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Dose Information
CTDI
W
and CTDI
Vol
The average dose in the scan plane is best described by
the CTDI
W
for the selected scan parameters. The CTDI
W
is measured in dedicated plastic phantoms – 16 cm
diameter for head and 32 cm diameter for body (as
defined in IEC 60601 – 2 – 44). For scan modes with z-
Sharp the CTDI100 is calculated using the single num-
ber of tomographic sections (not doubled by z-Sharp)
to remain within the terms of IEC 60601-2-44. The z-
coverage with and without z-Sharp is the same and so
is the dose. This dose index gives a good estimation of
the average dose applied in the scanned volume, as
long as the patient size is similar to the size of the
respective dose phantoms.
Since the body size can be smaller or larger than
32 cm, the CTDI
W
value displayed can deviate from the
dose in the scanned volume.
The CTDI
W
definition and measurement are based on
single axial scan modes. For clinical scanning, i.e.scan-
ning of entire volumes in patients, the average dose
will also depend on the table feed between axial scans
or the feed per rotation in spiral scanning. The dose,
expressed as the CTDI
W
, must therefore be corrected by
the pitch factor of the spiral scan or an axial scan series
to describe the average dose in the scanned volume.
For this purpose the IEC defined the term “CTDI
Vol
“ in
September 2002:
This dose number is displayed on the user interface for
the selected scan parameters.
CTDI
Vol
=
CTDI
w
Pitch factor
Summary of Contents for SOMATOM
Page 4: ...4 Overview Respiratory Gating 484 Children 508 ...
Page 5: ...Overview 5 ...
Page 121: ...Workflow Information 121 ...
Page 135: ...Contrast Medium 135 ...
Page 157: ...Application Information 157 Program to define capture options ...
Page 161: ...Application Information 161 ...
Page 167: ...Head 167 ...
Page 183: ...Head 183 ...
Page 187: ...Head 187 ...
Page 191: ...Head 191 ...
Page 195: ...Head 195 ...
Page 211: ...Neck 211 ...
Page 217: ...Neck 217 ...
Page 223: ...Shoulder 223 ...
Page 239: ...Thorax 239 ...
Page 249: ...Thorax 249 ...
Page 269: ...Abdomen 269 ...
Page 273: ...Abdomen 273 ...
Page 277: ...Abdomen 277 ...
Page 287: ...Abdomen 287 ...
Page 293: ...Abdomen 293 ...
Page 307: ...Spine 307 ...
Page 311: ...Spine 311 ...
Page 321: ...Pelvis 321 ...
Page 327: ...Pelvis 327 ...
Page 338: ...338 Upper Extremities Hints For image reconstruction of soft tissue use kernel B30s B31s ...
Page 339: ...Upper Extremities 339 ...
Page 342: ...342 Upper Extremities Hint For image reconstruction of soft tissue use kernel B30s B31s ...
Page 343: ...Upper Extremities 343 ...
Page 357: ...Lower Extremities 357 ...
Page 369: ...Vascular 369 ...
Page 375: ...Vascular 375 ...
Page 379: ...Vascular 379 ...
Page 383: ...Vascular 383 ...
Page 387: ...Vascular 387 ...
Page 393: ...Vascular 393 ...
Page 397: ...Vascular 397 ...
Page 401: ...Vascular 401 ...
Page 405: ...Vascular 405 ...
Page 409: ...Vascular 409 ...
Page 413: ...Vascular 413 ...
Page 421: ...Specials 421 ...
Page 423: ...Specials 423 ...
Page 435: ...Specials 435 ...
Page 455: ...Specials 455 CARE Vision and Biopsy layout for CAREView equal size display Biopsy two segment ...
Page 461: ...Specials 461 ...
Page 469: ...Radiation Therapy 469 ...
Page 483: ...Radiation Therapy 483 ...
Page 517: ...Children 517 ...
Page 521: ...Children 521 ...
Page 525: ...Children 525 ...
Page 529: ...Children 529 ...
Page 533: ...Children 533 ...
Page 537: ...Children 537 ...
Page 545: ...Children 545 ...
Page 553: ...Children 553 ...
Page 557: ...Children 557 ...
Page 561: ...Children 561 ...
Page 565: ...Children 565 ...
Page 573: ...Children 573 ...
Page 577: ...Children 577 ...
Page 581: ...Children 581 ...
Page 585: ...Children 585 ...