Scan Principles MR Contrast/Formulas* Flashcards
How does Gadolinium function as a contrast agent?
It shortens the T1 time of tissue
Gadolinium IV contrast shortens the T1 time of tissue, and only is utilized in T1 weighted sequences
The most common positive contrast agent used in clinical MR imaging is:
Gadolinium
The substances that bind to gadolinium ions are defined as:
Chelates
Gadolinium chelates used in MR imaging are
Paramagnetic
All of the following are true regarding gadolinium EXCEPT:
Gadolinium has six unpaired electrons
Gadolinium has 7 unpaired electrons in its 4f orbitals giving it a very large magnetic moment.
The FDA approved oral contrast agent for MRI makes bowel appear:
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
Contraindications for IV gadolinium contrast use are:
None of the above
T
here are no known contraindications to IV gadolinium contrast usage
What is the percentage of patients reported to have allergic reactions to gadolinium contrast agents?
Less than 1%
IV Gadolinium contrast administration is indicated for:
Central nervous system
IV Gadolinium contrast administration is indicated for the central nervous system, and for MRA of the lower extremities for AIOD, only.
____________ is used as an anti-peristalsis agent in MR Enterography procedures.
Glucagon
Metastatic lesions enhance after injecting a gadolinium chelate because of:
The breakdown in the blood brain barrier
Gadolinium is an example of a ___________ contrast agent
Paramagnetic
In MRI, the function of gadolinium is to:
Shorten the T1 and T2 times of tissues
The standard dose for the adminstration of IV gadolinium chelates is:
0.1 mmol/kg
The standard dose for the adminstration of IV gadolinium chelates is 0.1 mmol/kg
Gadolinium IV contrast:
Shortens the T1 and T2 times of tissues
Gadolinium IV contrast shortens the T1 and T2 times of tissues
Following the administration of IV gadolinium contrast, it is recommended to:
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.
Following the injection of contrast, which of the following patients are most likely to have a potentially serious reaction?
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.
VoLumen is a contrast agent used for:
Bowel enhancement
VoLumen would be selected for which MR procedure?
MR enterography
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.
16mL
Divide 176 lbs by 2.2 (lbs per kg), then multiply the kg (80) by 0.2 ml/kg = 16mL
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.
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.
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.
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
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.
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.
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.
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.
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.
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
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
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)
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
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)
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.
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)
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.
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)
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.
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)
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.
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)
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.
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
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.
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)
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.
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)
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.
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
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.
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
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.
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
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.
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
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.
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
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.
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
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.
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)
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
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
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.
0.49 mm2
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.
2.64 mm3
340 ÷ 512 = 0.66
0.66 x 0.66 = 0.44mm2 (pixel area)
0.44 x 6 = 2.64mm3 (voxel volume)
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.
2 min 51 sec
3000 x 512 x 2 ÷ 18 ÷ 1000 = 171 seconds
