Nasopharyngeal carcinoma (NPC) is an aggressive head and neck cancer ranked
as the 5th most common in Hong Kong. We aimed to study the role of dynamic
contrast-enhanced MRI (DCE-MRI) and dynamic 2-deoxy-2-[fluorine-18]fluoro
-D-glucose positron emission tomography (FDG-PET) for characterizing NPC
tumors in newly-diagnosed patients, and to quantitatively evaluate the
intratumoral heterogeneity of NPC.
In Chapter 2 we employed semi-quantitative analysis of DCE-MRI to study the
dynamic enhancement pattern by analyzing the time-intensity curves in 25 NPC
patients. Our findings suggested that high blood flow caused a high initial
intensity enhancement rate (ER), and that neovasculature due to tumor
angiogenesis in tumors of larger volume or higher T-stage caused more
accumulation of contrast agent which can be detected by DCE-MRI. PET and
semi-quantitative DCE-MRI parameters were not correlated and may reflect
different physiological/molecular processes in the microenvironment of NPC
tumor. However the major limitation of semi-quantitative analysis was that the
physiological correlates of these parameters were unclear.
In Chapter 3 we applied quantitative analysis of DCE-MRI to study the
permeability and perfusion characteristics in the same cohort as in Chapter 2.
Our findings implied that the permeability may be high compared to blood flow
in NPC tumor. We also observed significant correlations between iAUC (the
initial area under the time-intensity curve) by semi-quantitative analysis and ve
(the volume fraction of extravascular extracellular space) by quantitative analysis,
and between the two rate constants (kep’s) from these two methods, which
showed that semi-quantitative analysis was a feasible alternative in reflecting the
physiological characteristics of NPC. However, we did not observe any
significant correlation between PET and DCE-MRI quantitative parameters, also
suggesting that PET and DCE-MRI reflected different physiological information
in NPC.
In Chapter 4 we applied dynamic PET scan to study the glucose metabolism in
18 NPC tumors (16 included in DCE-MRI cohort). Our findings showed that
the overall FDG uptake was mainly composed of the FDG in tissue compartment
(Ki), which was governed by the phosphorylation (k3) but not the transport of
FDG (K1). This finding may further indicate a potential role of the
phosphorylation rate k3 in NPC. Dynamic PET parameters did not correlate
with DCE-MRI, indicating that the two modalities reflect different molecular
information in NPC.
In Chapter 5, intratumoral heterogeneity in NPC tumors of 40 patients was
studied using 18F-FDG PET scan. Our findings showed that as tumors grew to
a larger volume and higher T-stage, they showed more heterogeneous glucose
metabolism. It was found that more heterogeneous tumor was associated with
worse disease-free survival, indicating that tumor metabolic heterogeneity may
play an important role for NPC patient prognosis.
To summarize, these results showed that DCE-MRI and dynamic PET improved
our understanding about the physiological/molecular process of NPC, and, these
two modalities reflected different physiological information in the
microenvironment of NPC tumors. This indicated that the relationship between
supply of nutrients such as glucose and blood flow/permeability is complex and
not directly related. Moreover, intratumoral heterogeneity by PET scan was
also of importance in prognostication. / published_or_final_version / Diagnostic Radiology / Doctoral / Doctor of Philosophy
| Identifer | oai:union.ndltd.org:HKU/oai:hub.hku.hk:10722/161536 |
| Date | January 2012 |
| Creators | Huang, Bingsheng, 黄炳升 |
| Contributors | Khong, PL |
| Publisher | The University of Hong Kong (Pokfulam, Hong Kong) |
| Source Sets | Hong Kong University Theses |
| Language | English |
| Detected Language | English |
| Type | PG_Thesis |
| Source | http://hub.hku.hk/bib/B47869586 |
| Rights | The author retains all proprietary rights, (such as patent rights) and the right to use in future works., Creative Commons: Attribution 3.0 Hong Kong License |
| Relation | HKU Theses Online (HKUTO) |
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