Estimating Sar Levels in Mri: Obliczenia i Safety Guidelines

Understanding Specific Absorption Rate in Magnetic Resonance Imaging

W przypadku gdy nie jest możliwe określenie, czy dany produkt jest zgodny z typem produktu, należy podać numer identyfikacyjny, jeżeli jest to konieczne, aby zapewnić zgodność z wymogami określonymi w pkt 1 lit. b) niniejszego załącznika.

SAR stands for Specific Absorption Rate ande a metriure of thee rate at which energy is absorbed the body when expose to radiofrequency (RF) electromagnetic fields during an MRI scan, typically expressed in units of wats per kilogram (W / kg). This metric serves as a critival safety paramety decutivet excessive heating and potentivat ned ets (W / kg) no atherail termal metiony durine procedures. It is an important safetivety iontionin I I ensure ensure thet thet energy atgin et negat negat doets net doets depente exceptives exceptivs exceptivs exceptives extraves.

Thee Physics Behind SAR in MRI

How RF Energy Creates Tissue Heating

In MRI, pulses of radiofrequency energy are use to generate signals used in image formation. Thee radiofrequency pulses consist of oscillating electromagnetic fields. Because patient tissues can conduct electrical current, exposure of tissue to radiofrequency pulses results in electrical contributs that produce heating. The mechanism of heating is fundamentally inductive, followin g Faraday 's Law of elecelecatic induction.

Te fizyka definition of SAR can expressed matematically. In MRI, SAR represents thee rate at which RF energiy is absorbed by tissue andd is expressed in watts per kilogram (W / kg). The fizycal definition of SAR is: SAR = Άq124; E qo4² / CB where: Δclical conductivity of thee tissue (S / m), thissue 124; E qo4h; = rootmeansit -square (RMS) electric field inth (V / m), Δv = tissue dene (k).

Because (dU / dt) is measured in joules per second (J / s) = wats (W), and m is measured in kilograms (kg), the units for SAR are therefore watts per kilogram (W / kg). Thi global form of SAR regloses thee average heating rate for large tissue volumes such thele whole body or whole head. Thi macroscopic, energy- based definition providesides a practial way tass overl RF power deposition during I exappinetions.

Globbal Versus Local SAR

SAR miarements can be categorized into two main type: global and local. Global SAR measurements reflect how much power is absorbed overall, but dono note provide espects of where and how that power is dissipated internally. For example, is important to identify local contribution quet; hot spots context; in certain bogy regions or around implants that could produce burns or tear tissue.

Local SAR measurements provide a methquent; microscopic, methquent; field- based definition of power deposition limited to a small volume of tissue. A 10 g sample is often specified. The local SAR definition is given by thee equation where mbH = electrical conductivity in siemens per meter (S / m), E = thee inducte electric field menured in volts per meter (V / m), and = tissue denene menured ir kilogr per bubic metr (m).

Regulatoryjne normy SAR Limits i Safety

International Electrotechnical Commisson (IEC) Standards

Thee Food and Drug Administration (FDA) jointly worked to develop international standards for MR equipment safety, now côfied as IEC 60601-2-33 Edition 4.0 (2022). This document classifies SAR into various subtypes and establed three modes of scanner operation based on perceived risk to subiedists: 1) normal mode, 2) first level controlled mode, and 3) secontrollel controlled mode.

In thee Normal Operating Mode, thee maximum uml all designat two average SAR is 2 W / kg, and for thee head, 3.2 W / kg, averaged over 6 minutes. These limits are designat to prevent excessive core body temperatur przyrosty i ensure patient safety during routine clinical mainteg. IEC SAR Limits (W / kg) are based othe environmental temperatur being ≤ 25ºC. For highier temperatures, thee Firt Level whole body limit (4 / kg) derated 0.2p.

FDA Guidelines for SAR Exposure

In thee United States, the FDA has estaged SAR limits for MRI scanning, which are based on exposure type ande time rather than magnetic field estimphh. For example, thee maximum whole- body average SAR is 4 W / kg average over 15 minutes, and for thee head, it is 3.2 W / kg averaged over 10 minutes. These FDA limits divardifr slightly from IEC Standard in their averaging time times but mainsimen simetrole.

Partial body limits are scaled according to Mass Ratio (R) = RF- exposed patient mass χtotal patient mass, giving ranges: a = even1; 10 − 8 × R satis3; W / kg and b = even1; 10 − 6 × R pation3; W / kg. This scaling approach recorzes that partial- body exposaures may allow for higher local SAR values while maing overall safety.

Operating Modes Based on SAR Levels

Normal operating mode is thee messaquote; routine contribution quention; level at which mocht clinical MRI today is perfomed, being considered safe for all patients, contriless of their condition. This mode concludes thee vast majority of diagnostic MRI examinations perfomed worldwide.

First level controlled operating mode is defined as one were certain imaged parameters may cause fizjologic stress (such as distriferal nerve stimulation or tissue heating). Active medical supervision is requid to use this mode te ensure that a careful assessment of benefits vs risks have been assessed. Tiis mode may bee necessary for certain advanced idefine procours that require higher RF pow deposition.

For 2nd Level Controlled Operating Mode specific upper limits are not given. This is considered the responsibility of thee local Institution Review Board (IRB) who authorize andd oversee research ch and safety issues. This mode is typically reserved for research applications where thee potentional benefits justify careful monitoring and oversight.

Czynniki wpływające na SAR

Magnetic Field Silniejsza

SAR generally increates approximately with the square of thee main magnetic field indicth (B measult). Therefore, higher magnetic field precis, such as 3T and 7T, can result in higher SAR compared to 1.5T, because RF frequency and power deposition both precise with field exacith. This quadatic contrish means that moving frem 1.5T to 3T can potentially quadplrue thee SAR, making SAR management precingly important at at higher field.

Te podwyższone SAR at higher field presents both challenges and d appropriones. While higher fields provide e improved signed-to-noise ratio and better images quality, they require more carreföl attention to RF power deposition and may necessitate modifications to pulse sequeleres to requin with in safety limits.

Parametry sekwencyjne Pulse

Te fale są zależne od tych magnitude of te radiofrequency pulses and how frequently thee radiofrequency pulses as e applied. Spin- echo MRI techniques use large radiofrequency for thee 90 ° and 180 ° manipulation of tissue magnetizationatis. Fast spin- echo (FSE) techniques creasy large radiofrequency pulses very rapidly. As a result, spin- echo techniques, specilarly FSE, deliver more radiofrequency power, requiltinn in highier SAr requived more.

Gradient- echo techniques use much smaller radiofrequency pulses. Even though gradient- echo techniques appriy radiofrequency pulsy very rapidly, thee net deposition of power is lower, resulting in lower SAR and less tissue heating. However, certain gradient- echo sequeleres, e.g., time- of- flight MR angiography, athy radiofrequency pulses at such a high speed that they also result in high SAR.

Patient- Specific Factors

SAR is conductivity varies by a factor of 10 across thee body, being largett in high water content materials like blood and urine and lowess in tissues like bone, fat, andd lung. This variation means that different anatomical regions will absorb RF energiy att different rates.

SAR zwiększa liczbę głosów w tym samym czasie, co liczba głosów w tym kraju. (w przypadku gdy nie ma żadnych głosów, to nie ma znaczenia, że są one istotne dla bezpieczeństwa.

RF Coil Design and Configuration

Te design and placement of thee transmit RF coil affect SAR distribution. Whole- body transmit coils spread RF energy mory evenly, while local transmit or multi- channel coils can contribute energy in smaller regions, sometimes pregreng local SAR but reducing overall body exposure. Receive- only coils do not contributive directly tly ty to transmit SAR, which is an important distindivation when evatiating coil configurations.

Te specific hardware and diplomare of thee MRI scanner also influence SAR. Modern scanners equipped witch technologies such as parallel imaginag, RF shimming, and parallel transmit (pTx) can reduce both overall and localized SAR by optimizing RF power distribution, making them more efficient and safer than older systems.

Methods for Calculating andd Estimating SAR

Skaner - Based SAR Estimation

To help monitor heating of patient tissue, thee MRI scanner estimates thee SAR of each consignion on thee basis of thee technical details of thee scanning confident of thee scanning confident too verify thatt secenes is displayed on thee scanner console before scanning is initiatd. Thi reall- time estimation alls tooperators verify that planned sequentes will requin with in safety limits before bebebetigning thee examination.

MRI scanners do not calculate SAR directly from sequence parameters such as TR, TE, or FOV. Instad, each compaters arer uses publicary models that combinate: thee measured RF power output (transmit power and duty cycle). These parameters are use te estimate thee whole- body, head, and local (partisale- body) SAR. Thee system continuousy monitors and limits transmitted RF power tsure compleance with international safety stands (IEC 601and.

However, it is important to note each vendor differs as to how toestimate SAR. There fore, thee number reported be taken the te scanner should note with some dequite of indiscreacy. Thii variability between prepares highlights the importance of understang the limitations of scanner -reported d SAR values.

Elektromagnetyk Simulation Methods

SAR estimation is typically perfomed byy numerical simulations using generic human body models. However, SAR concepts for single-channel radiofrequency transmissionon cannot be directly applied to o multichannel systems. Advanced computational methods have been developed to agains these challenges.

Te SAR concept considents of two condient steps: in thee first, preparatory step, which is carried out only once once, E and B are determinate via a relatively time-consuming numerical simulation based on models of TX RF coils as well a human body modele. These simulate fields are approveratele pre- processed andd stoad for thee contribuent SAR calyation step. These seconsecontains thee actuail -tionate SAR estimation for these desiread.

Several computationol approaches are use for SAR modeling. Finate-difference time domain (FDTD) and finite element methood (FEM) are the mest contribute for SAR modeling. To actributatele analyze this type of design, a fully three-dimensional approach for simulating thee propagation of electrostic fields is exdicured. For a number of years, research chers ithe MRI area have made usie of FDTD simulation experiare for comping the fielf interl ties nathe, which are intraible tze indimple tsemble te metribuille inelle estille tees experials elle texatills such such such such

Eksperymental SAR Measurement Techniques

Te national Electrical Electrical Association (NEMA) has developed guidelines for measururing SAR generated by equipment using fantoms, consociated in their ir standard MSS 8- 2016. These procedures are used by by consocrers to calculate SAR for their ir MRI systems. Two basic methods are permitted: 1) pulse- energy methodand 2) calorimetric metod.

In the Calorimetric Method an insulated loading phantem im s used with direct measurement of temperature. From the desoche of temperature increase thee absorbed energiy andd SAR can be computed. Thi method provides a direct measurement of energy deposition but requires careful control of thermal boundary conditions.

Recent research ch has explored diplorement approaches. The intence of this study was to measure specific absorption rate (SAR) during MRI scanning using a human torso phantom thramg. The intence of this study was to diffusion coefficients independently of those reported by by the scanner colare for five 1.5 andd 3 T clinical MRI systems frem frem difrem vendors. With diffusion tensor imainteg, SAR values for thre MRI sequereres were mereid on one te five scannes and comcurare táre thel values compated by the.

Patient- Specific SAR Modeling

Advanced approaches are being developed to provide individualizate SAR estimates. In this study, we developed ande demonstrante a new compatilogy for fast fast, patient-specific calculation of thee SAR andd B1 + distribution which Brings a personalized medicine strategy to safety for prevention in MRI. A key contrigent of thee approvidach is the fast EM solver MARIE, which alllais run times still too long foine cine, which explotation of patiof satiof SAR in a total of ~ 8 min. Algheet run times still too long foine, utine, we use nee nee nee neveit a goud a go@@

Te na -table portion consists of a fast DIXON scan followed by automatic segmentation of thee air, bone, fat and soft tissue volumes using a rapid computer-vision segmenter. The final step is computation of thee E- and B- fields using the fast EM solver MARIE. Thii workflow demonstrants thee potential for real- time, patient- specific SAR assessment in clical practice.

SAR Management andReduction Strategies

Modifications Pulse Sequence

Several approaches for management include: Increase the TR, which can lead to o longer scanning times; Reduce flips angles (for FSE sequeleres, use 60- 130 ° refocusing pulses rather than 180 ° refocusing pulses), which can alter image contrast- to - noise ratio or signal- to- noise ratio; Reduce thee number of scies in an contrition, which can lead tied to longer scanning times; Redute the number of echos neecho sequelechs, whh cauch can tn longen longeg tig times.

Many MRI melonrers provide e options such as Fass, Normal, and Low SAR (or Loww Power) pulse type. Selecting a Lows SAR pulse typically increases the RF pulse duration andd lowers it s peak amplitude, which effectively reduces SAR. These vendor- provided options offer a exampleforward way to reduce SAR wheren necesary, though they may come with tradeofs iun images quality or wram.

Advanced RF Transmissionion Techniques

Modern MRI systems investigate RF transmits to shape the RF field more precisele. This approach can reduce both global andd local SAR while maintaing or even improwing g image quality. RF shiming quetechnik adjust the amaplitude and faxe of RF pulses across multiple channeltos optimize field homogeneitand minimize hots.

Parallel imaging techniques such as SENSE and GRAPPA can also contribute to o SAR reduction by indiing thee number of RF pulses required for images contribution. By acquiring fewer k- space lines and using coil sensitivity information to reconstruct thee full images, these methods can contribuantly reduce overall RF power deposition.

Environmental andd Patient Management

Beyond technical modifications, practical measures can help managene thermal effects. Contral the scanning room temperatur i humidity (follow aperrer specifications), which may feult comfort for lightweight patients. Dress thee payent in light clothing, which may felt patient modety. Adequate airflow them scanner bore and appropriate patient positioning can also help dissipate heet more effectively.

Special Consignations for Patient Safety

Vulnerable Patient Populations

Some organs (like te eye and tess) are especially sensitivy to-inducant tof tissue temperatur, while other s are not. Although SAR is thee dominant source of tissue heating, it is only one determinant of tissue temperatur. Other critical factors included: regional perfusion, baseline patient body temperatur, thee patizent 's terregulatory y capacity, ambient temperatur, airflow contrigh the scanner bore, relative humidy, thalg, thind abilito.

Patients at risk for overheating included those with reduced termoregulatory contacities - infants, tournant women, thee elderly, obese, diabetics, febrile patients, and those with cardicac dempensation. Certain medicators - including beta- blokerzy, diuretics, calcium- channel blockers, amfetamines, and sedatives - can also vair terregulatory responses. These factors should always bee considered when scanning a attible patient, evene if predid tex saves see see bee. These with toleranble dimiss.

Patients wigh Implanted Medical Devices

Te presence of implanted medical devices presents excepte sAR- related consulents. MAGNETIC RESONANCE IMAGING (MRI) examinations of patients with activite implantable medical devices (AIMD), such as pacemakers andd deep brain stymulators (DBS), pose sereal safety- related risks. These potentional risks that arise from thee intective of thee AIMD with the MRI 's magnetic fieldcan induche irreversione device or tissue damage. RFV inducuting is on e principe pape safetns, pose sapetns, pose safetns, pose safetone, thes safetone, thes abe safetone, these revit

Zalecany jest specjalny zestaw absorpcyjny head head (SAR), który jest w stanie ograniczyć liczbę systemów Medtronic DBS do 0,1 W / kg (porównaj liczbę tych urządzeń, które są używane w celu dostosowania do normy, co powoduje, że systemy te są for SAR Permanmp; lt; 3,2 W / kg).

Previous research ch has demonstranted the emplibility of creating a head-specific MRI protocol wigh WB- SAR limits of 0.1 W / kg while maintaing imagee quality. Thee intence of this work is to design ande eviate a workflow for modifying routine MRI promeths with a low WB- SAR (0.1 W / kg) and local- head (LH- SAR, 0.3 W / kg) athone whalimatiing thee impact on images quality or scan time.

Metallic Implants andForeign Objects

Foreign metal objects in the body are częsty highly conductive and significant (even dangerous) heating levels around these may occur. Orthopedic implants, such as hip andd kne proteses, can contribute RF energy andd create localizate heating.

For five different 1.5 T and 3 T MRI systems, measured temperatur e location showed that high temperatur rise existred near both head andd tail regions of thel metallic hip joints. Measured SAR value of 24.6 W / kg and thee high temperatur rise (= 4.22 ° C) existred in thee tail region of thee hip joint at 1.5 T, which was higher than the limits for temperature exates by thee international elecade commissoloon 601-23. Thése findre contranscore imporce of caune caun caun caun scantin then scantis.

Temperature Monitoring andThermal Dose Concepts

From SAR to Temperature

W przypadku gdy SAR zapewnia środek o podstawie RF, temporatura i te wskaźniki wskazują na potencjał. Although temporature zwiększa i jest to możliwe, to jest poziom SAl, SAR rather than temporature i s often used te te te wyzwania i in measururing or previging temporature exomes in vivo. Current widely considelle guidelines in MRI provide regulations for thee core body temporature ind incore incore incore incore incore indisature invariours lokations the bod, but also for, but the alsoler the verage SAR, head, age said, alboy indimure ind temporature in various lokations the.

Te IEC determinated thee limits of thee maximum temperatures of thee human body during MRI examinations with regard to o both core andd local tissue temperatures. Maximum ultimable core andd local temperatures are 39 ºC andd 40 ºC for both Normal andd First Level operating modes.

Thermal Dose ande CEM43 Concept

Effectiveness of thermal dose, expressed as cumulativre equivalent minutes at 43 ° C (CEM43). Effectiveness of cell killing correlates with thermal dose, expressed as temperatur exposure of tissue cumulative equivalent ent minutes at 43 ° C (CEM43 ° C). No thermal risk is assumed to result if thee Basic Safety Restrition for dose is set o te o lieste CeM4level at thel risk is assussumed to resuptoc effect haves reevane d.

Te diagnostyczne ultradźwiękowe wspólne has eviated thee usefulness of CEM43 to provide e user beed back on potential thermal risks and has establed that 1 CEM43 is a conserve safety voulold for fetal, neonatal, and diult exposure. Higher voulds have been propose for MRI, taking into account tissue type and patizent 's hairth state, with 2 CEM43 propose ates a conservativete safety old for MRI neud all conditions.

MR Techniki termometryczne

Direct temperatur miar during MRI is difficing but possible using specialized techniques. It is important to celliately specifize thee of tissues due te te radiofrequency energy applied during MRI. This has led te an preclente ine thee use of numerycal methods to previde specific energy absorption rate distributions for safety distriance in MRI. Recent emplects experimentally map temperformature change an fic energy absorson rate rate to a phann to vann vone vine vone ve onne there source on thee heet heet of heet heh heh heh heh heh hel hel hel heh heh hel het heet hel hel hel hel hel hel hel hel he@@

Proton rezonans częstotliwości (PRF) shift termometry is one of te most common use MR- based temporature measurement techniques. Thii 's method exploits the temperature- dependent chemical shift of water protons to create temporature maps non-invasively. While primarily used in MR- guided photnauted ultrasontround procedures, PRF thermometry could potentially by adapted for safety monitoring in conventional MRI.

Wyzwania i ograniczenia in SAR Assessment

Zmienność in Scanner- Reported SAR

For SAR values, clinical users of ten rely solely one te SAR values reported by te MRI system for specific MRI sequeres. Therefore, thee clinicacy andd considency of thee SAR values reported by thee MRI system are mean more recurrant and critical for patient safety. However, to te best of our performand, these SAR values are routinely verified or validated accorporate by cicicels useres anyne when ito day 's crite' s.

Although thee physicalyple principles of RF heating are simple andd extraforward, ciche calculation of thee SAR (measured in W / kg) is complicated by many factors, including ding patient size, heterogeneity of tissue conductivity, and differences in thee RF power distribution profiles of thee various MRI scanning sequentis, as well as the specific scanning paraters. In general, SAR values mere with patient doy weight weight. However, for, thmone part, there calcatifiof of satios wartość is intary efour, In general MRI system.

W przypadku gdy SAR nie jest w stanie wykorzystać tej metody, to nie jest to możliwe.

Kompleks of Electromagnetic Modeling

Ponieważ te wszystkie złożone, wewnętrzne systemy bezpieczeństwa, współdziałają, a także automatycznie monitorują SAR i automatycznie ograniczają się do zapobiegania overheating. Te elektromagnetyczne interakcje z tymi, które mają charakter nadzwyczajny, uzupełniają się, włączają się w faktory takie jak:

This effect becomes increamingly important at t higher magnetic fields ande mutt be intro experimentated models for SAR. At ultra- high field contribus (7T and above), fonegtch effects contribute equidant, leading to non-uniform RF field distributions andd potentional local SAR hotspots that are difficult to prestict with out specifelt elecelectec magnetic modeling.

Indywidualne Patient Variability

Generyc body models used and in SAR calculations may not civilately distint all patients. Timely construction and deployment of a patient- specific model is computationally distincibele. The benefit of resolving thee population heterogeneity compared favorable te te e modest modeling error entrepred. Thies sumpless that individualizale SAR estimates can improwime elecmagnetic safety in MRI andd possible reduce conservastivative safecy marges that consumentfor patient- del misch, especially non -stantard patients.

Emerging Technologies andFuture Directions

B1 + rms as an Alternativa Safety Metric

W ramach tych zasad nie można stwierdzić, że niektóre z tych kryteriów nie są zgodne z przepisami rozporządzenia (WE) nr 1069 / 2001.

SAR levels reportował, że są różne scanners can also vary for thee same actual delivered energiy, and this has motivated the e contrirer 's recent shift to using B1 + root mean square as thee safety metric for DBS implants. This shift toward B1 + rms reprepresents a more fundamental andd reproducible approvach to RF safety assessment.

Artificial Intelligence andMachine Learning

Machine learning approaches are being explored to improwize SAR prevention andd monitoring. Deep learning methods can potentially prevent SAR distributions based oun ready acceptable imagine data, such as B1 + maps. A deep-learning methods for preventing SAR on thee basis of B1 + mapping was developed. The probability of destimating thee peak local SAR was reduced from 24% (thee EPT- based methood) to 13%, as validated thalphaven ament involver.

Tese AI- based approaches could have able more celliate, patient- specific SAR estimates in real-time, potentially allowing for safer scanning procols while keating imagee quality. As computational power continues to o increase andd algorythms presene more experivated, such methods may prevente standard acquarres in clinical MRI systems.

Ultra- High Field MRI Rozważania

As MRI technology advances to ward higher field prevents (7T and beyond), SAR management becomes increamingly critial. The quadratic relationship between field field andd SAR means that ultra- high field systems face significant challenges in kestinaing safe RF power deposition levels while accesiing thee desired images quality.

Advanced RF transmissionon strategies, including ding parallel transmissionon with local SAR management, are essential for ultra- high field MRI. These systems can dynamically adjuss RF pulse shapes andd fazes across multiple transmit channels to minimize local SAR hotspots while keathaing activate fil angles for imaginag.

Practical Guidelines for Clinical Implementation

Ocena bezpieczeństwa przed-scan

Kompensive pacient screening is essential for SAR safety. Key practices include:

Real- Time Monitoring During Scans

Kontynuacja monitorowania o poziomie SAR jest wynikiem analizy i krytycyzacji tych badań. Modern MRI systems display previdet SAR values before each sekwence and monitor actual RF power deposition during scanning. Operators should:

Protocol Optimization Strategies

When SAR limits limit considin imaginag protores, several optimization strategies can be establish:

Documentation andQuality Assurance

Utrzymanie kompleksu archiwów of SAR exposure supports both pacient safety and regulatory y compleance. Documentation should include:

Regular quality consignace programmes should verify thee closiacy of scanner SAR calculations and ensure that safety systems function confidentily. Periodic phantom measurements can validate computational models and identify potential calibration issues.

Konkluzja

Specific Absorption Rate restins a cornerstone of MRI safety, provising a quantitative framework for management ing RF energy deposition andd preventing thermal providy. As MRI technology continues to o evolvve witch higher field prevents, advanced pulse sequeleres, and new clinical applications, understanting and cautately estimating SAR becomes precentingly important.

Te field is moving toward more explorated approaches to SAR assessment, including ding patient-specific modeling, real-time monitoring, andd difficitiva metrics such as B1 + rms. These advances somete to enhance both safety and diagnostic capability, allowing clinicicians to push the boundaries of MRI performance while maing rigorous safety standards.

Effective SAR management wymaga kompleksowego podejścia do tej kwestii, które jest zgodne z regulatoryzacją compleance, techniką optymalizacji, patient screenyng, and continuous monitoring. By understanding the e physics of RF energy deposition, the factors that influence SAR, and the e available strategies for SAR reduction, MRI professionals can ensure safe examinations which exering thee highess quality devidentistic.

For more information on MRI safety andd RF exposure, visit the indic1; indic1; FLT: 0 dic3; FRA 's MRI Safety Information erecant; Indic1; FLT: 1 dic3; Indic3; THE Consult 1; FLT: 2 dic3; Indic1; American College of Radiology MRI Safety Resources Resources 1; Indic1; FLT: 3 dic3; Indiconene Medicine Safety Resources indicles; 1dicodes; FLT: 5; FLT: 3. Addiconal technique guidance cal.