MRI and US

What are major laboratory tests/ signs that there is something wrong with the pancreas

Serum amylase: May be indicative of acute pancreatitis if raised

Lipase: Raised in acute pancreatitis and cancer of the pancreases

Glucose: Increased in diabetes

Which areas of the pancreas are which number

1: head

between 1 and 2: neck

2: body

3: tail

1. Portal vein

2. Pancreas

3. superior mesenteric artery (SMa)

4. IVC

5. Aorta

6. Splenetic vein

What is the patient preparation for standard abdominal ultrasound

• Minimum 6 hour fast. sips of water is okay, can take medication, diabetics may eat small meals but no fats (fatty food)

• Preferably a morning appointment

get a picture of pancreas long and label it

Pancreas scan technique

Many different techniques may be needed:

• Varied breathing patterns

• varied patient positions

• patient in a erect position

• water-filled stomach

Vascular landmarks are important

How to scan Pancreas

• Pt supine

• start in transverse scan plane in upper epigastrium region

• scan inferiority using left lobe of liver as a window

• identify vascular landmarks: aorta/IVC, celiac axis, SMA, splenic vein/ portal confluence, SMV

• Volume scan thoroughly in 2 scan planes

• Look for pancreatic duct and CBD

What is pt preparation for renal scan

• Fast for 4-6 hours

• A distended urinary bladder is required for a renal examination

• Ask the pt to finish drinking 600-1000ml one hour prior appointment time

What are indications for renal US

• Haematuria

• Abnormal renal function tests

• Abnormal PSA levels

• Back or pelvic pain

• Recurrent UTIs

• Known congenital abnormalities

• High blood pressure

How does the kidney appear on US

Renal capsule: echogenic line

Renal cortex: Outer most tissue, hypoechoic

Renal medulla: Consists of the medullary pyramids, less echogenic than cortex

Renal parenchyma: Consists of cortex and medullary pyramids

Renal sinus: Central, hyperechoic region that contains renal pelvis, calyces, blood vessels and variable amount of fat

What is the scan technique for renal US

• Check probe orientation

• Coronal and sagittal volume scans

• Long measurement (bipolar) (normal measurement is around 9-12 cm)

• Transverse axis volume scan

• Add CD to ensure that there is perfusion to the cortex of the kidney. Power Doppler is also useful.

How do you demonstrate pathology in renal US

Must be imaged and measured in two perpendicular planes

What are common pathology in renal US

• Renal cysts

• Calculi

• Obstructive uropathy

• Solid renal masses

• inflammatory disease

What pathology is shown here

Renal cortical cysts

• benign and fluid filled

• Anechoic

• well-defined thin walls

what pathology is this

Renal calculi

• Larger calculi = echongenic foci + shadowing

• Small calculi = echogenic foci - shadowing

What is the spleen US technique

1. Pt supine

2. Transducer in coronal plane

3. Inspiration, expiration or gentle respiration

4. Abnormality?

5. Oblique plane

6. Anterior scan?

7. Cant see spleen in supine position?

8. Which transducer?

What is the spleens appreacne in US

1. shape = inverted comma shape

2. normal surrounding structures =

3. echogenicity = haemogonious

4. Size = depends on age and gender (12 cm for female, 13cm for males)

5. Elastography role =

What is ultrasound frequency define as and what frequency does medical ultrasound use

• Ultrasound frequency is defined as the number of ultrasound waves per second

• Medical ultrasound machines use waves with a frequency ranging between 2 and 15 MHz.

What does frequency mean in US

Frequency refers to the number of cycles per second emitted by the ultrasound probe over one second and is expressed in hertz (Hz).

What does Amplitude mean in US

Amplitude is the height, or strength, of a wave defined by the distance between the peak and the average of the wave's highest and lowest points. Power in ultrasound refers to the square of wave amplitude, or difference between the maximum and average values, of propagated waves.

What are the 4 ways US waves interact with human tissue

• absorption of ultrasound by tissue

• reflection from interfaces (this includes diffuse and specular reflection);

• scattering of the ultrasound beam due to diffraction effects (this includes Rayleigh scattering from blood cells and often from tissue parenchyma)

• refraction, or the change in direction of the ultrasound beam when moving from one medium into another

What are the different US imaging modes and describe them

A-Mode (Amplitude mode): The transducer sends a single pulse of ultrasound into the medium

B-Mode (Brightness mode): B-mode is a 2d image of the area that is simultaneously scanned by a linear array of 100-300 piezoelectric elements rather than a single one as in A-mode.

M-mode (Motion mode): A single beam is an US scan can be used to produce a picture with a motion signal, where movement of a structure such as a heart valve can be depicted in a wave-like manner.

What are the 5 MRI-specific safety precautions

Magnetic field

Crogens

Gradients

RF power deposition

Contrast agents

How does MRI safety labeling work

red = MR unsafe: items should not enter the MRI scanner room

Yellow: MR conditional: items may safely enter the MRI scanner room only under very specific condtions

Green: MR safe: items pose no safely hazards in the MR enviroment

How many MRI zones are there an how do they work

Zone 1: general public/ MRI access area (negligble MRI hazard)

Zone 2: unscreended MRI patients/ MRI pt screening and preperation

Zone 3: Screened MRI patients and personal having access to MRI room

Zone 4: Screened MRI patient under direct supervision of MRI personal

What is the Gauss line

The 5 Gauss line refers to the boundary around the scanner where the magnetic filed strength falls to 5 gauss (0.5 millitesla). Beyond the the 5 Gauss line the magnetic field is considered sufficiently weak not to interfere with external devices or pose risks to general public health.

What is the Faraday cage

The Faraday cage is built around the MRI unit in zone 4. It is made of copper lining that has induced eddy currents that oppose the main magnetic field

What casues acoustic noise in MRI and how is it mitigated

The primary source of acoustic noise in the vibration of gradient coils due to rapidly switched electrical currents interacting with the strong static magnetic field. This is mitigated through the of ear protection such as earplugs and earmuffs

What is MRI quenching

Quenching refers to using a cryogen usually helium to cool the magnet in the MR scanner

What is MRI slew rate

The speed at which a gradient magnetic filed can be turned on and off during a n MRI scan. It measures how quickly the gradient reaches its maximum amplitude.

What is MRI SAR

SAR is specific absorption rate, it measures the rate at which energy is absorbed by the body when exposed to radio frequency electoprgenatic filed during an MRI scan. Units watts per kilogram (W/kg), is used. Factors affecting it are tissue conductivity, RF frequency, flip angle, duct cycle and pt size and shape.

What is gadolinium used for in MRI

Gadolinium is a positive contrast agent (T1 agent) that is primarily used to shorten T1 relaxation times leading to increased signal intensity

What must you do to MRI a pregent pt

• gain written contesnt

• scan using normal mode (SAR)

• Avoid IV GAD

• Monitor SAR levels and scan patient rolled 15 degrees to the left to reduce compressing the IVC

What are relaxation times in MRI

T1 (longitudinal relaxation time) represents the time it takes for the longitudinal magnetisation (aligned with the external magnetic field) to recover after perturbation (e.g., radiofrequency pulse). Gadolinium shortens T1 by enhancing the longitudinal magnetisation recovery.

T2 (transverse relaxation time) is the time it takes for the transverse magnetisation (perpendicular to the external field) to decay due to interactions between neighboring protons. Gadolinium has a minor impact on T2 relaxation.

What is GBCAs and what are its types

Extracellular Agents: These small molecules distribute nonspecifically in blood and extracellular spaces. They are commonly used for imaging tumors, inflammation, and magnetic resonance angiography (MRA)

Blood Pool Agents: Used mainly for MRA, these agents have longer intravascular half-lives, allowing extended imaging beyond the arterial first-pass phase.

Hepatobiliary Agents: Designed for liver lesion diagnosis, including gadobenate dimeglumine (MultiHance) and gadoxetic acid (Eovist, Primovist).

What are the different MRI coils and what do they do

Main filed coils: These are principal magnet windings and superconducting shim and shield coils

Shim coils: used to improve homogeneity

Gradient coils: essential for imaging and include active sheilds

RF body coils: transmits the B1 field

Surface coils: primarily detect MR signals

What is the aliasing (wrap) artifact in MRI

Aliasing refers to when the filed of view (FOV) is smaller than the body part being imaged

Resolved by:

• enlarging FOV

• Anti-aliasing software

• switch phase and frequency directions

What is the susceptibility artifact in MRI

Susceptibility artifact occurs due to differences in magnetic susceptibility between tissues or materials

What is the RF noise artifact in MRI

RF noise artifact appears as static on the image. Occurs die to electromagnetic interference from external sources such as nearby electrical equipment. A specific RF noise is herringbone artifact.

Resolved by:

• Shielding external sources of EMI

• keeping scanner room door closed

What is the Gibbs artifact in MRI

Gibbs artifact looks as a series of oscillations or ripples near sharp edges in the image. Caused by finite sampling of the signal during image reconstrucation

What is the Chemical shift artifact in MRI

The chemical shift artifact occurs due to spatial misregistration of fat and water molecules

What is the knee MRI protocol

Indications:

• ACL, mensical or ligament etars

• tumor

• infection

Sequences:

• 3 plane localizer

• Axial PD FS

• Coronal OD

• Sagittal PD

• Sagittal PD FS

Coil:

• knee coil or flexible coil

What is the Brain MRI protocol

Indications:

• Headssaches

• Tumour

• Infection

• Stroke

Sequences:

• 3 plane localizer

• Sagittal T1

• Axial T2

• Axial FLAIR

• Axial DWI

• Axial Gradient

Coil:

• head coil

What is the Spine MRI protocol

Indications:

• Tumor

• MS

• Nifection

• Trauma

Sequences:

• 3 plane localizer

• Sagittal T2

• Sagiottal T1

• Sagittal STIR

• Axial T2

Coil:

• C-spine: posterior element of head coil on table

• T-spine: posterior element of head coil on table

• LS spine: Spine array coil on table

• Whole spine: Spine array coil on table

What are these images

L-spine

How does an MRI work

• Each proton spins in a random way in the body creating a magnetic field. This filed is manipulated by MRI to create a signal to make an image

• The magnetic filed causes by the protons charge has a direction and magnitude which is given a vector symbol and called the magnetic dipole moment. These moments are random when not under the effect of a magnet. The net magnetic vector (NMV) is almost zero.

• When the patient is in the main magnetic filed (Bo) which is along the Z axis some charges align with some align against it (align with = low energy state, align against = high energy state. the difference between the low and high states is the NMV (same direction as Bo

• Spin of proton under the influence of Bo is called Larmor frequency

• Applying a radio frequency (RF) causes the protons axis to spin on the magnetic dipole moment, this is called resonace

• When the RF pulse is turned off the dipole moment of the protons can go back to align to Bo. This gives of energy which the MRI detector reads to create an image

• The time it takes for the magnetic vector to reach 63% of its original state is called the T1 time of relaxation for the tissue the proton is in

• T1 images are carted by taking the signal early TE (short time to echo) and T2 is taken from long TE

How are T1 MRI images done

• Protons spins are random and NMW is almost zero. patient is then placed in the magnetic filed of the machine

• RF pulse is is applied flipping magnetic moments of protons 90 degrees

• RF pulse is now turned off and the magnetic moment of each proton starts to spin back to align with Bo. This gives of energy the MRI detector reads to create an image

• The information to create the image is when the magnetic vectors reach 63% of its original state this is called the T1 time of relaxation

How are T2 MRI images done

• Protons spins are random and NMW is almost zero. patient is then placed in the magnetic filed of the machine

• RF pulse is is applied flipping magnetic moments of protons 90 degrees

• RF pulse is now turned off and the magnetic moment of each proton starts to spin back to align with Bo. This gives of energy the MRI detector reads to create an image

• Compared to T1 imaging T2 allows protons to de phase by using a longer TE and TR

• This longer TE and TR phase gives the T2 image

What are the difference between T1 and T2 MRi images

T1:

• has a short time to echo (TE) and repetition time (TR)

• CSF = dark

• muscle = gray

• spinal cord = gray

• fat = bright

• disk = gray

• air = very dark

• inflammation = dark

T2:

• has a long TE and TR

• CSF = bright

• muscle = dark gray

• spinal cord = light gray

• fat = light

• disk = bright

• air = very dark

• inflmation = bright

What is an ultrasound

• A very high frequency sound that travels at 1540 meters/second in soft tissue

• It causes pressure oscillations in the medium through which it is traveling

Explain diagnostic US

• A short pulse of Ultrasound is transmitted into the body by the trandcuer

• Structures in the tissues cause reflection and scattering of the ultrasound as it travels through the tissues

• Some of these reflected and scattered energy travels back to the transducer converting it into electrical signal (echoes)

• These signals are sued to create the image

What is Doppler US

Used to obtain information on blood-flow

Doppler effect: the change in perceived wave frequency when there is a relative motion between wave source and observer

What do the following mean

Echogenicity:

Anechoic:

Hyopechoic

Hyperechoic:

Isoechoic:

Echotexture:

Homogeneous:

Heterogeneous:

Echogenicity: describes the strength (brightness) of the echoes dispaled

Anechoic: no internal echoes

Hypoechoic: less echogehnic than adjacent tissue (dark)

Hyperechoic: More echogenic (bright)

Isoechoic: Same echogenicity as adjacent tissue

Echotexture: the echo consistency of the organ or structure

Homogeneous: smooth and uniform echotexture

Heterogeneous: coarse or irregular echotexture

What are the different imaging artifacts in US

Resolution artifacts: artifacts which diminish resolution within an image by giving incorrect representation of the shape and size of objects

• Axial and lateral resolution artifacts: closely separated objects may appear as one object in the image, due to inadequate axial and lateral resolution

• Acoustic speckle: The net echo signal received back at the transducer face from a small group of scatterers will be large or small depending on how the echoes from individual scatterers have interfered with each other. 

• Slice-thickness artifact: due to the finite thickness of the ultrasound beam in the elevational direction (perpendicular to the scan plane)

Attenuation artifacts: variation in the degree of attenuation of the US beam

• Acoustic enhancement: Increased amplitude of displayed echo signals from regions posterior to low attenuation structures such as fluid.

• Acoustic shadowing: decrease in amplitude of displayed signals from the region along the beam direction, posterior to solid or echogenic masses.

Propagation artifact: structures which incorrectly appear in the display as a result of non-convetional beam paths

Miscellaneous artifacts:

What is the pathology on this breast US

Well circumscribed hypoechoic fibroadenoma

What is the pathology on this breast US

Ductal carcinoma with extension seen invading surrounding parenchyma

What is the pathology on this breast US

Longitudinal and transverse images of a ‘typical’ ductal carcinoma

What pathology is this

An enlarged heterogeneous pancreas consistent with acute pancreatitis.

What pathology is this

Longitudinal and transverse views through the pancreatic head/uncinate process demonstrating a pancreatic carcinoma.

What pathology is this

Cholecystitis with bile stasis and obstructive calculus in neck.

What pathology is this

Septated right kidney lower pole cyst

What pathology is this

Renal cell carcinoma (RCC) of the upper pole of the left kidney seen as an isoechoic cortical mass.

What pathology is this

splenomegaly. It is described as splenomegaly if the longest axis measuring greater than 12-14 cm.

Which is which and why

1. T1 as only 1 tissue is bright which is the fat

2. T2 as 2 tissues are bright the fat and water

Which is which

1. T1

2. T2

3. T1 + contrast

Which is which

1. T1

2. T2

3. STIR (T2 image that is manipulated so that fat is nullified

Which is which

1. T2

2. Flair (T2 which has CSF nullified)

3. Flair

Which is which

1. T2

2. DWI

3. ADC

Normal?

Normal knee MRI

Normal?

ACL tear

What do the following =

• Short TR/Short TE →

• Long TR/Short TE →

• Long TR/Long TE →

• Short TR/Short TE → T1-Weighted image

• Long TR/Short TE → PD-Weighted image

• Long TR/Long TE → T2-Weighted image

What is this

Meniscus tear

When are the folwing usually perfomed:

nuchal translucency (NT)

morphology

growth assessment

nuchal translucency (NT): first trimester (11-14 weeks)

morphology: second trimester (18-22 weeks)

growth assessment: third trimester (32-36 weeks)

Explain the bio effects of thermal and non-thermal interactions in US

Thermal interactions: heat production by the ultrasound wave, the higher the frequency the greater the absorption and degree of heating obtained

Non-thermal interactions:

1. Cavitation: Sound waves traveling through liquid contain tiny gas bubbles they cause then to grow and then collapse causing high temperature and pressure that can damage surrounding tissue

2. Radiation force: Tiny pushes causes by ultrasound waves

3. Acoustic torque: Sounds waves twisting objects they encounter

4. Acoustic streaming: High-intensity sound waves can cause a flowing motion within a liquid, like tiny whirlpools.

How much heat is too much in US

Safe limit: When scanning fetus below 1.5 degrees celcius to avoid potential harm

What real timer labels can you use to monitor ultrasound safely

Thermal Index (TI): This measures how much a tissue's temperature might increase due to the ultrasound's power. A higher TI indicates a greater potential for heating.

Mechanical Index (MI): This measures the likelihood of transient cavitation occurring during the exam. Values below 0.7 are considered safe