standard operating procedure for dexa whole … · standard operating procedure for dexa whole body...

Version: 3 Effective date: 26.07.2017

Standard Operating Procedure for DEXA whole body scanner

Effective date: 26.07.2017

Review due date: 20.04.2019

Original Author

Name: Rebecca Travers Position: RA

Date: 14.12.2012

Reviewer

Name: Pippa Heath

Position: Physiology Technician

Signature:

Date: 21.04.2017

Approved by

Name: Dr Lisa Austin

Position: DfH Research Manager

Signature:

Date: 26.07.2017

Amendment Chronology Version number

Effective date

Reason for amendment Reviewed/Amended by

1 14.12.2012 First issue Rebecca Travers

2 27.07.2016 Some slight amendments regarding the location of the scanner, updated legal requirements of data recording, and updated info about archiving and backing up.

Emily Wood

3 26.07.2017

Minor amendments: updated RA link, changed Quartzy to LabAgenda, added X drive link for Local Rules and removed computer password.

Pippa Heath


DEXA whole body scanner

Using DEXA Scanner for assessment of body composition and bone mineral content

Safety Information:

IMPORTANT: Only those who have completed the required Ionising Radiation (Medical Exposure) Regulations and in-house training for this procedure and who have read and understood the risk assessment may perform this procedure. It is also very important to have read the Local Rules documentation too, which can be found next to the DEXA computer, in the DEXA manual in the folder in DASH office and on the X drive in the folder: X:\Health\Resources\Health and Safety\Emergency Procedures & Safety Manuals.

Investigators using this technique must have read the following risk assessment:

o 2013.1023RA_DEXA_scan To be done prior to beginning the scan:

In order to perform a scan make sure the following has been done:

You have completed the Ionising Radiation Worker registration form (see Appendix I) and register your name with the University Radiation Protection Officer and Departmental Radiation Protection Supervisor, once you have done the required IR (ME) R training. Courses can be found at www.sghrpc.co.uk, or through Vertec Scientific ([email protected]).

Ethics approval has been acquired and informed consent has been signed.

Any issues relating to research population has been addressed eg. Is there a risk of pregnancy?

DEXA room has been booked. This is done through LabAgenda (the online lab management software used by the Department for Health), which all users should have access too – if there are any issues with access please see the Physiology Lab Technicians. Click on the ‘Bookings’ option under “Schedule”, then select ‘DASH lab’ from the groups, and you should see the ‘Scanning room DASH’ as an option. To make a booking, select the appropriate date and time slot (standard slot for 1 scan is 30 min), and enter your name and any other relevant details – as we have another scanner in this room (pQCT), please ensure you specify that you will be using the DEXA scanner.

Participant will be wearing the same clothes if doing a repeat scan.

Participant needs to void before scan and weighing.

You have recorded the participant’s height and mass. Mass should be done immediately prior to scan so there will need to be scales in the DEXA room. Record mass in the log book, alongside the date, your initials as operator and whether the QC passed (see Appendix II for copy of log book).

You may want to standardise diet and hydration status. This will be study specific but generally subjects should be fasted and have drunk a predetermined volume of water at least 1 hour prior to scan.

Participant is NOT: wearing any metal, this includes watches, earrings, necklace, rings and bracelets. Female participants are not wearing underwired bras.


On entry to the room:

Clear the space around the bed, removing any equipment that surrounds the table. Remember that the table moves so make sure everything is out of the way.

Turn on the computer and Log in on QDR-82228.

Put ‘DEXA Scan in Progress’ sign on the door.

Please note that power cuts have been experienced in the DASH lab which have affected the DEXA. If the scanner doesn’t seem to be turning on, please check the fuse box located in the main DASH lab room. Also double check the AC switch on the DEXA scanner (located in on the back of the left pedestal) is on. The green light should be on, with the switch in the on position. If the fuse has gone, this may have tripped this switch. The engineer has recommended that we flick the AC switch back to ‘on’ before the flicking the fuse switch back.

You are now ready to start. The Hologic QDR software should load automatically – if not, you can open it by clicking on the icon on the desktop. Perform a Daily QC Scan

Click on ‘Daily QC’

Check the position of the purple bed cover as this can move as people get on and off the bed. At the top of the table make sure the black line is in line with the screw.


The DEXA arm will project a red laser cross on the bed. Get the Spine Phantom (located under the computer) and line the block up with the spine parallel to the long axis of the bed. Line up the red laser cross hairs with the small white circle on the phantom. Cross hairs should be towards the feet end of the table.

Check the laser runs straight through to the small dot at the end of the block. Make sure this is placed as accurately as possible.

Click ‘Continue’ on the screen. The machine should start scanning.

Upon completion the message ‘Daily QC has passed’ appears. If it doesn’t pass a scan cannot be performed but this is extremely rare.

Briefly look at the plot to check the graph. Click ‘Plot’ then BMC. The dot should be within the 2 lines. (it won’t pass without it being in the lines but it’s always worth checking)

Click ‘Close’ and put spine carefully back in its place.

Click ‘Continue’. If DEXA prompts to do an AirScan This is prompted for once a week. It is best practice to do it when prompted and will take an additional 7 minutes. There is no need to do it more than this.

Click ‘ok’ and the machine will run the scan.

Once finished it will give an SD value. Record both high and low values in the log book. The low value must be below 2. This number is recorded to identify any trends in the value and pre-empt a problem. If the number is only just below 2, so long as it hasn’t been steadily increasing over time, this is normal and the machine is ready to use.

Performing the scan on a participant.

Double check that the informed consent form has been signed. Double check participant ID.

If this is a repeat scan it is a good idea to get the previous scan up on the screen to check the position. o It is not possible to get the previous scan image up whilst performing the current scan as the

software only lets you do one thing at a time. One way to look at the previous scan whilst performing a scan is to do a Print Screen of the existing scan prior to going through the procedure for the new scan and pasting it into Word Pad. You can then look between the two software programmes as you set up for the current scan. (To access previous scan click ‘Analyse Scan’ from the main screen, tab to ‘analysed scans’ find patient in the list)

1. Participant Position:

After the participant has changed into appropriate clothing ask them to lie on the bed. Supine position is preferred, flat on the back with the head nearest the computer.

It is essential to get the position of the participant accurate as it will make the analysis a lot easier and more precise:

o First position the body so that the head is as close to the black marker at the head end of the table as possible.

o Align the body so that the head and spine line up exactly with the central long axis of the table. Use the black marker at the head of the mat to help.

o Ask the participant if they feel like their spine is straight. It is hard to judge exactly as it cannot be seen so it is always good to check by asking them.

o The legs should be apart and the feet turned in. o The arms should be as wide as possible. Ask the participant to bend at the elbow to allow for

maximum area between the arm and the torso. Lower arms should be straight and hands flat.


It is important here that there is sufficient room between the hand and the side of the body as you need a clear line for the analysis. It may help with larger participants to have the hands on the side. If you are concentrating on body composition rather than bone mineral density this positioning will be ok.

Once the participant is lying there they will have to remain in that position for approximately 10minutes and they must remain still.

If the participant is taller than length of the bed then position the person so that their feet are off the bottom rather than the head.

2. Performing the scan

On the computer click the icon ‘Perform Exam’ a list of scans appears.

If it is a first time scan click ‘New Patient’ and fill in the first name, surname, DOB, ethnicity, sex, operator (your initials), height and weight, leave the rest blank. Click OK. If this is a repeat scan, it will miss this step and go straight to the next step.

Your patient should be selected on the list. Click OK.

On the next screen fill in the participant’s height and weight as recorded from the scales that morning, put your initials in the operator box and leave accession number blank. Click OK.

On ‘Patient Confirmation’ select the type of scan that you want. It usually will be ‘Whole Body’.

Final check of participant. Click ‘Start’. Stand as far back as possible in the room.

The scan itself will take 7 minutes.

At the end of the scan, the prompt ‘Analyse scan’ will appear. Click it.

Now you have the 2 choices: ‘Analyse whole body scan’ or ‘Compare to previously analysed scans’.

If you aren’t going to analyse the scan straight away, please ensure you finish completing the log (Appendix II). This includes noting DEXA calculated mass, and Dose Area Product (DAP).


On the results screen, make sure ‘BCA’ is selected, and then record the DEXA calculated mass in the log book. Please put this in kg in the log.

Then when you close the scan, a window will appear giving the Dose Area Product (DAP). This is a measure of the standard radiation dose for the scan and should also be recorded in the log.


3. Analysing the scan

You can now perform the analysis either on the computer in the DASH scanning room or the computer in the 1West lab. If you will be taking the scan to use on the software in 1West, then please COPY the scan to your own external USB stick. It has been recommended that you use the copy function rather than archive/restore when transferring scans, as it is very important to still archive your scan twice (as normal) to the primary and secondary drives on the DEXA computer (see below, no. 8).

If you are coming at it without having performed the scan immediately prior to this then on the main page click the ‘analyse scan’ button at the bottom of the screen. Select the can you want, click ok and it will then take you through to the following;

On a First time scan

If you are doing a scan for the first time choose ‘Analyse whole body scan’

Make sure ‘Whole Body Fan Beam’ is selected in the white box. Click Next

A picture of the scan will now appear.

Repeat scan and you wish to compare to previous scan.

Choose the option ‘Compare to previously analysed scans’

A list of previous scans will appear. Select the previous scan. Click Next.

The 2 scans appear side by side.

You can use the previous scan to match region placement. NB. You cannot alter the regions on the previous scan, only the current scan. If you want to reposition the regions on the previous scan you have to come out of this analysis and go into the previous scan location (from the main screen click ‘Analyse scan’ tab to analysed scans find previous scan in list).

Analysis

In order to perform the analysis you may need to adjust the image display brightness by using the sun and moon contrast button on the bottom left. Click to use this function and change contrast by moving the black dot around. To come out of it, click the sun and moon again.

Define the regions using the Line Mode and Point Mode in the Regions toolbox on the left hand side.

View the results by clicking on the results box on the top right. It is possible to interchange between the results page and the regions page to allow for further modification of the lines.

It is best practice for the same person to analyse all the scans in a study. If this is not possible then at least the same person should analyse the pre and post scan of the same participant.

4. Location of the Regions

A detailed pictorial version of this can be found in the DEXA Manual in Chapter 11 in the DASH technician office or see the next few pages for diagrams.

In the Line Mode, click and drag the top line so that it is just under the mandible.

Click and drag the small horizontal line in the spine to the approximate level of T12-L1. If this is hard to see then change the contrast.

Click and drag the horizontal line above the pelvis just above the iliac crest.

Click and drag the vertical line on either side of the chest to bring each one close to the chest.

Click and drag the vertical line either side of the spine to bring each one close to the spine

Click and drag the vertical line on either side of the legs to bring each one close to the leg


Click and drag the bottom centre vertical line to separate the legs and feet.

To fine tune, change from Line Mode to Point Mode.

Click on the point on the left shoulder and drag so that it is positioned between the head of the humerus and scapula. Repeat for right side.

Click the left points along the spine, matching the curvature where possible. Repeat for right side.

If needed, click the left/right point above the iliac crest and drag it out to include the soft tissues of the chest and thighs.

Click and drag the lower point of the triangle below the pelvis. Depending on what you are analysing for will affect the position of this point:

o For body composition, make sure the point is as close to the pelvis as possible so that the upper thigh soft tissue is included in the leg region NOT in the trunk region; i.e. There should be no leg soft tissue in the triangle.

o For bone mineral density position the point so that is bisects the femoral necks.

Use the scroll bar to scroll the image to the bottom of the scan. Click and drag the points near the feet to include as much of the soft tissue in the legs and feet as possible without including the hands and fingers.

NB. If this is unavoidable, it is better to include some of the hand and fingers than to chop off the outer thigh soft tissue.


To fine tune using Point Mode


5. Viewing the results

To view the results click on the results button on the upper left hand side of the screen.

You will see a table on the right hand side with the figures. To get the body composition results click on the ‘BCA’ button of the left hand side.

If you are not happy with the results or your region placement you can return to the region screen by clicking ‘regions’ on the top left side of the screen.

Record the DEXA value for total mass in the log book. Check that the manual mass measurement and DEXA measured mass are within 1kg. If the values differ first check the mass on the scales, if they still differ perform either another scan or rearrange for another scan 24hrs later or another chosen time.

6. Schoeller Correction

It has been suggested that the particular model of DEXA used overestimates fat free mass (FFM).1

This was established by comparing results from 7 independent studies, with DEXA found to overestimate FFM by approximately 5%. In this correction the value for fat free mass is reduced with the discrepancy added to fat mass (FM). BMC remains unchanged.

This particular correction factor is employed by the company that manufacturers the scanner 2, and is built in to newer versions of their software.

It is up to each investigator to decide if this correction factor should be employed, with special note taken if comparing between data sets from different studies, as not all studies will have used the correction factor.

The calculations required are listed below. It should be noted that in the case of correcting results the original values from the DEXA scan are used to calculate the corrected values. Therefore even when the data is corrected the investigator should still have access to the “raw” values.

N.B. the correction factor is employed after obtaining the results from the scan; the method for completing the scan is exactly the same.

FFM (corrected) = 0.946 * FFM (measured)

FM (corrected) = DEXA weight – (FFM(corrected) + BMC)

Fat % = 100 (FM (corrected) / DEXA weight)

A worked example…

Person X original data

Weight 100kg, BMC 3.5kg, Fat free mass 80kg, Fat mass 16.5kg, Fat % 16.5

FFM (corrected) = 0.946 * 80kg

FFM (corrected) = 75.68kg

FM (corrected) = 100kg – (75.68kg + 3.5kg)

FM (corrected) = 20.82kg

Fat % = 100 (20.82 / 100)

Fat % = 20.82


Person X corrected data

Weight 100kg, BMC 3.5kg, Fat free mass 75.68kg, Fat Mass 20.82kg, Fat % 20.82

Original references

1 Schoeller, D.A., Tylavsky, F.A., Baer, D.J., Chumlea, W.C., Earthman, C.P., Fuerst, T., Harris, T.B., Heymsfield, S.B., Horlick, M., Lohman, T.G., Lukaski, H.C., Shepherd, J., Siervogel, R.M. and Borrud, L.G. (2005). QDR 4500A dual-energy x-ray absorptiometer underestimates fat mass in comparison with criterion methods in adults. American Journal of Clinical Nutrition, 81:1018-25. 2 Kelly, T.L., Wilson, K.E. and Heymsfield, S.B. (2009). Dual Energy X-Ray Absorptiometry Body Composition Reference Values from NHANES. PLoS one, 4 (9): e7038.

7. Printing the report

Exit the results screen by pressing ‘Close’

The Exit Analysis window appears. Click the ‘Report’ button. Follow the prompts, you can go straight to print or view the report first.

Click Exit and you will return to the main screen. It is a good idea to Archive your scan once you have analysed it.

8. Archiving your scan

It is very good practice and highly recommended from the Manufacturer that patient scans are archived daily. These can then be retrieved as and when necessary.

On the main screen click ‘Archive scan’ on the right side of the screen.


At the top of the screen in ‘Archive Location’ click on the drop down menu and select the F drive. This is the internal hard drive. There should be a folder for the appropriate year.

A list of scans appears underneath, you can either click ‘select all’ or select only the ones that you wish to archive (Ctrl + Click on scan)

Click ‘Archive Scans’

Upon completion it should say x out of x scans archived successfully OK.

Please remember to archive to 2 different locations so repeat the procedure. This time your scan will be under the ‘Archived Once’ tab. Select it again, and click Browse and on archive location change it to the G: Directory, the external hard drive. Again, select the folder for the appropriate year.

To restore an archived scan

On the grey toolbar on the main page choose ‘Archive’

Click Restore Scans.

A list of patients appears. Find your patient and select it.

Click Restore Scans.

You can select a few different ones using the CTRL function on keyboard.

To locate the restored file

On the main page go to ‘analyse scan’ along the bottom

Tab to ‘Analysed scans’

Your scan should now appear on the list

Select it and click ‘Next’

Choose your analysis method – it’ll usually be ‘Whole body’

You can compare this to a previous scan providing that scan is not in the Archive

9. Backing up the System


System backup is VERY important, and is the function used to periodically save all system files in case there is a system failure. It should be done AT LEAST once a week, or more frequently if the scanner is used more often. If it has been longer than one week since the last system backup, a message will appear on the main home page of the software, meaning the system is in need of backing up.

To carry out a system back up, click ‘System Backup’. A new screen will appear showing the destination for the backup. As with archiving, please backup to both the internal primary F drive, and then the external G secondary drive under the appropriate ‘System Backups’ folder in both locations.

We now have a third DEXA back up external hard drive which is set up to a scheduled Windows 7 backup weekly. This automatically backs up the primary F drive (including all archived scans and existing system backups), and a system image of the C drive for the DEXA computer. This third drive will be stored in the 6WS lab, and it is the responsibility of the technician to maintain a weekly backup. DO NOT perform a Windows 7 Backup during patient scanning as it can result in aborted scans.

For a hard copy please look in the Health and Safety folder in DASH lab or for any further information consult the User Manual and folder also located in DASH lab technician’s office.

Appendix I – Ionising Radiation Workers Registration Form


IONISING RADIATION

WORKERS REGISTRATION FORM 12/06

To work with sources of ionising radiation you are required to register with the University Radiation Protection Officer (URPO). To register, please complete this form on-screen, print it out, sign it and obtain the signatures of your work supervisor and RPS, then send it (via internal mail) or take it to the URPO (Debbie Robarts, UHS&E, Wessex House 3.14). For any questions regarding this form please email [email protected].

PLEASE COMPLETE ALL THE RELEVANT BOXED SECTIONS. To avoid delay in registering please read

the instructions carefully and complete the form as directed. This registration will only be valid for the ionising radiation source(s) listed and for the work or project given in Section 6. Users must apply to their RPS and URPO for additional sources or projects. No-one is permitted to work with ionising radiation sources until they have been registered with the URPO.

1. YOUR NAME AND PERSONAL DETAILS. Please complete all sections and give your full name and title. Some details are requested to further distinguish your registration from others. If you are issued with a personal radiation dose monitor then these details will be added to your exposure record.

Title (Mr/Miss/Mrs etc)

Post in University

First name(s) Your Date of Birth

Surname Gender (Male / Female)

Previous surname (if married)

National Insurance no.

2. YOUR UNIVERSITY CONTACT POINT.

School / Department Internal telephone no.

Building & Room Email address

3. YOUR EXTERNAL CONTACT POINT. This information is only needed in an emergency.

Home Address Telephone no.

Postcode

4. YOUR WORK/PROJECT SUPERVISOR. (They will need to sign section 11.)

Name of Supervisor Their internal telephone no.

Their Department Your Departmental RPS (If you’re not sure contact

[email protected])

5. LOCATION FOR YOUR IONISING RADIATION WORK. Only complete this section if your work with

ionising radiation will take place in a different location to your internal contact point (2 above).

Location supervisor Building & Room

Department Telephone

6. WORK DETAILS (for your ionising radiation project).

Project start date Expected project end date

What are the radiation sources (isotopes or power of X-rays) you will be working with?

Please give a brief description of the work to be undertaken (your RPS can help with this and supply the relevant set(s) of Local Rules). The URPO will contact you if additional details are required.

mailto:[email protected]



7. PREVIOUS EXPERIENCE OF WORK WITH IONISING RADIATION.

When? Radiation source(s)

(isotopes), and type of

work

Where?

8. PREVIOUS TRAINING ON THE USE OF IONISING RADIATION.

When? Subjects covered/

lecture or practical?

Where?

9. PREVIOUS OCCUPATIONAL EXPOSURE. Please complete this section if you have been

occupationally exposed to ionising radiation sources in the past, either at the University of Bath or elsewhere. (Occupational exposure does not include exposure for medical reasons.) The URPO will contact you if additional details are required

Occupational Exposure Record;

Approx. year Source of exposure Establishment Recorded exposure

Have you previously been registered for radiation work at the University of Bath (yes or

no)

If “yes”, approximate year of first registration

10. YOUR DECLARATION. Before submitting the form please check that you have completed all the relevant parts and that the information you have given is accurate.

The details given in this registration form are accurate, to the best of my knowledge. I understand that if I wish to undertake an additional project involving ionising radiation or if I wish to use additional sources of ionising radiation not listed on this registration form then I must inform the RPS and URPO.

Signature

Date

11. YOUR SUPERVISOR’S DECLARATION.

I confirm that appropriate instruction, training and supervision will be provided for the worker to ensure they are able to work safely with ionising radiation in the activity detailed in section 6 above. If this department cannot provide an identified training need I will contact the RPS.

Signature

Date

12. ACKNOWLEDGEMENT BY DEPARTMENTAL RPS.

I confirm that I have provided the worker with copies of the relevant Local Rules to enable them to work safely with Signature


ionising radiation outlined in section 6 above, and comply with any relevant permit.

Date

Thank you for completing this form. Please send it by internal post to the URPO (Debbie Robarts, UHS&E, Wessex House). You, your supervisor and your RPS, will be contacted by email either for more information or to authorise you to conduct work outlined in section 6. Do not start that work until authorisation is received.

For any questions regarding this form please email [email protected]..

ACKNOWLEDGEMENT BY URPO.

I confirm that I have registered the worker and provided them with copies of the relevant University Policy and guidance document(s) to support their work with ionising radiation outlined in section 6 above.

Signature

Date



Appendix II - DEXA Log Book

DEXA Log Book

Please fill out every time a scan is performed. This is for monitoring the machine’s technical operation and must be completed every time.

Date Operator QC

Pass

Air scan SD

high

Air scan SD Low

Mass on

scales

DEXA calculated

mass

Dose Area

Product (DAP)

Archived

End of Document

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