Siemens SOMATOM Sensation Cardiac Version A60 Operations Instructions download pdf (Page 27)

100

101

Dose Information

CTDI

and CTDI

Vol

The average dose in the scan plane is best described

by the CTDI

for the selected scan parameters. The

CTDI

is measured in the dedicated plastic phantoms –

16 cm diameter for head and 32 cm diameter for body

(as deﬁned in IEC 60601–2– 44). This dose index gives

a good estimate for 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

value displayed can deviate from the

dose in the scanned volume.

The CTDI

deﬁnition and measurement is based on

single axial scan modes. For clinical scanning, i.e.

scanning of entire volumes in patients, the average

dose will also depend on the table feed in between

axial scans or the feed per rotation in spiral scanning.

The dose, expressed as the CTDI

, 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:

CTDI

Vol

= CTDI

/Pitch Factor

This dose number is displayed on the user interface for

the selected scan parameters.

Please note: Up to now the dose display on the

Somaris\5 user interface was labeled “CTDI

“.

This displayed CTDI

was also corrected for the pitch.

General

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Siemens SOMATOM Sensation Cardiac Version A60 Operations Instructions Page 27

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