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21NRM05 STASIS
D1: Repo on he de elopmen and calib a ion o an implan sa e y concep in
MRI, comp ised o senso -equipped sma medical implan s and pTx capable
MRI scanne s ha enable o assess and mi iga e in si u RF induced implan
hea ing
O ganisa ion name o he lead pa icipan o he deli e able:
Physikalisch-Technische Bundesans al (PTB)
Due da e o he deli e able: 30 Sep embe 2025
Ac ual submission da e o he deli e able: 30 Sep embe 2025
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Glossa y
MRI Magne ic Resonance Imaging
RF Radio equency
SAR Speci ic Abso p ion Ra e
DBS Deep B ain S imula o
pTx Pa allel T ansmission
IPG Implan able Pulse Gene a o
AIMD Ac i e Implan able Medical De ice
CP Ci cula Pola iza ion
OP O hogonal P ojec ion
WC Wo s Case
ADC Analog o Digi al Con e e
RMS Roo Mean Squa e
21NRM05 STASIS
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TABLE OF CONTENTS
1 Summa y ................................................................................................................................. 4
2 In oduc ion .............................................................................................................................. 4
3 Vi ual es en i onmen o RF senso -equipped sma medical implan s ................................ 5
3.1 Simula ed senso signals ................................................................................................... 6
3.2 Calib a ion o senso signals .............................................................................................. 8
3.3 Re e ence Implan (s) ........................................................................................................ 10
3.4 Re e ence implan (ii): simula ed calib a ion esul s .......................................................... 11
4 New app oach o assessing unce ain ies o sa e y- ele an pa ame e s in pTx-based MRI
sys ems .................................................................................................................................. 15
4.1 Expe imen al backg ound ................................................................................................. 15
4.2 Q-Ma ix app oach ........................................................................................................... 17
5 Calib a ion se up o senso -equipped sma medical implan s ............................................... 21
5.1 Final calib a ion se up/ es bed based on 8Ch pTx body coil om DKFZ ........................... 22
5.2 Final calib a ion se up: in luence o nonlinea i ies............................................................. 25
5.3 Final calib a ion se up: esul s o senso calib a ion ......................................................... 26
5.4 Final Calib a ion se up: senso ou pu s B1+ ms ............................................................ 27
6 Summa y and conclusions ..................................................................................................... 29
7 Re e ences ............................................................................................................................ 31
8 Rela ed o he Deli e ables ..................................................................................................... 33
21NRM05 STASIS
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1 Summa y
Medical implan s pose a sa e y isk o pa ien s in magne ic esonance imaging (MRI) due o
adio equency induced issue hea ing. Cu en sa e y p ac ices ely on simula ions co e ing a la ge
a ie y o exposu e scena ios leading o o e ly conse a i e RF powe limi s ha educe image
quali y and impose a high bu den on he clinics. A sma medical implan sa e y concep can be used
o pe sonalized sa e y assessmen s and on- he- ly moni o ing o RF-induced hea ing, subs an ially
imp o ing cu en clinical p ac ice. In his epo a simula ion-based app oach was in oduced o
de elop and build a pa allel ansmission (pTx) calib a ion sys em, which will allow he de e mina ion
o sa e y- ele an RF pa ame e s o elonga ed senso equipped implan s as well as he calib a ion
o he senso signals including he de ec ion o possible ailu e scena ios. The main ea u e o he
epo ed app oach is he abili y o he pTx based calib a ion and es ha dwa e o apply a la ge
numbe (> 1000) o di e en exposu e condi ions o he implan and o de e mine a ious haza d
me ics in ela ion o B1+ ms, which complies wi h he no ma i e equi emen s o IEC60601-2-33
and ISO/TS 10974.
2 In oduc ion
When an MR scan is conduc ed on a pa ien wi h an ac i e implan able medical de ice (AIMD), such
as a deep b ain s imula o (DBS), he in e ac ion o he RF exci a ion coil o he MR sys em wi h he
elec ically conduc i e wi es and elec odes o he AIMD can cause subs an ial inc eases in RF-
induced local SAR and espec i e issue hea ing a ound he implan ed elec odes.6,7 The induced
local SAR is pa ien -, implan -, MR- and exam-speci ic leading o complex simula ion models and
high unce ain ies in he RF sa e y assessmen applied in cu en s anda ds8 o p e en po en ial
issue damage, e.g. in he b ain.9 As a consequence SAR limi s a e subs an ially educed in he
p esence o AIMDs, hese limi a ions a ec he imaging, hus, diagnos ic pe o mance o he MRI
sys em.
In Deli e able D2 he sma medical implan sa e y concep was al eady in oduced which is based
on pe sonalized measu emen s a he han gene alized simula ions1–4. Small and inexpensi e
physical senso s can be a ached o he implan elec odes2, embedded in he implan casing3 o
e en unmodi ied comme cial componen s, such as shown o DBS implan s15,16, can be used o
21NRM05 STASIS
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assess he momen a y and pa ien -speci ic RF haza d. I he MR sys em and RF coil suppo mo e
han one independen RF ansmission channel, i.e. so-called pa allel ansmission (pTx), he sensed
implan in o ma ion can be in elligen ly u ilized o subs an ially mi iga e he RF-induced hea ing
wi hou he need o educe he ansmi ed RF powe and comp omise image quali y2–4,17.
Sui able pTx-based es ing and calib a ion p ocedu es a e essen ial o he subsequen applica ion
o he sa e y concep desc ibed abo e. Compa ed o es ablished implan es ing p ocedu es o
con en ional MR sys ems wi h a single RF ansmission channel, he la ge numbe o deg ees o
eedom in a pTx sys em leads o signi ican ly g ea e complexi y. On he o he hand, pTx-based es
sys ems enable a much la ge numbe o exposu e scena ios o be gene a ed in a e y sho ime,
e.g., 1000 ield con igu a ions in 100 ms. This in u n enables s ochas ic es p ocedu es and hus
bo h he eliable iden i ica ion o po en ially dange ous si ua ions and a simple de e mina ion o
unce ain ies in he sys em. Such pTx-based es sys ems could he e o e also be ad an ageous o
es ing implan s wi hou buil -in senso s and o passi e implan s. A c ucial poin he e is ha he es
sys em can gene a e aceable elec omagne ic ield con igu a ions ha e lec he ypical exposu e
condi ions in 1.5 T o 3 T whole-body MR scanne s.
This is achie ed in he se up desc ibed he e by using a body coil wi h 8 ansmi channels, which is
geome ically equi alen o he body coil o a con en ional 3T MR scanne (see Deli e able D3). This
allows he RF exposu e o be ela ed o he B1+ ms in ci cula ly pola ized mode (CP) in acco dance
wi h he s anda d. The aceable de e mina ion o B1+ ms a he cen e o he coil in pTx mode is an
impo an esul o he p ojec . This allows sa e y- ele an pa ame e s, such as he empe a u e ise
a he implan ip, o be measu ed o a a ie y o exposu e condi ions in he sense o an end- o-end
es . Wi h hese da a, bo h implan and MR manu ac u e s can de elop op imiza ion s a egies o
minimize he isks o RF-induced issue hea ing while imp o ing MR imaging pe o mance.
3 Vi ual es en i onmen o RF senso -equipped sma medical
implan s
21NRM05 STASIS
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In a i s s ep a simula ion-based app oach was in oduced o e alua e he cha ac e is ics o a pa allel
ansmission (pTx) calib a ion and es sys em, which will allow he de e mina ion o sa e y- ele an
RF pa ame e s o elonga ed senso equipped implan s as well as he calib a ion o he senso signals
including he de ec ion o possible ailu e scena ios.
The i ual es en i onmen consis s o a se ies o model calcula ions ha can be used o de e mine
sa e y- ela ed pa ame e s, such as he poin SAR and he local empe a u e ise as a unc ion o he
senso signal om he sma implan . This allows s a egies o calib a ing he senso signals o be
de eloped and possible e o scena ios due o in e e ence and signal loss o be iden i ied. This
would enable he implan manu ac u e o pe o m a simula ion-based isk assessmen . The model
calcula ions ocused on he use o RMS senso s o pTx mi iga ion, which p o ed o be he mos
a o dable op ion in he p e ious p ojec .1–4
3.1 Simula ed senso signals
The AIMDs p ima ily conside ed a e neu os imula o s (DBS), in which a hin (< 2 mm) elec ode
measu ing 30 cm o 50 cm in leng h is equipped wi h a se ies o elec ode pads. The elec odes,
which a e usually shielded, ha e co esponding wi es inside ha connec o he implan able pulse
gene a o (IPG), al hough he connec ion o he IPG is ypically no comple ely RF shielded. The RF
signals om he ip o he implan conduc ed ia he wi es may he e o e be a ec ed by RF
in e e ence in he a ea o he IPG and he e o e only e lec he condi ions a he ip o he implan
o a limi ed ex en . In addi ion, an RF signal is conduc ed o he IPG om each elec ode pad in
p inciple, and he SAR dis ibu ion a he a ious elec ode pads may also a y. I is he e o e e y
impo an o cla i y in ad ance o u he de elopmen s whe he he senso -based sa e y concep
desc ibed in D2 s ill wo ks in he case o a eal implan wi h signi ican ly highe complexi y.
To his end, simula ion calcula ions we e ca ied ou on a simpli ied model o a shielded DBS
elec ode wi h 4 in e nal leads and 4 pads a he ip (see Fig. 1). The IPG, including he connec ions,
was modelled on eal AIMDs. The RF exci a ion is ealised ia 16 loop coils, each o which was
assigned o an RF channel. The FDTD simula ion was ca ied ou wi h an iso opic mesh wid h o
0.5 mm. F om he 4 di e en senso signals measu ed inside he IPG, a linea supe posi ion can
21NRM05 STASIS
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hen be de e mined in he sense o a bes i , which co ela es bes wi h he maximum poin SAR,
e.g. a he loca ion o elec ode pad #1 (s. Fig. 2)
Figu e 1 Simula ed se up wi h 16 exci a ion coils and 4 elec ode pads.
Figu e 2 Co ela ion o simula ed haza d measu e (poin SAR a elec ode #1) wi h bes i o senso signal su oga e.
As a esul , he e is ce ainly an inc eased unce ain y in he de e mina ion o he poin SAR a he
elec ode pads o he selec ed model con igu a ion, which is caused by EMF in e e ence. This
should be aken in o accoun when designing senso -equipped sma implan s. In any case, he
simula ion calcula ions p esen ed allow such e ec s o be analysed in ad ance o implan
de elopmen . Howe e , he e a e also o he measu able a iables ha can be used as senso
21NRM05 STASIS
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signals, e.g. changes in impedance be ween di e en elec ode pads15,16, which a e di e en ly
sensi i e o in e e ence. In he end, he eliabili y o he conside ed senso -equipped sma implan
can only be e alua ed expe imen ally wi h a pTx-based es bed.
3.2 Calib a ion o senso signals
Fo he p esen ed sa e y concep o be applicable, he eco ded senso signals mus be as clea ly
ela ed as possible o a haza d me ic. This allows his haza d me ic o be eco ded o e ime be o e
o du ing an MR examina ion and isk-minimising measu es o be aken. The mos ele an haza d
me ic is he empe a u e ise a he implan ip. I he empe a u e ise is limi ed o 1K o 2K, o
example, he isk o possible issue damage can be es ima ed and aken in o accoun in he implan
manu ac u e 's isk managemen .
I is he e o e necessa y o ca y ou app op ia e simula ions o he ela ionship be ween he senso
signal and he empe a u e inc ease a he implan ip o he simple e e ence implan s conside ed
in his p ojec in o de o iden i y possible sys ema ic sou ces o e o . Fu he mo e, hese simula ions
also allow he measu emen se ups o he calib a ion measu emen s o be op imised, especially
wi h ega d o he posi ioning o ibe op ic empe a u e p obes.
In Fig. 3, o example, i was shown o he e e ence implan ul ima ely selec ed, based on a semi-
igid coaxial cable, ha he empe a u e cu es in he p oximi y o he implan ip can be ma ched
e y well wi h he simula ed cu es i he measu emen posi ion is chosen app op ia ely.
21NRM05 STASIS
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Figu e 3 Simula ion o empe a u e ise (inhouse code21). (A) Simula ion se up o he coaxial cable ip. (B) Simula ed
no malized empe a u e in he plane o he coaxial cable. (C) No malized empe a u e di e ence as a unc ion o ime o
posi ion A and B compa ed o a measu ed cu e o posi ion A.
In u he simula ions, he e ec o di e en issue pa ame e s on he empe a u e cu es was
analysed in compa ison o he PVP-based phan om luid (PVP - poly inylpy olidone) used in he
expe imen al es se up. The compa ison conside s he issue ypes 'whi e ma e ', 'g ey ma e ' and
'ce eb ospinal luid' ele an o DBS elec odes. Fig. 4 and Fig. 5 summa ise he esul s o 3T and
7T espec i ely. These simula ions allow conclusions o be d awn abou he eal condi ions in i o
and would ha e o be ca ied ou by he implan manu ac u e in acco dance wi h Tie 3 ISO/TS
10974 anyway.
Figu e 3: Simula ion esul s (Sim4Li e) o (A-D) RF induced E- ields o a e e ence implan elec ode o a 128MHz RF
exposu e and di e en backg ound issue ypes and (E-H) co esponding he mal simula ions a he elec ode. (I)
Tempe a u e e olu ion o e an RF hea ing pe iod o 60s a he loca ion ma ked wi h ‘x’.
21NRM05 STASIS
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condi ions in hese head coils a e no sui able o widely applicable es ha dwa e, which mus be
based on s anda d MR sys ems (1.5T and 3T wi h body coil).
Figu e 12: (A) Co ela ion o he senso signal wi h adial E- ield o 1000 andom pTx ol age ec o s. pTx ol age ec o s
ma ked wi h a diamond we e scaled by a ac o o 5 and a e used in (B). (B) Co ela ion o squa ed coaxial senso signal
wi h empe a u e ise a e o hea ing o 10 andom pTx ec o s. Figu e aken om Re .4.
Figu e 13: E- ield and empe a u e ise calib a ion se up used o de e mine co ela ion o he senso signal wi h adial E-
ield and wi h empe a u e espec i ely. Mo e de ails abou he se up, ield and empe a u e p obes can be ound in he
co esponding e e ences1,3,4. Figu e aken om Re .3.
21NRM05 STASIS
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4.2 Q-Ma ix app oach
The c ucial poin in he de elopmen and calib a ion o an implan sa e y concep o sma implan s
equipped wi h senso s in connec ion wi h pTx-capable MR scanne s is he implemen a ion o an
a o dable me hod o de e mining unce ain ies ha adequa ely akes in o accoun he high numbe
o deg ees o eedom esul ing om he use o a pTx sys em. Ano he poin is ha MR-compa ible
implan s, i.e., medical de ices labelled “MR condi ional,” a e now mos ly labelled wi h ega d o
B1+ ms, as speci ied in he la es e sions o IEC 60601-2-33 and ISO/TS 10974, especially i MROC
(MR Equipmen Ou pu Condi ioning) is used in he u u e5,8.
An app oach is he e o e being sough ha will also allow he B1+ ms o be de e mined in he es
se up. Fo his eason alone, only a pTx body coil can be conside ed as he exposu e sys em o
u he de elopmen s. Such a coil is desc ibed in Deli e able D3, o he STASIS p ojec and was
used in u he wo k.
We will now conside he ollowing ele an pa ame e s: (i) senso signal, (ii) E- ield/SAR a he ip
o he implan , (iii) B1+ ms a he cen e o he body coil, (i ) empe a u e inc ease a he ip o he
implan , all o which a e ela ed o quan i ies ha esul om he supe posi ion o he ields gene a ed
by he pTx coil.
These quan i ies can all be ep esen ed by a co esponding quad a ic o m, he so-called Q-ma ix
QX, whe e X is ela ed o quan i ies (i) o (i ). QX is a posi i e de ini e He mi ian ma ix, meaning i
has only posi i e eigen alues. QX is de ined locally o he measu ed a iables unde conside a ion,
i.e., only one eigen alue should be di e en om ze o, and he associa ed eigen ec o ep esen s
he maximum cons uc i e in e e ence o he complex- alued ield a iables, including he phase
angle o he indi idual RF channels in ela ion o a selec ed channel (e.g., channel #1). F om
measu ed QX ma ices, i is he e o e also possible o in e he phase e o s o he pTx sys em wi hou
using a phase-sensi i e ecei ing sys em wi h he need o ha e a e e ence phase a ailable. Hence,
only he RMS alues need o be eco ded, which conside ably simpli ies measu emen da a
acquisi ion. This means ha e en o phase-dependen a iables, such as he induced ol age a a
pick-up coil (PUC) used o B1 measu emen o he ol age a he implan senso , only RMS alues
need o be de e mined. The phase in o ma ion is p o ided solely by he cohe en pTx sys em.
21NRM05 STASIS
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The e o e, he Q-Ma ix QX con ains all ele an in o ma ion abou he pTx sys em i sel , which is
why his app oach enables end- o-end es ing.
Ma hema ically, his can be summa ised as ollows:
X= u|QX|u (1)
Fo senso signals ha a e ep esen ed by a complex alue Us, e.g. he RF ol ages measu ed a
he implan senso o he B1 pick-up coil, X would hen be equal o |Us|2. Fo SAR- ela ed quan i ies
o empe a u e- ela ed alues, X would be e.g. equal o he SAR alue o ΔT, espec i ely. The
ol age ec o |u deno es he complex alued RF exci a ion signal se ing in he pTx MRI sys em.
The ank o QX is de e mined by he numbe o independen RF channels Nchan.
Based on hese p ope ies o QX, he ollowing p ocedu e is used o de e mine quan i ies (i) o (i )
and he associa ed measu emen unce ain ies.
1. Measu emen o QX wi h a simple pTx sequence:
Nchan2 measu emen s a e equi ed o cons uc QX as ollows:
2𝑄𝑋,𝑘𝑙={(𝑋𝑘𝑙− 𝑋𝑘− 𝑋𝑙)+𝑗(𝑋𝑘𝑙
†− 𝑋𝑘− 𝑋𝑙) o 𝑘≠𝑙 𝑎𝑛𝑑 𝑘<𝑙
(𝑋𝑘𝑙− 𝑋𝑘− 𝑋𝑙)−𝑗(𝑋𝑘𝑙
†− 𝑋𝑘− 𝑋𝑙) o 𝑘≠𝑙 𝑎𝑛𝑑 𝑘>𝑙
2𝑋𝑘 o 𝑘=𝑙 , (2)
whe e 𝑋𝑘 is he signal X when only channel 𝑘 ansmi s, 𝑋𝑘𝑙 deno es he signal X when channels 𝑘
and 𝑙 ansmi simul aneously in phase, and 𝑋𝑘𝑙
† he same o a 𝜋/2 phase di e ence be ween bo h
channels, while he channels’ ampli udes a e always iden ical.
21NRM05 STASIS
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2. App oxima e ep esen a ion o QX by he eigen ec o ec o |e Xmax a he la ges eigen alue
λXmax.
QX can be ep esen ed as ollows:
QX = λXmax |e Xmaxe Xmax| (3)
Then he ollowing esul s o any pTx ol age ec o |u o he complex alued ol age Us:
Us = (λXmax )0.5 e Xmax|u (4)
3. Unce ain ies ia s ochas ic app oach
A s ochas ic app oach is p esen ed o de e mine he unce ain ies in he sys em, bo h he sys ema ic
de ia ions, e.g. hose caused by non-linea i ies, and he andom e o s (s. Fig.14,15). Fo example,
1000 andom pTx ol age ec o s a e gene a ed, whe eby he maximum ampli ude ac oss all
ansmi channels is limi ed o a speci ied alue. A senso alue can hen be p edic ed om (4) based
on he measu ed Q-ma ix QS. This alue can hen be compa ed wi h he ac ual measu ed senso
alues, which p o ides in o ma ion abou he unce ain ies in he sys em. Thus, de ia ions om he
p edic ed alues o m a genuine me ic o he unce ain ies in his mul idimensional pTx sys em.
21NRM05 STASIS
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Figu e 14 Sca e plo o he p edic ed e sus measu ed senso signal o 1000 andomly selec ed ol age ec o s (7T
head coil, s. Fig. 13). When using he eigen ec o wi h he highes eigen alue o Qs, he co ela ion is be e and he e
a e ewe ou lie s.
Figu e 15 Sca e plo o he p edic ed e sus measu ed E-Field a he implan ip o 1000 andomly selec ed ol age
ec o s (7T head coil, s. Fig 13). By using he eigen ec o wi h he highes eigen alue o Qs, some sys ema ic e o s can
be a oided, especially o low senso signals.
21NRM05 STASIS
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Based on his me hodology, he inal calib a ion and es se up was de eloped.
5 Calib a ion se up o senso -equipped sma medical implan s
The indi idual componen s o he se up a e desc ibed below. The 8ch pTx body coil (Deli e able D3,
Fig.16) is d i en by he es bed se up om Re .1 (see also
h ps://www.opensou ceimaging.o g/p ojec /p x-implan -sa e y- es bed/). The ampli ie s used allow
a maximum ou pu powe pe channel o 20W, whe eby he linea i y o he ampli ie s is sa is ac o y
o ou pu powe s o up o 10W. Wi h his se up, up o app ox. 100W o al powe can be applied o
he pTx body coil o hea ing expe imen s o e a longe pe iod o ime, which also esul s in easily
measu able empe a u e inc eases a he implan ip.
The phan om used is based on he ASTM phan om (Fig.17), bu is sho e in o de o educe i s
mass, which g ea ly acili a es measu emen s. In p inciple, howe e , he pTx body coil is also
sui able o he ASTM phan om. The e e ence implan is posi ioned in he phan om, which is illed
wi h a PVP-wa e mix u e3. Fo his pu pose, a mechanical holde was 3D p in ed o ix he implan
in posi ion a he ip and simul aneously accommoda e he sensing ibe 3 o he FBG empe a u e
ins umen (Fig.18). A he end o he coaxial cable used as he e e ence implan , an SMA connec o
is a ached o he co e , gi ing he se up he necessa y mechanical s abili y, which is essen ial o
ep oducible measu emen s.
The de e mina ion o B1+ ms in he cen e o he pTx body coil is essen ial o he end- o-end es s.
Fo his pu pose, a mechanical holde o he OSI2 pick-up coil was 3D p in ed (Fig.19), which allows
he p ecise and ep oducible ixa ion o he PUC in wo mu ually pe pendicula posi ions. This allows
he ield ampli udes B1x and B1y o be de e mined, om which B1+ and B1- a e hen de i ed. B1+ o B1-
in CP+ o CP- mode is selec ed as he e e ence alue. The speci ic di ec ion o o a ion o he
co esponding B1 ield depends on he o ien a ion o B0. The e o e, implan s should always be es ed
in bo h di ec ions o o a ion, as he geome ic condi ions a e no necessa ily symme ical.
De e mining he B1 ield componen s equi es in-si u calib a ion in a TEM cell22, a calculable ield
sou ce in which he applied ol age is de i ed om he measu emen o he RF powe used. This
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powe is de e mined using a highly accu a e calib a ed powe measu emen head (R&S NRP18TN),
which ensu es he aceabili y o he measu emen s. The FBG senso s used o empe a u e
measu emen s we e also calib a ed using a aceable PT100, which means ha he de e mina ion
o empe a u e- ela ed haza d me ics is also aceable in p inciple.
As i la e became appa en , nonlinea i ies ha e a signi ican impac on he de e mina ion o he QX
ma ix. These nonlinea i ies can o igina e om bo h he RF powe ampli ie s and he signal
acquisi ion o he senso s. Fo his eason, he p ima y measu emen s we e pe o med wi h he
e e ence implan connec ed di ec ly and no wi h ibe op ic ansduce s o wi eless ansmission o
ec i ied senso signals. Ne e heless, he se up can also be used o es ing o - he-shel implan s i
an E- ield senso o an iso opic SAR p obe is placed a he ip o he implan , allowing o su icien ly
as eadou . This can hen also be used o calib a e a senso signal wi h espec o he selec ed
haza d me ic16.
5.1 Final calib a ion se up/ es bed based on 8Ch pTx body coil om DKFZ
The ollowing igu es (Fig.16-19) isualize all ha dwa e componen s used in he calib a ion
p ocedu e.
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Figu e 16 8-channel pTx body coil used o he calib a ion and es ing se up oge he wi h PVP phan om, e e ence implan
inside he phan om, ip holde wi h empe a u e sensing ibe (FBG). A he end o he coaxial cable an SMA connec o is
a ached o he co e and connec ed o he ecei e sys em (blue cable). The mechanical holde o he OSI2 pick-up coil
is seen in he cen e o he coil
Figu e 17 De ailed iew o he phan om wi h e e ence implan ( ed lead), ip holde wi h empe a u e sensing ibe ), SMA
connec o and OSI2 pick-up coil.
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Figu e 18 Mo e de ailed iews au he componen s used, uppe ow le : o e iew as seen in Fig. 17, uppe ow middle:
de ailed iew o ip holde wi h empe a u e sensing ibe , uppe ow igh : CAD model o PUC moun o TEM cell, lowe
ow le : CAD model o ip holde , lowe ow middle: CAD model o holde o he OSI2 pick-up coil, lowe ow igh : de ailed
iew OSI2 pick-up coil wi h holde .
Figu e 19 Componen s o he TEM calib a ion se up. Le : PUC in moun o TEM cell, middle: MR-TEM cell22 wi h PUC
inse ed, igh : used calib a ed powe measu emen p obe head (R&S NRP18TN).
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5.2 Final calib a ion se up: in luence o nonlinea i ies
Fig. 20 shows examples o esul s o he implan senso a di e en powe le els. The a enua ion
le el a =0.3 co esponds o a maximum o wa d powe o app oxima ely 1W pe channel, whe eby
i should be no ed ha his powe is no measu ed di ec ly a he coil because, in he sense o an
end- o-end es , all measu ed quan i ies a e ela ed o he B1+ ms a he cen e o he coil. CP+ and
CP- modes a e pa icula ly highligh ed pTx ol age ec o s, whe eby he implan senso signal is
e y di e en o bo h modes. This emphasizes ha es s mus be pe o med in bo h modes. The
in luence o he nonlinea i ies o he RF powe ampli ie s is e iden ; he co esponding unce ain ies
(s. Fig. 21) would ha e o be aken in o accoun in a eal pTx sys em.
Figu e 20 Final calib a ion se up: esul s o he e e ence implan senso signal o di e en powe le els.
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10. Bou e A, Chow CT, Na ang K, e al. Imp o ing Sa e y o MRI in Pa ien s wi h Deep B ain
S imula ion De ices. Radiology. 2020;296(2):250-262. doi:10.1148/ adiol.2020192291
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wi h magne ic esonance-condi ional pacemake and implan able ca dio e e -de ib illa o
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equipped implan s and MR scanne s o imp o ed sa e y and imaging. Magn Reson Med.
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19. Physikalisch-Technische Bundesans al (PTB). Wi eless Re e ence Implan . Open Sou ce
Imaging. h ps://www.opensou ceimaging.o g/p ojec /wi eless- e e ence-implan /. Published
2023. Accessed Ma ch 27, 2025.
20. ASTM F2182 - 11. ASTM F2182 - 11 S anda d Tes Me hod o Measu emen o Radio
F equency Induced Hea ing Nea Passi e Implan s Du ing Magne ic Resonance Imaging.
h ps://www.as m.o g/DATABASE.CART/HISTORICAL/F2182-11.h m. Accessed Ma ch 22,
2020.
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21. Sei e F, Weidemann G, I e mann B. Co ela ion o psSAR and issue speci ic empe a u e o
7T pTx head coils - a la ge scale simula ion s udy. In: P oc. In l. Soc. Mag. Reson. Med. Vol 23,
380. To on o, Canada; 2015.
22. Klepsch T, Lindel TD, Ho mann W, Bo e weck H, I e mann B. and Sei e F. Calib a ion o ibe -
op ic RF E/H- ield p obes using a magne ic esonance (MR) compa ible TEM cell and dedica ed
MR measu emen echniques. Biomedical Enginee ing/Biomedizinische Technik, ol. 57, no. SI-
1-T ack-B, 2012, pp. 000010151520124428. h ps://doi.o g/10.1515/bm -2012-4428
8 Rela ed o he Deli e ables
D2: Repo on he echnical speci ica ions and he communica ion wo k low o senso -equipped
sma medical implan s wi hin an MRI scanne , h ps://doi.o g/10.5281/zenodo.15502183
D3: Repo on he de elopmen o open-sou ce e e ence ha dwa e (RF coil, exci e , modula o s,
RF powe ampli ie ) and open-sou ce con ol so wa e, including aceable measu emen
p ocedu es ha allow es ing o implan s unde pTx MR condi ions
