Fluke 76-419-4150 User Manual

Nuclear Associates

76-419-4150

Adult/Pediatric CT Head and Body Dose Phantoms

March 2005
Manual No. 76-419-4150-1 Rev. 1
©2004, 2005 Fluke Corporation, All rights reserved. Printed U.S.A.
All product names are trademarks of their respective companies

Users Manual

Fluke Biomedical

Radiation Management Services

6045 Cochran Road
Cleveland, Ohio 44139

440.498.2564

www.flukebiomedical.com/rms

Table of Contents

Section 1: General Information.......................................................................................................................... 1-1

1.1 Introduction ................................................................................................................................................................1-1

1.2 Applications.................................................................................................................................................................1-1

Section 2: Operation............................................................................................................................................... 2-1

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General Information

Introduction

1

Section 1

General Information

1.1 Introduction

These phantoms can be used with any computed tomography (CT) system designed to image both adult and
pediatric head and body. They can separate dose information for each. When performing dose profile measurements,
the dose phantoms allow the user to collect information for the maximum, minimum and mid-range value of the
nominal tomographic section thickness.

This essential phantom kit consists of three parts: an adult body phantom, an adult head phantom that doubles as a
pediatric body phantom and a pediatric head phantom. All are made of solid acrylic, 15 cm thick, with diameters of
32 cm, 16 cm, and 10 cm respectively. Each part contains five probe holes, one in the center and four around the
perimeter, 90° apart and 1 cm from the edge. The inside diameter of the holes is 1.31 cm. Each part includes five
acrylic rods for plugging all the holes in the phantom. A storage and carrying case is available as an option.

1.2 Applications

The CT Dose Phantoms were designed in accordance with the Food and Drug Administration's performance
standard for diagnostic x-ray systems, which includes regulations specifically applicable to CT systems (21 CFR

1020.33).

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Operation

§1020.33 Computed Tomography (CT) Equipment

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Section 2

Operation

§1020.33 Computed Tomography (CT) Equipment

Reprinted from: “21CFR 1020.33” pages 535-540.

A. Applicability

1. The provisions of this section, except for paragraphs (b), (c)(1), and (c)(2) are applicable as specified herein to
CT x-ray systems manufactured or remanufactured on or after September 3,1985.

2. The provisions of paragraphs (b), (c)(1), and (c)(2) are applicable to CT x-ray systems manufactured or
remanufactured on or after November 29, 1984.

B. Definitions

As used in this section, the following definitions apply:

1) Computed Tomography Dose Index (CTDI) Means

The integral of the dose profile along a line perpendicular to the tomographic plane divided by the product
of the nominal tomographic section thickness and the number of tomograms produced in a single scan;
that is:

Where:

z = position along a line perpendicular to the tomographic plane.

D(z) = Dose at position z.

T = Nominal tomographic section thickness.

n = Number of tomograms produced in a single scan.

This definition assumes that the dose profile is centered around z=0 and that, for a multiple tomogram
system, the scan increment between adjacent scans is nT.

2) Contrast Scale Means

The change in linear attenuation coefficient per CT number relative to water; that is:

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Where:

μ

Linear attenuation coefficient of water.

w =

μ

= Linear attenuation coefficient of material of interest.

x

(CT)

= CT number of water.

w

(CT)

= CT number of material of interest.

x

3) CT Conditions of Operation Means

All selectable parameters governing the operation of a CT x-ray system including nominal tomographic
section thickness, filtration, and the technique factors as defined in §1020.30(b)(36).

4) CT Number Means

The number used to represent the x-ray attenuation associated with each elemental area of the CT image.

5) [Reserved]

6) CT Dosimetry Phantom Means

The phantom used for determination of the dose delivered by a CT x-ray system. The phantom shall be a
right circular cylinder of polymethl-methacrylate of density 1.19±0.01 grams per cubic centimeter. The
phantom shall be at least 14 centimeters in length and shall have diameters of 32.0 centimeters for testing
any CT system designed to image any section of the body (whole body scanners) and 16.0 centimeters for
any system designed to image the head (head scanners) or for any whole body scanner operated in the
head scanning mode. The phantom shall provide means for the placement of a dosimeter(s) along its axis of
rotation and along a line parallel to the axis of rotation 1.0 centimeter from the outer surface and within the
phantom. Means for the placement of a dosimeter(s) or alignment device at other locations may be
provided for convenience. The means used for placement of a dosimeter(s) (i.e., hole size) and the type of
dosimeter(s) used is at the discretion of the manufacturer. Any effect on the doses measured due to the
removal of phantom material to accommodate dosimeters shall be accounted for through appropriate
corrections to the reported data or included in the statement of maximum deviation for the values obtained
using the phantom.

7) Dose Profile Means

The dose as a function of position along a line.

8) Modulation Transfer Function Means

The modulus of the Fourier transform of the impulse response of the system.

9) Multiple Tomogram System Means

A CT x-ray system which obtains x-ray transmission data simultaneously during a single scan to produce
more than one tomogram.

10) Noise Means

The standard deviation of the fluctuations in CT number expressed as a percent of the attenuation
coefficient of water. Its estimate (S

) is calculated using the following expression:

n

Where:

CS = Contrast scale.

μ

= Linear attenuation coefficient of water.

w

s = Estimated standard deviation of the CT numbers of picture elements in a specified area of the CT

image.

Nominal Tomographic Section Thickness Means

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The full-width at half-maximum of the sensitivity profile taken at the center of the cross-sectional volume
over which x-ray transmission data are collected.

11) Picture Element Means

An elemental area of a tomogram.

12) Remanufacturing Means

Modifying a CT system in such a way that the resulting dose and imaging performance become
substantially equivalent to any CT x-ray system manufactured by the original manufacturer on or after
November 29, 1984. Any reference in this section to "manufacture", "manufacturer", or "manufacturing"
includes remanufacture, remanufacturer, or remanufacturing, respectively.

13) Scan Increment Means

The amount of relative displacement of the patient with respect to the CT x-ray system between successive
scans measured along the direction of such displacement.

14) Scan Sequence Means

A preselected set of -two or more scans performed consecutively under preselected CT conditions of
operations.

15) Sensitivity Profile Means

The relative response of the CT x-ray system as a function of position along a line perpendicular to the
tomographic plane.

16) Single Tomogram System Means

A CT x-ray system which obtains x-ray transmission data during a scan to produce a single tomogram.

17) Tomographic Plane Means

That geometric plane which the manufacturer identifies as corresponding to the output tomogram.

18) Tomographic Section Means

The volume of an object whose x-ray attenuation properties are imaged in a tomogram.

C. Information to be Provided for Users

Each manufacturer of a CT x-ray system shall provide the following technical and safety information, in addition to
that required under § 1020.30(h), to purchasers and, upon request, to others at a cost not to exceed the cost of
publication and distribution of such information. This information shall be identified and provided in a separate
section of the user's instruction manual or in a separate manual devoted only to this information.

1) Conditions of Operation. A statement of the CT conditions of operation used to provide the information

required by paragraph (c) (2) and (3) of this section.

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2) Dose information. The following dose information obtained by using the CT dosimetry phantom. For any CT

x-ray system designed to image both the head and body, separate dose information shall be provided for each
application. All dose measurements shall be performed with the CT dosimetry phantom placed on the patient
couch or support device without additional attenuating materials present.

(i) The CTDI at the following locations in the dosimetry phantom:

(a) Along the axis of rotation of the phantom.

(b) Along a line parallel to the axis of rotation and 1.0 centimeter interior to the surface of the phantom

with the phantom positioned so that CTDI is the maximum obtainable at this depth.

(c) Along lines parallel to the axis of rotation and 1.0 centimeter interior to the surface of the phantom at

positions 90, 180, and 270 degrees from the position in paragraph (c)(2)(i)(b) of this section. The CT
conditions of operation shall be the typical values suggested by the manufacturer for CT of the head or
body. The location of the position where the CTDI is maximum as specified in paragraph (c)(2)(i)(b) of
this section shall be given by the manufacturer with respect to the housing of the scanning mechanism
or other readily identifiable feature of the CT x-ray system in such a manner as to permit placement of
the dosimetry phantom in this orientation.

(ii) The CTDI in the center location of the dosimetry phantom for each selectable CT condition of operation that

varies either the rate or duration of x-ray exposure. This CTDI shall be presented as a value that is normalized
to the CTDI in the center location of the dosimetry phantom from paragraph (c)(2)(i) of this section, with the
CTDI of paragraph (c)(2)(i) of this section having a value of one. As each individual CT condition of operation
is changed, all other independent CT conditions of operation shall be maintained at the typical
values described in paragraph (c)(2)(i) of this section. These data shall encompass the range of each CT
condition of operation stated by the manufacturer as appropriate for CT of the head or body. When more
than three selections of a CT condition of operation are available, the normalized CTDI shall be provided, at
least, for the minimum, maximum, and mid-range value of the CT condition of operation.

(iii) The CTDI at the location coincident with the maximum CTDI at 1 centimeter interior to the surface of the

dosimetry phantom for each selectable peak tube potential. When more than three selections of peak tube
potential are available, the normalized CTDI shall be provided, at least, for the minimum, maximum, and a
typical value of peak tube potential. The CTDI shall be presented as a value that is normalized to the
maximum CTDI located at 1 centimeter interior to the surface of the dosimetry phantom from paragraph
(c)(2)(i) of this section, with the CTDI of paragraph (c)(2)(i) of this section having a value of one.

(iv) The dose profile in the center location of the dosimetry phantom for each selectable nominal tomographic

section thickness. When more than three selections of nominal tomographic section thicknesses are
available, the information shall be provided, at least, for the minimum, maximum, and midrange value of
nominal tomographic section thickness. The dose profile shall be presented on the same graph and to the
same scale as the corresponding sensitivity profile required by paragraph (c)(3)(iv) of this section.

(v) A statement of the maximum deviation from the values given in the information provided according to

paragraph (c)(2) (i), (ii), (iii), and (iv) of this section. Deviation of actual values may not exceed these limits.

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Operation

§1020.33 Computed Tomography (CT) Equipment

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3) Imaging Performance Information. The following performance data shall be provided for the CT conditions

of operation used to provide the information required by paragraph (c)(2)(i) of this section. All other aspects of
data collection, including the x-ray attenuation properties of the material in the tomographic section, shall be
similar to those used to provide the dose information required by paragraph (c)(2)(i) of this section. For any CT x­ray system designed to image both the head and body, separate imaging performance information shall be
provided for each application.

(i) A statement of the noise.

(ii) A graphical presentation of the modulation transfer function for the same image processing and display

mode as that used in the statement of the noise.

(iii) A statement of the nominal tomographic section thickness(es).

(iv) A graphical presentation of the sensitivity profile, at the location corresponding to the center location of the

dosimetry phantom, for each selectable nominal tomographic section thickness for which the dose profile is
given according to paragraph (c)(2)(iv) of this section.

(v) A description of the phantom or device and test protocol or procedure used to determine the specifications

and a statement of the maximum deviation from the specifications provided in accordance with paragraphs
(c)(3)(i),(ii),(iii), and (iv) of this section. Deviation of actual values may not exceed these limits.

D. Quality Assurance

The manufacturer of any CT x-ray system shall provide the following with each system. All information required by
this subsection shall be provided in a separate section of the user's instructional manual.

1) A phantom(s) capable of providing an indication of contrast scale, noise, nominal tomographic section

thickness, the spatial resolution capability of the system for low and high contrast objects, and measuring the
mean CT number of water or a reference material.

2) Instructions on the use of the phantom(s) including a schedule of testing appropriate for the system, allowable

variations for the indicated parameters, and a method to store as records, quality assurance data.

3) Representative images obtained with the phantom(s) using the same processing mode and CT conditions of

operation as in paragraph (c)(3) of this section for a properly functioning system of the same model. The
representative images shall be of two forms as follows:

(i) Photographic copies of the images obtained from the image display device

(ii) Images stored in digital form on a storage medium compatible with the CT x-ray system. The CT x-ray

system shall be provided with the means to display these images on the image display device.

E. [Reserved]
F. Control and Indication of Conditions of Operation

1) The CT conditions of operation to be used during a scan or a scan sequence shall be indicated prior to

initiation of a scan or a scan sequence. On equipment having all or some of these conditions of operation at
fixed values, this requirement may be met by permanent markings. Indication of the CT conditions of
operation shall be visible from any position from which scan initiation is possible.

2) Timers, (i) Means shall be provided to terminate the x-ray exposure automatically by either de-energizing the

x-ray source or shuttering the x-ray beam in the event of equipment failure affecting data collection. Such
termination shall occur within an interval that limits the total scan time to no more than 110 percent of its
preset value through the use of either a backup timer or devices which monitor equipment function. A visible
signal shall indicate when the x-ray exposure has been terminated through these means and manual resetting
of the CT conditions of operation shall be required prior to the initiation of another scan.

(ii) Means shall be provided so that the operator can terminate the x-ray exposure at any time during a scan,

or series of scans under x-ray system control, of greater than one-half second duration. Termination of the

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x-ray exposure shall necessitate resetting of the CT conditions of operation prior to the initiation of
another scan.

G. Tomographic Plane Indication and Alignment

1) For any single tomogram system, means shall be provided to permit visual determination of the tomographic

plane or a reference plane offset from the tomographic plane.

2) For any multiple tomogram system, means shall be provided to permit visual determination of the location of

a reference plane. The relationship of the reference plane to the planes of the tomograms shall be provided to
the user in addition to other information provided according to §1020.30(h). This reference plane can be offset
from the location of the tomographic planes.

3) The distance between the indicated location of the tomographic plane or reference plane and its actual

location may not exceed 5 millimeters.

4) For any offset alignment system, the manufacturer shall provide specific instructions with respect to the use of

this system for patient positioning, in addition to other information provided according to §1020.30(h).

5) If a mechanism using a light source is used to satisfy the requirements of paragraphs (g) (1) and (2) of this

section, the light source shall allow visual determination of the location of the tomographic plane or reference
plane under ambient light conditions of up to 500 lux.

H. Beam-On and Shutter Status Indicators

1) Means shall be provided on the control and on or near the housing of the scanning mechanism to provide

visual indication when and only when x rays are produced and, if applicable, whether the shutter is open or
closed. If the x-ray production period is less than one-half second, the indication of x-ray production shall be
actuated for one-half second. Indicators at or near the housing of the scanning mechanism shall be discernible
from any point external to the patient opening where insertion of any part of the human body into the
primary beam is possible.

2) For systems that allow high voltage to be applied to the x-ray tube continuously and that control the emission

of x rays with a shutter, the radiation emitted may not exceed 100 milliroentgens (2.58 x 10
coulomb/kilogram) in 1 hour at any point 5 centimeters outside the external surface of the housing of the
scanning mechanism when the shutter is closed. Compliance shall be determined by measurements averaged
over an area of 100 square centimeters with no linear dimensions greater than 20 centimeters.

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I. Scan Increment Accuracy

The deviation of indicated scan increment from actual scan increment may not exceed 1 millimeter. Compliance shall
be measured as follows: The determination of the deviation of indicated versus actual scan increment shall be based
on measurements taken with a mass 100 kilograms or less, on the patient support device. The patient support device
shall be incremented from a typical starting position to the maximum incrementation distance or 30 centimeters,
whichever is less, and then returned to the starting position. Measurement of actual versus indicated scan increment
may be taken anywhere along this travel.

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§1020.33 Computed Tomography (CT) Equipment

J. CT Number Mean and Standard Deviation

1) A method shall be provided to calculate the mean and standard deviation of CT numbers for an array of

picture elements about any location in the image. The number of elements in this array shall be under user
control.

2) The manufacturer shall provide specific instructions concerning the use of the method provided for

calculation of CT number mean and standard deviation in addition to other information provided according to

§ 1020.30(h).

(

The information collection requirements in paragraphs (c), (d), (g), and (j) were approved by the Office of
Management and Budget under control number 0910-0025)
[49 FR 34712, Aug. 31, 1984; 49 37381, Sept. 24, 1984, as amended at 49 FR 47388, Dec. 4, 1984; 56 FR 36098. Aug.
1,1991]

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Fluke Biomedical

Radiation Management Services

6045 Cochran Road
Cleveland, Ohio 44139

440.498.2564

www.flukebiomedical.com/rms