Title: CBCT Absorbed Radiation Dose in Pediatric Patients Authors: Ella Choi, DDS and Nancy Ford, PhD Objectives: To study the characteristics of the patients who received CBCT at British Columbia Children’s Hospital (BCCH), and to compare the absorbed radiation dose using adult and pediatric phantoms Methods: The patients under the age of 18 years who received iCAT CBCT scans at BCCH between 2010 and 2011 met the inclusion criteria. Their soft and hard tissue head dimensions were measured. The information on ethnicity, age, gender, co-morbidities, CBCT protocol, and indications for CBCT were obtained. A Sedendex DI adult head phantom and a custom-made pediatric head phantom were used with Radcal thimble ionization chamber (0.6 cm3) and AccuDose Dosimeter to measure the absorbed dose in different locations at the two most common protocols. The two most common protocols were at 60 mm and 130 mm field of view with kVp 120, mA 5, 0.4 voxel size, and exposure time of 4 seconds. Results: Thirty-two patients aged 5 to 17 at BCCH met the inclusion criteria. The most common indications for CBCT were for orthodontic treatment (39%), craniofacial abnormality (25%), and cleft lip and palate (19%). The soft and hard head dimensions varied depending on ethnic background and craniofacial abnormality. The absorbed radiation dose varied depending on the CBCT protocol and location. In the adult phantom, the absorbed dose ranged from 1.1 mGy at the surface to 1.5 mGy at the centre; in the pediatric phantom, it ranged from 1.7 mGy at the surface to 2.2 mGy at the centre. Conclusions: Children from a wide variety of ethnic and medical backgrounds received CBCT at BCCH. Higher absorbed radiation was measured in all locations in pediatric head phantom compared to the adult phantom. The highest measurement of absorbed radiation was at the edge of the phantom, the second highest at the centre, and the lowest at the surface. UBC Faculty of Dentistry Research Equipment Grant

Use  of  Cone  Beam  Computed  Tomography  in  the  Pediatric  Pa8ent  

   Ella  Choi,  D.D.S.  Graduate  Pediatric  Den.stry  

UBC,  Vancouver  

Nancy  Ford,  Ph.D.  Research  Supervisor  UBC,  Vancouver  

 

CT  scans  in  childhood  linked  to  increased  risk  of  cancer:  study  

 •  2  to  3  CT  scans  could  triple  the  risk  of  developing  brain  cancer  later  in  life  

•  5  to  10  such  scans  could  triple  their  risk  of  leukemia  

June  6,  2012  

Global  Annual  Effec.ve  Dose  Source    Annual  Effec8ve  Dose  (mSv)  

Natural  Background   2.4  

Diagnos.c  medical  radiology   0.62  

Diagnos.c  dental  radiology   0.0018  

Nuclear  medicine   0.031  

Fallout     0.005  

Total   3.1  

UNSCEAR  2008  

Increasing  number  of  elec8ve  CBCT  imaging    

Decreasing  radia.on  dose  

Cumula8ve  effect  lasts  for  a  life  8me  

 The  length  of  life  aJer  radia8on  is  longer  

 Higher  cancer  risk  per  radia8on  received  

 

Children  are  more  affected  by  radia8on  

Research  Ques8ons  

Ø Who  receives  CBCT  at  BC  Children’s  Hospital?  

Ø What  is  the  amount  of  radia.on  from  CBCT?  

Research  Ques8ons  

Ø Who  receives  CBCT  at  BC  Children’s  Hospital?  

Ø What  is  the  amount  of  radia.on  from  CBCT?  

•  Retrospec.ve  Study:  2010  and  2011      •  Ethics  approved  •  Inclusion  criteria  

– Under  the  age  of  18  – CBCT  

                       

Pa8ents  who  received  CBCT  

32  pa.ents  met  the  inclusion  criteria  •  16  boys  and  16  girls  •  Aged  5  to  17  years  

Craniofacial  Abnormality    

25%  

CleZ  Palate  19%  

Orthodon.c  Pa.ents  39%  

Oral  Pathology  7%  

Pre-­‐surgical  Assessment  

10%  

CBCT  Pa8ents  at  BC  Children's  Hospital  

Total  of  32  pediatric  pa.ents    

Ethnic  Background  

European:  8  East  and  South  East  Asian:  9  East  Indian:  1  Aboriginal:  3  Unknown:  11  

6  Pa8ents  had  Previous  Radia8on  Exposure  

•  5  pa.ents  with  history  of  CT  scan  •  1  pa.ent  with  history  of  radiotherapy  of  pituitary  gland  

These  pa8ents  are  at  more  risk  because  radia8on  is  cumula8ve  for  a  life  8me  

Common  CBCT  Se_ng  Fixed:    •  kVp  120  •  mA  5      

Variable:    •  FOV:  60  mm  and  130  mm  •  Resolu.on  (voxel  size):  0.4mm    •  Exposure  .me:  4  seconds  

Measurements  

     Skeletal            

SoJ  Tissue  

A  wide  range  of  head  dimensions  •  Healthy  •  Different  ethnic  background  •  Craniofacial  abnormality  

Movingforward.com  

Research  Ques8ons  

Ø Who  receives  CBCT  at  BC  Children’s  Hospital?  

Ø What  is  the  amount  of  radia.on  from  CBCT?  

Dosimetry  Phantom  Study  

Adult  Phantom        Adolescent  Phantom  Average  12  year  old  “orthodon.c”  pa.ent  

 Child  Phantom  Average  4  year  old    

•  120  kVp,  5mA,  16cm  diameter,  0.4  voxel,  4s  exposure  .me  

1.1    1.3              1.1      1.7    1.9          1.8  1.3      1.6          1.5  

Average  Absorbed  Radia8on  in  mGy  FOV  60  mm  

Average  Absorbed  Radia8on  in  mGy  FOV  130  mm  

•  120  kVp,  5mA,  16cm  diameter,  0.4  voxel,  4s  exposure  .me  

1.2    1.5                1.4       1.5    1.9              1.9   1.9    2.1            2.2  

Conclusion  1.  Children  from  a  wide  variety  of  ethnic  and  

medical  backgrounds  receive  CBCT  at  BC  Children’s  Hospital    

2.  Pediatric  phantom  absorbed  more  radia.on  than  adult  phantom  in  all  loca.ons  

3.  Highest  absorbed  radia.on  is  at  the  edge  of  the  phantom,  second  highest  in  the  centre,  and  the  lowest  on  the  surface.    

What  can  you  do?  •  Lowest  possible  dose  se_ng  •  Posi.oning  +  Shielding  •  Buy  CBCTs  that  allows  you  to  customize  •  Familiarize  and  Develop  guidelines  •  More  research  •  Request  informa.on  from  manufacturers  

Thank  you!  •  Dr.  Nancy  Ford,  Research  Supervisor  •  Research  Commikee:  Dr.  Rosamund  Harrison  and  Dr.  David  MacDonald  

•  Dr.  Robin  Coope  at  BC  Cancer  Agency  for  fabrica.ng  the  pediatric  phantom  

•  Pierre  Deman  •  Funding  from  Faculty  of  Den.stry  Research  Equipment  Grant  

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•  UNSCEAR  2008  Report:  Sources  and  effects  of  ionizing  radia.on  •  Movingforward.com  •  Absorp.on  in  medium  •  Ludlow  JB,  Davies-­‐Ludlow  LE,  Brooks  SL.  Dosimetry  of  two  extraoral  direct  digital  imaging  

devices:  NewTom  cone  beam  CT  and  Orthophos  Plus  DS  panoramic  unit.  Dentomaxillofac  Radiol  2003:  32:  229–234.    

•  Imagewisely.org  •  Imagegently.org