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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 17  |  Issue : 2  |  Page : 163-172

Role of MRI in diagnosis and preoperative staging of rectal carcinoma


Department of Radiodiagnosis, Faculty of Medicine (for Boys), Al-Azhar University, Cairo, Egypt

Date of Submission08-Mar-2019
Date of Decision31-Mar-2019
Date of Acceptance28-Apr-2019
Date of Web Publication23-Oct-2019

Correspondence Address:
Mohamed S Elfeshawy
Lecturer of Radiodiagnosis, Al-Hussein University Hospital, Faculty of medicine, Al-Azhar Universality, Cairo
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/AZMJ.AZMJ_44_19

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  Abstract 


Background and objectives High-resolution phased-array MRI is recommended as a standard imaging modality for preoperative local staging of rectal cancer with excellent soft tissue contrast, functional imaging ability, and multiplanar capability. With these inherent proprieties, MRI fills a gap in clinical practice and helps accurate local staging of rectal cancer before management decisions. Invention of diffusion-weighted image has also improved utility of MRI in patients with rectal cancer. Addition of diffusion-weighted image to T2-weighted imaging improved accuracy of rectal cancer detection and can facilitate lymph node detection (6% more nodes) than T2-weighted imaging alone.
Aim of the work The aim of this study is to detect the role of MRI in diagnosis and preoperative staging of rectal carcinoma.
Patients and methods This study was conducted on 40 patients with rectal neoplasms and/or highly suspected clinically to have rectal neoplasms who were referred from oncology medicine department to radiodiagnosis department for MRI preoperative evaluation and staging of rectal neoplasm. A prospective study was conducted using randomized controlled trials. Informed consent from a parent or guardian was obtained.
Results Phased array surface coil MRI has proved high agreement with postoperative histopathological examination, reaching 100% in T staging and 90% in N stages and 100% in detection of circumferential resection margin involvement, which match with many previous similar studies.
Conclusion Our study results demonstrate that high-resolution MRI has a pivotal role in accurate staging of rectal cancer, prediction of negative circumferential resection margin and involvement of the perirectal and pelvic lymph nodes. Thus, we conclude MRI has a golden standard value in the establishment of the best treatment strategy.

Keywords: apparent diffusion coefficient, diffusion-weighted image, magnetic resonance imaging, rectal neoplasm


How to cite this article:
Abdelmoty MF, Elfeshawy MS, Elhawary AE. Role of MRI in diagnosis and preoperative staging of rectal carcinoma. Al-Azhar Assiut Med J 2019;17:163-72

How to cite this URL:
Abdelmoty MF, Elfeshawy MS, Elhawary AE. Role of MRI in diagnosis and preoperative staging of rectal carcinoma. Al-Azhar Assiut Med J [serial online] 2019 [cited 2019 Dec 7];17:163-72. Available from: http://www.azmj.eg.net/text.asp?2019/17/2/163/269761




  Introduction Top


Colorectal cancer is the third most common cancer worldwide. Around 42% of colorectal cancers are located in the rectum, accounting for 5% of malignant tumors, and ranking as the fifth most common cancer in adults. Prognosis of rectal cancer is determined by depth of invasion, number of involved lymph nodes (LNs), and involvement of circumferential resection margin (CRM) [1].

Initial strategy of clinical diagnosis followed by surgery and postoperative chemotherapy had a high local recurrence rate (27%) and poor survival (48% 5-year survival). Later studies showed that neoadjuvant chemoradiation improves survival and decreases local recurrence rates significantly [2].

Neoadjuvant chemoradiotherapy is not indicated in stage I tumors (confined to rectal wall with no nodal involvement) but is recommended for stage II and stage III tumors. Therefore, to avoid unnecessary chemoradiation in stage I cancers, a reliable imaging modality is crucial to precisely define depth of invasion and to identify LN involvement [3].

Current approach in the management of rectal cancer includes preoperative staging with different imaging modalities followed by neoadjuvant chemoradiotherapy (for stage II/III cancers). This approach has lowered the local recurrence rate (11%) and improved survival (58% 5-year survival) [4].

Preoperative imaging for rectal cancer staging is also useful to determine which surgical technique would be more appropriate. Ideal imaging modality should accurately assess the depth of tumor penetration (T stage), LN involvement (N stage), presence of distant metastatic disease (M stage), mesorectal fascia involvement, and anal sphincter involvement [5].

Endoscopic ultrasonography, one of the oldest and most widely used imaging modalities, is reported to assess T staging with 67–97% accuracy and nodal involvement with 64–88% accuracy. Its value is also limited in the evaluation of near-obstructing tumors, tumors in the upper rectum, and mesorectal fascia involvement [6].

Computed tomography (CT) is commonly used in rectal cancer because of its ability to assess the entire pelvic anatomy and presence or absence of distant metastasis. A recent study showed T stage accuracy of 87.1% and N stage accuracy of 87.1%. Although newer multidetector CT technology has improved the accuracy, soft tissue resolution of CT is still inadequate to evaluate early rectal cancers [7].

On the contrary, high-resolution phased-array MRI is recommended as a standard imaging modality for preoperative local staging of rectal cancer, with excellent soft tissue contrast, functional imaging ability, and multiplanar capability. With these inherent proprieties, MRI fills a gap in clinical practice and helps accurate local staging of rectal cancer before management decisions [8].

Invention of DWI has also improved utility of MRI in patients with rectal cancer. Addition of DWI to T2-weighted imaging improved accuracy of rectal cancer detection and can facilitate LN detection (6% more nodes) than T2-weighted imaging alone, but it is not reliable for differentiating between benign and malignant LNs in patients with rectal cancer who have received concurrent chemotherapy and radiation therapy before surgery [9].


  Patients and methods Top


This study was conducted according to the guidelines of the ethics committee of our university and was approved by our institutional review board. All patients gave written informed consent to be imaged.

The study was conducted on 40 patients with rectal neoplasms and/or highly suspected clinically to have rectal neoplasms who were referred from oncology medicine department to radiodiagnosis department for MRI preoperative evaluation and staging of rectal neoplasm.

The age of 40 patients of our study ranged between 40 and 70 years, with mean age of 55 years.

All patients were subjected to pelvic MRI examination with the following instruments:
  1. The MRI machine, 1.5T system (Acheiva Philips, Netherlands).
  2. Pelvic phased-array coil .


Inclusion criteria

  1. All patients had histologically proved rectal cancer and were not treated with preoperative chemotherapy and/or radiotherapy.


Exclusion criteria

The following were the exclusion criteria:
  1. Cardiac pacemakers.
  2. History of allergy of intravenous contrast media (Gadolinium, Bayer Health care pharmaceuticals Inc., Whippnay, Germany).
  3. Pregnant patients (Gadolinium crosses the placenta blood barrier).
  4. Renal impairment.


Technique of examination

  1. Preparation before the examination:
    • The aim of patient preparation is to familiarize the patients with the procedure and to stress the importance of minimizing motion.
      1. The patients were instructed to wear hospital gowns and remove all metallic objects.
      2. The patient lies in the supine position
      3. The pelvic phased-array coil was used.
      4. 20-ml (mg) Buscopan intravenously for control of peristalsis.
  2. MR protocol ([Table 1]).
    Table 1 MR protocol

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  Results Top


This study included 40 patients, comprising 24 (60%) men and 16 (40%) women ([Table 2],[Table 3],[Table 4],[Table 5],[Table 6],[Table 7],[Table 8],[Table 9],[Table 10]).
Table 2 Percentage of age of patients

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Table 3 Number and percentage of different pathological lesions

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Table 4 Location of the rectal lesions and the number of cases at the affected site

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Table 5 T staging by MRI and histopathological results

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Table 6  N staging by MRI and histopathological results

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Table 7 Correctly diagnosed N stage, overstaged, and understaged cases by MRI

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Table 8 Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MRI in the evaluation of lymph node involvement in correlation to the histopathological examination

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Table 9 Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MRI in evaluation of circumferential resection margin in correlation to the histopathological examination

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Table 10 Number of patients diagnosed by MRI in relation to pathology in each T and N stages and circumferential resection margin as well as agreement % and total agreement % in each title

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According to T stage

  1. Of 40 patients, by MRI, four patients were staged as T1/T2, 28 were staged as T3, and eight were staged as T4.
  2. Histopathological examination showed that there were four T1/T2, 28 T3, and eight T4 tumors ([Table 5]).
  3. MRI diagnosed four lesions as T2, which were confirmed by histopathological examination in four patients (agreement 100%).
  4. Twenty eight lesions were diagnosed as T3 by MRI. Histopathological assessment confirmed this diagnosis in all patients (presence of perirectal fat infiltration) (agreement 100%).
  5. MRI diagnosed eight lesions as T4. Histopathological examination confirmed the MRI findings (agreement 100%).
  6. P value for T stage is 0.001 (<0.05), which is considered statistically significant.


According to N stage

  1. Of 40 patients, by MRI, 20 were N0, 16 were N1, and four cases were N2.
  2. By histopathological examination, 20 cases were N0, 12 were N1, and eight were N2.
  3. MRI diagnosed 20 lesions as N0, which were then confirmed by histopathological assessment (agreement 100%).
  4. Sixteen lesions were diagnosed by MRI as N1, confirmed by histopathological assessment in 12 patients, whereas four lesions proved to be N2 (agreement 75%).
  5. MRI diagnosed four lesions as N2, which were then confirmed by histopathological assessment (agreement 100%).
  6. P value for N stage is 0.001 (<0.05), which is considered statistically significant ([Table 6],[Table 7],[Table 8]).


According to CRM

  1. By MRI, 20 of 28 patients were diagnosed to have no CRM involvement (negative CRM), whereas eight patients were shown to have positive CRM.
  2. By histopathological examination, 20 had negative CRM, whereas eight patients were diagnosed with positive CRM.
  3. MRI has correctly predicted CRM involvement in all cases (agreement 100%).
  4. P value is 0.001 (<0.05), which is considered statistically significant ([Table 9] and [Table 10]).


Statistical analysis

Data were analyzed using Statistical Program for Social Science, version 20.0 (SPSS Inc., Chicago, Illinois, USA). Quantitative data were expressed as mean±. Qualitative data were expressed as frequency and percentage.

The following tests were done:
  1. Receiver operating characteristic curve analysis was used to find out the overall predictivity of parameters and to find out the best cutoff value with detection of sensitivity and specificity at this cutoff value.
    1. Sensitivity=(true positive)/[(true positive)+(false negative)].
    2. Specificity=(true negative)/[(true negative)+(false +ve)].
    3. PPV=(true positive)/[(true positive)+(false positive)].
    4. NPV=(true negative)/[(true negative)+(false negative)].
  2. The confidence interval was set to 95% and the margin of error accepted was set to 5%. So, the P value was considered significant as follows:
  3. Probability (P value)
    1. P values less than 0.05 was considered significant.
    2. P values less than 0.001 was considered as highly significant.
    3. P values greater than 0.05 was considered insignificant.


Selected cases

Case 1

Clinical history: A 68-years-old male patient presented with bleeding per rectum not responding to medical treatment. Per rectal examination (PRE) revealed a large rectal mass 6 cm from anal verge. Rectal endoscopy and biopsy revealed rectal adenocarcinoma. MRI was done ([Figure 1]).
Figure 1 Case 1. (a) Sagittal T2-weighted images show a large mass involving upper and mid rectum about 7 cm from anal verge. (b) Axial T2-weighted images show a large circumferential mass of intermediate signal intensity extending beyond the rectal wall with maximum distance from mesorectal fascia of 13 mm (circumferential resection margin=1.3 cm threatened). (c) Coronal T2-weighted images show perirectal fat with no evidence of EXMVI or perirectal lymph node. (d) Diffusion-weighted image shows rectal mass of restrictive diffusion.

Click here to view


Findings

  1. Sagittal T2-weighted images show a large mass involving upper and mid rectum about 7 cm from anal verge.
  2. Axial T2-weighted images show a large circumferential mass of intermediate signal intensity extends beyond rectal wall, with maximum distance from mesorectal fascia being 13 mm (CRM=1.3 cm threatened)
  3. Coronal T2-weighted images show perirectal fat with no evidence of Extramural vascular invasion (EXMVI) or perirectal LN.
  4. DWI shows rectal mass of restrictive diffusion.


MRI staging: T3N0. Threatened CRM.

Surgery: abdominoperineal resection.

Postoperative pathological staging: T3N0.

Case no. 2

Clinical history: A 57-year-old female patient presented with diarrhea and tenesmus not responding to medical treatment. PRE revealed large rectal mass 4 cm from anal verge. Rectal endoscopy and biopsy revealed rectal adenocarcinoma. MRI was done ([Figure 2]).
Figure 2 Case 2. (a) Sagittal T2-weighted images show a large mass involving middle and lower rectum with about 4 cm from anal verge. (b) Coronal T2-weighted images show rectal mass and perirectal fat with no evidence of EXMVI or perirectal lymph node. (c) Axial T2-weighted images show large circumferential mass of intermediate signal intensity infiltratin the rectal wall and reaching perirectal fat, with maximum distance from mesorectal fascia of 25 mm (circumferential resection margin>2 cm negative). (d) Axial T2-weighted images show a small oval-shaped lymph node of irregular border with short axis diameter of 8 mm.

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Findings

  1. Sagittal T2WI MR images show a large mass involving middle and lower rectum with about 4 cm from anal verge.
  2. Coronal T2WI MR images show a rectal mass and perirectal fat with no evidence of EXMVI or perirectal LN.
  3. Axial T2WI MR images show a large circumferential mass of intermediate signal intensity infiltrating rectal wall and reaching perirectal fat, with maximum distance from mesorectal fascia of 25 mm (CRM>2 cm negative).
  4. Axial T2WI MR images show a small oval-shaped LN of irregular border with short axis diameter of 8 mm.


MRI staging: T3N1. Negative CRM.

Surgery: low anterior resection.

Postoperative pathological staging: T3N0

Case No 3

Clinical history: A 42-year-old male patient presented with bleeding per rectum and abdominal pain not responding to medical treatment. Rectal endoscopy and biopsy revealed rectal adenocarcinoma. MRI was done [Figure 3].
Figure 3 Case 3. (a) Sagittal T2-weighted images show a rectosigmoid mass involving upper rectum with about 15 cm from anal verge. (b) Axial T2-weighted images show endophytic mass of intermediate signal intensity infiltrating rectal wall between 11 o’clock and 12 o’clock position in circumferential location and invading mesorectal fascia to reach to anterior peritoneum. (d) Coronal T2-weighted images show an upper rectal mass and perirectal fat with no evidence of EXMVI or perirectal lymph node. (e) Diffusion-weighted image shows rectal mass of restrictive diffusion that invades mesorectal fascia.

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Findings

  1. Sagittal T2WI MR images show rectosigmoid mass involving upper rectum with about 15 cm from anal verge.
  2. Axial T2WI MR images show endophytic mass of intermediate signal intensity infiltrating the rectal wall between 11 o’clock and 12 o’clock position in circumferential location and invading mesorectal fascia to reach to anterior peritoneum.
  3. Coronal T2W MR images show upper rectal mass and perirectal fat with no evidence of EXMVI or perirectal LN.
  4. DWI shows rectal mass of restrictive diffusion that invades mesorectal fascia.


MRI staging: T4N0.

Surgery: low anterior resection.

Postoperative pathological staging: T4N0

Case No 4

Clinical history: A 37-year-old male patient presented with diarrhea and tenesmus not responding to medical treatment. PRE revealed a large rectal mass 5 cm from anal verge. Rectal endoscopy and biopsy revealed rectal adenocarcinoma. MRI was done [Figure 4].
Figure 4 Case 4. (a) Sagittal T2-weighted images show circumferential rectal mass involving middle and lower rectum with about 5 cm from anal verge. (b) Axial T2-weighted images show a circumferential mass of intermediate signal intensity infiltrating rectal wall with speculation reaching perirectal fat with maximum distance from mesorectal fascia of 12 mm. (c) Coronal T2-weighted images show a rectal mass and perirectal fat with no evidence of EXMVI or perirectal lymph node. (d) Diffusion-weighted image shows a rectal mass of restrictive diffusion that invades mesorectal fascia.

Click here to view


Findings

  1. Sagittal T2WI MR images show circumferential rectal mass involving middle and lower rectum with about 5 cm from anal verge.
  2. Axial T2WI MR images show circumferential mass of intermediate signal intensity infiltrating rectal wall with speculation reaching perirectal fat with maximum distance from mesorectal fascia of 12 mm.
  3. Coronal T2WI MR images show rectal mass and perirectal fat with no evidence of EXMVI or perirectal LN.
  4. DWI shows rectal mass of restrictive diffusion that invades mesorectal fascia.


MRI staging: T3N0.

Surgery: Abdominal perineal resection.

Postoperative pathological staging: T3N0.

Case No 5

Clinical history: A 55-year-old female patient presented with bleeding per rectum not responding to medical treatment. PRE revealed large rectal mass of 5 cm from anal verge. Rectal endoscopy and biopsy revealed rectal adenocarcinoma. MRI was done [Figure 5].
Figure 5 Case 5. (a) Sagittal T2-weighted images show a circumferential rectal mass involving middle and lower rectum with about 6 cm from anal verge. (b) Axial T2-weighted images show circumferential mass of intermediate signal intensity infiltrating mesorectal fascia with invasion to the uterus and posterior wall of the bladder. (c) Coronal T2-weighted images show a rectal mass with internal iliac lymph of mixed signal intensity measuring 13 mm in short axis diameter. (d) Axial T1-weighted images show a circumferential rectal mass with invasion to the uterus and the bladder.

Click here to view


Findings

  1. Sagittal T2WI MR images show circumferential rectal mass involving middle and lower rectum with about 6 cm from anal verge.
  2. Axial T2WI MR images show circumferential mass of intermediate signal intensity infiltrating the mesorectal fascia, with invasion to the uterus and posterior wall of the bladder.
  3. Coronal T2WI MR images show rectal mass with internal iliac lymph of mixed signal intensity measuring 13 mm in short axis diameter.
  4. Axial T1WI MR images show circumferential rectal mass with invasion to the uterus and the bladder.


MRI staging: T4N2.

Surgery: abdominal perineal resection.

Postoperative pathological staging: T4N2.


  Discussion Top


Accurate preoperative staging is crucial for management of patients with rectal cancer and for making effective therapeutic decisions [10].

Rectal cancer has a highly variable outcome, with local pelvic recurrence after surgical resection, usually leading to incurable disease. The prognosis of rectal cancer is closely related to the stage at diagnosis and the choice of treatment because appropriate preoperative treatment decisions require knowledge of the exact stage of a tumor and accurate radiologic T staging (depth of cancer invasion) and N staging (LN metastasis) [11].

High-resolution MRI with phased-array surface coil represents the most advanced staging modality, providing physicians with the detailed information regarding the depth of tumor invasion, relationship of the tumor to the mesorectal fascia, CRM, extramural vascular invasion, and LN status, which are crucial points in the therapeutic planning of locally advanced tumors [12].

In this study, we included 40 patients with primary rectal cancer and focused on the evaluation of the role of MRI in staging of this malignancy.

The age range was between 20 and 70 years, with a mean age of 52.9 years. On the contrary, the study carried out by Zheng et al. [13], which included 38 patients with clinically suspected rectal carcinoma, found that the mean age was 65 years.

Of 40 patients who had confirmed histopathologically to have rectal neoplasms, 28 patients were histopathologically diagnosed as adenocarcinoma, that is, 70%, whereas the study by Veruttipong et al. [14] reported that adenocarcinoma was the most common histopathologic type of tumors (87.0%).

Akasu et al. [15], in agreement with our study, stated that rectal carcinoma is more common at the lower third of rectum (73.5%). In our study, we found that 40% of the lesions were located at the lower third of rectum.

The MRI T staging based on MRI findings is summarized in [Table 5]. T staging revealed intramural lesions (T1+T2 stage) in four (10%) patients, T3 in 28 (70%) patients, and T4 in eight (20%) patients.

MRI correctly assessed T staging in all patient with correlation to histopathologically staging, that is, accuracy is 100%. This agrees with Matsuoka et al. [16], who stated that the accuracy of MRI in local staging of rectal cancer was 100% in T staging. This did not match with the results of Algebally et al. [17] who showed that MRI T staging matched with histological T staging in 48 of 56 patients (85.7% accuracy) and mismatched in eight patients. Furey et al. [18] reported that the use of high-resolution MRI achieved accuracy of more than 85% in T staging.

The assessment of nodal involvement remains a confounding factor. Patients with malignant lymphadenopathy should receive chemoradiotherapy; however, cross-sectional imaging relies on the size as a criterion for nodal involvement, which has significant limitations. High-resolution MRI allows the assessment of nodal morphology, which significantly improves specificity in the assessment of nodal involvement [19].

In this study, sensitivity, specificity, and accuracy of LNs involvement were 100, 83.3, and 90%, respectively. This disagrees with Zhang et al. [13] who stated that sensitivity, specificity, and accuracy were 64.7, 90.5, and 79%, respectively.

It is well established that nodal size is of limited value in assessment for the presence of metastasis. LNs reported to be suspicious of metastasis, that is, at least 8 mm in short axis diameter in the mesorectal nodes and at least 10 mm in short axis diameter in the extramesorectal nodes [20].

The limited accuracy of nodal size might be related to the fact that 30–50% of metastases in rectal cancer occur in nodes that are less than 5 mm. Recently, it was reported that nodal margins and internal nodal characteristics are the most reliable indicators of malignancy. Features that are suggestive of malignancy include irregular or speculated nodal margins and heterogeneous signal intensity in addition to the restricted diffusion pattern of the involved node. The evaluation of these features requires high-resolution images that cover all LNs of importance, including superior rectal and pelvic sidewall LNs [21].


  Conclusion Top


Our study results demonstrate that high-resolution MRI has pivotal role in accurate staging of rectal cancer and prediction of negative CRMs and involvement of the perirectal and pelvic LNs. Thus, we conclude MRI has a golden standard value in the establishment of the best treatment strategy.

MRI of the rectum may be performed with either an endorectal coil or a phased-array surface coil. Use of an endorectal coil yields high-resolution images that fully depict the wall layers of the bowels, although clear differentiation between the mucosa and submucosa is still difficult. The major drawback of endorectal coil MRI is difficulty in evaluating stenosing and high rectal carcinomas. Moreover, a complete assessment of the perirectal structures is rather difficult because of portions of the mesorectal fascia and mesorectal fat.Rectal MRI with a phased-array surface coil yields high spatial-resolution images, thereby providing a full evaluation of the rectal wall layers, and has the additional advantage of a large field of view. Moreover, the use of a phased-array surface coil improves patient comfort compared with the use of an endorectal coil and lacks the hazards of radiation as in CT and PET/CT and is not operator dependent as in ultrasonography. Finally, stenosing lesions and tumors at the rectosigmoid junction can be evaluated in all cases, and the mesorectal fat and mesorectal fascia can be visualized. So in this study, we used a phased-array surface coil. The most suitable MR sequence for rectal cancer staging is the T2-weighted image sequence as it best depicts the anatomy of the rectal wall.

Acknowledgements

This work was supported by Radiodiagnosis Department, Faculty of Medicine (for Boys), Al Hussein Univeristy Hospital.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10]



 

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