, IV pyelogram/IVP) - inject contrast into the blood vessels, give time and it will pass to designated area to enhance visibility of structures in imaging.

-Blood Vessels (angiography)

-Vertebral Column (myelography) - contrast to CSF to light up column

Computed Tomography (CT)

x-ray and detector system move through an arc of 360 degrees

-read as if you are standing at the patient's feet

-intensity of radiation is measured, analyzed assigning differing shades of gray based on attenuation

-computer reconstructs image

Traditional CT

-single-dimensional view

-approx. 2 mins

Spiral/Helical CT

-3D view

-20-30 secs

why should diabetics withold medication when IV contrast is used for a CT, specifically metformin (glucophage)?

it may cause acidosis when combined

a patient needs a screening for abdominal trauma, which form of imaging is the best?

computated tomography (CT)

CT Contrast

when hit with radiation, the x-ray beam is weakened by the uptake of the contrast

-appears radiopaque

-common forms: iodine, barium, gastrografin

what are some CT Contrast reactions

allergic reaction (good history): pretreat with steriods and diphenhydramine

contrast-induced nephropathy: check creatinine clearance and GFR

• kidney may not be able to filter the contrast

Population Considerations for Contrast-induced Nephropathy

-kidney failure

-diabetics

-HTN

-elderly

-autoimmune disorders

Nuclear Imaging

uses radioisotopes (most common technetium 99m)

-emits gamma rays, short half-life

Static vs Dynamic in nuclear imaging

"one shot" vs. series in sequential order

"hot" vs "cold" spots in nuclear imaging

increased uptake of radioisotopes vs. decreased uptake of radioisotopes

When would we want to use nuclear imaging?

• helps diagnose things that are not acutely dangerous

• maps cancer and where it has metastasized to

• watching the body uptaking or not of radioisotope can watch for function and perfusion

_______ imaging is NOT for anatomy

nuclear

If we were to use nuclear imaging, what would we be looking for these these organs or areas?

1. Heart

2. Thyroid

3. Liver

4. Bone

5. Lung

1. Heart - myocardial perfusion, function, viability

2. Thyroid - nodules, cancer

3. Liver - masses, metastases, cholestasis

4. Bone - metastases, pain

5. Lung - pulmonary embolism (quantification of perfusion)

Positron Emission Tomography (PET) Scan (nuclear imaging)

high-energy particles emit positrons

• type of radiographic imaging

VQ Scan (nuclear imaging)

inhalation/injection of radioisotope

-injection determines perfusion

-inhalation determines alveolar function

Physical Half-Life (nuclear imaging)

element would decay on its own

Biological Half-life (nuclear imaging)

normal physiological removal of the substance to which the isotope has been attached

Effective Half-life (nuclear imaging)

Formula combines the two to determine actual time the isotope remains "effective" in the body

When would we utilize PET/CT?

PET/CT combines metabolic and anatomical imaging.

• perfusion + function and looking at anatomy

Magnetic Resonance Imaging (MRI)

magnetic fields and radio waves to produce computer-generated images that distinguish soft tissue types

non-invasive, no ionizing radiation

can produce images in any plane

Mechanism of MRI

nuclei of any atom with odd number of protons and neutrons behave like weak magnents in presence of a strong magnent

-most common is hydrogen ion

which form of imaging can produce images in any plane including sagital, coronal, and axial?

MRI

Indications for MRI

-intracranial abnormalities

-intraspinal abnormalities

-musculoskeletal abnormalities

-heart

-abdominal visceral abnormalities

-vascular abnormalities

T1 MRI vs T2 MRI

T1: weighted scans are a standard basic scan, in particular differentiating fat from water - with water darker and fat brighter

T2: weighted scans similar to T1 where fat is differentiated from water but T2 fats shows darker than water

______ imaging is for detailed info rather than acute. Not for diagnosing but for needing a clear photo

MRI

Ultrasound

uses sonic energy (non-ionizing form of energy); echoes (reflections) of u/s beam from interfaces between tissues

-real-time

-demonstrates size, shape, and internal structure of organs/masses

Doppler Ultrasound is for …

-arterial stenosis

-venous occlusion

M-mode Ultrasound is used for…

echocardiography

• can see movement of heart murmurs

Intervention Ultrasound is used for …

-fluid aspiration

-drainages (abscess)

-biopsies

-line placement

______ can be used for fetus anatomy, view ligament tears, tendon tears, cystic lesions, and even the eye

ultrasound

Where would we use Barium Contrast

GI tract

-oral or enema

-not if perforation is suspected (risk of peritonitis)

where would we use Iodine Contrast

used intravenously for x-ray and CT

-risk of contrast-induced neuropathy

PACS (picture archiving and communication system) was used to read medical imaging but is now _____ replacing the traditional view box and film. Also called “night hawk”

MIMPS - Medical imaging management and processing system

• safer and more time efficient

If there is a GI tract perforation, and imaging is needed, how would we continue on getting a CT?

Water soluble contrast and IV hydration is needed for the patient