Esophageal varices are a significant complication of portal hypertension. Endoscopic variceal ligation (EVL) is one of the clinical standards for treating these varices and preventing their hemorrhage. Limitations of EVL include the risk of stricture formation and postband ulcer bleeding due to the damage caused to the esophageal mucosa, as well as the need for multiple endoscopic treatment sessions to eradicate the varices. The goal of this study is to develop a device and evaluate the technical feasibility of microwave ablation to seal esophageal varices, while preventing thermal damage to the surface mucosal tissue. A microwave applicator with a directional radiation pattern was developed for endoscopic ablation of esophageal varices. Electromagnetic and bioheat transfer computational models were employed to optimize the design of the microwave applicator and evaluate energy delivery strategies for this application. Experiments in ex vivo and in vivo tissue were employed to verify simulation results. Simulations predicted enhanced heating performance of the antenna using an angled monopole radiating element. Further, simulations indicate that while the endoscopic cap attenuated electric fields in tissue, it also enhanced surface cooling of tissue, increasing the likelihood of preserving mucosal tissue. Experiments in ex vivo tissue indicated the feasibility of sealing veins with 77 W microwave power delivered for 30 s. In vivo experiments demonstrated the ability to seal veins, while preserving surface tissue. This study demonstrated the technical feasibility of microwave thermal ablation for treating esophageal varices using a 2.45 GHz water-cooled directional microwave applicator.

References

References
1.
Sarin
,
S. K.
,
Lahoti
,
D.
,
Saxena
,
S. P.
,
Murthy
,
N. S.
, and
Makwana
,
U. K.
,
1992
, “
Prevalence, Classification and Natural History of Gastric Varices: A Long-Term Follow-Up Study in 568 Portal Hypertension Patients
,”
Hepatology
,
16
(
6
), pp.
1343
1349
.
2.
Garcia-Tsao
,
G.
,
Sanyal
,
A. J.
,
Grace
,
N. D.
, and
Carey
,
W.
,
2007
, “
Prevention and Management of Gastroesophageal Varices and Variceal Hemorrhage in Cirrhosis
,”
Hepatology
,
46
(
3
), pp.
922
938
.
3.
U.S. Center for Disease Control and Prevention
,
2014
, “
Chronic Liver Disease and Cirrhosis Mortality Rates
,” CDC/National Center for Health Statistics, Atlanta, GA.
4.
Scaglione
,
S.
,
Kliethermes
,
S.
,
Cao
,
G.
,
Shoham
,
D.
,
Durazo
,
R.
,
Luke
,
A.
, and
Volk
,
M. L.
,
2015
, “
The Epidemiology of Cirrhosis in the United States: A Population-Based Study
,”
J. Clin. Gastroenterol.
,
49
(
8
), pp.
690
696
.
5.
Ramstedt
,
M.
,
2001
, “
Per Capita Alcohol Consumption and Liver Cirrhosis Mortality in 14 European Countries
,”
Addiction
,
96
(
1s1
), pp.
19
33
.
6.
Petrasch
,
F.
,
Grothaus
,
J.
,
Mössner
,
J.
,
Schiefke
,
I.
, and
Hoffmeister
,
A.
,
2010
, “
Differences in Bleeding Behavior After Endoscopic Band Ligation: A Retrospective Analysis
,”
BMC Gastroenterol.
,
10
(
5
), pp.
1
10
.
7.
Viviane
,
A.
, and
Alan
,
B. N.
,
2008
, “
Estimates of Costs of Hospital Stay for Variceal and Nonvariceal Upper Gastrointestinal Bleeding in the United States
,”
Value Health
,
11
(
1
), pp.
1
3
.
8.
Tang
,
S.
,
2013
, “
Ligation of Esophageal Varices
,”
Video J. Encycl. GI Endoscopy
,
1
(
1
), pp.
83
85
.
9.
Villanueva
,
C.
,
Colomo
,
A.
,
Aracil
,
C.
, and
Guarner
,
C.
,
2008
, “
Current Endoscopic Therapy of Variceal Bleeding
,”
Best Pract. Res., Clin. Gastroenterol.
,
22
(
2
), pp.
261
278
.
10.
Dunn
,
C. W.
,
Kabnick
,
L. S.
,
Merchant
,
R. F.
,
Owens
,
R.
, and
Weiss
,
R. A.
,
2006
, “
Endovascular Radiofrequency Obliteration Using 90 C for Treatment of Great Saphenous Vein
,”
Ann. Vasc. Surg.
,
20
(
5
), pp.
625
629
.
11.
Giglio
,
N. C.
,
Hutchens
,
T. C.
,
Perkins
,
W. C.
,
Latimer
,
C.
,
Ward
,
A.
,
Nau
,
W. H.
, and
Fried
,
N. M.
,
2014
, “
Rapid Sealing and Cutting of Porcine Blood Vessels, Ex Vivo, Using a High-Power, 1470-Nm Diode Laser
,”
J. Biomed. Opt.
,
19
(
3
), p.
038002
.
12.
Zhang
,
L.
,
Zhu
,
H.
,
Jin
,
C.
,
Zhou
,
K.
,
Li
,
K.
,
Su
,
H.
,
Chen
,
W.
,
Bai
,
J.
, and
Wang
,
Z.
,
2009
, “
High-Intensity Focused Ultrasound (HIFU): Effective and Safe Therapy for Hepatocellular Carcinoma Adjacent to Major Hepatic Veins
,”
Eur. Radiol.
,
19
(
2
), pp.
437
445
.
13.
Subwongcharoen
,
S.
,
Praditphol
,
N.
, and
Chitwiset
,
S.
,
2009
, “
Endovenous Microwave Ablation of Varicose Veins: In Vitro, Live Swine Model, and Clinical Study
,”
Surg. Laparoscopy Endoscopy Percutaneous Tech.
,
19
(
2
), pp.
170
174
.
14.
Song
,
H.-P.
,
Yu
,
M.
,
Zhang
,
J.
,
Han
,
Z.-H.
,
Su
,
H.-L.
,
Ren
,
X.-L.
,
Wei
,
Z.-R.
,
Luo
,
W.
,
He
,
J.-G.
, and
Zhou
,
X.-D.
,
2008
, “
Hemostasis of Active Bleeding From the Liver With Percutaneous Microwave Coagulation Therapy Under Contrast-Enhanced Ultrasonographic Guidance: An Experimental Study
,”
J. Ultrasound Med.: Off. J. Am. Inst. Ultrasound Med.
,
27
(
6
), pp.
867
874
.
15.
Brace
,
C. L.
,
2010
, “
Microwave Tissue Ablation: Biophysics, Technology and Applications
,”
Crit. Rev. Biomed. Eng.
,
38
(
1
), pp.
65
78
.
16.
Ryan
,
T.
, and
Clegg
,
P.
,
2009
, “
Novel Microwave Applicators for Thermal Therapy, Ablation, and Hemostasis
,”
Proc. SPIE
,
7181
, pp.
1
15
.
17.
Hamazoe
,
R.
,
Hirooka
,
Y.
,
Ohtani
,
S.
,
Katoh
,
T.
, and
Kaibara
,
N.
,
1995
, “
Intraoperative Microwave Tissue Coagulation as Treatment for Patients With Nonresectable Hepatocellular Carcinoma
,”
Cancer
,
75
(
3
), pp.
794
800
.
18.
Reuter
,
N. P.
, and
Martin
,
R. C. G.
,
2009
, “
Microwave Energy as a Precoagulative Device to Assist in Hepatic Resection
,”
Ann. Surg. Oncol.
,
16
(
11
), pp.
3057
3063
.
19.
McWilliams
,
B. T.
,
Schnell
,
E. E.
,
Curto
,
S.
,
Fahrbach
,
T. M.
, and
Prakash
,
P.
,
2015
, “
A Directional Interstitial Antenna for Microwave Tissue Ablation: Theoretical and Experimental Investigation
,”
IEEE Trans. Biomed. Eng.
,
62
(
9
), pp.
2144
2150
.
20.
Sebek
,
J.
,
Curto
,
S.
,
Bortel
,
R.
, and
Prakash
,
P.
,
2017
, “
Analysis of Minimally Invasive Directional Antennas for Microwave Tissue Ablation
,”
Int. J. Hyperthermia
,
33
(
1
), pp.
51
60
.
21.
Sebek
,
J.
,
Albin
,
N.
,
Bortel
,
R.
,
Natarajan
,
B.
, and
Prakash
,
P.
,
2016
, “
Sensitivity of Microwave Ablation Models to Tissue Biophysical Properties: A First Step Toward Probabilistic Modeling and Treatment Planning
,”
Med. Phys.
,
43
(
5
), pp.
2649
2661
.
22.
Ji
,
Z.
, and
Brace
,
C. L.
,
2011
, “
Expanded Modeling of Temperature-Dependent Dielectric Properties for Microwave Thermal Ablation
,”
Phys. Med. Biol.
,
56
(
16
), pp.
5249
5264
.
23.
Lopresto
,
V.
,
Pinto
,
R.
, and
Cavagnaro
,
M.
,
2014
, “
Experimental Characterisation of the Thermal Lesion Induced by Microwave Ablation
,”
Int. J. Hyperthermia
,
30
(
2
), pp.
110
118
.
24.
Pennes
,
H. H.
,
1948
, “
Analysis of Tissue and Arterial Blood Temperatures in the Resting Human Forearm
,”
J. Appl. Physiol.
,
1
(
2
), pp.
93
122
.http://jap.physiology.org/content/85/1/5.article-info
25.
Groeschl
,
R. T.
,
Pilgrim
,
C. H.
,
Hanna
,
E. M.
,
Simo
,
K. A.
,
Swan
,
R. Z.
,
Sindram
,
D.
,
Martinie
,
J. B.
,
Iannitti
,
D. A.
,
Bloomston
,
M.
,
Schmidt
,
C.
,
Khabiri
,
H.
,
Shirley
,
L. A.
,
Martin
,
R. C. G.
,
Tsai
,
S.
,
Turaga
,
K. K.
,
Christians
,
K. K.
,
Rilling
,
W. S.
, and
Gamblin
,
T. C.
,
2014
, “
Microwave Ablation for Hepatic Malignancies: A Multiinstitutional Analysis
,”
Ann. Surg.
,
259
(
6
), pp.
1195
1200
.
26.
Chakaravarthi
,
G.
, and
Arunachalam
,
K.
,
2016
, “
Influence of Dissolved Gases in Coupling Waterbolus on Superficial Hyperthermia and Evaluation of a Water Conditioning System With Inline Degassing
,”
Biomed. Phys. Eng. Express
,
2
(
5
), p.
055003
.
27.
Curto
,
S.
,
Taj-Eldin
,
M.
,
Fairchild
,
D.
, and
Prakash
,
P.
,
2015
, “
Microwave Ablation at 915 MHz versus 2.45 GHz: A Theoretical and Experimental Investigation
,”
Med. Phys.
,
42
(
11
), pp.
6152
6161
.
28.
Sawicki
,
J. F.
,
Shea
,
J. D.
,
Behdad
,
N.
, and
Hagness
,
S. C.
,
2016
, “
The Impact of Frequency on the Performance of Microwave Ablation
,”
Int. J. Hyperthermia
, 33(1), 61–68.
29.
Luyen
,
H.
,
Gao
,
F.
,
Hagness
,
S. C.
, and
Behdad
,
N.
,
2014
, “
Microwave Ablation at 10.0 GHz Achieves Comparable Ablation Zones to 1.9 GHz in Ex Vivo Bovine Liver
,”
IEEE Trans. Biomed. Eng.
,
61
(
6
), pp.
1702
1710
.
30.
Gabriel
,
S.
,
Lau
,
R. W.
, and
Gabriel
,
C.
,
1996
, “
The Dielectric Properties of Biological Tissues: III. Parametric Models for the Dielectric Spectrum of Tissues
,”
Phys. Med. Biol.
,
41
(
11
), pp.
2271
2293
.
31.
Moitinho
,
E.
,
Escorsell
,
À.
,
Bandi
,
J.-C.
,
Salmerón
,
J.-M.
,
García-Pagán
,
J.-C.
,
Rodés
,
J.
, and
Bosch
,
J.
,
1999
, “
Prognostic Value of Early Measurements of Portal Pressure in Acute Variceal Bleeding
,”
Gastroenterology
,
117
(
3
), pp.
626
631
.
32.
Hall
,
S. K.
,
Ooi
,
E. H.
, and
Payne
,
S. J.
,
2015
, “
Cell Death, Perfusion and Electrical Parameters Are Critical in Models of Hepatic Radiofrequency Ablation
,”
Int. J. Hyperthermia
,
31
(
5
), pp.
538
550
.
You do not currently have access to this content.