Scan Principles MR Contrast/Formulas*

Question 1

How does Gadolinium function as a contrast agent?

Answer 1

It shortens the T1 time of tissue
Gadolinium IV contrast shortens the T1 time of tissue, and only is utilized in T1 weighted sequences

Question 2

The most common positive contrast agent used in clinical MR imaging is:

Answer 2

Gadolinium

Question 3

The substances that bind to gadolinium ions are defined as:

Answer 3

Chelates

Question 4

Gadolinium chelates used in MR imaging are

Answer 4

Paramagnetic

Question 5

All of the following are true regarding gadolinium EXCEPT:

Answer 5

Gadolinium has six unpaired electrons

Gadolinium has 7 unpaired electrons in its 4f orbitals giving it a very large magnetic moment.

Question 6

The FDA approved oral contrast agent for MRI makes bowel appear:

Answer 6

T1 & T2 hypointense

Perflubron, a type of perflorocarbon, has been used as a gastrointestinal MRI contrast agent for pediatric imaging, and works by reducing the amount of protons (as hydrogen) in a body cavity, thus causing it to appear dark in the images

Question 7

Contraindications for IV gadolinium contrast use are:

Answer 7

None of the above
T
here are no known contraindications to IV gadolinium contrast usage

Question 8

What is the percentage of patients reported to have allergic reactions to gadolinium contrast agents?

Answer 8

Less than 1%

Question 9

IV Gadolinium contrast administration is indicated for:

Answer 9

Central nervous system

IV Gadolinium contrast administration is indicated for the central nervous system, and for MRA of the lower extremities for AIOD, only.

Question 10

____________ is used as an anti-peristalsis agent in MR Enterography procedures.

Answer 10

Glucagon

Question 11

Metastatic lesions enhance after injecting a gadolinium chelate because of:

Answer 11

The breakdown in the blood brain barrier

Question 12

Gadolinium is an example of a ___________ contrast agent

Answer 12

Paramagnetic

Question 13

In MRI, the function of gadolinium is to:

Answer 13

Shorten the T1 and T2 times of tissues

Question 14

The standard dose for the adminstration of IV gadolinium chelates is:

Answer 14

0.1 mmol/kg

The standard dose for the adminstration of IV gadolinium chelates is 0.1 mmol/kg

Question 15

Gadolinium IV contrast:

Answer 15

Shortens the T1 and T2 times of tissues

Gadolinium IV contrast shortens the T1 and T2 times of tissues

Question 16

Following the administration of IV gadolinium contrast, it is recommended to:

Answer 16

Follow the injection with a flush of 5 mL saline

Following the administration of IV gadolinium contrast, it is recommended to follow the injection with a flush of 5 mL saline.

Question 17

Following the injection of contrast, which of the following patients are most likely to have a potentially serious reaction?

Answer 17

Those with asthma or allergic respiratory disorders

Patients with asthma or allergic respiratory disorders are more likely to have a potentially serious reaction following the injection of contrast.

Question 18

VoLumen is a contrast agent used for:

Answer 18

Bowel enhancement

Question 19

VoLumen would be selected for which MR procedure?

Answer 19

MR enterography

Question 20

Calculate the dose of contrast (0.1mmol/kg) that should be administered to a patient weighing 176 lbs with normal kidney function in a routine MR examination.

Answer 20

16mL

Divide 176 lbs by 2.2 (lbs per kg), then multiply the kg (80) by 0.2 ml/kg = 16mL

Question 21

Calculate the scan time for a spin echo sequence with the following parameters: TR 450, TE 20, 224 x 256 matrix, 3 NSA, 4mm slice thickness.

Answer 21

5 min 2 sec

TR x Phase Matrix x NSA/NEX = Scan Time in a Spin Echo sequence, Divide by 1000 to convert ms (milliseconds) into seconds. 450 x 224 x 3 ÷ 1000 = 302 seconds.

Question 22

Calculate the scan time for a spin echo sequence with the following parameters: TR 400, TE 25, 192 x 256 matrix, 2 NSA, 3mm slice thickness.

Answer 22

2 min 34 sec

TR x Phase Matrix x NSA/NEX = Scan Time in a Spin Echo sequence, Divide by 1000 to convert ms (milliseconds) into seconds. 400 x 192 (phase matrix) x 2 ÷ 1000 = 153.6 seconds

Question 23

Calculate the scan time for a spin echo sequence with the following parameters: TR 400, TE 24, 208 x 256 matrix, 2 NSA, Flip angle 90, 3.5 mm slice thickness.

Answer 23

2 min 46 sec

TR x Phase Matrix x NSA/NEX = Scan Time in a Spin Echo sequence, Divide by 1000 to convert ms (milliseconds) into seconds. 400 x 208 x 2 ÷ 1000 = 166 seconds.

Question 24

Calculate the scan time for a spin echo sequence with the following parameters: TR 500, TE 24, 224 x 256 matrix, 3 NEX, 4 mm slice thickness.

Answer 24

5 min 36 sec
TR x Phase Matrix x NSA/NEX = Scan Time in a Spin Echo sequence, Divide by 1000 to convert ms (milliseconds) into seconds. 500 x 224 x 3 ÷ 1000 = 336 seconds.

Question 25

Calculate the scan time for a spin echo sequence with the following parameters: TR 350, TE 10, 256 x 256 matrix, 2 NEX, 5 mm slice thickness.

Answer 25

2 min 59 sec TR x Phase Matrix x NSA/NEX = Scan Time in a Spin Echo sequence, Divide by 1000 to convert ms (milliseconds) into seconds. 350 x 256 x 2 ÷ 1000 = 179 seconds

Question 26

Calculate the scan time for a fast spin echo sequence with the following parameters: TR 3500, TE 100, 256 x 256 matrix, 4 NEX, 5 mm slice thickness, 14 ETL

Answer 26

4 min 16 sec Scan Time in a Fast Spin Echo Sequence : TR x Phase Matrix x NEX ÷ ETL, ÷ 1000 to convert to seconds. 3500 x 256 x 4 ÷ 14 ÷ 1000 = 256 seconds (4 min 16 sec)

Question 27

Calculate the scan time for a fast spin echo sequence with the following parameters: FOV 20cm, TR 3000, TE 120, 224 x 256 matrix, 3 NEX, 5 mm slice thickness, 12 ETL

Answer 27

2 min 48 sec Scan Time in a Fast Spin Echo Sequence : TR x Phase Matrix x NEX ÷ ETL, ÷ 1000 to convert to seconds. 3000 x 224 x 3 ÷ 12 ÷ 1000 = 168 seconds (2 min 48 sec)

Question 28

Calculate the scan time for a fast spin echo sequence with the following parameters: FOV 16cm, TR 2500, TE 90, 208 x 256 matrix, 6 NEX, 5 mm slice thickness, 18 ETL.

Answer 28

2 min 53 sec Scan Time in a Fast Spin Echo Sequence : TR x Phase Matrix x NEX ÷ ETL, ÷ 1000 to convert to seconds. 2500 x 208 x 6 ÷ 18 ÷ 1000 = 173 seconds (2 min 53 sec)

Question 29

Calculate the scan time for a fast spin echo sequence with the following parameters: TR 2000, TE 30, 192 x 224 matrix, 3 NEX, 4 mm slice thickness, 6 ETL.

Answer 29

3 min 12 sec Scan Time in a Fast Spin Echo Sequence : TR x Phase Matrix x NEX ÷ ETL, ÷ 1000 to convert to seconds. 2000 x 192 x 3 ÷ 6 ÷ 1000 = 192 seconds (3 min 12 sec)

Question 30

Calculate the scan time for a fast spin echo sequence with the following parameters: TR 1800, TE 25, 208 x 224 matrix, 4 NEX, 3 mm slice thickness, 8 ETL.

Answer 30

3 min 7 sec Scan Time in a Fast Spin Echo Sequence : TR x Phase Matrix x NEX ÷ ETL, ÷ 1000 to convert to seconds. 1800 x 208 x 4 ÷ 8 ÷ 1000 = 187 seconds (3 min 7 sec)

Question 31

Calculate the scan time for a 3D gradient echo sequence with the following parameters: FOV 16cm, TR 20, TE 9, 192 x 256 matrix, 2 NEX, 5 mm slice thickness, 40 slices.

Answer 31

5 min 7 sec 3D sequence scan time : TR x Phase Matrix x NSA/NEX x # Slices = 3D Scan Time, ÷ 1000 to convert to seconds. 20 x 192 x 2 x 40 ÷ 1000 = 307 seconds (5 min 7sec)

Question 32

Calculate the scan time for a 3D gradient echo sequence with the following parameters: FOV 16cm, TR 25, TE 12, 208 x 256 matrix, 1 NEX, 4 mm slice thickness, 36 slices.

Answer 32

3 min 7 sec 3D sequence scan time : TR x Phase Matrix x NSA/NEX x # Slices = 3D Scan Time, ÷ 1000 to convert to seconds. 25 x 208 x 1 x 36 ÷ 1000 = 187 seconds (3 min 7 sec

Question 33

Calculate the scan time for a 3D gradient echo sequence with the following parameters: FOV 20cm, TR 24, TE 10, 224 x 256 matrix, 1 NEX, 3.5 mm slice thickness, 40 slices.

Answer 33

3 min 35 sec 3D sequence scan time : TR x Phase Matrix x NSA/NEX x # Slices = 3D Scan Time, ÷ 1000 to convert to seconds. 24 x 224 x 1 x 40 ÷ 1000 = 215 seconds (3 min 35sec)

Question 34

Calculate the pixel size for a fast spin echo sequence with the following parameters: FOV 20cm, TR 3000, TE 120, 224 x 256 matrix, 3 NEX, 5 mm slice thickness, 12 ETL.

Answer 34

0.89 mm x 0.78 mm FOV ÷ Matrix = pixel size FOV ÷ phase matrix = phase dimension pixel FOV ÷ frequency matrix = frequency pixel Convert 20cm to 200 mm before calculating. 200 ÷ 224 = 0.89mm (phase dimension) 200 ÷ 256 = 0.78mm (frequency dimension)

Question 35

Calculate the pixel size for a fast spin echo sequence with the following parameters: FOV 28cm, TR 2000, TE 30, 256 x 320 matrix, 2 NEX, 4 mm slice thickness, 8 ETL.

Answer 35

1.09 mm x 0.88 mm FOV ÷ Matrix = pixel size FOV ÷ phase matrix = phase dimension pixel FOV ÷ frequency matrix = frequency pixel Convert 28cm to 280 mm before calculating. 280 ÷ 256 = 1.09mm (phase dimension) 280 ÷ 320 = 0.88mm (frequency dimension

Question 36

Calculate the pixel size for a fast spin echo sequence with the following parameters: FOV 30cm, TR 600, TE 10, 320 x 320 matrix, 4 NEX, 3 mm slice thickness, 3 ETL.

Answer 36

0.94 mm x 0.94 mm FOV ÷ Matrix = pixel size FOV ÷ phase matrix = phase dimension pixel FOV ÷ frequency matrix = frequency pixel Convert 30cm to 300 mm before calculating. 300 ÷ 320 = 0.94mm (phase dimension) 300 ÷ 320 = 0.94mm (frequency dimension

Question 37

Calculate the pixel area for a fast spin echo sequence with the following parameters: FOV 20cm, TR 3000, TE 120, 224 x 256 matrix, 3 NEX, 5 mm slice thickness, 12 ETL.

Answer 37

0.69 mm2 FOV ÷ phase matrix = phase dimension pixel FOV ÷ frequency matrix = frequency pixel Multiply phase pixel size x frequency pixel size = Pixel area (answer squared) Convert 20cm to 200 mm before calculating. 200 ÷ 224 = 0.89mm (phase dimension) 200 ÷ 256 = 0.78mm (frequency dimension) 0.89mm x 0.78mm = 0.69mm2

Question 38

Calculate the pixel area for a fast spin echo sequence with the following parameters: FOV 28cm, TR 2000, TE 30, 256 x 320 matrix, 2 NEX, 4 mm slice thickness, 8 ETL.

Answer 38

0.96 mm2 FOV ÷ phase matrix = phase dimension pixel FOV ÷ frequency matrix = frequency pixel Convert 28cm to 280 mm before calculating. 280 ÷ 256 = 1.09mm (phase dimension) 280 ÷ 320 = 0.88mm (frequency dimension) 1.09 x 0.88 = 0.96 mm2

Question 39

Calculate the pixel area for a fast spin echo sequence with the following parameters: FOV 30cm, TR 600, TE 10, 320 x 320 matrix, 4 NEX, 3 mm slice thickness, 3 ETL.

Answer 39

0.88 mm2 FOV ÷ phase matrix = phase dimension pixel FOV ÷ frequency matrix = frequency pixel Multiply phase pixel size x frequency pixel size = Pixel area (answer squared2) Convert 30cm to 300 mm before calculating. 300 ÷ 320 = 0.94mm (phase dimension) 300 ÷ 320 = 0.94mm (frequency dimension) 0.94 x 0.94 = 0.88 mm2

Question 40

Calculate the voxel volume for a fast spin echo sequence with the following parameters: FOV 20cm, TR 3000, TE 120, 224 x 256 matrix, 3 NEX, 5 mm slice thickness, 12 ETL.

Answer 40

3.45 mm3 FOV ÷ phase matrix = phase dimension pixel FOV ÷ frequency matrix = frequency pixel Multiply phase pixel size x frequency pixel size = Pixel area (answer squared2) Pixel area x slice thickness = Voxel volume (answer cubic3) Convert 20cm to 200 mm before calculating. 200 ÷ 224 = 0.89mm (phase dimension) 200 ÷ 256 = 0.78mm (frequency dimension) 0.89 x 0.78 = 0.69mm2 (pixel area) 0.69 x 5mm(slice thickness) = 3.45mm3

Question 41

Calculate the voxel volume for a fast spin echo sequence with the following parameters: FOV 28cm, TR 2000, TE 30, 256 x 320 matrix, 2 NEX, 4 mm slice thickness, 8 ETL.

Answer 41

3.84 mm3 FOV ÷ phase matrix = phase dimension pixel FOV ÷ frequency matrix = frequency pixel Multiply phase pixel size x frequency pixel size = Pixel area (answer squared2) Pixel area x slice thickness = Voxel volume (answer cubic3) Convert 28cm to 280 mm before calculating. 280 ÷ 256 = 1.09mm (phase dimension) 280 ÷ 320 = 0.88mm (frequency dimension) 1.09 x 0.88 = 0.96mm2 (pixel area) 0.96mm x 4 (sl thickness) = 3.84mm3 (voxel volume)

Question 42

Calculate the voxel volume for a fast spin echo sequence with the following parameters: FOV 30cm, TR 600, TE 10, 320 x 320 matrix, 4 NEX, 3 mm slice thickness, 3 ETL

Answer 42

 2.64 mm3 FOV ÷ phase matrix = phase dimension pixel FOV ÷ frequency matrix = frequency pixel Multiply phase pixel size x frequency pixel size = Pixel area (answer squared2) Pixel area x slice thickness = Voxel volume (answer cubic3) Convert 30cm to 300 mm before calculating. 300 ÷ 320 = 0.94mm (phase dimension) 300 ÷ 320 = 0.94mm (frequency dimension) 0.94 x 0.94 = 0.88 mm2 (pixel area) 0.88 x 3mm (thickness) = 2.64mm3

Question 43

Calculate the pixel area for a fast spin echo sequence with the following parameters: FOV 36cm, TR 600, TE 10, 512 x 512 matrix, 4 NEX, 5 mm slice thickness, 3 ETL.

Answer 43

0.49 mm2

Question 44

Calculate the voxel volume for a fast spin echo sequence with the following parameters: FOV 34cm, TR 3000, TE 120, 512 x 512 matrix, 3 NEX, 6 mm slice thickness, 12 ETL.

Answer 44

2.64 mm3 340 ÷ 512 = 0.66 0.66 x 0.66 = 0.44mm2 (pixel area) 0.44 x 6 = 2.64mm3 (voxel volume)

Question 45

Calculate the scan time for a fast spin echo sequence with the following parameters: TR 3000, TE 100, 512 x 512 matrix, 2 NEX, 5 mm slice thickness, 18 ETL.

Answer 45

2 min 51 sec 3000 x 512 x 2 ÷ 18 ÷ 1000 = 171 seconds