Con iden iali y S a us: PU - Public, ully open ( emembe o deposi public deli e ables in a us ed eposi o y)
Deli e able Co e Shee
Funded by he Eu opean Union. Views and opinions exp essed a e
howe e hose o he au ho (s) only and do no necessa ily e lec hose
o he Eu opean Union o EURAMET. Nei he he Eu opean Union no
he g an ing au ho i y can be held esponsible o hem.
The p ojec has ecei ed unding om he Eu opean Pa ne ship on
Me ology, co- inanced om he Eu opean Union’s Ho izon Eu ope
Resea ch and Inno a ion P og amme and by he Pa icipa ing S a es.
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21NRM05 STASIS
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 s) and open-sou ce con ol so wa e,
including aceable measu emen p ocedu es ha allow es ing o implan
unde pa allel ansmission (pTx) MR condi ions
O ganisa ion name o he lead pa icipan o he deli e able:
Ge man Cance Resea ch Cen e (DKFZ)
Due da e o he deli e able: 30 h o Sep embe 2025
Ac ual submission da e o he deli e able: 30 h o Sep embe 2025
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Glossa y
B1+ Ci cula ly pola ized lux densi y, ansmi ield
DAC Digi al- o-analogue con e e
FPGA Field p og ammable ga e a ay
GUI G aphical use in e ace
IQ-Modula o Inphase/quad a u e modula o
LDMOS La e ally di used me al-oxide-semiconduc o
MR Magne ic esonance
MRI Magne ic esonance imaging
RF Radio equency
RMS Roo mean squa e
𝜀𝑟 Rela i e pe mi i i y
𝜎 Conduc i i y
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TABLE OF CONTENTS
1 Summa y ................................................................................................................................. 4
2 In oduc ion .............................................................................................................................. 4
2.1 Pu pose ............................................................................................................................. 4
2.2 Sys em O e iew ............................................................................................................... 5
3 RF a ay ................................................................................................................................... 5
3.1 In oduc ion ........................................................................................................................ 5
3.2 Mechanical Design ............................................................................................................. 6
3.3 Elec ical Design ................................................................................................................ 7
3.4 RF ield simula ion esul s .................................................................................................. 8
4 RF Gene a ion Sys em ............................................................................................................. 9
4.1 O e iew ............................................................................................................................ 9
4.2 Timing .............................................................................................................................. 10
4.3 Modula ion ....................................................................................................................... 10
5 RF powe ampli ie s ............................................................................................................... 11
6 G aphical Use In e ace ........................................................................................................ 12
6.1 O e iew .......................................................................................................................... 12
6.2 Main window .................................................................................................................... 12
6.3 Pulse Tool ........................................................................................................................ 12
6.4 Calib a ion ........................................................................................................................ 13
7 Summa y and Conclusion ...................................................................................................... 14
8 Re e ences ............................................................................................................................ 14
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1 Summa y
This epo p o ides an o e iew o he ha dwa e and so wa e componen s o he STASIS open-sou ce
exposu e sys em. The a ious pa s o he sys em a e b ie ly desc ibed. As he sys em is open sou ce, de ailed
in o ma ion is a ailable in he co esponding eposi o ies. Pho og aphs o he RF coil a ay and he ansmi
chain a e shown in Figu e 1.
Figu e 1: The 8-channel ansmi a ay (le ) and he con ol sys em and ampli ie s in a 19” ack ( igh ).
2 In oduc ion
2.1 Pu pose
The STASIS RF exposu e sys em is an open-sou ce ha dwa e and so wa e pla o m designed o implan
es ing unde exposu e o adio equency (RF) ields, such as hose encoun e ed in he en i onmen o an MRI
sys em. Fo his pu pose, he a ge RF equency is 128 MHz, co esponding o he esonan equency o
p o ons in a 3 Tesla magne ic ield. The sys em is capable o ansmi ing on eigh independen RF channels,
enabling pa allel ansmission.
To ensu e he design is easily accessible o po en ial use s, all design iles and so wa e a e publicly a ailable
and can be accessed ia he ollowing eposi o ies:
h ps://gi hub.com/sO zada/STASIS_Exposu e_Ha dwa e
h ps://gi hub.com/sO zada/STASIS_Con ol
All ha dwa e componen s o he exposu e sys em a e licensed unde he CERN-OHL-W while he so wa e is
licensed unde a GNU GPL 3. In addi ion, he p ojec has been submi ed o he con o mi y assessmen body
o he Open Sou ce Imaging Ini ia i e e.V. (h ps://www.opensou ceimaging.o g) o assess i s open-sou ce
s a us acco ding o DIN SPEC 3105.
To u he imp o e accessibili y, s anda d componen s wi h long p oduc ion li espans we e selec ed whe e e
possible. Fo example, s anda d logic componen s we e used ins ead o specialised mic ocon olle s o
FPGAs.
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2.2 Sys em O e iew
Figu e 2: Schema ic o e iew o he STASIS exposu e sys em.
The STASIS exposu e sys em consis s o 4 main pa s as shown in Figu e 2. The use in e ac s wi h he
sys em ia a g aphical use in e ace (GUI), om which he con ol ha dwa e can be p og ammed. The con ol
sys em manages iming and gene a es eigh independen RF signals, which a e ansmi ed o eigh sepa a e
RF ampli ie s. These ampli ie s hen deli e high-peak and a e age powe signals o he an enna a ay,
c ea ing he RF ields o which he objec unde es is exposed.
The an enna a ay is an eigh -channel mic os ip line a ay wi h an inne diame e o 59.5 cm, ma ching he
size o a s anda d clinical MRI sys em bo e. A mo e de ailed desc ip ion is p o ided in Sec ion 3.
The RF gene a ion sys em comp ises all elec onics equi ed o d i e he RF chain in a manne ha simula es
an MRI en i onmen . I handles ansmission iming and pseudo- ecep ion (pauses), gene a es he RF cen e
equency, and modula es he baseband signals on o he cen e equency o all eigh channels. Fu he
de ails can be ound in Sec ion 4.
The RF ampli ie s a e solid-s a e powe ampli ie s capable o peak ou pu powe s exceeding 1 kW. They a e
also capable o con inuous wa e (CW) ansmission a lowe oo mean squa e (RMS) powe le els. These
ampli ie s ope a e as s and-alone uni s and can po en ially be used independen ly o he STASIS sys em. A
de ailed desc ip ion is gi en in Sec ion 5.
To p o ide a use - iendly ope a ing expe ience, cus om so wa e wi h an in ui i e g aphical use in e ace was
de eloped. To ensu e main ainabili y, he so wa e is w i en in Py hon and ollows an objec -o ien ed design.
The GUI allows ull sys em con igu a ion and all equi ed calib a ions, such as g adien linea iza ion. A ull
desc ip ion o he so wa e is p o ided in Sec ion 6.
3 RF a ay
3.1 In oduc ion
The RF a ay is designed o esemble an eigh -channel ansmi a ay o a size and ype sui able o use wi hin
a 3 Tesla MRI sys em. I s design is closely based on he con igu a ion p oposed by Ve nickel e al. (1) in 2007.
The a ay consis s o eigh mic os ip an enna elemen s, each elec ically connec ed o i s adjacen neighbou s.
A pho og aph o he RF a ay moun ed on i s olley is shown in Figu e 3.
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Figu e 3: Pho o o he 8-channel RF a ay.
3.2 Mechanical Design
The coil housing is cons uc ed om poly(me hyl me hac yla e) (PMMA). A schema ic is shown in Figu e 4.
The o e all leng h o he housing is 820 mm, comp ising 800 mm cylind ical walls and 10 mm end ings on
each side. The inne diame e o he housing is 594 mm, closely ma ching he inne diame e o a Siemens 60
cm bo e (ac ual diame e : 595 mm).
The inne cylinde o he housing has a wall hickness o 8 mm, while he ou e cylinde ’s wall hickness is 6
mm. The ou e diame e o he housing is 700 mm, esul ing in a 39 mm gap be ween he wo cylinde s, wi hin
which he an enna elemen s a e posi ioned.
The inne su ace o he ou e cylinde is lined wi h adhesi e coppe oil, se ing as he g ound plane o he
mic os ip an ennas. As he a ay is no in ended o use in an MR en i onmen , he e is no equi emen o
eddy cu en mi iga ion; he e o e, he coppe cladding is con inuous. The g ound plane consis s o ou la ge
sec ions o coppe oil, joined by coppe bands wi h elec ically conduc i e adhesi e applied ac oss he seams.
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Figu e 4: Ske ch o he a ay including he housing. The inne side o he ou e cylinde is clad wi h coppe oil. No e ha he small
holde s o he imme ods a e placed di ec ly in line wi h he cen e o he mic o-s ip lines. Fo mo e in o ma ion e e o he
CAD model in he Da a.
Each an enna elemen has a wid h o 100 mm and a leng h o 450 mm. The dis ance be ween he cen e o
he mic os ip and he g ound plane is 37.3 mm, main ained by 3D-p in ed mechanical holde s made om PLA.
The coppe laye o he mic os ips is loca ed on he side o he boa d acing he g ound plane. Consequen ly,
he capaci o s a e also moun ed on his side, which allows he mic os ips o be posi ioned close o he inne
cylinde o he housing.
3.3 Elec ical Design
The elec ical design o he a ay closely ollows he con igu a ion p oposed by Ve nickel e al. (1). The ci cui
schema ic o a single an enna elemen , including i s elec ical connec ions o adjacen elemen s, is shown in
Figu e 5. The componen alues indica ed in he schema ic ep esen o al capaci ances, inclusi e o pa asi ic
capaci ances om he PCBs.
To achie e a homogeneous cu en dis ibu ion along he mic os ip, each elemen is di ided in o i e sec ions,
in e connec ed by pai s o 33 pF capaci o s. A 22 pF capaci o is placed a he end o he s ip. To minimize
coupling be ween adjacen elemen s, a decoupling ne wo k is implemen ed. This consis s o a 560 pF
capaci o connec ed o wo coaxial cables, each 130 mm in leng h, o each di ec ly adjacen elemen . These
cables a e e mina ed wi h 7.6 pF capaci o s, which in e ace wi h he co esponding coaxial lines om
neighbou ing elemen s.
Simula ions e ealed ha signi ican peak ol ages can occu ac oss hese coupling capaci o s. In he ac ual
implemen a ion, i is he e o e necessa y o eplace each wi h mul iple capaci o s in se ies o ensu e ol age
handling capabili y and eliabili y.
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Figu e 5: Schema ic showing one mic os ip elemen wi h he connec ion o he neighbo ing an ennas. The capaci o alues gi en in
his schema ic a e o al capaci ances. Some o he lumped elemen s on he ac ual coil ha e di e en alues due o pa asi ic
capaci ances o he PCBs.
3.4 RF ield simula ion esul s
All simula ions o he RF a ay we e ca ied ou in CST Mic owa e S udio (Dassaul Sys ème, F ance).
Fo he simula ions he a ay was loaded wi h a homogeneous phan om wi h elec ical p ope ies ha
co espond o he mean o he human body a 128 MHz (𝜀𝑟=52; 𝜎=0.47 S/m).
A ans e se iew o he B1+ ield dis ibu ion o he bi dcage mode and a s imula ed powe o 1W is shown in
Figu e 6. I shows he pa e n ypical o 3T body imaging wi h a high in ensi y in he cen e and wo lowe
in ensi y bands.
Figu e 6: Simula ed B1+ ield dis ibu ion o he CP+ mode (bi dcage mode) o s imula ed powe o 1W. The ypical pa e n wi h a
high in ensi y cen e and wo lowe in ensi y bands as known om 3T body imaging is isible.
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Figu e 7 shows he B1+ o he bi dcage mode and s imula ed powe o 8 kW on a cen al line on he z-axis
wi hin he phan om. The alues a y be ween 18 µT and 22µT. This ield s eng h is su icien o emula e he
ansmi ields o an MRI sys em.
Figu e 7: B1+ o he bi dcage mode and a s imula ed powe o 8 kW on a cen al line on he z-axis h ough he phan om. The alues
a y be ween 18 µT and 22 µT.
4 RF Gene a ion Sys em
4.1 O e iew
The RF Gene a ion Sys em (Figu e 8) p oduces bo h digi al and analogue signals equi ed o he ope a ion
o he RF exposu e sys em. I emula es he signal and iming gene a ion o an MRI sys em, allowing he use
o con igu e a sequence o RF pulses and pauses ha eplica e an ac ual imaging sequence.
The sys em is buil a ound IEC 60603-2 ( o me ly DIN 41612) connec o s and housed in a Eu oca d ack
sys em (IEC 60297), acili a ing modula i y and ease o componen exchange. Fo example, by adding
addi ional acks wi h ex a modula o ca ds, he numbe o RF channels can be easily expanded.
Figu e 8: A pic u e o he on o he Con ol Sys em.
A simpli ied schema ic o he RF Gene a ion Sys em is shown in Figu e 9. The Con ol Sys em comp ises a
signal gene a o ha p o ides a s able 128 MHz RF signal, a iming con ol module ha swi ches be ween
ansmi and pseudo- ecei e modes, and modula o modules capable o adjus ing he ampli ude and phase o
