WO2010089693A1 - An alignment device for dental cone beam computed tomography - Google Patents

An alignment device for dental cone beam computed tomography Download PDF

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Publication number
WO2010089693A1
WO2010089693A1 PCT/IB2010/050431 IB2010050431W WO2010089693A1 WO 2010089693 A1 WO2010089693 A1 WO 2010089693A1 IB 2010050431 W IB2010050431 W IB 2010050431W WO 2010089693 A1 WO2010089693 A1 WO 2010089693A1
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WO
WIPO (PCT)
Prior art keywords
alignment
cbct
fov
previous
alignment device
Prior art date
Application number
PCT/IB2010/050431
Other languages
French (fr)
Inventor
Andrew Dawood
Shanon Patel
Veronique Sauret-Jackson
Original Assignee
Cavendish Imaging
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cavendish Imaging filed Critical Cavendish Imaging
Publication of WO2010089693A1 publication Critical patent/WO2010089693A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/04—Positioning of patients; Tiltable beds or the like
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/08—Auxiliary means for directing the radiation beam to a particular spot, e.g. using light beams
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/50—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications
    • A61B6/51—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications for dentistry
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/50—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications
    • A61B6/51—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications for dentistry
    • A61B6/512—Intraoral means
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C19/00—Dental auxiliary appliances

Definitions

  • CBCT Dental cone beam computed tomography
  • CBVT cone beam volumetric tomography
  • CBCT scanners have the x-ray detector/sensor positioned opposite the x-ray source to collect the map of x-ray absorption through the head of the patient.
  • the central axis of the patient's anatomical volume of interest determines the position of the x-ray source and sensor: the axis of rotation of source and sensor needs to correspond to the central axis of the volume of data.
  • image data is produced by reconstruction software to create a data set for a given volume.
  • the volume reconstructed is called the field of view (FOV).
  • FOV field of view
  • the quality of the image data is at its best towards the centre of the FOV.
  • Contemporary CBCT scanners are available with a variety of FOVs ranging from small, e.g. 4cm diameter by 4cm height, to large, e.g. 17cm diameter by 23cm height.
  • the patient is aligned in the scanner, which may require the patient to stand, sit or lie such that their head is positioned between source and sensor.
  • the position of the patient in the scanner is then adjusted so that the desired structures lie within the boundaries of the selected field of view. This is achieved by moving the patient's head in the FOV or moving the FOV over the patient's region of interest.
  • the FOV and the patient's region of interest are typically aligned with the aid of e.g. laser alignment beam projecting an illuminated line onto the patient's face.
  • laser alignment beam projecting an illuminated line onto the patient's face.
  • two or three intersecting laser "lines” which represent the visible projection of a 2d projection of a plane onto the patient's face, which typically run in X Y and Z alignment.
  • the central axis or the centre of the volume is defined by the intersection of these lines, but alternative alignments may be sometimes required, depending upon the precise alignment and set-up of the system.
  • the FOV and patient's position may be confirmed or improved with "scout" view exposures.
  • the "scout" views are lateral or anterior-posterior plain x-ray projections on to the sensor that allow the operator to check that the region of interest actually lies within the boundaries of the chosen FOV.
  • Radiation exposure to the patient may be reduced by reducing the size of the FOV, as less radiation is needed to acquire high quality image data for a smaller FOV.
  • it is easier to ensure that data for a particular Region Of Interest (ROI) is acquired using a larger FOV, but this clearly results in increased radiation exposure.
  • ROI Region Of Interest
  • the difficulty with imaging a small ROI with a small FOV, of size optimised for that of the ROI, is overcome if it is possible to easily centre the FOV over the central axis of the ROI.
  • This invention provides for an aiming device for cone beam CT scanners capable of imaging the teeth and jaws, which will facilitate the centering of the FOV over the central axis of the ROI and will also indicate the optimum FOV size to use.
  • Using the invention in a clinical CBCT examination will thus allow the main structures of interest within the ROI to be centred within the FOV and will allow the operator to ensure that the FOV is just large enough to include the entire ROI, without extending beyond it. This will result in improved accuracy, higher definition of the desired structures and a lower radiation dose to the patient.
  • the invention will speed up the alignment process and eliminate the need for 'scout' radiographs and the resulting additional X-ray dose, even if small.
  • a site marker (1) which is intended to be positioned over the main point of interest (POI), in the centre of the region of interest (ROI) which is intended to lie within the selected FOV.
  • each arm is a rectangular target piece (4) upon which are marked lines or other markings intended for alignment purposes.
  • vertical grooves and horizontal grooves (5) are provided on the target pieces such that planes projected perpendicular to the vertical grooves, as may be visualised on grooved perpendicular extensions from the target pieces (6), intersect at a right angle to each other such that the line of intersection is coincident with the axis of a cylinder centred on the target piece.
  • a horizontal groove (7) may also be scored upon the target pieces, such that a plane projected from the groove or marking, perpendicular to the plane of the target piece intersects at a point along the afor mentioned axis, in this case marking the centre/middle of the vertical axis of the cylindrical FOV.
  • a FOV marking (9) describes the diameter of the FOV, centred on the target piece, enabling the ideal positioning of the FOV over the ROI and also allowing the size of the FOV to be selected to match that of the ROI.
  • FIG 4 the device is illustrated in position for a small FOV examination of the molar and premolar regions as depicted by the shaded cylinder (8).
  • an arch shape (1) with a right angled projecting arm (3) supports anterior and side targets (4). Grooves on the targets (5) and perpendicular extensions (6) orientate the FOV to enclose the ROI, such that when the patient bites upon the arch shape placed over the jaw in between the teeth (if present), the centre of the FOV and the ROI are in optimal alignment.
  • the axis (10) of the FOV is marked with a cross.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Medical Informatics (AREA)
  • Engineering & Computer Science (AREA)
  • Animal Behavior & Ethology (AREA)
  • Veterinary Medicine (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Radiology & Medical Imaging (AREA)
  • Optics & Photonics (AREA)
  • Surgery (AREA)
  • Biophysics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Molecular Biology (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Physics & Mathematics (AREA)
  • Pathology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Biomedical Technology (AREA)
  • Oral & Maxillofacial Surgery (AREA)
  • Dentistry (AREA)
  • Epidemiology (AREA)
  • Apparatus For Radiation Diagnosis (AREA)

Abstract

A practical external alignment device to optimize the positioning of a patient, and assist in the selection of the most appropriate size of the scanned field of view (FOV) in dental Cone Beam Computed Tomography (CBCT). The device may be used to optimize the patient exposure, and to train the radiographer. This device is fitted in the patient's mouth during scout and CBCT exposures. The device incorporates targets (4), (6), and markings (5), (7), for guiding the positioning of the patient, by alignment with the scanner laser line indicators. With the device in position, markings (9) represent the extent of the FOV and the axis of the FOV.

Description

An Alignment Device for Dental Cone Beam Computed Tomography
Dental cone beam computed tomography (CBCT), also called cone beam volumetric tomography (CBVT), uses a single sweep of a conical x-ray beam around the patient's head to acquire a volume of anatomical data, e.g. a patient's jaws or part thereof.
Similarly to single or multi-slice CT scanner, CBCT scanners have the x-ray detector/sensor positioned opposite the x-ray source to collect the map of x-ray absorption through the head of the patient. In CBCT, the central axis of the patient's anatomical volume of interest determines the position of the x-ray source and sensor: the axis of rotation of source and sensor needs to correspond to the central axis of the volume of data.
In general terms, image data is produced by reconstruction software to create a data set for a given volume. The volume reconstructed is called the field of view (FOV). Typically the quality of the image data is at its best towards the centre of the FOV.
Contemporary CBCT scanners are available with a variety of FOVs ranging from small, e.g. 4cm diameter by 4cm height, to large, e.g. 17cm diameter by 23cm height.
In standard usage the patient is aligned in the scanner, which may require the patient to stand, sit or lie such that their head is positioned between source and sensor. The position of the patient in the scanner is then adjusted so that the desired structures lie within the boundaries of the selected field of view. This is achieved by moving the patient's head in the FOV or moving the FOV over the patient's region of interest.
The FOV and the patient's region of interest are typically aligned with the aid of e.g. laser alignment beam projecting an illuminated line onto the patient's face. Where only laser beams are used to align the patient there are usually provided two or three intersecting laser "lines" which represent the visible projection of a 2d projection of a plane onto the patient's face, which typically run in X Y and Z alignment. Typically the central axis or the centre of the volume is defined by the intersection of these lines, but alternative alignments may be sometimes required, depending upon the precise alignment and set-up of the system. The FOV and patient's position may be confirmed or improved with "scout" view exposures. The "scout" views are lateral or anterior-posterior plain x-ray projections on to the sensor that allow the operator to check that the region of interest actually lies within the boundaries of the chosen FOV.
Radiation exposure to the patient may be reduced by reducing the size of the FOV, as less radiation is needed to acquire high quality image data for a smaller FOV. In practice, it is easier to ensure that data for a particular Region Of Interest (ROI) is acquired using a larger FOV, but this clearly results in increased radiation exposure. The difficulty with imaging a small ROI with a small FOV, of size optimised for that of the ROI, is overcome if it is possible to easily centre the FOV over the central axis of the ROI.
This invention provides for an aiming device for cone beam CT scanners capable of imaging the teeth and jaws, which will facilitate the centering of the FOV over the central axis of the ROI and will also indicate the optimum FOV size to use. Using the invention in a clinical CBCT examination will thus allow the main structures of interest within the ROI to be centred within the FOV and will allow the operator to ensure that the FOV is just large enough to include the entire ROI, without extending beyond it. This will result in improved accuracy, higher definition of the desired structures and a lower radiation dose to the patient. The invention will speed up the alignment process and eliminate the need for 'scout' radiographs and the resulting additional X-ray dose, even if small.
A specific embodiment of the device will now be described with reference to figures 1-4.
In this embodiment there is provided a site marker (1) which is intended to be positioned over the main point of interest (POI), in the centre of the region of interest (ROI) which is intended to lie within the selected FOV.
Projecting from this site marker is an 'h' - shaped extension having a straight projecting arm (2) and a right-angled projecting arm (3).
Affixed to each arm is a rectangular target piece (4) upon which are marked lines or other markings intended for alignment purposes. In this embodiment vertical grooves and horizontal grooves (5) are provided on the target pieces such that planes projected perpendicular to the vertical grooves, as may be visualised on grooved perpendicular extensions from the target pieces (6), intersect at a right angle to each other such that the line of intersection is coincident with the axis of a cylinder centred on the target piece.
A horizontal groove (7) may also be scored upon the target pieces, such that a plane projected from the groove or marking, perpendicular to the plane of the target piece intersects at a point along the afor mentioned axis, in this case marking the centre/middle of the vertical axis of the cylindrical FOV.
A FOV marking (9) describes the diameter of the FOV, centred on the target piece, enabling the ideal positioning of the FOV over the ROI and also allowing the size of the FOV to be selected to match that of the ROI.
In this way laser alignment lines projected onto the target pieces with the said lines aligned with the orthogonal vertical and horizontal grooves will position the central axis of the cylindrical FOV directly over through the site marker.
In this embodiment there is a plane of symmetry through the "h" shaped arm, such that the device may be used interchangeably up- side down or down- side up depending upon whether the left or right side of the jaw is being imaged.
In figure 4 the device is illustrated in position for a small FOV examination of the molar and premolar regions as depicted by the shaded cylinder (8).
Other embodiments:
Imaging of anterior regions. As depicted in figure 5.
In this case there would be no necessity for the straight projecting arm described above because the small target may be replaced by an arch form (1) which the patient may bite upon. Right angled extensions (3) carry target pieces (4) having multiple grooves (5) to allow the FOV to be aligned with different ROIs, Large FOV Imaging. As depicted in figure 6.
For larger FOV scanners, an arch shape (1) with a right angled projecting arm (3) supports anterior and side targets (4). Grooves on the targets (5) and perpendicular extensions (6) orientate the FOV to enclose the ROI, such that when the patient bites upon the arch shape placed over the jaw in between the teeth (if present), the centre of the FOV and the ROI are in optimal alignment. In Figure 6, the axis (10) of the FOV is marked with a cross.

Claims

Claims
1. A physical aiming device for aligning dental CBCT which is seated in the mouth or between the teeth or between the dental arches during exposure.
2. An alignment device for dental CBCT having marked targets for alignment using laser lines projected from the CBCT scanner.
3. A physical CBCT aiming device having alignment markings to align with the projected laser alignment beam of the CBCT scanner which facilitate positioning of the patient's volume of interest within the Field Of View (FOV) of the CBCT scanner.
4. An alignment device as described in previous claims with an intraoral element which indicates the desired optimum rotational axis of the CBCT scanner and extra oral targets for alignment of the CBCT scanner.
5. An alignment device for dental CBCT having alignment markings on targets which extend extra- orally from an intraoral portion, and the said intra- oral portion may incorporate a site marker to indicate the centre and the central axis of the FOV.
6. An alignment device for dental CBCT having alignment markings on targets which extend extra- orally from an intraoral portion, and the position of the target allows the central axis of the FOV to be deduced, so that the region of interest may be correctly positioned within the FOV.
7. An alignment device for dental CBCT having alignment markings on targets which extend extra- orally from an intraoral portion, and the said targets incorporate a horizontal projection to allow the projected plane of the laser alignment system of the scanner to be perpendicularly aligned with the targets.
8. An alignment device as described in the previous claims accepting that it is configured for CBCT alignment in situations where off-axis geometrical reconstruction is utilised.
9. An alignment device as described in previous claims accepting that it is configured for CBCT alignment in situations where laser alignment beams are configured in non-standard configurations
10. An alignment device as described in previous claims with markings which indicates the distance from the centre of the ROI, such that the FOV can be set to enclose the region of interest.
11. A device as described in previous claims in which calibrated markings on intra- or extra- oral elements of the device allow the operator to set a FOV on the CBCT scanner which will allow incorporation of the ROI.
12. A CBCT alignment device as described in previous claims where said intraoral part incorporates a scatter- reducing device to limit scatter from directly irradiated structures to regions above or below the FOV.
13. An alignment device as described in previous claims in which extraoral extensions from an intraoral element may be disconnected and reconnected to the intraoral element depending upon the precise position of the ROI.
14. An alignment device as described in the previous claim in which the intraoral element is made of material that reduces scatter as described in previous claims.
15. An alignment device for dental CBCT substantially as described in the accompanying description and illustrations and figures.
PCT/IB2010/050431 2009-02-05 2010-02-01 An alignment device for dental cone beam computed tomography WO2010089693A1 (en)

Applications Claiming Priority (2)

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GB0901873.0 2009-02-05
GB0901873A GB2467556A (en) 2009-02-05 2009-02-05 An alignment device for dental cone beam computed tomography

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015038986A1 (en) * 2013-09-13 2015-03-19 Baek Seung H Dental x-ray imaging system having higher spatial resolution
CN107080554A (en) * 2017-05-17 2017-08-22 杭州口腔医院有限公司 Remporomandibular joint measuring method, bite plate preparation method
US9980789B2 (en) 2014-12-05 2018-05-29 Convergent Dental, Inc. System and methods for alignment of a laser beam

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US3609358A (en) * 1970-04-09 1971-09-28 Benedict J Salesi Hand held x-ray guide
US5652779A (en) * 1995-09-01 1997-07-29 Paul Levy Film positioning system for dental X-ray procedures
EP0904733A1 (en) * 1997-09-27 1999-03-31 Kantonsspital Basel A method and apparatus for recording a three-dimensional image of a body part
US5947981A (en) * 1995-01-31 1999-09-07 Cosman; Eric R. Head and neck localizer
DE19908903A1 (en) * 1999-03-02 2000-09-14 Deutsches Krebsforsch Localization unit for imaging and positioning devices
US6178229B1 (en) * 1998-11-16 2001-01-23 Shen-Po Ko Mouth held plate for use in tomograph
US6424694B1 (en) * 1999-10-08 2002-07-23 Dentsply Research & Development Corp. Positioning apparatus and method for transversal dental x-ray tomography
WO2004000097A2 (en) * 2002-06-19 2003-12-31 University Of Florida Interactive patient positioning system
WO2004075716A2 (en) * 1994-06-20 2004-09-10 Sherwood Services Ag A stereotactic localizer system with dental impression

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US5921927A (en) * 1997-11-12 1999-07-13 Axialtome Australia Pty. Ltd. Positioning method and apparatus for X-ray tomography
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2392109A (en) * 1943-04-26 1946-01-01 Vlock Mark X-ray film packet holder and angle indicator
US3609358A (en) * 1970-04-09 1971-09-28 Benedict J Salesi Hand held x-ray guide
WO2004075716A2 (en) * 1994-06-20 2004-09-10 Sherwood Services Ag A stereotactic localizer system with dental impression
US5947981A (en) * 1995-01-31 1999-09-07 Cosman; Eric R. Head and neck localizer
US5652779A (en) * 1995-09-01 1997-07-29 Paul Levy Film positioning system for dental X-ray procedures
EP0904733A1 (en) * 1997-09-27 1999-03-31 Kantonsspital Basel A method and apparatus for recording a three-dimensional image of a body part
US6178229B1 (en) * 1998-11-16 2001-01-23 Shen-Po Ko Mouth held plate for use in tomograph
DE19908903A1 (en) * 1999-03-02 2000-09-14 Deutsches Krebsforsch Localization unit for imaging and positioning devices
US6424694B1 (en) * 1999-10-08 2002-07-23 Dentsply Research & Development Corp. Positioning apparatus and method for transversal dental x-ray tomography
WO2004000097A2 (en) * 2002-06-19 2003-12-31 University Of Florida Interactive patient positioning system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015038986A1 (en) * 2013-09-13 2015-03-19 Baek Seung H Dental x-ray imaging system having higher spatial resolution
US9980789B2 (en) 2014-12-05 2018-05-29 Convergent Dental, Inc. System and methods for alignment of a laser beam
US10470843B2 (en) 2014-12-05 2019-11-12 Convergent Dental, Inc. Systems and methods for alignment of a laser beam
CN107080554A (en) * 2017-05-17 2017-08-22 杭州口腔医院有限公司 Remporomandibular joint measuring method, bite plate preparation method
CN107080554B (en) * 2017-05-17 2020-06-02 杭州口腔医院集团有限公司 Temporomandibular joint measuring method and dental lamina preparation method

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GB0901873D0 (en) 2009-03-11
GB2467556A (en) 2010-08-11

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