Computed tomography dose index - Revision history

Karen Clement at 19:21, 12 September 2019

2019-09-12T19:21:18Z

Intern at 19:19, 6 June 2019

2019-06-06T19:19:51Z

Intern at 19:12, 6 June 2019

2019-06-06T19:12:25Z

Intern: Created page with "A dose quantity defined to give indication of doses to the patient undergoing CT scans. The basic CTDI is the average absorbed dose at the center of the standard CT phantom im..."

2019-06-06T19:09:43Z

Created page with "A dose quantity defined to give indication of doses to the patient undergoing CT scans. The basic CTDI is the average absorbed dose at the center of the standard CT phantom im..."

New page

A dose quantity defined to give indication of doses to the patient undergoing CT scans. The basic CTDI is the average absorbed dose at the center of the standard CT phantom imparted by a single axial acquisition of 100 mm by a CT scanner, CTDI<sub>100</sub>:

<div style='text-align: center;'>
<math>
CTDI_100 = \frac{1}{C}\int\limits_{-50 mm}^{+50 mm}dzD(z)
</math>
</div>

where C is the radiographic exposure (mAs) and D(z) is the radiation dose measured at position z along the scanner's main axis.

Since doses at center of body are approximately two times of those at shallow depths in typical CT scans, improved indices are proposed and used. One of them is the weighted CTDI, CTDI100w, defined as:

<div style='text-align: center;'>
<math>
CTDI_100w = \frac{1}{3}CTDI_{100}^{central} + \frac{2}{3}CTDI_{100}^{peripheral}
</math>
</div>

where <math>CTDI_{100}^{central}</math> and <mtah>CTDI_{100}^{peripheral}</math> are the CTDIs at the center and peripheral, respectively. The standard CT phantoms are PMMA cylinders having defined diameters (32 cm for torso and 16 cm for head-and-neck) and appropriate length enough to cover the 100 mm (usually 15 cm is employed). There are holes to place the detectors: one at the center and a few on a peripheral circle. Traditionally pencil ion chambers of 100mm long were used as the detectors but detectors of other types may be used as calibrated appropriately.

''[[ICRP Glossary]] entry - May 2019''

← Older revision		Revision as of 19:21, 12 September 2019
Line 20:		Line 20:
	where <math>CTDI_{100}^{central}</math> and <math>CTDI_{100}^{peripheral}</math> are the CTDIs at the center and peripheral, respectively. The standard CT phantoms are PMMA cylinders having defined diameters (32 cm for torso and 16 cm for head-and-neck) and appropriate length enough to cover the 100 mm (usually 15 cm is employed). There are holes to place the detectors: one at the center and a few on a peripheral circle. Traditionally pencil ion chambers of 100mm long were used as the detectors but detectors of other types may be used as calibrated appropriately.		where <math>CTDI_{100}^{central}</math> and <math>CTDI_{100}^{peripheral}</math> are the CTDIs at the center and peripheral, respectively. The standard CT phantoms are PMMA cylinders having defined diameters (32 cm for torso and 16 cm for head-and-neck) and appropriate length enough to cover the 100 mm (usually 15 cm is employed). There are holes to place the detectors: one at the center and a few on a peripheral circle. Traditionally pencil ion chambers of 100mm long were used as the detectors but detectors of other types may be used as calibrated appropriately.

		+	''ICRP Glossary entry - May 2019''


−	''[[ICRP Glossary]] ~~entry - May 2019~~''	+	'''Return to [[ICRP Glossary\|Glossary]]'''

@@ Line 9: / Line 9: @@
 where C is the radiographic exposure (mAs) and D(z) is the radiation dose measured at position z along the scanner's main axis.
-Since doses at center of body are approximately two times of those at shallow depths in typical CT scans, improved indices are proposed and used. One of them is the weighted CTDI, <math>CTDI_{100w}</math>, defined as:
+Since doses at center of body are approximately two times of those at shallow depths in typical CT scans, improved indices are proposed and used. One of them is the weighted CTDI, CTDI<sub>100w</sub>, defined as:
 <div style='text-align: center;'>

@@ Line 3: / Line 3: @@
 <div style='text-align: center;'>
 <math>
-CTDI_100 = \frac{1}{C}\int\limits_{-50 mm}^{+50 mm}dzD(z)
+CTDI_{100} = \frac{1}{C}\int\limits_{-50 mm}^{+50 mm}dzD(z)
 </math>
 </div>
@@ Line 9: / Line 9: @@
 where C is the radiographic exposure (mAs) and D(z) is the radiation dose measured at position z along the scanner's main axis.
-Since doses at center of body are approximately two times of those at shallow depths in typical CT scans, improved indices are proposed and used. One of them is the weighted CTDI, CTDI100w, defined as:
+Since doses at center of body are approximately two times of those at shallow depths in typical CT scans, improved indices are proposed and used. One of them is the weighted CTDI, <math>CTDI_{100w}</math>, defined as:
 <div style='text-align: center;'>
 <math>
-CTDI_100w = \frac{1}{3}CTDI_{100}^{central} + \frac{2}{3}CTDI_{100}^{peripheral}
+CTDI_{100w} = \frac{1}{3}CTDI_{100}^{central} + \frac{2}{3}CTDI_{100}^{peripheral}
 </math>
 </div>
-where <math>CTDI_{100}^{central}</math> and <mtah>CTDI_{100}^{peripheral}</math> are the CTDIs at the center and peripheral, respectively. The standard CT phantoms are PMMA cylinders having defined diameters (32 cm for torso and 16 cm for head-and-neck) and appropriate length enough to cover the 100 mm (usually 15 cm is employed). There are holes to place the detectors: one at the center and a few on a peripheral circle. Traditionally pencil ion chambers of 100mm long were used as the detectors but detectors of other types may be used as calibrated appropriately.
+where <math>CTDI_{100}^{central}</math> and <math>CTDI_{100}^{peripheral}</math> are the CTDIs at the center and peripheral, respectively. The standard CT phantoms are PMMA cylinders having defined diameters (32 cm for torso and 16 cm for head-and-neck) and appropriate length enough to cover the 100 mm (usually 15 cm is employed). There are holes to place the detectors: one at the center and a few on a peripheral circle. Traditionally pencil ion chambers of 100mm long were used as the detectors but detectors of other types may be used as calibrated appropriately.
 ''[[ICRP Glossary]] entry -  May 2019''