Radiation Dose Index monitoring (RDIM) systems and establishment of local DRLs

Transcription

1 IAEA RER/9/135 COURSE ON OPTIMIZATION IN COMPUTED TOMOGRAPHY Sofia, Bulgaria, Radiation Dose Index monitoring (RDIM) systems and establishment of local DRLs Dean Pekarovič UMC Ljubljana, Institute of Radiology Quality and Safety office

2 Dose and DRL Mandatory? Why? Yes With modern CT the exam is quick, multiphase and outcome is great. According publications with regular audit the clinical practice can be improved ( RP Justification and Optimisation).

3 EU Legislation Provide the highest possible protection of workers, members of the public and patients against the dangers arising from exposure to ionising radiation. First Directive in 1959, 1962,1966,1976,1980,1984, February 2018

4 Procedures written protocols for every type of standard medical radiological procedure are established for each equipment for relevant categories of patients; e.g. paediatric, indication, DRL... information relating to patient exposure forms part of the report of the medical radiological procedure; e.g. Modality DICOM RDSR or calculated retrospectivly or on displays DLP, CTDI vol, DAP, IRP, Air Kerma..) referral guidelines for medical imaging, taking into account the radiation doses, are available to the referrers; appropriate local reviews are undertaken whenever diagnostic reference levels are consistently exceeded and that appropriate corrective action is taken without undue delay ( Article 58.)

5 Equipment d) any equipment used for interventional radiology and computed tomography and any new equipment used for planning, guiding and verification purposes has a device or a feature informing the practitioner, at the end of the procedure, of relevant parameters for assessing the patient dose.( Q where you can see it?) e) equipment used for interventional radiology and computed tomography has the capacity to transfer the information required to the record of the examination. Equipment installed prior to 6 February 2018 may be exempted from this requirement. f) without prejudice to points (c), (d) and (e) of paragraph 3, new medical radiodiagnostic equipment producing ionising radiation has a device, or an equivalent means, informing the practitioner of relevant parameters for assessing the patient dose. Where appropriate, the equipment shall have the capacity to transfer this information to the record of the examination. ( Article 60.)

6 Dose paths Exposed workers Personal dosimetry Patient Periodically dose collection Using standard patient size Standard CT examinations

7 Time consuming (mistakes..) Small samples 1. DATA collection (on site -radiographers)

8 1. DATA collection (on site -radiographers) Small samples, but sometimes still usefull 100 Kv 2 localizer 120 Kv 1 localizer Št Spol Letnik Masa I It CTDIvol DLP Scan Št Spol Letnik Masa I It CTDIvol DLP Scan kg ma mas mgy mgy cm Lenght kg ma mas mgy mgy cm Lenght 1. ž /180 3, ,7 1. m /180 9, ,9 2. ž /180 3, ,8 2. m /180 4, ,2 3. ž /200 5, ,0 3. ž /160 3, ,2 4. ž /180 3, ,1 4. ž /160 3, ,2 5. ž /180 5, ,7 5. m /180 4, ,4 6. m /160 3, ,4 6. m /160 4, ,2 7. ž /140 3, ,2 7. ž /160 1, ,7 8. m /180 4, ,7 8. ž / ,3 9. ž /180 3, ,1 9. m / ,7 10. ž /180 3, ,4 10. m /180 5, ,9 Ave 69,8 4,028 29,1 11. m /180 8, ,3 Mediana 69,5 3,8 27,4 12. m /140 1, ,2 Ave 68,6 4,7 31,3 Mediana 69,5 4,3 30,8

9 2. Data analysis (MP) Average dose for most common CT examinations. Often the small samples (20-50). Not included-patient size.

10 2. Data analysis (MP) CT FACIAL BONES CT HEAD

11 3. Comparison with DRL National level EU level

12 3. Comparison with DRL DRL

13 3. In SI 5 years

14 Frequency 5 y

15 If dose is stabile

16 If changing

17 we can detect on next data sampling

18 We have CT Image Using CT Image DICOM Header On Diagnostic Display Cofigurable (DICOM Tags) On Modality Display

19 Digital Imaging and Communications in Medicine is the international standard for medical images and related information (ISO 12052). It defines the formats for medical images that can be exchanged with the data and quality necessary for clinical use. DICOM is implemented in almost every radiology, cardiology imaging, and radiotherapy device (X ray, CT, MRI, ultrasound, etc.), and increasingly in devices in other medical domains such as ophthalmology and dentistry. DICOM is a file format and a networking protocol.

20 What DICOM is? Digital Imaging and Coimmunization in Medicine. Committee formed to develop a standard for imaging equipment to communicate with other devices. Both an image format & a network protocol.

21 DICOM Log files may include time date patient ID study ID event type series description operator name operator-provided reason for event did operator use password ReferringPhysicianName ReferringPhysicianTelephoneNumber CTDIvol value that triggered notification event programmed notification value (CTDIvol) DLP value that triggered notification event programmed notification value (DLP) And many other info

22 Modality in DICOM Network Basic Worklist Management (BWLM). Storage of images on a remote DICOM system. Commitment of stored images on a remote DICOM system (Push Model). Study Management per Modality Performed Procedure Step (MPPS). Storage and retrieval of images per DICOM media (CD-R).

23 ..and now Source is there! Sytems communicates- standards HL7 Dicom 3.0 IHE PACS RIS HIS EMR(Electronic Medical Record) Dose Register (ACR DIR)

24 DICOM Structure

25 DICOM File A single DICOM file contains both a header as well as all of the image data. header - stores information about the patient's name, the type of scan, image dimensions, etc image data - contain information in three dimensions

26 DICOM Header Header and image data stored in the same file so the important info can t be lost. Stores hundreds of pieces of data about the patient, machine, and data acquisition.

27 DICOM Tag A unique identifier for an element of information composed of an ordered pair of numbers (a Group Number followed by an Element Number),which is used to identify Attributes and corresponding Data Elements. Tags are two 4 digit hexadecimal numbers Length of the field is stored after the tag Allows header fields to be of variable length

28 DICOM Group (0018,xxxx)

29 How we see it

30 CT IMAGE MODULE ATTRIBUTES Tag Attribute Type Description (0008, 0008) Image Type 1 Image identification characteristics. See C for specialization. (0028, 0002) Samples per Pixel 1 Number of samples (planes) in this image. See C for specialization. (0028, 0004) Photometric Interpretation 1 Specifies the intended interpretation of the pixel data. See C for specialization. (0028, 0100) Bits Allocated Number of bits allocated for each pixel sample. Each sample shall have the same number of bits allocated. See C for specialization. (0028, 0101) Bits Stored Number of bits stored for each pixel sample. Each sample shall have the same number of bits stored. See C for 1 specialization. (0028, 0102) High Bit 1 Most significant bit for pixel sample data. Each sample shall have the same high bit. See C for specialization. (0028, 1052) Rescale Intercept T 0028he value b in relationship between stored values (SV) and Hounsfield (HU). HU = m*sv+b (0028, 1053) Rescale Slope 1 m in the equation specified in Rescale Intercept (0028,1052). (0018, 0060) KVP 2 Peak kilo voltage output of the x-ray generator used (0020, 0012) Acquisition Number 2 A number identifying the single continuous gathering of data over a period of time which resulted in this image (0018, 0022) Scan Options 3 Parameters of scanning sequence. (0018, 0090) Data Collection Diameter 3 The diameter in mm of the region over which data were collected (0018, 1100) Reconstruction Diameter Diameter in mm of the region from within which data were used in creating the reconstruction of the image. Data may 3 exist outside this region and portions of the patient may exist outside this region. (0018, 1110) Distance Source to Detector 3 Distance in mm from source to detector center (0018, 1111) Distance Source to Patient 3 Distance in mm from source to isocenter (center of field of view) (0018, 1120) Gantry/Detector Tilt 3 Nominal angle of tilt in degrees of the scanning gantry. Not intended for mathematical computations. (0018, 1130) Table Height 3 The distance in mm of the top of the patient table to the center of rotation; below the center is positive. (0018, 1140) Rotation Direction Direction of rotation of the source when relevant, about nearest principal axis of equipment. Enumerated Values: CW = 3 clockwise CC = counter clockwise (0018, 1150) Exposure Time 3 Time of x-ray exposure in msec (0018, 1151) X-ray Tube Current 3 X-ray Tube Current in ma. (0018, 1152) Exposure 3 The exposure expressed in mas, for example calculated from Exposure Time and X-ray Tube Current. (0018, 1153) Exposure in µas 3 The exposure expressed in µas, for example calculated from Exposure Time and X-ray Tube Current. (0018, 1160) Filter Type 3 Label for the type of filter inserted into the x-ray beam. (0018, 1170) Generator Power 3 Power in kw to the x-ray generator. (0018, 1190) Focal Spot Size of the focal spot in mm. For devices with variable focal spot or multiple focal spots, small dimension followed by large 3 dimension. (0018, 1210) Convolution Kernel 3 A label describing the convolution kernel or algorithm used to reconstruct the data

31 Radiation Exposure Monitoring The REM Profile requires imaging modalities to export radiation exposure details in a standard format. Radiation reporting systems can either query for these "dose objects" periodically from an archive, or receive them directly from the modalities. The radiation reporting system is expected to perform relevant dose QA analysis and produce related reports.

32 Available Dose Information - CT Sources of Dose Information: DICOM SC dose sheets (Dose Report) DICOM Headers DICOM Modality Performed Procedure Step (MPPS) DICOM DOSE SR Dose Quantities : Mean Volume Computed Tomography Dose Index (CTDIvol) Dose Length Product (DLP) Effective dose (E) Effective dose evaluation method Size-Specific Dose Estimate (SSDE) Number of irradiation events Weight/height, age and sex Ref : A.Jahnen, LIST

33 From CT dose image -OCR For CT scanners with only dose page, one typically uses Optical Character Recognition (OCR) software to extract numbers representing CTDIvol or DLP. Optical character recognition perform text recognitions of CT dose report images. Evaluation of multiple CT examinations, including text recognition, parsing, error correction, and exporting data. to spreadsheets. Ref: 2016 Phillip Cheng, MD MS

34 OCR and DICOM Headers For all newer scanners, CT vendors have adopted DICOM standards and the radiation dose related attributes at the series and image level. Dose values can be extracted electronically from DICOM attributes. Most commercially available software uses both approaches for hospitals with mixed generation of scanners. Limitations OCR software is sensitive to the resolution and/or contrast (WW and WL settings) of the dose page. Change to the character location may also impact the accuracy of OCR. Image-based DICOM header may have duplicated dose value if the image is derived from the original, i.e., reconstructed with different kernel or thickness. Some radiation exposure events may not be captured if the images resulting from these events are not reconstructed or forwarded from the scanner. Ref : CT radiation dose report from DICOM,Frank Dong, PhD,

35 Radiation Dose Index Monitoring Radiation dose index monitoring (RDIM) systems may generally be identified as Software that passively or actively collect radiation dose indices (RDI). Collect data from diagnostic studies using ionizing radiation. Store RDI in a relational database along with patient demographic and study information.

36 Radiation Dose Index Monitoring Compared to the does page and DICOM header, RDSR is a much better way to capture and store radiation exposure related information. CT Dose SR is described in detail by DICOM Supplement 127: CT Radiation Dose Reporting (Dose SR). For CT, the contents have three parts: 1) The DICOM header. 2) The dose accumulation container. 3) The container holding the information for each irradiation event.

37 Fundamental Functions Independent of Modality AAPM Medical Physics Practice Guideline (MPPG) 6.a. Radiation Dose Index Monitoring System Practice Guideline. Renée (Dickinson) Butler, M.S, 2015 Spring Clinical Meeting, St. Louis, MO Tracking of dose index essential dose indices must be recorded automatically (preferred) or manually Dose indices of each acquisition, including rejected images, must be recorded unambiguously. Essential acquisition parameters should be recorded together with the corresponding dose index data. If the information cannot be automatically recorded. User management RDIM access must be limited to a group of authorized users The level of data access and system configuration must be granted according to the specific role of each user or group of users. Configured based on access level (all access) or limited access (e.g. by modality). Notifications for dose indices outside the defined range thresholds that trigger notifications to a set of end users must be configurable Can be based on quality/safety assurance and regulatory compliance. Based on a variety of criteria, including but not limited to modality, type of exam, and patient age. Predetermined target users must be notified in a timely manner, typically by . Dose analysis tools should assist users in utilizing the collected information, include but not be limited to: Comparing dose indices of user-selected protocols across machines. Analyzing the trending of dose indices as a QA tool. Reviewing patient history which could include exams of multiple different imaging modalities.

38 Radiation Dose Module Atributes

39 RDSR On modality Summary

40 RDSR On modality Localizer

41 RDSR On modality Exam 24 x 1,2?

42 RDSR Persistent document-like object Store to PACS, RIS, XDS, CD media Extensible, coded, structured content Allows transfer and addition of more content Contains accumulated & per event exposure Contains detailed technique description Contains exposure data not patient dose + -

43 Why we need data? Patients need CT scans! BUT Same moadility, different LDRL or NDRL. Different Image Quality needs for same indications. Reasons? ( too personal question?) Will you pay for the same product (e.g. Car..) double or triple?

44 How to identify right dose? The one that makes pretty pictures. The one that the vendor specifies. The one that you used previously. The one presented at meetings. The one that keeps the radiologists happy (i.e., they don t complain). The lowest one you can still read. The one proven to provide the required diagnostic accuracy. AAPM Dose Alerts, Dose Notifications, and Diagnostic Reference Levels: How are they different?, Cody and McCollough

45 RDIM and DRL Data for determining national DRL values are obtained from surveys. Values of DRL quantities from patient examinations are collected from at several different health facilities. The 75th percentile value of the distribution of median values (the 50 th percentile) of a DRL quantity at healthcare facilities throughout a country is used as the national DRL. DYNAMIC When national DRL values exist for many or most countries within a region (e.g. The European Union), regional DRL values may be determined by using the median value of the available national DRL values. National and regional DRLs should be revised at regular intervals of 3-5 years, or more frequently when substantial changes in technology, new imaging protocols or improved post-processing of images become available. Since national DRLs require large surveys, which can require substantial effort to perform and analyse, they are not always as responsive to changes in technology. (Local DRL are important).

46 RDIM and DRL Median values of the DRL quantity for medical imaging procedures for a specific x-ray room or for a radiology department or other facility should be compared with DRL values to identify whether the data for the location are substantially higher or lower than might be anticipated. If a DRL value for any procedure is exceeded, an investigation should be undertaken without undue delay to determine possible reasons, and a corrective action plan should be implemented and documented. The objectives of these comparisons is to identify and improve shortcomings in the optimisation of the patient doses within the healthcare facility or group of healthcare facilities, to follow up the patient dose levels and to find out if there are any unexpected changes in the levels, e.g. due to equipment malfunction, unauthorized change of the imaging practice or lack of sufficient training of new users.

47 Vendors Radimetrics Bayer HealthCare TQM Qualum DoseTrack Sectra DoseWatch GE RaySafe Unfors Siemens: RightDose Philips DoseWise OpenREM.org Dose Monitor Radiance (UPenn)...

48 Cumulative Dose Tracking Track absorbed dose by organ/region, ICRP 60 Effective Dose, ICRP 103 Effective Dose, DLP, and CTDI Customizable display of patient cumulative dose record Protocol specific alert thresholds based on patient age, gender, protocol

49 Protocol Management Revision control helps track changes Access and search protocols with any web browser Customizable protocol entry forms Dose reference levels can be set using CTDI, DLP, ICRP 103, TCRP 60, or absorbed organ dose

50 Local DRL Setting up the local DRL for CT Head by using a predefined value (e.g from local government), DRL for DLP and CTDIvol of course possible. All patients with ages between 1-15 years of last year (left: DLP body, right: DLP Head). Histogram with calculated statistical parameters of distribution. Age filter applied.

51 GE Dose Watch -SSDE

52 TQM - Qaelum

53 TQM - Qaelum Ref : Qaelum/Slideshare

54 CT Dose Track by Age

55 Trend Age, height, wight

56 Free ones

57 UMC Ljubljana PACS ORQA HTTPS ORQA OLAP ORQA byzvd OnLine Radiological Quality Assurance Involved : MP, Radiographer, Radilogist, IT

58 Basic DICOM Tags from CT

59 Advanced DICOM Tags

60 Needs or wish? Live monitoring patient exposure On-line comparison with DRL (Local and National) Monitoring of potential trends / deviations Looking for fugitives = Quality Control

61 Dose Tracking

62 Fugitive

63 Fugitive

64 Reason

65 When reasons are found Exact time, date, radiographer, radiologist. Powerfull tool when it is adressed personally. It is no more some one, but not me. Identification for additional training.

66 LDRL and NDRL

67 0-6 months kv Same Radiographers Same Radiologist Same CT modality

68 Overview for training - Radiographers Study Description Age Group Nu. Of Average of Average of Average of Patients kv CTDI1 DLP CT HEAD no CM 1: 0-4 months , : 4 months - 1 y , : 1-5 y , : 6 y or older ,0 708 CT HEAD no CM Total ,6 694 CT CHEST ROUTINE 1: 0-4 months ,6 14 2: 4 months - 1 y ,1 21 3: 1-5 y ,1 29 4: 6 y or older ,6 108 CT CHEST ROUTINE Total ,4 91 CT ABDOMEN with CM 3: 1-5 y ,9 80 4: 6 y or older ,8 511 CT ABDOMEN with CM Total ,4 458 CT FACIAL BONES 3: 1-5 y , : 6 y or older ,5 413

69 Database evaluation / EDRL Age groups Nu.Procedures AVE. DLP DRL-adult DLP/DRL PiDRL EU (DLP) 4 month - 1 year CT HEAD , , year CT HEAD , , CT PARANASAL 1 263, ,99 CT SINUS 1 215, ,22 CT ORBIT NO CM 2 152, ,57 CTA PE 1 8, , year or older ( 15) CT ABDOMEN , , CT HEAD , , CT GLAVE S KS , , CT PARANASAL , ,95 CT SINUS , ,74 CT ORBIT NO CM , ,95 CTA HEAD , ,01 CTA PE , ,00 SUM/AVE , ,89 European DRLs for computed tomography Computed tomography Exam Age or weight group EDRL DLP, mgy cm CTDI vol, mgy Head 0-<3 months months-<1 y <6 y y Thorax <5 kg 2, <15 kg 2, <30 kg 4, <50 kg 4, <80 kg 6,9 200 Abdomen <5 kg 95 5-<15 kg 5, <30 kg 5, <50 kg 7, <80 kg

70 Thank you!