Row 4

The observer context may include both a Person Observer identification, as well as the identity of the equipment providing the values for the irradiation event (Device Observer identification), if not inherited.

Row 5

Start, Date Time of the first CT Irradiation Event of the accumulation

Row 6

End, Date Time of the last CT Irradiation Event of the accumulation

Row 12

The primary source of information from which this dose object was constructed.

Row 13

The physician responsible for determining that the irradiating procedure was appropriate for the indications. The value may come from Requesting Physician (0032,1032), Requesting Physician Identification Sequence (0032,1031) or somewhere else based on hospital policies.

Rows 5, 6

Total Number of CT irradiation events.

A CT irradiation event is one continuous irradiation procedure and is defined through consistent acquisition parameters.

In the case of dose modulation the calculations are based on the effective parameters (e.g., the effective mA recorded in the Mean X-Ray Tube Current), and these acquisition parameters are consistent.

Rows 5, 6

The Dose Length Product (DLP) is calculated for every irradiation event. The Dose Length Product Total is the sum of the DLP values. The calculation is based on the CTDI_vol result of each irradiation event.

Rows 5, 6

Effective dose (E, in units of mSv) evaluated as a total over the scope is defined in Row 6 of template TID 10011 “CT Radiation Dose”.

Effective dose is defined by the reference in Rows 5 or 6 of this template.

It may be calculated from a product of DLP and an 'Effective Dose Conversion Factor' (E/DLP). Or it may be calculated from a product of the Mean CTDIfreeair and the ratio E/CTDIfreeair. The ratios E/DLP or E/CTDIfreeair may be evaluated either from computer simulations applying Monte Carlo (MC) sampling techniques or from dosimetric measurements in an anthropomorphic phantom, e.g., the Alderson-Rando phantom.. The specific method used is identified in Rows 7 through 11.

Row 5 - 6

Reference of the base publication defining the Effective Dose, either as a coded value, or a textual bibliographic reference. ICRP Publications shall be referenced using their assigned coded values.

Row 7

Description of the method used for Effective Dose evaluations.

Row 8

Description of the reference-patient mathematical or computational model used when Effective Dose is derived via Monte Carlo simulations of radiation transport in such models. Examples of publications that specify particular reference patient models are NUREG/CR-1159, ORNL/NUREG/TM-367 (1980); NRPB-R186 (1985); GSF-Bericht S-885 (1986); Fill et al., Health Physics Vol. 86 (3): 253-272 (2004).

Row 9

Description of the condition Effective Dose measured

Row 10

Type of Effective Dose phantom used, e.g., Alderson-Rando

Row 11

Type of dosimeter used, e.g., TLD (Thermo Luminescence Dosimeter)

Row 13

The device that produced the irradiation accumulated in this template. I.e., the CT Scanner. This is not required to be present if the information is the same as that already recorded in TID 1004 “Device Observer Identifying Attributes” encoded via the inclusion of TID 1002 “Observer Context” in TID 10011 “CT Radiation Dose” Row 4, which in turn may be absent if identical to the content in the Enhanced General Equipment Module, or if more than one device produced the accumulated irradiation.

Row 2

User-defined type of clinical acquisition protocol for creating images or image-derived measurements. May be taken from Protocol Name (0018,1030) or from Performed Procedure Step Description (0040,0254).

Row 3

The target region is the anatomy exposed.

Row 4

Description of the method used during acquisition of this CT irradiation event, may be derived from Acquisition Type (0018,9302).

Row 4b

Though not a characteristic of the acquisition per se, the type of reconstruction intended has a bearing on the technique used. If multiple types of reconstruction are performed, multiple values can be listed. These values should correspond to the values of Reconstruction Algorithm (0018,9315) in the reconstructed images.

Row 5

The acquisition was performed with or without contrast medium application.

Row 8

Total time the patient has received X-Ray exposure during the irradiation event.

Row 10

The value of the nominal width (referenced to the location of the isocenter along the z axis) of a single collimated slice in mm.

Row 11

The value of the nominal width (referenced to the location of the isocenter along the z axis) of the nominal total collimation in mm over the area of active X-Ray detection (z-coverage).

Row 12

Pitch Factor: For Spiral Acquisition, the Pitch Factor is the ratio of the Table Feed per Rotation to the Nominal Total Collimation Width. For Sequenced Acquisition, the Pitch Factor is the ratio of the Table Feed per single sequenced scan to the Nominal Total Collimation Width.

Row 14

CT X-Ray source parameters related to the acquisition. For each X-Ray source an item must be present. For multi-energy acquisitions, multiple items may be present for each X-Ray source, each item describing one energy level.

Row 15

Identification of the X-Ray source. Identifies the particular X-Ray source (in a multi-source CT system) for which the set of X-Ray source parameter values is reported.

Row 16

KVP value as measured/recorded by system.

Row 18

Mean tube current as measured/recorded by system.

Row 19

Exposure time as measured/recorded by the system per rotation.

Row 20

Thickness of an equivalent filter constructed from aluminum, in case of multi-source CT systems AND if Row 4 is not present

Row 21

CT Dose for one acquisition

Rows 5, 6

"Mean CTDI_vol" refers to the average value of the CTDI_vol applied within this acquisition.

CTDI_vol is the volume CTDI_w, where CTDI_w is the weighted computed tomography dose index 100 as defined in IEC 60601-2-44.

For Sequenced and Spiral scanning, CTDI_vol = CTDI_w / Pitch Factor.

For Stationary and Free scanning, CTDI_vol = CTDI_w ✕ Cumulative Exposure Time/ Exposure Time Per Rotation.

According to IEC 60601-2-44 Ed 3 for Constant Angle Acquisition may be calculated as CTDIvol = (CTDIw / Current Time Product (mAs)) ✕ X-Ray Tube Current (mA) x (Nominal Total Collimation Width (mm) / Table Speed (mm/s)).

See also CTDIvol (0018,9345) and Spiral Pitch Factor (0018,9311) in the “Enhanced Computed Tomography Image IOD” in PS3.3 .

Row 23

The type of phantom used for CTDI measurement according to IEC 60601-2-44(e.g., Head 16 cm diameter PMMA, Body 32 cm diameter PMMA).

Rows 5, 6

The CTDI_{free air} Calculation Factor is the CTDI_{free air} per mAs, expressed in units of mGy/mAs. The CTDI_{free air} Calculation Factor may be used in one method calculating Dose. For example, for this acquisition, Effective Dose = Mean X-Ray Tube Current ✕ Cumulative Exposure Time ✕ CTDI_{free air} Calculation Factor ✕ (Effective Dose/ CTDI_{free air}).

Rows 5, 6

MeanCTDI_{free air} is the mean CTDI for this acquisition, evaluated free-in-air according to IEC 60601-2-44. MeanCTDI_{free air} = Mean X-Ray Tube Current ✕ Cumulative Exposure Time ✕ CTDI_{free air} Calculation Factor. The CTDI_{free air} may be used in one method of calculating Effective Dose.

Rows 5, 6

For Spiral scanning, DLP = CTDI_vol ✕ Scanning Length. For Sequenced scanning, DLP = CTDI_vol ✕ Nominal Total Collimation Width ✕ Cumulative Exposure Time / Exposure Time per Rotation. For Stationary and Free scanning, DLP = CTDI_vol ✕ Nominal Total Collimation Width (according to IEC 60601-2-44).

Row 27

Effective Dose in mSv of the single continuous time-frame of the irradiation computed as described in TID 10012 “CT Accumulated Dose Data”.

Row 29

The Effective Dose Conversion Factor is the ratio of the Effective Dose to the DLP, expressed in units of mSv/mGy.cm, and it is used as a factor in one method of estimating Effective Dose. Monte Carlo Simulations (or dosimetric measurements in an anthropomorphic phantom, e.g., the Alderson-Rando phantom) may be used as a basis for the evaluation of Effective Dose Conversion Factors.

Row 30

More than one Size Specific Dose Estimation may be included, for example if different computation methods are used.

Row 31

The methods of AAPM Report 204 are listed in CID 10023 “Size Specific Dose Estimation Method for CT”; other methods may be used.

The phantom size (16cm or 32cm) used for the calculation is available from the phantom type defined in Row 23.

Row 32

The condition specifies inclusion of the Measured Lateral Dimension if it was used in the calculation.

Row 33

The condition specifies inclusion of the Measured AP Dimension if it was used in the calculation.

Row 34

The Derived Effective Diameter is conditionally included, whether it was derived from measurements or estimated from age, but may not be used for other (non-AAPM Report 204) methods.

Row 35

Record of details associated with using the NEMA Dose Check Standard (NEMA XR-25-2010).

Row 36

The type of exposure modulation. May use the value of Exposure Modulation Type (0018,9323) from CT Exposure Macro or from CT Image Module.

Row 38

People responsible for the administration of the radiation reported in the irradiation event. May include values that would appear in Performing Physicians' Name (0008,1050), Performing Physician Identification Sequence (0008,1052), Operators' Name (0008,1070) and/or Operator Identification Sequence (0008,1072).

Row 39

The device that produced the irradiation in this Irradiation Event. I.e., the CT scanner. This is not required to be present if the information is the same as that already recorded in the TID 1004 “Device Observer Identifying Attributes” encoded via the inclusion of TID 1002 “Observer Context” in TID 10011 “CT Radiation Dose” Row 4, which in turn may be absent if identical to the content in the Enhanced General Equipment Module.

Row 1

For Spiral scanning, the scanning length is normally the table travel in mm during the tube loading (see Figure A-16).

For Sequenced scanning, the scanning length is the table travel between consecutive scans times the number of scans.

For Stationary and Free scanning, the scanning length is the nominal width of the total collimation.

Row 2

The length of the reconstructable volume is the maximum z-range between the outermost edges of the top and bottom slices that can be reconstructed from the acquisition.

For Spiral scanning, the length of reconstructable volume is the z-range between the outermost beginning of the first reconstructable slice and the outermost end of the last reconstructable slice (see Figure A-16).

For Sequenced scanning, the length of reconstructable volume is the z-range between the outermost beginning of the first slice and the outermost end of the last slice (i.e., including any skip).

For Stationary and Free scanning, the length of reconstructable volume is the nominal width of the total collimation.

Row 3

For Spiral scanning, the exposed range is as defined in IEC 60601-2-44 (Ed. 3) 302.115(b) (see Figure A-16).

Exposed range is not defined for other modes of scanning.

Rows 4-5

The Top and Bottom Z Locations of the Reconstructable Volume are independent of the slice width of any actual reconstructed slices. They are measured from the edges of the volume, and hence are not equal to the Z locations encoded in the images of any actual reconstructed slices, which are recorded as the center of the slice.

Rows 4-7

These locations are patient (not table or gantry) relative, to allow them to be defined in the Patient Coordinate System and hence related to the Image Position (Patient) in the reconstructed images. They are also defined in terms of the top (towards the patient's head), and bottom (towards the patient's feet) of the corresponding ranges, in order to make them independent of whether the scan starts at the top or the bottom or shuttles back and forth in between (see Figure A-16).

Row 1

Container for Dose Check Alert details.

Row 2

Indicates whether a DLP Alert Value was configured (e.g., by the institution) for the exam to which this irradiation event belongs.

Row 3

Indicates whether a CTDIvol Alert Value was configured (e.g., by the institution) for the exam to which this irradiation event belongs.

Row 4

The configured value applicable to the current exam that would trigger an alert if the accumulated DLP were projected to exceed it.

Row 5

The configured value applicable to the current exam that would trigger an alert if the Accumulated CTDIvol at any given location were projected to exceed it.

Row 6

The value estimated prior to performing this irradiation event of the projected DLP accumulated during this exam, including this irradiation event. The estimate may include assumptions such as those described in NEMA XR 25-2010.

Row 7

The value estimated prior to performing this irradiation event of the projected CTDIvol accumulated during this exam, including this irradiation event. The value is for the location with the highest estimated accumulation. The actual location is not recorded. The estimate may include assumptions such as those described in NEMA XR 25-2010.

Row 8

The reason provided by the operator for proceeding with an irradiation event projected to exceed an alert value.

Row 9

Person responsible for authorizing irradiation projected to exceed an alert value.

Row 10

Container for Dose Check Notification details.

Row 11

Indicates whether a DLP Notification Value was configured (e.g., by the institution) for the Protocol Element Group to which this irradiation event corresponds.

Row 12

Indicates whether a CTDIvol Notification Value was configured (e.g., by the institution) for the Protocol Element Group to which this irradiation event corresponds.

Row 13

The configured value applicable to the current irradiation event that would trigger a notification if the DLP were projected to exceed it.

Row 14

The configured value applicable to the current irradiation event that would trigger a notification if the CTDIvol were projected to exceed it.

Row 15

The value estimated prior to performing this irradiation event of the DLP for this irradiation event. The estimate may include assumptions such as those described in NEMA XR 25-2010.

Row 16

The value estimated prior to performing this irradiation event of the CTDIvol for this irradiation event. The value is for the location with the highest estimated value. The actual location is not recorded. The estimate may include assumptions such as those described in NEMA XR 25-2010.

Row 17

The reason provided by the operator for proceeding with an irradiation event projected to exceed a notification value.

Row 18

Person responsible for authorizing irradiation projected to exceed a notification value.