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#include <odinseq/seqall.h>
class METHOD_CLASS : public SeqMethod {
private:
SeqPulsar exc;
SeqPulsarReph exc_reph;
SeqPulsar exc_prep;
SeqGradTrapez exc_prep_reph;
SeqDelay prepdelay;
SeqDelay postdelay;
SeqDelay relaxdelay;
SeqDelay grechdummy;
SeqGradEcho grech;
SeqGradConstPulse crusher;
SeqObjList kernel;
SeqObjList dummykernel;
SeqObjList readout;
SeqObjList shot;
SeqObjList scan;
SeqObjLoop reploop;
SeqObjLoop sliceloop;
SeqObjLoop peloop;
SeqObjLoop phaseloop;
SeqObjLoop dummyloop;
LDRint DummyCycles;
LDRenum PhaseEncoding;
public:
////////////////////////////////////////////////////
METHOD_CLASS(const STD_string& label) : SeqMethod(label) {
set_description("Single-shot TrueFISP (balanced SSFP) sequence. See for example Scheffler et.al. Eur Radiol (2003) 13:2409-2418 ");
}
////////////////////////////////////////////////////
void method_pars_init() {
commonPars->set_EchoTime(0.0,noedit);
commonPars->set_FlipAngle(60.0);
DummyCycles=3;
DummyCycles.set_description("Number of dummy cycles before actual acquisition");
PhaseEncoding.add_item("Linear",linearEncoding);
PhaseEncoding.add_item("CenterOut",centerOutEncoding);
PhaseEncoding=linearEncoding;
PhaseEncoding.set_description("Phase encoding order");
append_parameter(DummyCycles,"DummyCycles");
append_parameter(PhaseEncoding,"PhaseEncoding");
}
void method_seq_init(){
double gamma=systemInfo->get_gamma();
///////////////// Pulses: /////////////////////
float slicethick=geometryInfo->get_sliceThickness();
float spatres=slicethick/4.0;
// Excitation Pulse
exc=SeqPulsarSinc("exc",slicethick,false,2.0,commonPars->get_FlipAngle(),spatres);
dvector freqlist=gamma * exc.get_strength() / (2.0*PII) * geometryInfo->get_sliceOffsetVector();
exc.set_freqlist(freqlist);
exc.set_pulse_type(excitation);
// +/- flipangles for FISP
dvector phaselist(2);
phaselist[0]=0.0;
phaselist[1]=180.0;
exc.set_phaselist(phaselist);
// rephasing lobe for excitation pulse
exc_reph=SeqPulsarReph("exc_reph",exc);
// initial preparation pulse
exc_prep=exc;
exc_prep.set_label("exc_prep");
exc_prep.set_flipangle(0.5*commonPars->get_FlipAngle());
exc_prep.set_phase(180.0);
exc_prep_reph=SeqGradTrapez("exc_prep_reph",2.0*exc_reph.get_gradintegral().sum(),0.8*systemInfo->get_max_grad(),sliceDirection);
////////////////// Geometry: /////////////////////////////////
// calculate the resolution in the read Channel and set the number of phase encoding
// steps so that we will obtain a uniform resolution in read and phase Channel:
float resolution=secureDivision(geometryInfo->get_FOV(readDirection),commonPars->get_MatrixSize(readDirection));
commonPars->set_MatrixSize(phaseDirection,int(secureDivision(geometryInfo->get_FOV(phaseDirection),resolution)+0.5),noedit);
//////////////// Balanced Gradient Echo Module (2D mode): //////////////
grech=SeqGradEcho("grech", exc, commonPars->get_AcqSweepWidth(),
commonPars->get_MatrixSize(readDirection), geometryInfo->get_FOV(readDirection),
commonPars->get_MatrixSize(phaseDirection), geometryInfo->get_FOV(phaseDirection),
encodingScheme(int(PhaseEncoding)), interleavedSegmented, 2,
commonPars->get_ReductionFactor(),DEFAULT_ACL_BANDS,true,commonPars->get_PartialFourier());
grech.set_phaselist(phaselist); // +/- phase switching for SSFP
//////////////// crusher Gradient: //////////////////////////////
double crusher_strength=0.5*systemInfo->get_max_grad();
double crusher_dur=4.0;
crusher=SeqGradConstPulse("crusher",readDirection,crusher_strength,crusher_dur);
//////////////// Loops ////////////////////
reploop=SeqObjLoop("reploop");
sliceloop=SeqObjLoop("sliceloop");
peloop=SeqObjLoop("peloop");
phaseloop=SeqObjLoop("phaseloop");
//////////////// Timing Delays ////////////////////
prepdelay=SeqDelay("prepdelay");
postdelay=SeqDelay("postdelay");
relaxdelay=SeqDelay("relaxdelay");
grechdummy=SeqDelay("grechdummy",grech.get_duration()-exc.get_duration()-exc_prep_reph.get_duration());
//////////////// building the sequence //////////////////////////////
kernel=SeqObjList("kernel");
kernel= grech + postdelay;
dummykernel=SeqObjList("dummykernel");
dummykernel = exc + exc_prep_reph + grechdummy + postdelay;
readout=SeqObjList("readout");
readout = dummyloop (
phaseloop(
dummykernel
)[exc.get_phaselist_vector()]
)[DummyCycles]
+
peloop(
phaseloop(
kernel
)[exc.get_phaselist_vector()][grech.get_phaselist_vector()][grech.get_pe_reorder_vector()]
)[grech.get_pe_vector()];
shot=SeqObjList("shot");
shot = exc_prep + exc_prep_reph + prepdelay + readout + crusher;
scan=SeqObjList("scan");
scan += reploop(
sliceloop(
shot + relaxdelay
)[exc][exc_prep]
)[commonPars->get_NumOfRepetitions()];
set_sequence( scan );
}
//////////////////////////////////////////////////
void method_rels(){
Log<Seq> odinlog(this,"method_rels");
// TrueFISP timings, use minimum TE
double TEprep=exc_prep.get_duration()-exc_prep.get_magnetic_center()+
exc_prep_reph.get_duration()+
exc.get_magnetic_center();
double TEpre=grech.get_acquisition_center()-exc.get_magnetic_center();
double TEpost=grech.get_duration()-grech.get_acquisition_center()+
exc.get_magnetic_center();
double TEmax=maxof3(TEprep,TEpre,TEpost);
ODINLOG(odinlog,significantDebug) << "TEprep/pre/post/max=" << TEprep << "/" << TEpre << "/" << TEpost << "/" << TEmax << STD_endl;
prepdelay=TEmax-TEprep;
postdelay=TEmax-TEpost;
commonPars->set_EchoTime(TEmax,noedit);
// calculate relaxdelay to get the desired repetition time
float scandur=shot.get_duration()*float(geometryInfo->get_nSlices());
if(scandur>commonPars->get_RepetitionTime()) commonPars->set_RepetitionTime(scandur);
relaxdelay=(commonPars->get_RepetitionTime()-scandur)/float(geometryInfo->get_nSlices());
}
//////////////////////////////////////////////////
void method_pars_set(){
}
};
//////////////////////////////////////////////////
// entry point for the sequence module
ODINMETHOD_ENTRY_POINT
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