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Comparative study of laparoscopy vs. laparotomy for ovarian mass removal

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Comparative study of laparoscopy vs. laparotomy for ovarian mass removal

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Content 1

Comparative study of Laparoscopy vs. Laparotomy
for ovarian mass removal
by
Chenwei Hu
A Thesis Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE (BIOSTATISTICS)

December 2015

Copyright 2015 Chenwei Hu

2
Table of contents
ABSTRACT ................................................................................................................................... 3
INTRODUCTION ......................................................................................................................... 5
Methods ........................................................................................................................................ 7
Study population and design ......................................................................................................... 7
Assessment of operative room details ....................................................................................... 8
Statistical analysis .............................................................................................................................. 8
Results ....................................................................................................................................... 10
Analysis Sample ............................................................................................................................... 10
Comparison of Estimated blood loss, Length of stay in hospital, Total anesthesia
time and Total operative time among the group ................................................................. 10
Comparison of Complications .................................................................................................... 12
Discussion ................................................................................................................................ 21
Reference .................................................................................................................................. 25

3
ABSTRACT
Objective: This study sought to compare the clinical outcomes of laparoscopy and
laparotomy for removal of ovarian masses. Outcomes compared included estimated
blood loss, length of stay in hospital, total anesthesia time, total surgery time and
risk of complications.
Methods: The data arose from a retrospective chart review of the patients seen
between December 2007 to October 2012 at LAC+USC Medical Center. Patients were
identified from a surgical procedure database and included the CPT codes associated
with the oophorectomy, ovarian cystectomy, salpingo-oophorectomy, salpingectomy
and salpingostomy surgeries. Patients with hysterectomy surgeries were excluded.
Clinicopathologic information and intraoperative events were abstracted from a
review of both inpatient and outpatient records. Outcomes were compared among
three groups: (1) laparotomy, (2) laparoscopy and (3)conversion from laparoscopy
to laparotomy.
Result: A total of 1227 patients (423 laparotomy, 709 laparoscopy, 95 conversion)
were included in the analysis. The average (SD) estimated blood loss of laparotomy
group was 128.95(226.7) ml higher than the laparoscopy group (P<0.001). Total
length stay in hospital after surgery was 3 days less on average for laparoscopy
compared to laparotomy patients (P<0.001). The total anesthesia and operative
times were longest for the conversion group, about 30 minutes more than the
4
laparotomy group and 20 minutes more than the laparoscopy group. The difference
between each of the two groups was significant (P<0.001). The risk of ruptured
mass upon entry was higher in the laparotomy group than the other two groups
(P<0.001). The risk of other complications, ranging from uterine manipulator
perforation to liver laceration, to hemorrhagic shock, to incomplete procedure, to
incorrect surgical count was highest in conversion group.
Conclusion: Planned laparoscopic surgery resulted in less blood loss, less length of
stay in hospital, less surgery time and higher risk of complications than laparotomy.
Women whose surgery converted from planned laparoscopy to laparotomy had
more blood loss, longer surgery time and higher risk of complications.
Key words: Laparoscopy, Laparotomy

5
INTRODUCTION
Ovarian cysts are common gynecologic findings, occurring in symptomatic and
asymptomatic women of all age groups
1
. Detection of ovarian masses often occurs
incidentally during imaging or pelvic examination and occasionally secondary to
symptomatic manifestation. While functional cyst formation is necessary for normal
ovarian tissue function, persistent or enlarged or abnormal densities found in the
adnexa may be the only indicators of malignant cellular function
2-4
. Prior to surgical
removal, pre-operative evaluation of the adnexal mass to determine malignant
potential requires radiologic examination and measurement of indicated serum
tumor marker levels
5
. However, the final diagnosis is assigned only upon pathologic
analysis of a surgically resected specimen
6
. The gold standard for surgical resection
is via a large abdominal incision, laparotomy, which is associated with blood loss,
long recovery periods, and postoperative pain.
Despite the favorable side effects of laparoscopy for this surgery to achieve
similar outcomes, laparotomy continues to play a prominent role in the removal of
adnexal masses
7
. This is partly due to the uncertainty of ovarian diagnosis
pre-operatively combined with a higher incidence of cyst rupture / spillage of
malignant cells during laparoscopy. Thus currently the preferred surgical approach
for resection of adnexal masses greater than 8cm is laparotomy
8-9
.
The laparoscopic approach is currently considered the preferred treatment of
6
benign adnexal cysts because of less postoperative pain, shorter recovery time, less
loss of blood and better abdominal cosmetic effect
10
. However, the introduction of
laparoscopic approaches to surgery has some limitations. The laparoscopic
equipment is expensive, the operation is relatively complex, and the technical
requirements for the surgeons are higher
11-13
. Moreover, the operation time is
difficult to estimate before the surgery, in some special laparoscopy cases, need to
intraoperative changed to laparotomy. Finally, sometimes the risk of conversion
during the surgery associated with laparoscopic surgery is higher than the
laparotomy. This study seeks to determine and characterize the parameters that
guide and dictate pure laparoscopic ovarian resection without conversion to
laparotomy and compare the difference of estimated blood loss, total length of stay
in hospital, total anesthesia time, total operative time and risk of complications
between laparotomy and laparoscopy.

7
Methods
Study population and design
The decision of laparotomy vs. laparoscopy is based upon the surgical attending
physician’s assessment – both at the time of initial presentation and at the time of
surgery. Occasionally these two opinions will differ, thus the ultimate CPT code
(laparotomy vs. laparoscopy) is based upon the surgeon who performed the
procedure. Using CPT codes
14-15
, we reviewed the surgical database of all patients
who underwent adnexal surgery between December 2007 to October 2012 at
LAC+USC Medical Center. Among the total of 1958 cases, we excluded 731 cases
whose surgery included the post-partum tubal ligation or did the hysterectomy
surgery. Hysterectomies were excluded because of the additional risk for
complication, increased blood loss, and fact that hysterectomies can be performed
without ovarian removal. The focus was not on uteri but ovaries (Figure 1).
Postpartum tubal ligations and cesarean deliveries with bilateral tubal ligations
were not equivalent procedures to the other adnexal procedures and can vary wildly
in their post-operative recovery. Types of surgery for the remaining 1227 patients
were determined retrospectively by examination of the CPT codes associated with
laparoscopic adnexal procedures including oophorectomy, ovarian cystectomy,
salpingo-oophorectomy, salpingectomy, and salpingostomy, using a surgical
procedure database.
8
Assessment of operative room details
Anesthesia start time, time into operative room, anesthesia end time and time
out of operative room were recorded. Data comes from the standard practice of
collecting anesthesia and operative time within the practice of operating. The total
anesthesia time and total operative time were calculated in minutes. Estimated
blood loss (EBL) was estimated by anesthesia and surgeon depending upon suction
collection as well as blood soaked sponges in ml. Surgical conversions from
laparoscopy to laparotomy were recorded. The admission and discharge dates were
recorded, and total length of stay was calculated in days.
Surgical patients were followed one year from intervention; complications of the
patients were recorded. Complications including bladder injury, ureteral injury,
bowel injury, vascular injury, intraoperative mass rupture and pre-surgical mass
rupture were abstracted from patient charts.
Statistical analysis
The analysis included 1227 patients who were identified from a surgical
procedure database from December 2007 to October 2012 at LAX+USC Medical
Center. Groups were separated by the CPT codes, 423 were laparotomy group, 709
were laparoscopy group and 95 were conversion group. Calculated BMI used the
formula: BMI (kg/m
2
) = Weight (lb.) / (Height (in) x Height (in)) x 703. We
calculated the average and standard deviation for each group in estimated blood loss,
total length of stay, total anesthesia time and total operative time. The complications
9
were summarized as number of patients, percentage of the complications over total
number in each groups were calculated. Missing items were replaced by the average
value of non-missing items in the same group.
Kruskal-Wallis H test was used to test for differences in estimated blood loss,
length of stay in hospital, total anesthesia time and total operative time. The main
effect in the test was method of surgery (laparoscopy, laparotomy, conversion). We
selected a non-parametric group comparison because the normality and
homoscedasticity of the continuous data were not satisfied as measured by a
goodness of fit of a normal model to the data and the Kolmogorov–Smirnov test.
While log transformation improved normality, the variable distributions were still
not normal and the variances over groups were not equal.
Rejection of the null hypothesis of the Kruskal-Wallis H test indicates that at
least two groups differ on the dependent variable, but does not specify which groups
differ. We performed pairwise comparisons of ranks using a Bonferroni correction
for each pair (α<0.017).
The Mantel-Haenzel (MH) chi-square test was used to evaluate dichotomous
outcome variables, such as complication variables. All statistical analysis used SAS
software v. 9.3 (SAS Inc., Cary, NC).

10
Results
Analysis Sample
There were 1958 patients who underwent adnexal surgery, 1227 of whom met
the inclusion criteria (Figure 1). Of those, 423 had CPT codes indicating laparotomy
surgery, 709 had laparoscopy surgery, and 95 had codes indicating conversion from
laparoscopy to laparotomy during the surgery.
Table 1 provides the descriptive statistics of the characteristics and operative
room details for the Laparoscopy, Laparotomy and conversion groups. Only 435
(35.5%) of patients had completed BMI information. Most patients included in our
study were Hispanic (77.3% for laparotomy, 81.5% for laparoscopy, and 89.5% for
conversion group). Rates of Asian/Pacific Islander differed across groups (3.6% for
laparotomy, 8.0% for laparoscopy, and 1.1% for conversion group). Other ethnicities
were similar across surgical groups.
Comparison of Estimated blood loss, Length of stay in hospital, Total anesthesia time
and Total operative time among the group
Women who had their ovarian mass removed via laparoscopy or converted to
Laparoscopy during the surgery had higher estimated blood loss than women in the
Laparotomy group (p<0.001; Figure 2). There were total 40 missing value in EBL.
The median estimated blood loss for Laparotomy group was 100 ml, with
interquartile range of 150 ml, for Laparoscopy group was 25 ml, with interquartile
11
range of 40 ml. The median estimated blood loss in Conversion group was 100 ml,
with interquartile range of 175 ml. The median EBL (Figure2) in Laparotomy group
was statistically significant higher than the Laparoscopy group (P<0.001, by
Kruskal-Wallis H test). The median EBL in Conversion group was also statistically
significant higher than the Laparoscopy group (P<0.001, by Kruskal-Wallis H test).
The Laparotomy and Conversion groups did not significantly differ on estimated
blood loss (P=0.18, by Kruskal-Wallis H test).
Length of hospitalization was significantly associated with the surgical
approach. The median total length of stay was 3 days for Laparotomy group, with
interquartile range of 1 day. The median total length of stay in Laparoscopy group
was 0, with interquartile range of 1 day. The median total length of stay in
Conversion group was 3 days, with interquartile range of 1 day. The median length
of stay (Figure3) in hospital after the surgery for Laparotomy group was significant
higher than Laparoscopy and Conversion group (p<0.001 and P=0.0089, respectively,
by Kruskal-Wallis H test). The Conversion group also had a significant higher length
of stay in hospital than Laparotomy (p<0.001, by Kruskal-Wallis H test). Patients
who received laparotomy surgery or conversion to laparotomy spent more time in
hospital after the surgery than the laparoscopy surgery.
The total anesthesia time (TAT) was also associated with the surgical approach.
The median TAT for group Laparotomy, Laparoscopy, Conversion was 190 mins, 212
mins and 225 mins, with interquartile range of 88 mins, 68 mins and 100 mins
12
separately. The median TAT (Figure4) is longest in Conversion group and lowest in
Laparotomy group. The difference between each two groups were all statistically
significant different (P<0.001, by Kruskal-Wallis H test). Conversion from
laparoscopy to laparotomy required significantly more time than pure laparoscopy
or laparotomy surgery alone (P’s<0.001, by Kruskal-Wallis H test). The laparoscopy
surgery also needed more anesthesia and operative time than the laparotomy
surgery (P<0.001).
Comparison of Complications
We measured the number of patients having any complications during the 1
year follow up after surgery; 37 (8.75%) patients in the Laparotomy, 143 (20.17%)
patients in the Laparoscopy, and 16 (16.8%) patients in the Conversion groups had
some complications (P<0.001). The Laparoscopy group was more likely to have
complications after the surgery than other groups (Figure 6).
The risk of mass rupturing intra-operatively is highest among all the
complications. 4.96% of group Laparotomy, 16.64% of group Laparoscopy and 10.53%
of group Conversion had mass ruptured during the operative. The risk of mass
rupture was significantly higher for patients who in the laparoscopy surgery group
than the laparotomy surgery and converted surgery (P’s<0.001). Patients who
started with laparoscopy and then converted to laparotomy were also more likely to
have an intra-operative mass rupture than patients who started with the laparotomy
13
surgery directly (P<0.001).
The risks for other complications including bladder injury, ureteral injury
bowel injury, vascular injury and mass already ruptured upon entry were very low.
In the Laparotomy group, two patients had bladder injury, three had bowel injury,
and four patients had a ruptured mass upon entry. In the Laparoscopy group, one
patient had bladder injury, two had bowel injury, and five patients had a ruptured
mass upon entry. In the Conversion group, four patients had bowel injury and two
patients had a ruptured mass upon entry; no patients had a bladder injury.
We also recorded the risk for other kind of complications. The risk of other
kind of complications range from uterine manipulator perforation to liver laceration,
to hemorrhagic shock, to incomplete procedure, to incorrect surgical count is only
0.95% for laparoscopy and 0.85% for laparotomy groups; the risk was higher
(4.21%) in the conversion group (P<0.001).

14

Notes: Numbers are mean (SD) or n (%)
a
N=119, N=282, N=34 for Laparotomy, Laparoscopy, Conversion group separately.
b
N=408, N=687, N=92 for Laparotomy, Laparoscopy, Conversion group separately.

c
N=708 for Laparoscopy group.
d
N=420, N=704 for Laparotomy, Laparoscopy group separately.
e
N=418, N=699, N=93 for Laparotomy, Laparoscopy, Conversion group separately.

Table 1. Clinical Characteristics Of Patients

Laparotomy
N=423
Laparoscopy
N=709
Conversion
N=95
Patient Characteristics
BMI
a
, kg/m
2
28.67(7.0) 29.35(6.5) 28.66(5.0)
Race
White Non-Hispanic 18(4.26%) 25(3.53%) 5(5.26%)
Black Non-Hispanic 19(4.49%) 30(4.23%) 2(2.11%)
Hispanic 327(77.3%) 578(81.52%) 85(89.47%)
Asian/Pacific Islander 51(3.55%) 57(8.04%) 1(1.05%)
Native American 1(0.02%) 3(0.42%) 0(0%)
Other 7(1.65%) 16(2.26%) 2(2.11%)
Operation details
Estimated blood loss
b
, ml 183.05(238.0) 54.10(100.2) 188.21(269.9)
Total length of stay
c
, day 3.82(4.7) 0.76(1.4) 3.04(4.7)
Total Anesthesia time
d
, mins 211.28(106.0) 222.57(75.9) 234.84(92.4)
Total Operative time
e
, mins 145.64(79.5) 157.47(60.0) 175.66(68.2)
Complications
None 386(91.25%) 566(79.83%) 79(85.2%)
Bladder injury 2(0.47%) 0(0.00%) 0(0.00%)
Ureteral injury 0(0.00%) 0(0.00%) 0(0.00%)
Bowel injury 3(0.71%) 3(0.42%) 0(0.00%)
Vascular injury 0(0.00%) 2(0.28%) 0(0.00%)
Mass ruptured intra operatively 21(4.96%) 118(16.64%) 10(10.53%)
Mass already ruptured upon entry 4(0.95%) 4(0.56%) 2(2.11%)
15
Figure1. Study algorithm

1958
adnexal surgeries
Dec 2007-Oct 2012
1227
731 cesarean deliveries and
tubal ligations
423
Laparotomy
95
Conversion from
laparoscopy to laparotomy
709
Laparoscopy
16
Figure2

Notes: Group1: Laparotomy, Group2: Laparoscopy, Group3: Conversion
The box included 5 points from up to down were: upper whisker, upper quartile,
median, lower quartile, lower whisker.

17
Figure3

Notes: Group1: Laparotomy, Group2: Laparoscopy, Group3: Conversion
The box included 5 points from up to down were: upper whisker, upper quartile,
median, lower quartile, lower whisker. The plots outside the box were outliers.

18
Figure4

Notes: Group1: Laparotomy, Group2: Laparoscopy, Group3: Conversion
The box plots included 5 points from up to down were: upper whisker, upper
quartile, median, lower quartile, lower whisker.

19
Figure 5

Notes: Group1: Laparotomy, Group2: Laparoscopy, Group3: Conversion
The box plots included 5 points from up to down were: upper whisker, upper
quartile, median, lower quartile, lower whisker.

20
Figure 6. A comparison of ratios of complications between Laparoscopy vs.
Laparotomy

91%
5%
0.95%
80%
17%
0.56%
77%
11%
2.11%
None Mass already ruptured upon
entry
Other
Complications
Laparoscopy Laparotomy Conversion
21
Discussion
This study compared surgical and outcome characteristics among patients
whose ovarian masses were removed via laparoscopy, laparotomy and conversion
from laparoscopy to laparotomy. Our findings are consistent with other studies. The
Predictors of Clinical Outcomes in the Laparoscopic Management of Adnexal Masses
study showed that conversion to laparotomy occurred in 25% and was associated
with larger mass
16-17
. The estimated blood loss was not significantly different
between Conversion group and Laparotomy group and was approximately triple
that of the Laparoscopy group. The total length of stay in hospital after surgery is
highest in the Laparotomy group requiring patients to stay about one day more on
average than the patients who underwent the conversion surgery and three days
more than the patients who underwent laparoscopy. Surgery time was longest for
conversion. The laparotomy surgery is 30 minutes less and laparoscopy surgery is
20 minutes less than the conversion. The occurrences of bladder injury, ureteral
injury, bowel injury, vascular injury and mass ruptured upon entry were low across
all groups. The risk of experiencing any kind of complication was highest in the
conversion group with having the mass rupture intra operatively being the most
frequent complication. The laparoscopy surgery was more risk to cause the mass
ruptured than the laparotomy.
The large sample size is a strength of this study, as is the ethnic diversity of the
22
study sample. However, as is common with record reviews, there was a good deal of
missing data, including 792 patients (64.5%) missing BMI and 40 (3.3%) missing
estimated blood loss. We replaced the missing data for estimated blood loss with
the average value of each subject’s surgery group. Since most BMI and age data were
not completed at the analyses time, possible covariates were not included in the
model. The difference between each groups may be overestimated since beside the
surgery approach, there may be other unmeasured factors associated with the
estimated blood loss, total length of stay in hospital, total anesthesia time and total
operative time that also differed by study group.
Another weakness of this study was that patients were not randomized to
laparoscopy or laparotomy; surgical method was based on the patient’s need,
surgical skills, doctor’s advice and so on. It is very likely that some of these findings
(for example complications) are due to the fact that they were higher risk patients
who were more likely to have complications.
In conclusion, removal of ovarian masses via Laparoscopy compared to
Laparotomy can result in reduced blood loss, hospital length of stay ，and total
operative time. Laparoscopy is however associated with higher overall surgical
complication rates. When doctors and patients decide which surgery approach to
choose, they should consider the risk of blood loss and other complications. The
time and money associated with the surgery and stay in hospital also should be
taken into consideration. While the risk for many negative outcomes increase with
23
conversion, it is worth to start with a laparoscopy when in doubt, since the risks and
outcomes related to conversion are not really greater than with laparotomy. Another
area of investigation that would add to the literature is to document the true impact
of laparoscopy as the initial surgical management of adnexal masses of greater than
8cm
18-19
.

24
REFERENCE

1. National Institutes of Health Consensus Development Panel on Ovarian Cancer.
NIH consensus conference. Ovarian cancer: screening, treatment, and follow-up.
JAMA 1995;273: 491-7.
2. Vergote I, De Brabanter J, Fyles A, et al. Prognostic importance of degree of
differentiation and cyst rupture in stage I invasive epithelial ovarian carcinoma.
Lancet 2001;357:176-82.
3. Voitk AJ, Tsao SG, Ignatius S. The tail of the learning curve for laparoscopic
cholecystectomy. Am J Surg 2001; 182:250–3.
4. J Pediatr Adolesc Gynecol. Laparoscopic Outcomes for Pelvic Pathology in
Children and Adolescents among Patients Presenting to the Pediatric and
Adolescent Gynecology Service. 2015 Jun;28(3):157-62.
5. Salem A, Hesham Hegab M, Hassan Elkaffash M, Dalal Azb H, Hosny AT .
Assessment of the ovarian reserve before and after laparoscopic surgery using
two different techniques for ovarian endometrioma. IOSR Journal of dental and
medical sciences. 2013;6(5):43–48.
6. Abdelmageed WM, Elquesny KM, Shabana RI, Abushama HM, Nassar AM.
Analgesic properties of a dexmedetomidine infusion after
uvulopalatopharyngoplasty in patients with obstructive sleep apnea. Saudi J
Anaesth 2011;5:150–156.
25
7. Brown DC, Miskovic D, Tang B, Hanna GB. Impact of established skills in open
surgery on the proficiency gain process for laparoscopic surgery. Surg Endosc.
2010;24:1420–1426
8. Rosenthal ME, Ritter EM, Goova MT , et al. Proficiency-based Fundamentals of
laparoscopic surgery skills training results in durable performance
improvement and a uniform certification pass rate. Surg Endosc.
2010;24:2453–2457
9. Gupta N, Rath GP , Prabhakar H, Dash HH. Effect of intraoperative
dexmedetomidine on postoperative recovery profile of children undergoing
surgery for spinal dysraphism. J Neurosurg Anesthesiol 2013;25:271–278.
10. Wang JJ, Ho ST , Uen YH, Lin MT , Chen KT , Huang JC, et al. Small dose
dexamethasone reduces nausea and vomiting after laparoscopic
cholecystectomy: a comparison of tropisetron with saline. Anesth Analg
2002;95:229–232.
11. Jain G, Bansal P , Ahmad B, Singh DK, Yadav G. Effect of the perioperative
infusion of dexmedetomidine on chronic pain after breast surgery. Indian J
Palliat Care 2012;18:45–51.
12. Arch Gynecol Obstet. Bilateral dermoid cysts of the ovary in a pregnant woman:
case report and review of the literature. 2009 Feb;279(2):105-8.
13. Yoon BS, Park H, Seong SJ, Park CT , Park SW, Lee KJ. Single-port laparoscopic
salpingectomy for the surgical treatment of ectopic pregnancy. J Minim Invasive
26
Gynecol 2010;17:26–29.
14. WIKIPEDIA http://en.wikipedia.org/wiki/Current_Procedural_Terminology
15. American Medical Association; American Medical Association (COR); Michelle
Abraham; Jay T . Ahlman; Angela J. Boudreau; Judy L. Connelly (30 October
2010). CPT 2011 Professional Edition. American Medical Association Press.
ISBN 978-1-60359-217-8. Retrieved 26 May 2011.
16. Obstet Gynecol. A comparative study of laparoscopy and colpotomy for the
removal of ovarian dermoid cysts 1996 Jun;87(6):1009-13.
17. Paek J, Nam EJ, Kim YT , Kim SW. Overcoming technical difficulties with
single-port access laparoscopic surgery in gynecology: using conventional
laparoscopic instruments. J Laparoendosc Adv Surg Tech A 2011;21:137–141.

18. Ugurlucan F G, Bastu E, Dogan M. et al. Management of cesarean heterotopic
pregnancy with transvaginal ultrasound-guided potassium chloride injection
and gestational sac aspiration, and review of the literature. J Minim Invasive
Gynecol. 2012;19:671–673.
19. Kim SH, Oh YJ, Park BW, Sim J, Choi YS. Effects of single-dose dexmedetomidine
on the quality of recovery after modified radical mastectomy: a randomized
controlled trial. Minerva Anestesiol 2013;79:1248–1258.

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Asset Metadata

Creator Hu, Chenwei (author)

Core Title Comparative study of laparoscopy vs. laparotomy for ovarian mass removal

School Keck School of Medicine

Degree Master of Science

Degree Program Biostatistics

Publication Date 09/04/2015

Defense Date 09/03/2015

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag laparoscopy,laparotomy,OAI-PMH Harvest

Format application/pdf (imt)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Lane, Christianne (committee chair), Azen, Stanley (committee member), Mack, Wendy (committee member)

Creator Email chenweih@usc.edu,chenweihu0310@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c40-175242

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