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ARMRIT ARRT > Scan Principles MR Contrast/Formulas* > Flashcards

Scan Principles MR Contrast/Formulas* Flashcards

1
Q

How does Gadolinium function as a contrast agent?

A

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

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2
Q

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

A

Gadolinium

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3
Q

The substances that bind to gadolinium ions are defined as:

A

Chelates

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4
Q

Gadolinium chelates used in MR imaging are

A

Paramagnetic

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5
Q

All of the following are true regarding gadolinium EXCEPT:

A

Gadolinium has six unpaired electrons

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

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6
Q

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

A

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

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7
Q

Contraindications for IV gadolinium contrast use are:

A

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

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8
Q

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

A

Less than 1%

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9
Q

IV Gadolinium contrast administration is indicated for:

A

Central nervous system

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

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10
Q

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

A

Glucagon

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11
Q

Metastatic lesions enhance after injecting a gadolinium chelate because of:

A

The breakdown in the blood brain barrier

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12
Q

Gadolinium is an example of a ___________ contrast agent

A

Paramagnetic

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13
Q

In MRI, the function of gadolinium is to:

A

Shorten the T1 and T2 times of tissues

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14
Q

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

A

0.1 mmol/kg

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

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15
Q

Gadolinium IV contrast:

A

Shortens the T1 and T2 times of tissues

Gadolinium IV contrast shortens the T1 and T2 times of tissues

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16
Q

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

A

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.

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17
Q

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

A

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.

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18
Q

VoLumen is a contrast agent used for:

A

Bowel enhancement

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19
Q

VoLumen would be selected for which MR procedure?

A

MR enterography

20
Q

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.

A

16mL

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

21
Q

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.

A

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.

22
Q

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.

A

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

23
Q

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.

A

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.

24
Q

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.

A

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.

25
Q

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.

A

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

26
Q

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

A

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)

27
Q

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

A

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)

28
Q

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.

A

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)

29
Q

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.

A

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)

30
Q

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.

A

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)

31
Q

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.

A

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)

32
Q

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.

A

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

33
Q

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.

A

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)

34
Q

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.

A

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)

35
Q

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.

A

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

36
Q

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.

A

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

37
Q

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.

A

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

38
Q

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.

A

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

39
Q

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.

A

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

40
Q

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.

A

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

41
Q

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.

A

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)

42
Q

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

A

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

43
Q

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.

A

0.49 mm2

44
Q

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.

A

2.64 mm3

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

45
Q

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.

A

2 min 51 sec

3000 x 512 x 2 ÷ 18 ÷ 1000 = 171 seconds

ARMRIT ARRT (17 decks)

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