Unit 2- Intro to cross sectional anatomy

cross sectional anatomy overview

• physical relationship among structures

• 3D

• evaluation of soft tissue structures

• slices taken in a sequence

sagittal/median plane=

left/right (X)

axial or transverse plane=

inferior/superior (Z)

coronal or frontal plane=

posterior/anterior (Y)

thickness of a slice is dependent on…

technical settings (ex: thinner slices= more detail)

slice thicknesses vary from several__ to ___

millimeters to centimeters

slices overall are determined by

procedure protocols (institution controls protocol)

scout is also known as

scanogram

breathing can drastically affect

image quality

this modality is 3D and taken around a single axis of rotation

CT

when was CT developed & what was the first scan

1971; brain scan 2.5 hours

scans are taken on 1 plane & reconstructed to create…

sagittal & coronal planes

___represents the densities of each tissue

hounsfield unit

bone HU

10000 (bright white)

water HU

0 (grey)

air HU

-1000 (black)

what year was MRI discovered

1973

what utilizes a powerful magnetic field to align the magnetization of some atoms in the body

MRI

human body is what percent of hydrogen?

80%

how MRI works

1. a “COIL” is placed around the area of interest to obtain the info of that specific area of anatomy.

2. magnet aligns the single protons in the hydrogen nuclei within the field

3. radiowaves enter patient from another angle- the radiowaves cause the nuclei to flip positions and either align with the magnet or against it

4. at termination of radio signals, nuclei return to OG position by spinning like a top back into their varied position

5. energy that is released from that relaxation is used to generate images

T1 weighted images

• fat appears BRIGHT

• water appears DARK

• best for ANATOMY

T2 weighted images

• water appears BRIGHT (white)

• fat appears DARK

• best for PATHOLOGY

____ is a contrast used in MRI to improve clarity of the images

gadolinium

iodine vs gadolinium

gadolinium is a safer contrast due to less adverse reactions & eliminated through kidneys easier

example of gadolinium visibility

• inflammation

• tumors

• blood vessels

• some blood supply within organs

MRI advantages over CT

• no radiation

• superior contrast resolution

• superior tissue characterization

• visualization of angiography WITHOUT using contrast

ultrasound uses

high frequency sound waves w/ a transducer generated at 20,000 vibrations per second (hertz/second)

megahertz used in ultrasound

3-20 mHz

how does ultrasound work

• reflected soundwave echoes are recorded & shown as an image in real time

• transducer transmits inaudible soundwaves into the body as it echoes from the body’s fluid & tissues, transducer records the strength and character of the waves, then displayed

each kind of tissue has a different___ in ultrasound

attenuation coefficient

what is an attenuation coefficient?

• how much of the sound wave will get absorbed

• how much passes through

• how much bounces back

piezoelectric crystals

converts electricity into soundwaves and then echoes into electricity

2 functions of the transducer

1. generates sound waves- speaker

2. detects reflected sound waves- like a microphone

purpose of the gel in ultrasound

creates a surface to help the probe transmit sound waves

curvilinear transducer overview

• low frequency 5mHz

• abdominal, obstetrics, pelvis

linear transducer overview

• high frequency 15 mHz

• great detail

• superficial structures

• thyroid, scrotal, musculoskeletal, soft tissue masses

intraoperative probe

• very high frequency

• directly on organ or vessel

• liver transplants, vascular stuff

endocavity transvaginal transrecetal probe mHz

8

what probe is this?

curvilinear

what probe is this?

linear

what probe is this?

endocavity, transvaginal, transrectal

what probe is this?

intraoperative probe

what are the imaging planes in ultrasound?

• long (sagittal)

• transverse

**occasionally oblique images are obtained**

describes the tissue in relation to another tissue, or as compared to its normal state

echogenicity

each tissue type, such as a liver, spleen, or kidney, has a particular___ in its normal state

echogenicity

in an abnormal state, the echnogenicity of an organ can be….

altered (hyperechoic, hypoechoic, anechoic)

observations of echogenicity can help the radiologisy

to categorize the type of disease process involved

hyperechoic is

white/ bright structure

hypoechoic is

grayish black

anechoic

no color, entirely black

abnormality of kidney; accumulation of calculi within the renal pelvis and kidney calices

staghorn calculus (coral calculi)

what organ scan is this?

liver (can see hepatic tree)

what organ scan is this?

kidney (bean shape)

what organ scan is this?

gallbladder