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Patient exposure record


One key to compliance with IR(ME)R is to ensure that you have recorded all the essential data from a patient episode. This downloadable patient record form  prompts you to enter the data, ensure that the patient checks his/her name and pregnancy status, pass the x-ray request to the operator, and record your findings. The patient data panel should fit into most i.d. cameras, to ensure that this data is transferred to each film.

 



Radiographic exposure factors - a universal chart


click here to go to a printable version

Using the exposure factor chart

 

1. Measure the thickness of the part to be radiographed

 

2. Find the nearest thickness in the appropriate column of the Patient Points table

 

                                Use the first column for all AP and PA views and all cervical views

 

                                Use the second column for lateral lumbar and pelvic views

 

                                Use the third column for lateral thoracic views

 

3. Read off the corresponding "Points" value.  Add 1 - 2 points for muscular patients. Subtract 1 - 2 points for adiposity or osteopaenia.

 

4. Add the System Correction (see "Calibration" below)

 

5. Choose an appropriate kV and find the corresponding Points value, then finally

 

6. Select mAs so that

 

                Patient Points + System Correction = kV Points + mAs Points

 

Example

 

AP lumbar, 25 cm thick            >>>>>             34 points

System correction                     >>>>>             -1

very muscular                          >>>>>              2

 

Total                                     >>>>>             35 points

 

Choose 81 kV                         >>>>>             16 points

so we need another                   >>>>>             19 points        >>>>>     80 mAs               

           

 

 

Calibration - establishing the System Correction

 

In an established practice, it is sufficient to work the calculation backwards from a "known good" image of an average-build patient to derive the System Correction.

 

The initial calibration of a new installation can be made using about 20 cm thickness of 80 gsm photocopier paper to represent soft tissue, and 2p copper coins as "vertebrae". Radiograph the combination as for a PA lumbar spine at 80 - 81 kV and adjust the mAs value until detail can just be discerned in the coins, then calculate the initial System Correction.

 

 

Nominal correction values

 

Focus-film distance                100 cm    - 3           150 cm     0              180 cm    + 2

 

Screen speed                         200        +3            400          0              800         -  3

 

Grid                                    no grid   - 4            10:1         0              16:1        + 2

 

Generator                             1-phase  + 4            6-pulse     0             HF/12pulse -2      

 

 

Review and adjust the System Correction in the light of clinical experience, and after any changes e.g. to processor temperature or screen speeds

 

 

 

Patient points + System points  = kV points + mAs points

 

            Patient thickness (cm)                                     

all AP/PA         lateral              lateral             

and all             lumbo-             thoracic                      

cervical          pelvic              (axilla)                        Points              kV        mAs    

                                               

                                                                                    0                      40         1         

                                                                                    1                      41         1.25     

                                                                                    2                      42         1.6       

                                                                                    3                      44         2         

                                                                                    4                      46         2.5       

                                                                                    5                      48         3.2       

                                                                                    6                      50         4

                                                                                    7                      52         5         

                                                                                    8                      55         6.3       

                                                                                    9                      57         8         

           

                                                                                    10      knee....   60         10        

                                                                                    11                     63         12.5

                                                                                    12                     66         16

                                                                                    13      neck....   70         20

                                                                                    14                     73         25

                                                                                    15                     77         32

                                                                                    16     PALx....   81         40

                                                                                    17                     85         50

                                                                                    18      LatLx....  90         63

                                                                                    19                     96         80

           

            4                                                                      20                   102       100      

            5.5                                                                   21                   109       125      

            7                                                                      22                   117       160      

            8.5                                            16.5                23                   125       200      

            10                                             18                   24                   133       250      

            11.5                                          19.5                25                   141       320      

            13                                             21                   26                   150       400      

            14.5                                          22.5                27                                500      

            16                                             24                   28                                630      

            17.5                                          25.5                29                                800      

 

            19                     15                     27                  30                              1000    

            20.5                  17                     28.5               31                                            

            22                     19                     30                  32                                            

            23.5                  21                     31.5               33                                            

            25                     23                     33                  34                                            

            26.5                  25                     34.5               35                                            

            28                     27                     36                  36                                            

            29.5                  29                     37.5               37                                            

            31                     31                                           38                                            

            32.5                  33                                           39                                            

 

            34                     34.5                                        40                                            

                                    36                                            41                                            

                                    37.5                                         42                                            

                                    39                                            43                                            

                                    40.5                                         44                                            

                                    42                                            45                                            

 

System correction =         points

 

 



adjusting the appearance of a radiograph


The "points" system will give you a radiograph of  average overall density.

The suggested kV factors will  produce a "chiropractic" image (slightly low contrast, good penetration of L5/S1) with a properly calibrated x-ray generator and film processor.

For a darker image, increase the total number of points, say by adding 0.5 - 1 point to both the kV and the mAs values. But first, check that the processor is working properly - the usual reason for "thin" films is cold, exhausted  or contaminated developer.

For a lighter image, decrease the number of points.

If you want more contrast (a "hospital" image) try reducing the kV by one or two points, and increasing the mAs by the same number of points.

If you want less contrast, increase the kV points and decrease the mAs points. This is particularly useful if you want to see the upper cervical vertebrae clearly in lateral projection: decreasing the mAs value means using a shorter exposure, so you don't get motion blurring of C1 and C2.

 

 

 



IR(ME)R procedures for chiropractic radiography


Every Employer is required to establish and maintain procedures that define how every aspect of his operation (apart from matters of professional judgement) that may affect a patient's exposure to ionising radiation, is carried out. These generic draft procedures cover most of the requiremets for chiropractic radiography. The apparent convolutions are due tot he fact that IR(ME)R requires any person acting in more than one capacity (as employer, referrer, practitioner or operator) to carry out the all the duties applicable to each capacity. For most single-handed practices "this means you".

click here for a printable version

1. The Employer, for the purposes of the Ionising Radiations Regulations, is ..........................  Any registered chiropractor employed in a direct or locum capacity, is entitled to act as Referrer, and if qualified in chiropractic radiological examination, as Practitioner and Operator. The names of such employees, and others entitled to act in specific capacities, are listed in an appendix to these Procedures. The following procedures are the Employer's Procedures required by Schedule 1 of the Ionising Radiation (Medical Exposure) Regulations 2000.

2. The Employer's referral criterion is that any patient who in the opinion of the Referrer is likely to benefit from x-ray examination may if he consents be referred to the Practitioner for x-ray examination.

3. Referrer: Make written clinical notes in the patient's record sufficient to permit yourself in your capacity as Practitioner to justify any x-ray exposure which in your capacity as Referrer you may consider appropriate to the patient's treatment.

4 Practitioner: Consider the data which you have provided to yourself and  decide whether in the light of the specific objectives of the exposure, the characteristics of the patient, the total potential benefits to society and the patient, the individual detriment that the exposure may cause, and the efficacy risks benefits and availablility of alternative techniques, whether to justify the exposure.

5.  Practitioner: Ask and record the date of the last menstrual period of any female patient, and invite her to sign the declaration that she is not pregnant. If she says she is pregnant, or is not certain, explain the "28-day rule" and invite her to sign consent to x-ray examination if in your opinion the benefits of such examination will outweigh the risks arising from it. A patient who has missed a period may not be x-rayed in this practice unless she signs the delaration that she is not pregnant. A patient who is unwilling to sign the declaration or consent may not be x-rayed in this practice.

6.  Whilst there is no statutory requirement to record the Practitioner's justification, the Employer requires the Practitioner to use the "tick list" or write in the reasons for proceeding to x-ray examination, on the patient record form, for statistical purposes.

7. Practitioner: If the exposure is justified, authorise the exposure by signing the appropriate box on the x-ray record form.

8. Practitioner: Ask the patient to check that his/her name, date of birth and address are correctly recorded on the x-ray record form. Hand the form to the patient to give to the Operator, if you are not the Operator.

9. Operator: Refer to the exposure chart to select appropriate technique factors, record the projection and factors for each exposure in the journal against the patient's name, and initial the entry. Standard projections used in this clinic are referred from the textbooks held in........................................................ Optimise each exposure in keeping with good professional practice regarding positioning collimation and patient instruction.

10. Operator: Ensure that the patient's name and date of birth, exactly as written on the x-ray record form, and the date of the exposure, are recorded on every film.

11. Operator: Ensure that the film stock is compatible with the screens in use and is in date; that the chemicals are properly stored, in date, and prepared according to the manufacturer's instructions; and that the processor is cleaned and maintained according to the manufacturer's schedule, adequately warmed up and cleaned before processing any clinical films, and is subjected to regular quality control.

12. Operator: Process films immediately after they are exposed. Reload the cassettes and replace them correctly.

13. Operator: Use pre-exposed test films as directed, to test the processor. Initial, date and file each test film. If the test film is not within the normal range, you must prevent further use of the x-ray equipment, investigate, correct and repeat the test. Do not allow anyone to process any clinical films until you are satisfied that the processor is working correctly. If in doubt, consult the Radiation Protection Supervisor named in the Appendix. 

14. Operator: Hand all the processed films to the relevant Practitioner as soon as possible, including any rejects.

15. Practitioner: Read and report every film. "NAD" or "Normal" is unlikely to be true in the case of any patient presenting for chiropractic examination and treatment. If there is No Visible Contraindication to manipulative treatment and no other outstanding pathology to report, record "NVC" as a minimum. Sign and date the report.

16. Practitioner: medico-legal and other "third party" referrals may be accepted from  Referrers who have established specific contracts with the Employer. The terms of each such contract are held by the Employer to whom reference must be made if the Referrer is not familiar to you.

17. Practitioner and Operator: third party referrals are considered to have been justified and authorised by the Referrer acting in the capacity of Practitioner but good practice requires that you should carry out relevant parts of these Procedures from 5 onwards and record your actions.

18. Practitioner: Once a month, review the Operator's journal and check whether exposure factors for similar projections of similar patients have altered from those delivered a month and a year earlier. If not, it may be presumed that patient doses remain in line with the diagnostic reference levels (DRLs) for this practice. The DRLs adopted are those set out in the current edition of the British Chiropractic Association's Guidance Notes. These are expected not to be exceeded when good and normal practice is applied. If you suspect that doses have increased, contact the Employer or the Medical Physics Expert whose name appears in the Appendix to these Procedures.

19. Operator: Report any suspected malfunction or irregularity in equipment or materials to the Employer immediately.

20. All personnel: The most significant cause of excess patient dose in hospital practice is "lost films". Do not permit any person to remove original films from the practice without signing an explicit receipt with sufficient detail to transfer liability to that person. Preferably, give the films to the patient rather than store them.

 


 

 



Exposure log


A simple record of the details of every exposure, is invaluable for quality assurance and as a means of estimating individual patient doses. Click here exposure log.doc to go to a printable template.

After identifying the patient, the most important column from a legal point of view is for the operator's initials. In a multi-handed practice, or if you employ a locum, you must be able to identify the person who took each film.

With a glance at a well-kept log , you can estimate your radiographic workload. Is your film turnover too low to keep the stock fresh? Consider reducing the number of sizes of film you use: 18 x 43 cm may save money of you take 200 lateral lumbar films per year, but if you take less than 50, you may be throwing away unused film, or compromising image quality with stale film.

Once a week, compare the factors you used for an average male PA lumbar spine, with those you used a week, a month,  and a year ago. If the mAs has increased, perhaps the developer temperature has decreased. If the kV has changed, there may be a fault in the x-ray generator. 

Using the recorded factors for a given exposure, and the "specific output" chart in your x-ray unit's latest inspection report, you can estimate patient skin dose. Your physics adviser will need this data if you have to counsel a patient who discovers she is pregnant after you have x-rayed her, and you should be able to demonstrate compliance with consensus norms for any particular examination.

 date name  exam  cm  kV  mA  ffd 
 12/12/03 John Smith  APLx  25  80  200  0.2  150 

"ffd" - "cm" (patient thickness) = focus-skin distance : 125 cm in this instance

the specific output chart shows, say, 20 microgray/mAs at 100 cm for an 80 kV exposure (this is a typical value for modern generators). In this case we have used 200 x 0.2 = 40 mAs, giving a dose "in air" of 800 microgray at 100 cm.

Applying the inverse square law, the dose incident on the patient at 125 cm would be 800 x (100/125) x (100/125) = 512 microgray - well within the EU diagnostic reference level.

 

 

 

 

 

 



X-ray room design: risk assessment


A prior risk assessment must be carried out, and design constraints set, before designing any radiation facility. In the case of chiropractic radiography, we can use a universal diagram showing the scattered radiation from a "worst case", say 2000 radiographs per year at 100 kV, 100 mAs, 150 cm focus/film distance, at various distances and angles from the centre of the film. This has been derived from a seminal paper (Trout & Kelley, Radiology 104: 161-169 (1972)) and adjusted for common UK chiropractic radiography practice.

A printable scatter diagram can be downloaded here risk assessment data.rtf along with the transmission coefficients for some common building materials.

 

 



Indicative doses


IR(ME)R requires every Employer to establish Diagnostic Reference Levels for common examinations. These are the entrance skin doses that are expected not to be exceeded for average patients. Where possible, these must be established with regard to the European consensus DRLs. For the common chiropractic projections, the following EU DRLs are appropriate

 

Skull                  AP                   5 mGy

                        Lat                   3

 

T Spine             AP                     7

                        Lat                   20

 

L spine               AP                   10

                         Lat                   30

                        L5/S1                40

 

It is most unlikely that these will be exceeded in normal UK chiropractic practice, and in most cases, thanks to the use of long focal distances and high-sensitivity film/screen systems, the actual delivered skin dose will be about half of the consensus DRL. However it is wise to use these values as indicative doses for external contracts, if you are offering to take x-rays for another referrer.

 

    

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©2004 Alan Calverd