Presentation on theme: "Preventing accidental exposures from new external beam radiation therapy technologies ICRP Publication 112 Task Group: P. Ortiz López (chairman), J.M."— Presentation transcript:
1Preventing accidental exposures from new external beam radiation therapy technologies ICRP Publication 112Task Group:P. Ortiz López (chairman), J.M. Cosset, O. Holmberg, J.C. Rosenwald, P. Dunscombe, J.J. Vilaragut, L. Pinillos, S. Vatnitsky
2Lessons from accidental exposures with conventional techniques are available They have been useful inimproving safety
3The key questions are:Are lessons from conventional techniques applicable to newer technologies?Are there new lessons from new technologies?Can we anticipate “what else can go wrong?”We will address the following questionsCan we apply the lessons from conventional techniques to new technologies,Do we have already new lessons i from new technologiesAppart from these lessons, ¿is there anything else we have to take care of?INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
4Applicable to new technologies? 1st questionAre lessons from conventional techniques applicable to newer technologies?Applicable to new technologies?Let us start with the first of the three questions. There are lessons from conventional techniques. Are these lessons still valid
5Overall lesson from conventional techniques “…purchasing new equipment without a concomitant effort on education and training and on a programme of quality assurance is dangerous”.Valid for new technologies?The most general lesson is that purchashing new equipment without due attention to training is dangerous. Is it stil valid??? Of course, it isYes, indeed
6Lessons from conventional techniques valid for new technologies? Beam calibration: independent verification of absorbed dose at the reference pointFrom the accidental exposure in Costa Rica we have learnd this lesson that independent verification of absorbed dose is necessary.Is this also applicable to new technologies. Of course, yes115 patients severely affectedINTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
7Lessons from conventional techniques valid for new technologies? Need for commissioning of treatment planning systems (TPS)Validation of procedures and of their modifications, particularly TPSFor individual patients: check of the dose to a point, independently fromTPS calculations28 patients severely overdosed in Panama1045 patients underdosed in the UKThe lesson from the wrong use of a treatment planing system and the UK and Panamá accidental exposures was that, not being TPS a radiation source, it requires proper commissioning and validation of procedures, like an accelerator does.In addition, for each individual treatment there is a need for checking the dose to a point, in a way that is independent from the TPS calculations
8Lessons from conventional techniques valid for new technologies? Clear notification of maintenance and repairs to the person responsible for radiotherapy physics, before resuming patient treatments27 patients severely affected in SpainThe lesson from the accidental exposure in Spain is the need for clearly notifinying any maintenance or repair to the medical physicist before resuming treatments. And yes, this is also applicable to new technologies, as well
9All these lessons from conventional techniques are valid for new technologies They should be part of training programmes, and incorporated into procedures in radiotherapy departmentsIn summary, most lessons from conventional techniques are applicable and should be used for training and developing procedures
102nd question Are there new lessons from new technologies? Yes, the followingLet us go now to the second questionDo we have new lessons from new technologiesINTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
11New lessons: Software control of accelerator functions data integrity may be lost after computer “crash” or “frozen”
12Loss of data integrityWhen saving data on treatment plan, the computer got “frozen”. After restarting, data on collimator setting was “lost” from the data fileAs a result, open fields instead of small fields were appliedConsequences: one patient received 39 Gy in the first three sessionsChecking procedures are required for computer “crashes”. Irradiation parameters may be wrong uponINTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
13Interlock misadjustment Interlock understanding Test of interlocks at equipment acceptance
14Tolerances and interlocks Misadjustment of the tolerance limits of a dose-rate interlock occurred on a tomotherapy unitImportant: understanding interlocks and ensuring their testing at equipment acceptanceINTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
15Wrong calibration files for an applicator were supplied by the manufacturer
16Intraoperative radiotherapy Supply of wrong calibration file for a given applicatorMeasurements revealed a discrepancy, the physicist asked the installation engineer and received an erroneous adviceThe radiotherapy department accepted the advice, assuming that the maintenance engineer was right and the measurements by the physicist may be wrongThe problem was discovered later at a surveyAvoid “believes or assumptions” and base the treatment on proper understanding and verification!INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
17Errors from imaging: Wrong site treatment (right-left) Image distortion
18Multiple imaging modalities: problem with consistency in identification and labelling Left-right errorDistorsion of images when transferring them from the TPS to the “record and verify”Potential problems of image artefacts and wrong tissue densityWiith increased use of different imaging modalities, consistency in imaging identification and image labelling becomes more criticalINTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
19Image reconstructionGeometric distorsion of CT images, when being uploaded in the graphics memory of the TPSMisplacement of the field coordinatesAttention to image data transfer: Specific verifications requiredINTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
21Reference markers in virtual simulation The tatoo for the initial plane of virtual simulation (A) was taken as the isocenter plane (B).Understanding and becoming fully familiar with details of new techniques(A)(B)INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
22Significant radiation dose from daily imaging for verification
23Daily imaging for localization Significant radiation dose was given from daily localization imagesNeed to integrate significant imaging doses into the therapy dose planned by the TPSINTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
24Several events due to poor understanding of new techniques and poor communication and recording And finally, there is risk in poor understanding of complex techniques or in poor recording and communication
25Calibration of very small beams (micro multileaf collimators) Partial volume irradiation of the chamber. Wrong absorbed dose determinationKnowledge needs to be sharper, as well as the level of awareness of the task at handEducation and specific training essential for new technologiesINTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
26Record and verify systems Old system: TPS calculation for normalized dose (1Gy) followed by manual scaling up to the prescribed dose when transferring the plan to the record and verify systemNew system: direct scaling up by the TPS and automatic transferUnusual treatment modality. Scaling up was done twice.A check procedure was not followed. About 67% overdoseINTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
27Dynamic wedgesErroneous selection of the type of wedges with the result of excessive monitor unitsMonitor units for physical wedges, treatment with dynamic wedgeMisunderstanding of the acronym (enhanced wedges, EW)23 patients overdosed, four of them died in the first yearINTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
28Small fields in stereotactic treatment with applicator INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
29Confusion 40 mm - 40 cm Patient died from the accidental exposure INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
30Avoid poor understanding of new techniques and poor communication and recording Lesson No “quick” training…A common conclusion of all these problems of poor understanding is that proper training can not be replaced by a quick or short briefing, from which many risks may not be appreciated.… but solid training
31All these new lessons are useful in preventing reported types of risks, but INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
323rd question: Can we anticipate what else can go wrong? INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
33The unknown or unreported What about possible unreported events?What about other types of potential events, which have not happened yet?Do we need to wait until they occur, to learn the lesson?¿What should be done about increasing equipment complexity and thus ever larger lists of double checks and verifications?INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
34There are proactive methods of safety assessment Failure mode and effect analysis (FMEA)Probabilistic Safety Assessment (PSA)Risk Matrix ApproachExamples: work done by the Ibero American FORO of Nuclear and Radiation Safety Regulatory Agencies and by the American Association of Physicists in Medicine, briefly described in ICRP 112INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
35Example No. 1 of major finding from probabilistic safety assessment Much attention has been focused on major catastrophic, multiple-patient events with very low probability, butOther types of events with much higher probability, involving single patients, can also be severe, may more easily go unreportedThey deserve increased attention and preventive measures
36Example No. 2 of major finding from probabilistic safety assessment Increased software control (control of linear accelerator functions, treatment planning, virtual simulation, image guided radiotherapy, record and verify control, radiotherapy information systems, electronic charts) confers software safety a paramount importanceSoftware deserves increased attention in standards and by regulatory bodies and professional bodies;
37Example No. 3 of major finding from probabilistic safety assessment Safety aspects related to the approval of the treatment plan by the radiation oncology and measures on the patient directly such as in vivo dosimetry or its equivalent measures, daily observation of the patient and periodic medical control bear an important part in risk reduction, in terms of prevention and mitigation of accidental exposures
39Introducing new technologies Decision to implement a new technology should be based on an evaluation of the expected benefit, rather than being driven by technology itselfA step-by-step approach should be followed to ensure a safe implementation.
40Staff training, availability and dedication Replacement of proper training with a short briefing or demonstration should be avoided, because important safety implications of new techniques cannot be fully appreciated from a short briefing.Certain safety-critical tasks, such as calibration, beam characterization, complex treatment planning and pretreatment verification, require a substantial increase in staff allocation.
41Safety awareness of responsible persons for radiotherapy Independent verification of beam calibration remains essential.Investigating discrepancies in dose measurements before applying the beam to patient treatments.Hospital administrators of radiation therapy departments should provide a work environment that encourages working with awareness, facilitates concentration and avoids distraction.
42ManufacturersManufacturers should be aware of their responsibility for delivering the correct equipment with the correct calibration files and accompanying documents.They also have a responsibility to provide correct information and advice, upon request, from users.Procedures to meet these responsibilities should be developed and quality controlled.
43Programme of purchasing, acceptance and commissioning Programmes for purchasing, acceptance testing and commissioning should not only address treatment machines but also treatment planning systems, radiation therapy information systems, imaging equipment used for radiation therapy, software, procedures and entire clinical processes.Devices and processes should be re-commissioned after equipment modifications including software upgrades and updates.
44Need for new protocols for treatment prescription and dosimetry Protocols for treatment prescription, reporting and recording, such as found in ICRU reports, should be revised to accommodate new technologies.They should be adopted at a national level with the support of professional bodies. Similarly, dosimetry protocols should be developed for small and non-standard radiation fields.
45Dose escalationDose escalation without a concomitant increase in normal tissue complication probability generally implies a reduction of geometrical margins.Such a reduction is only possible with conformal therapy accompanied by precise, image-guided patient positioning and effective immobilization together with a clear understanding of the accuracy achieved in clinical practice.Without these features, target dose escalation could lead to severe patient complications
46Safety-critical communication and notifications Unambiguous, well structured communication is essential, considering the complexity of radiation therapy and the multidisciplinary nature of the health care environment.In particular, procedures to notify physicists of maintenance and repair activities, identified as crucial in conventional technology, are even more necessary with new technologies.
47Computers and data integrity Procedures should be in place to deal with situations created by computer “crashes”, which may cause loss of data integrity and lead to severe accidental exposures.
48Updating of quality control tests When conventional tests and checks are not applicable or not effective for new technologies, the safety philosophy should aim at finding measures to maintain the required level of safety.This may require the design of new tests or the modification and validation of the old ones.
49Using lessons from experience Lessons learned from past accidental exposure should be incorporated into training. Radiation therapy facilities are encouraged to share their experiences of actual and potential safety incidents through participation in databases such as Radiation Oncology Safety Information System (ROSIS), often referred to in this report.
50Overcoming the lack of experience when introducing new technologies Prior to the introduction of new techniques and technologies, there is little or no operational experience to share. Two complementary measures are recommended:Prospective safety assessments should be undertaken in order to develop risk-informed and cost-effective quality assurance programmes.Moderated electronic networks and panels of experts supported by professional bodies should be established in order to expedite knowledge sharing at the early phase of introducing a new technology.
51RecapMost lessons from conventional techniques are applicable to new technologiesAdditional lessons for new technologies have become available (ICRP 112)Anticipative approaches provide a risk-informed and rational choice of safety provisionsINTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION ——————————————————————————————————————
52Thank youYou are invited to use these lessons for training and to apply them in practiceMore details in ICRP publication 112