Question

Parties to the conflict / type of medical service: Medical physicist, radiotherapist, operator (nurse-apparatus), topometrist / external radiation therapy on a gamma-therapy device

I. According to the treatment of the patient on the gamma-therapeutic apparatus according to the Regulations of the department, the patient undergoes topometric preparation.

Mandatory participants in patient topometric preparation:
 a doctor - a radiotherapist in the radiation and topometric preparation maps indicates the location and apparatus for treatment, determines the set of additional fixation devices to the base set according to the approved irradiation method, selects a convenient position for the patient taking into account the localization and condition of the patient, fills in the patient registry, topometric preparation protocol and transmits information to the topometrist (radiologist);
 the topometrist doctor (radiologist)will coordinate with the radiotherapista set of additional fixing devices to the base set and make them as needed (thermoplastic masks), and also selects the patient’s convenient position taking into account the locations and the set of fixing devices used, then completes the topometric protocol preparation for radiation therapy and checks the number of images from a computer tomograph (CT images);
 the medical physicistselects the desired position of the patient, taking into account the technical characteristics of the therapeutic unit, adjusted for the geometry of the fields at which the treatment will be carried out.

II. After topometric preparation, digital X-ray images from a Toshiba Aquilion computer tomograph are transmitted to the Monaco Sim contouring station. Radiotherapistchecks the number of CT images (not more than 300 according to the requirements of the contouring system), performs contouring of the target (GTV, CTV) and the planned exposure volume (PTV), organs of risk (OAR) in accordance with the literature.
 contouring for conventional radiation therapy (CRT) to prepare 1 working day;
Note: In the case of multi-stage treatment, PTVs are allocated for each stage of treatment with the corresponding value of the total dose for this stage of planning.

III. Next, the radiotherapist fills out a prescription protocol with a description of the course of radiation therapy: name of the patient, diagnosis, patient ID, area of exposure, irradiation technique (Conventional RT), therapeutic unit, total dose per RT course, fractionation mode, and also necessary conditions for target coverage in accordance with the objectives of RT:
 Conventional RT: At least 85% -90% of the prescribed dose should be irradiated with at least 90% of the planned exposure. No more than 107% of the prescribed dose can be irradiated with no more than 5% of the planned exposure. Radiotherapist prescribes restrictions on risk organs in accordance with the literature and fills out a prescription protocol.
Note:All calculations of the isoeffective dose for the planned volume of exposure and risk organs in the case of using a fractionation regimen other than the standard regime, as well as interruption of the radiation therapy course, should be carried out according to the linear-quadratic radiobiological model
according to the literature.

IV. A radiotherapistconfirms in writing with the head. or senior physician - radiotherapist, contours of anatomical structures and prescription protocol.

V. Radiotherapistcompletes treatment in the MOSAIQ administrative system:
 Select a patient and open the Diagnoses and Invasive Procedures tab;
 Establish a patient diagnosis;
 Create a prescription for radiation therapy (indicate the name of the area; prescribed dose, number of fractions and fractional mode);
 For each stage of treatment, a prescription is created.

VI. Radiotherapistverifies the fulfillment of the necessary points according to the Checklist on the preparation of a patient for remote radiation therapy approved by the radiotherapy department on the Theratron Equinox 100 gamma apparatus.

VII. Radiotherapistsends contoured CT images to the planning station (XIO) and makes an entry in the journal “Application for planning of radiotherapy”.

VIII. Medical physicist checks the fulfillment of the necessary points according to the Checklist for preparing the patient for remote radiation therapy for the Theratron Equinox 100 gamma-ray apparatus approved in the radiotherapy department, the presence of contoured CT images, the approved prescription and entry in the journal “Application for planning of radiotherapy”.

IX. Medical physicistcreates a dosimetric treatment plan. If necessary and the complexity of the location of the localization creates several dosimetric treatment plans for the possible selection of the most optimal in accordance with the recommendations. Options for dosimetric plans are discussed between
medical physicists of the Department of Medical Physics (DMP). A plan is created for the entire course of radiation therapy.
 dosimetric planning for conventional radiation therapy (Conventional RT) to prepare 1 working day;
Note: All calculations of the isoeffective dose for the planned volume of exposure for the area of nonirradiation (“cold spots”) and the area of overexposure (“hot spots”) of the isodose distribution, as well as for risk organs with an area of high isodose lines, should be carried out according to the linear quadratic radiobiological model according to the literature.

X. Medical physicist and radiotherapist approve the optimal exposure plan according to the following criteria:
 FOR TARGET:
 According to the histogram of the distribution of dose - volume DVH:
 at least 85% -90% of the prescribed dose should be irradiated with at least 90% of the planned exposure. No more than 107% of the prescribed dose can be irradiated with no more than 5% of the planned exposure;
 According to the parameters of the statistical dose distribution;
 By visual inspection of the scores distribution of percentage isodose lines (107%, 100%, 95%, 90%, 85%, 80% 50%, 20%) relative to the prescribed total dose for the entire course of radiation therapy.
 FOR ORGAN AT RISK (OAR):
 the maximum dose in the OAR should not exceed x Gy not more than v% of the volume of ROI can receive x Gy (Dv%≤ x);
 isoeffective doses for "hot spots" are calculated according to the linear-quadratic radiobiological model according to the literature;
 according to the international QUANTEC and RTOG protocols, if a risk organ with a third level of priority is not passed, the radiotherapist decides to accept or reject this treatment plan;
 for any deviations according to the statistical data of the dose distribution from the prescribed, the doctor also makes a decision on the choice or deviation of this plan and fixes his decision in the radiation map.

XI. The final version of the patient’s dosimetric plan for irradiation is approved at the general meeting of the radiotherapy department in accordance with the Regulations of the radiotherapy department and signed by the head of Medical Physics Department (MPD) and head of the radiotherapy department.

XII. Medical physicistenters in the patient’s radiation card the following necessary documentation:
 exposure protocol (geometric and dosimetric parameters of the exposure plan), which is signed by the second medical physicist;
 histogram dose volume (DVH) for the required set of anatomical structures;
 statistical dose distribution for the entire set of anatomical structures;
 shift of the radiation field relative to reference marks to determine the isocenter of the treatment field on the patient and the displacement of the therapeutic table with the patient relative to the isocenter of the installation.

XIII. Medical physicistenters the following necessary information and documentation to the MOSAIQ system:
 exports information on the created treatment plan (parameters of each radiation field, statistical dose distribution for each structure and dose distribution depending on the volume of the structure in the form of a DVH histogram) as a file with the extension.pdf.

XIV. Medical physicistchecks the fulfillment of the necessary points according to the Checklist on the preparation of the patient for remote radiation therapy approved by the radiotherapy department on the Theratron Equinox 100 gamma apparatus.

XV. Topometrist on a computed tomograph, the patient is displaced along the laser system relative to the reference marks to the isocenter position of the treatment plan.

XVI. Topometristenters the patient into the schedule of operation of this device, confirms in the MOSAIQ system the treatment courses and prescription of the patient, as well as the area of exposure.

XVII. Radiotherapisttransmits documentation (radiation card) for the patient to the nurse operator.

XVIII. Operatorchecks the fulfillment of the necessary points according to the Checklist for the preparation of a patient for remote radiation therapy approved by the radiotherapy department for the Theratron Equinox 100 gamma apparatus and the availability of all necessary documentation in the radiation card.

XIX. When the patient is first laid on the therapeutic unit, the following actions are performed with the participation of the following responsible persons:
1) Radiotherapist- together with the operator, they prepare and lay the patient on the treatment table of the therapeutic unit according to the established position marks of the isocenter of the dosimetric plan, which were installed on a computer tomograph;
2) Topometrist- ascertains the correct position of the patient and the use of an appropriate set of fixing devices according to the protocol with topometric preparation;
3) Medical physicist - makes sure that the created dosimetric treatment plan (patient position and radiation field) is correctly reproduced on the patient;
4) The operator conducts irradiation;
5) If the plan contains several isocenters and the stage of treatment is changing, then it is necessary to carry out the procedure in accordance with paragraphs 1)-4).
Note:In case of technical malfunctions of the therapeutic unit, as well as dosimetric changes in the radiation plan, the engineer / physical engineer / medical physicist of MPD.

XX. In subsequent sessions of radiation therapy, the patient is laid on the treatment table and treatment at
the appropriate installation is carried out by the operator.
Note: n the event of a change in the patient's laying parameters at the therapeutic unit and the general
condition of the patient, a radiotherapistis called.

XXI. In the event of a change in the patient’s position on the therapeutic unit during the course of RT, it is necessary to carry out the procedure in accordance with I-ХIX.

1. What is the assessment of time savings (device resources) in accordance with this regulation?
2. How much does accuracy increase in the delivery of the prescribed dose, increasing the effectiveness of RT?
3. How will this regulation affect the regulations on the Quality Assurance of the apparatus and topometry?
4. How will this regulation affect the qualifications and compactness of each employee?

Answer 1

Brachytherapy and Orthovoltage

Orthovoltage device has mosfet tubes and beryllium windows which makes it partially expensive.

Brachytherapy device also come in varients based on the region of interest. There are seperate devices for skin, breast tissue, rectum and GI tumors. There are also much advanced varients in intrabeam and photoelectric therapy and they are effectively costly. Zeiss lens for intrabeam is much costlier. Voltage based varients also exist and they are based on the capacity and usage characteristics

2. Accuracy in delivery: Beam align verification in conventional radiotherapy are visualized through port films and electronic portal imaging. In Orthovoltage RT there is non uniform dose disribution and maximum dose is applied on the skin. Dose distribution is apparantly non-present in Conventional RT.

Delivery verificationa nd modification is adept and is done by pulse by pulse basis and hence there is much more accuracy in Brachyherapy RT devices.

3. Effect on the regulations on quality assurance:

Feasibility sub studies and toxic assessment is performed on more number of random patients in coventioanl RT. Example: A thoracic SABR safety sub study had minimum of 50 patients and unacceptable deviation is much higher

For Brachytherapy and Orthovoltage there is comparatively more number of acceptable variation and less deviation per protocol

4. Impact of the tech specifications on each employee:

For conventional radiography a radiophysist and a physician are compatible to work with the machine. Brachytherapy and Orthovoltage devices need a tomographist and a radiophysist for effective treatment, Adjustability of the volatages and the device handling should be professional and any error through deviation proves costly.