MR thermometry for focused ultrasound monitoring utilizing model predictive filtering and ultrasound beam modeling.
BACKGROUND
A major challenge in using magnetic resonance temperature imaging (MRTI) to monitor focused ultrasound (FUS) applications is achieving high spatio-temporal resolution over a large field of view (FOV). This is important to accurately monitor all ultrasound (US) power depositions. Magnetic resonance (MR) subsampling in conjunction with thermal model-based reconstruction of the MRTI utilizing Pennes bioheat transfer equation (PBTE) is one promising approach. The thermal properties used in the thermal model are often estimated from a pre-treatment, low-power sonication.


METHODS
In this proof-of-concept study we investigate the use of US simulations computed using the hybrid angular spectrum (HAS) method to estimate the US power deposition density Q, thereby avoiding the pre-treatment sonication and any potential tissue damage. MRTI reconstructions are performed using a thermal model-based reconstruction method called model predictive filtering (MPF). Experiments are performed in a homogeneous gelatin phantom and in a gelatin phantom with embedded plastic skull. MPF reconstructions are compared to separate sonications imaged with fully sampled data over a smaller FOV. Temperature root-mean-square errors (RMSE) and focal spot positions and shapes are evaluated.


RESULTS
HAS simulations accurately predict the location of the focal spot (to within 1 mm) in both phantoms. Accurate temperature maps (RMSE below 1 °C), where the location of the focal spot agrees well with fully sampled "truth" (to within 1 mm), are also achieved in both phantoms.


CONCLUSIONS
HAS simulations can be used to accurately predict the focal spot location in homogeneous media and when focusing through an aberrating plastic skull. The HAS simulated power deposition (Q) patterns can be used in the MPF thermal model-based reconstruction to obtain accurate temperature maps with high spatio-temporal resolution over large FOVs.
Utah Center for Advanced Imaging Research, Department of Radiology, University of Utah, Salt Lake City, UT USA.
Henrik
H
Odéen
School of Computing, University of Utah, Salt Lake City, UT USA.
Scott
S
Almquist
Utah Center for Advanced Imaging Research, Department of Radiology, University of Utah, Salt Lake City, UT USA.
Joshua
J
de Bever
Department of Bioengineering, University of Utah, Salt Lake City, UT USA ; Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT USA.
Douglas A
DA
Christensen
Utah Center for Advanced Imaging Research, Department of Radiology, University of Utah, Salt Lake City, UT USA.
Dennis L
DL
Parker
Hybrid angular spectrum; MR thermometry; Model predictive filtering; Proton-resonance frequency shift; Ultrasound modeling
J Magn Reson Imaging. 2008 Feb;27(2):376-90
18219673
Phys Med. 2010 Oct;26(4):192-201
20096617
Magn Reson Med. 1998 Dec;40(6):908-13
9840836
J Ther Ultrasound. 2014 Oct 16;2:19
25343028
J Magn Reson Imaging. 2004 Oct;20(4):706-14
15390144
IEEE Trans Med Imaging. 2015 Jan;34(1):148-55
25163055
Magn Reson Med. 2012 Mar;67(3):724-30
21702066
Int J Hyperthermia. 2005 Sep;21(6):533-46
16147438
J Acoust Soc Am. 1991 Jul;90(1):507-21
1880299
N Engl J Med. 2013 Aug 15;369(7):640-8
23944301
Magn Reson Med. 2004 May;51(5):913-23
15122673
Med Phys. 2015 May;42(5):2223-33
25979016
J Ther Ultrasound. 2015 Jun 16;3:9
26146557
IEEE Trans Med Imaging. 2012 Mar;31(3):533-42
21997254
Magn Reson Med. 2003 Aug;50(2):322-30
12876709
J Magn Reson Imaging. 1994 Sep-Oct;4(5):733-41
7981519
Med Phys. 2008 Aug;35(8):3748-58
18777934
AJR Am J Roentgenol. 2015 Jul;205(1):150-9
26102394
J Magn Reson Imaging. 2000 Oct;12(4):525-33
11042633
Lasers Surg Med. 2014 Sep;46(7):558-62
24902949
Conf Proc IEEE Eng Med Biol Soc. 2008;2008:2526-9
19163217
Magn Reson Med. 2014 Apr;71(4):1394-404
23670981
Magn Reson Med. 1995 Jan;33(1):74-81
7891538
J Magn Reson Imaging. 2012 May;35(5):1089-97
22170814
Magn Reson Med. 2007 Jun;57(6):1027-36
17534924
Magn Reson Med. 2016 Sep;76(3):803-13
26445135
Magn Reson Med. 2005 Mar;53(3):658-65
15723414
NMR Biomed. 2011 Feb;24(2):145-53
21344531
Magn Reson Med. 2013 Mar 1;69(3):724-33
22555751
Magn Reson Med. 2000 Jun;43(6):909-12
10861889
Magn Reson Med. 1995 Dec;34(6):814-23
8598808
Magn Reson Med. 2004 Oct;52(4):704-8
15389940
Phys Med Biol. 2016 Aug 7;61(15):N373-85
27385508
Magn Reson Med. 2004 Jun;51(6):1205-11
15170841
Magn Reson Med. 2010 May;63(5):1269-79
20432298
J Appl Physiol. 1948 Aug;1(2):93-122
18887578
Magn Reson Med. 2011 Feb;65(2):515-21
20882671
Med Phys. 2014 Sep;41(9):092301
25186406
Magn Reson Med. 2015 May;73(5):1914-25
24935053
Conf Proc IEEE Eng Med Biol Soc. 2014;2014:310-3
25569959
J Magn Reson Imaging. 2004 Apr;19(4):438-46
15065167
Magn Reson Med. 2011 Jul;66(1):112-22
21337421
J Acoust Soc Am. 2011 Nov;130(5):2687-93
22087896
Magn Reson Med. 2009 Aug;62(2):406-19
19353648
Radiology. 2000 Aug;216(2):517-23
10924580
Int J Hyperthermia. 2014 Sep;30(6):362-71
25198092
Phys Med Biol. 2012 Jul 21;57(14):4527-44
22722656
IEEE Trans Med Imaging. 2012 Apr;31(4):984-94
22203706
Med Phys. 2009 Aug;36(8):3521-35
19746786
Phys Med Biol. 2013 Oct 21;58(20):7291-307
24077026
Magn Reson Med. 2010 Apr;63(4):1080-7
20373409
Magn Reson Imaging. 2006 Sep;24(7):903-15
16916708
Magn Reson Med. 2012 Sep;68(3):932-46
22246646
Magn Reson Med. 2015 Apr;73(4):1420-31
24753099
IEEE Trans Ultrason Ferroelectr Freq Control. 2012 Jun;59(6):1093-100
22711405
Magn Reson Med. 2016 Jan;75(1):207-16
25726934
Phys Med Biol. 2014 Jul 7;59(13):3599-614
24909357