Colonography by CT, MRI and PET/CT combined with conventional colonoscopy in colorectal cancer screening and staging

Colorectal cancer （CRC） remains a leading cancer killer worldwide. But the disease is both curable and preventable at an early stage. Regular CRC cancer screening has been shown to reduce the risk of dying from CRC. However, the importance of large-scale screening is only now starting to be appreciated. This article reviews a variety of imaging procedures available for detecting ulcerative colitis （UC） and Crohn＇s disease （CD）, polyps and CRC in their early stage and also presents details on various screening options. Detecting, staging and re-staging of patients with CRC also require multimodality, multistep imaging approaches. Staging and re-staging with conventional colonoscopy （CC）, computer tomography colonography （CTC）, magnetic resonance colonography （MRC） and positron emission tomography/computer tomography colonography （PET/CTC） are of paramount importance in determining the most appropriate therapeutic method and in predicting the risk of tumor recurrence and overall prognosis. The advantages and limitations of these modalities are also discussed.     

Role of preoperative CT colonography in patients with colorectal cancer

In patients with colorectal cancer(CRC),accurate preoperative evaluation is essential for a correct therapeutic plan.Colonoscopy and intravenous contrastenhanced computed tomography(CT)are currently recommended in the preoperative work-up for CRC.Preoperative colonoscopy has some limitations such as misdiagnosis of synchronous cancers in cases of incomplete exploration of the colon and inaccurate tumor localization.Intravenous contrast-enhanced CT successfully documents distant metastases although it sometimes enables unsatisfactory locoregional staging.Computed tomography colonography(CTC)is obtained after gas insufflation of the colon and offers a comprehensive preoperative evaluation in patients with CRC,including a definition of the segmental location of the tumor,presence of synchronous lesions or lack thereof,and fairly accurate locoregional staging.CTC has some limitations,including a lack of biopsy capability,suboptimal sensitivity for synchronous small polyps,and unsatisfactory nodal staging.Bearing in mind these limitations,CTC could be employed as a"one-stop-shop"examination for preoperative assessment in patients with CRC.     

(18)F-DG PET/CT in detection of recurrence and metastasis of colorectal cancer

AIM To evaluate the value of 18F-DG PET/CT in detecting recurrence and/or metastasis of colorectal cancer (CRC).METHODS Combined visual analysis with semiquantitative analysis, the 18F-DG PET/CT wholebody imaging results and the corresponding clinical data of 68 postoperative CRC patients including 48 male and 20 female with average age of 58.1 were analyzed retrospectively.RESULTS Recurrence and/or metastasis were confirmed in 56 patients in the clinical follow-up after the PET/CT imaging. The sensitivity of PET/CT diagnosis of CRC recurrence and/or metastasis was 94.6%, and the specificity was 83.3%. The positive predictive value (PPV)was 96.4% and the negative predictive value (NPV) was 76.9%. PET/CT imaging detected one or more occult malignant lesions in 8 cases where abdominal/pelvic CT and/or ultrasonography showed negative findings, and also detected more lesions than CT or ultrasonography did in 30.4% (17/56) cases. Recurrence and/or metastasis was detected in 91.7% (22/24) cases with elevated serum CEA levels by 18F-DG PET/CT imaging.CONCLUSION 18F-DG PET/CT could detect the recurrence and/or metastasis of CRC with high sensitivity and specificity.     

Colorectal cancer screening:The role of CT colonography

Computed tomography colonography(CTC) in colorectal cancer(CRC) screening has two roles:one present and the other potential.The present role is,without any further discussion,the integration into established screening programs as a replacement for barium enema in the case of incomplete colonoscopy.The potential role is the use of CTC as a first-line screening method together with Fecal Occult Blood Test,sigmoidoscopy and colonoscopy.However,despite the fact that CTC has been officially endorsed for CRC scre...     

Radiomics in colorectal cancer patients

The main therapeutic options for colorectal cancer are surgical resection and adjuvant chemotherapy in non-metastatic disease. However,the evaluation of the overall adjuvant chemotherapy benefit in patients with a high risk of recurrence is challenging. Radiological images can represent a source of data that can be analyzed by using automated computer-based techniques,working on numerical information coded within Digital Imaging and Communications in Medicine files: This image numerical analysis...     

Role of advanced imaging techniques in the evaluation of oncological therapies in patients with colorectal liver metastases

In patients with colorectal liver metastasis (CRLMs) unsuitable for surgery, oncological treatments, such as chemotherapy and targeted agents, can be performed. Cross-sectional imaging [computed tomography (CT), magnetic resonance imaging (MRI), 18-fluorodexoyglucose positron emission tomography with CT/MRI] evaluates the response of CRLMs to therapy, using post-treatment lesion shrinkage as a qualitative imaging parameter. This point is critical because the risk of toxicity induced by oncological treatments is not always balanced by an effective response to them. Consequently, there is a pressing need to define biomarkers that can predict treatment responses and estimate the likelihood of drug resistance in individual patients. Advanced quantitative imaging (diffusion-weighted imaging, perfusion imaging, molecular imaging) allows the in vivo evaluation of specific biological tissue features described as quantitative parameters. Furthermore, radiomics can represent large amounts of numerical and statistical information buried inside cross-sectional images as quantitative parameters. As a result, parametric analysis (PA) translates the numerical data contained in the voxels of each image into quantitative parameters representative of peculiar neoplastic features such as perfusion, structural heterogeneity, cellularity, oxygenation, and glucose consumption. PA could be a potentially useful imaging marker for predicting CRLMs treatment response. This review describes the role of PA applied to cross-sectional imaging in predicting the response to oncological therapies in patients with CRLMs.     

Colorectal cancer: Parametric evaluation of morphological,functional and molecular tomographic imaging

Colorectal cancer(CRC) represents one of the leading causes of tumor-related deaths worldwide. Among the various tools at physicians' disposal for the diagnostic management of the disease, tomographic imaging(e.g., CT, MRI, and hybrid PET imaging) is considered essential. The qualitative and subjective evaluation of tomographic images is the main approach used to obtain valuable clinical information, although this strategy suffers from both intrinsic and operator-dependent limitations. More recently, advanced imaging techniques have been developed with the aim of overcoming these issues. Such techniques,such as diffusion-weighted MRI and perfusion imaging, were designed for the"in vivo" evaluation of specific biological tissue features in order to describe them in terms of quantitative parameters, which could answer questions difficult to address with conventional imaging alone(e.g., questions related to tissue characterization and prognosis). Furthermore, it has been observed that a large amount of numerical and statistical information is buried inside tomographic images, resulting in their invisibility during conventional assessment. This information can be extracted and represented in terms of quantitative parameters through different processes(e.g., texture analysis). Numerous researchers have focused their work on the significance of these quantitative imaging parameters for the management of CRC patients. In this review, we aimed to focus on evidence reported in the academic literature regarding the application of parametric imaging to the diagnosis, staging and prognosis of CRC while discussing future perspectives and present limitations. While the transition frompurely anatomical to quantitative tomographic imaging appears achievable for CRC diagnostics, some essential milestones, such as scanning and analysis standardization and the definition of robust cut-off values, must be achieved before quantitative tomographic imaging can be incorporated into daily clinical practice.     

PET/CT Colonography for the Preoperative Evaluation of the Colon Proximal to the Obstructive Colorectal Cancer

Purpose  This study was designed to evaluate the usefulness of 18-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) colonography in preoperative diagnosis of the tumors proximal to obstructive colorectal cancers, which were defined as cancers that cannot be traversed colonoscopically. Methods  A whole-body PET/CT protocol for tumor staging and a protocol for CT colonography were integrated into one examination. No cathartic bowel preparation was used before this examination. Thirteen prospective patients with obstructive cancer were examined. We compared the detection rates for obstructive colorectal cancers and tumors proximal to the obstruction using air-inflated PET/CT colonography to intraoperative examinations, histopathologic outcome, and follow-up colonoscopy. Results  PET/CT colonography correctly identified all 13 primary obstructive colorectal cancers and all 2 synchronous colon cancers proximal to the obstruction. The two synchronous colon cancers detected at PET/CT colonography were confirmed and removed at single-stage surgical procedures. PET/CT colonography was able to localize all colorectal cancers precisely. There were no false-negative or false-positive proximal colorectal cancers by PET/CT colonography. Other preoperative examinations missed the synchronous colon cancers. Conclusions  In patients with obstructive colorectal cancers, preoperative PET/CT colonography provided valuable anatomic and functional information of the entire colon to properly address surgery of colorectal cancer.     

Virtual gastrointestinal colonoscopy in combination with large bowel endoscopy: Clinical application

Although colorectal cancer (CRC) has no longer been the leading cancer killer worldwide for years with the exponential development in computed tomography (CT) or magnetic resonance imaging, and positron emission tomography/CT as well as virtual colonoscopy for early detection, the CRC related mortality is still high. The objective of CRC screening is to reduce the burden of CRC and thereby the morbidity and mortality rates of the disease. It is believed that this goal can be achieved by regularly screening the average-risk population, enabling the detection of cancer at early, curable stages, and polyps before they become cancerous. Large-scale screening with multimodality imaging approaches plays an important role in reaching that goal to detect polyps, Crohn’s disease, ulcerative colitis and CRC in early stage. This article reviews kinds of presentative imaging procedures for various screening options and updates detecting, staging and re-staging of CRC patients for determining the optimal therapeutic method and forecasting the risk of CRC recurrence and the overall prognosis. The combination use of virtual colonoscopy and conventional endoscopy, advantages and limitations of these modalities are also discussed.     

CT colonography in the diagnosis and management of colorectal cancer:Emphasis on pre-and post-surgical evaluation

This article addresses the use of computed tomographic colonography(CTC)for the diagnosis and management of colorectal cancer,focusing on presurgical evaluation of the colon proximal to an occlusive cancer and surveillance after cancer resection surgery.The key evidences accumulated in the literature and future work needed are summarized.CTC is a technically robust and the most practical method to evaluate the colon proximal to an occlusive cancer,which prevents colonoscopic examination past the occlusion,either before or after metallic stent placement.The high sensitivity of CTC for detecting cancers and advanced adenomas in the proximal colon can help prevent additional surgical procedures in patients showing negative results.However,the accuracy of CTC for distinguishing intramural cancers from adenomas is low,and the technique is limited in guiding management when a medium-sized lesion that do not show invasive features such as pericolic extension or nodal metastasis is found in the proximal colon.A maximal diameter≥15 mm has been proposed as a criterion for surgical removal of proximal lesions.However,this needs to be verified in a larger cohort.In addition,the influence of presurgical CTC results on the current post-cancer resection colonic surveillance timeline remains to be determined.CTC can be readily added to the routine abdominopelvic CT in the form of contrast-enhanced CTC,which can serve as an effective stand-alone tool for postcancer resection surveillance of both the colorectum and extracolonic organs.Although the accuracy of CTC has been demonstrated,its role in the current colonoscopy-based postoperative colonic surveillance protocols remains to be determined.Readers of CTC also need to be knowledgeable on the colonic lesions that are unique to the postoperative colon.     

PET/CT and Histopathologic Response to Preoperative Chemoradiation Therapy in Locally Advanced Rectal Cancer

Purpose

The objective of this study was to investigate the possibility of using positron emission tomography/computer tomography to predict the histopathologic response in locally advanced rectal cancer treated with preoperative chemoradiation.

Methods

The study included 30 patients with locally advanced rectal adenocarcinoma treated with a combination of radiotherapy and concurrent Uftoral® (uracil, tegafur) and leucovorine. All patients were evaluated by positron emission tomography/computer tomography scan seven weeks after end of chemoradiation, and the results were compared to histopathologic tumor regression as the “standard.” The pathologic response was quantified by tumor regression grade.

Results

Positron emission tomography/computer tomography correctly identified six of eight patients (specificity 75 percent) with complete pathologic response. However, the sensitivity of positron emission tomography/computer tomography was only 45 percent and the accuracy 53 percent. The positive and negative predictive values were 83 and 33 percent, respectively.

Conclusions

We conclude that positron emission tomography/computer tomography performed seven weeks after the end of chemoradiation is not able to predict the histopathologic response in locally advanced rectal cancer. There is an obvious need for other complementary methods especially with respect to the low sensitivity of positron emission tomography/computer tomography.

     

Identification of the fascia propria by magnetic resonance imaging and its relevance to preoperative assessment of rectal cancer

PURPOSE: If rectal cancer does not penetrate the fascia propria of the rectum and the rectum is removed with the fascial envelope intact (extrafascial excision), then local recurrence of the cancer will be minimal. Modern imaging techniques have identified a fascial plane surrounding the rectum and mesorectum, and it has been suggested that this is the fascia propria. The aim of this study was to identify whether this plane is the rectal fascia propria and whether tumor invasion through this fascia can be identified preoperatively. METHODS: Two separate experiments were performed: 1) pelvic magnetic resonance imaging was performed before and after dissection and marking of the plane of extrafascial dissection of the rectum of a cadaver; and 2) magnetic resonance imaging was performed in 43 rectal cancer patients preoperatively. Two radiologists independently reported the depth of tumor invasion in relation to the fascia propria. The tumors were resected by extrafascial excision, and a pathologist independently reported the relation of the tumor to the fascia propria. RESULTS: The marker inserted in the extrafascial plane showed that the plane visualized on pelvic magnetic resonance imaging was the fascia propria dissected in extrafascial excision of the rectum. The magnetic resonance imaging detected tumor penetration through the fascia propria with a sensitivity of 67 percent, a specificity of 100 percent, and an accuracy of 95 percent. CONCLUSION: The surgical fascia propria can be identified on preoperative magnetic resonance imaging in patients with rectal cancer. Tumor invasion through this fascia can be detected on magnetic resonance imaging. This method of assessment offers a new way to select those patients who require preoperative radiotherapy.Supported by a research grant from The Maurice and Phyllis Paykel Trust, Parnell, Auckland, New Zealand.     

Magnetic resonance imaging based colonography for diagnosis and assessment of diverticulosis and diverticulitis

Background and aims MRI-based colonography is a new minimally invasive imaging modality to assess the colon and abdomen. This new method which is applied mainly for polyp screening could be an integrative approach for colonic diverticulitis assessment. This study evaluated the feasibility of MRI-based colonography to assess diverticulosis or diverticulitis.Patients and methods Fourteen consecutive patients with clinically suspected diverticulitis were examined by MRI colonography on a 1.5-T scanner. All patients underwent abdominal CT as gold standard. N-Butyl-scopalamin was given intravenously to reduce bowel peristalsis. After rectal administration of a T1-positive enema T1- and T2-weighted acquisitions with additional intravenous contrast were obtained. A 3D FLASH sequence was acquired for virtual colonography. The results were compared with CT and biological parameters such as white blood cell count and C-reactive protein.Results Of 56 bowel segments (sigmoid colon, descending colon, transverse colon, ascending colon) in all 14 patients 54 were assessed to have good to fair image quality. Having CT as standard of reference, all sigmoid diverticula were diagnosed based on MRI. Inflammation as judged by CT was identically assessed on MRI. 3D models of the colon revealed further diverticula in the remaining colon; additionally, the 3D models gave a comprehensive image for surgical planning.Conclusion In our preliminary study MRI colonography revealed the same diagnosis as CT in all patients without ionizing radiation. Additionally, 3D-rendered models and virtual colonoscopy can be performed. This comprehensive 3D models could replace presurgical planning barium enema with concurrent assessment of the residual colon.     

Computed tomography and magnetic resonance imaging evaluation of lymph node metastasis in early colorectal cancer

AIM: To assess the role of computed tomography(CT) and magnetic resonance imaging(MRI) and establish imaging criteria of lymph node metastasis in early colorectal cancer.METHODS: One hundred and sixty patients with early colorectal cancer were evaluated for tumor location, clinical history of polypectomy, depth of tumor invasion, and lymph node metastasis. Two radiologists assessed preoperative CT and/or MRI for the primary tumor site detectability, the presence or absence of regional lymph node, and the size of the largest lymph node. Demographic, imaging, and pathologic findings were compared between the two groups of patients based on pathologic lymph node metastasis and optimal size criterion was obtained.RESULTS: The locations of tumor were ascending, transverse, descending, sigmoid colon, and rectum. One hundred and sixty early colorectal cancers were classified into 3 groups based on the pathological depth of tumor invasion; mucosa, submucosa, and depth unavailable. A total of 20(12.5%) cancers with submucosal invasion showed lymph node metastasis. Lymph nodes were detected on CT or MRI in 53 patients. The detection rate and size of lymph nodes were significantly higher(P = 0.000, P = 0.044, respectively) in patients with pathologic nodal metastasis than in patients without nodal metastasis. Receiver operating curve analysis showed that a cut-off value of 4.1 mm is optimal with a sensitivity of 78.6% and specificity of 75%.CONCLUSION: The short diameter size criterion of≥ 4.1 mm for metastatic lymph nodes was optimal for nodal staging in early colorectal cancer.     

Incidental focal colorectal 18F-fluorodeoxyglucose uptake on positron emission tomography/computed tomography

AIM: To assess the clinical significance of incidental focal colorectal 18 F-fluorodeoxyglucose ( 18 F-FDG) uptake on 18 F-FDG-positron emission tomography/computed tomography (PET/CT). METHODS: The records of all the cases which had undergone colonoscopy after PET/CT within a two weeks interval were reviewed. Adenomas were considered advanced when they were villous, ≥ 10 mm in size, or had high-grade dysplasia. Colorectal cancers and advanced adenomas are collectively referred to as advanced colorectal neoplasms. Receiver-operating characteristic curve analysis was used to determine thesignificant predictive maximum standardized uptake value (SUVmax) cutoff value for advanced colorectal neoplasms and cancer. RESULTS: Ninety-five colorectal lesions matched the site of incidental focal colorectal 18 F-FDG uptake on PET/CT and 146 did not. Colonoscopy showed advanced colorectal neoplasms corresponding to the site of 18 F-FDG uptake in 49 of the 95 (51.5%) lesions with incidental uptake. Of the lesions without incidental uptake, only 6 of 146 (4.1%) had advanced colorectal neoplasms on colonoscopy, indicating a statistically significant difference between the two groups (P < 0.001). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of incidental focal 18 F-FDG uptake in identifying advanced colorectal neoplasms were 89.1%, 75.3%, 51.6%, 95.9%, and 78.4%, respectively. In detecting only CRC, these values were 89.2%, 69.6%, 34.7%, 97.3%, and 72.6%, respectively. The significant SUVmax cutoff value for advanced colorectal neoplasms (area under the curve 0.755, P < 0.001) was 4.35, with a sensitivity, specificity, PPV, NPV, and accuracy of 75.5%, 65.2%, 69.8%, 71.4% and 70.5%, respectively. For CRC, 5.05 was the significant SUVmax cutoff value (area under the curve 0.817, P < 0.001), with a sensitivity, specificity, PPV, NPV, and accuracy of 84.8%, 71.0%, 80.9%, 89.8%, and 75.8%, respectively. CONCLUSION: The presence of incidental focal colorectal 1     

结肠癌术前影像学评估的研究进展

术前影像学评估对于结肠癌临床治疗决策具有重要价值。随着影像学技术的不断发展,综合影像学检查方法将成为结肠癌术前评估的主要方式,其临床价值明显提高。该文对结肠癌术前影像学评估的研究进展作一综述。     

Preoperative staging of rectal cancer

With the widespread introduction of preoperative radiotherapy for rectal cancer and the development of transanal endoscopic microsurgery for selected early lesions, preoperative radiological staging of these tumours has taken on increasing importance. This study is a systematic review to evaluate computed tomography (CT), endorectal sonography (ES) and magnetic resonance imaging (MRI) as preoperative staging modalities in rectal cancer. A Medline-based search identifying studies using CT, ES, or MRI in preoperative staging of rectal cancer between 1980 and 1998 was undertaken. The list of papers was supplemented by extensive cross-checking of citation lists. Studies were included if they met predetermined criteria. Data from the accepted studies were entered into pooled tables comparing radiological and pathological staging results for each modality both in determining bowel wall penetration and involvement of lymph nodes. Accuracy, sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio and negative likelihood ratio were determined for the pooled results. Eighty-three studies from 78 papers including 4897 patients met the inclusion criteria. In determining the wall penetration of the tumour the values for sensitivity for CT, ES, MRI and MRI with endorectal coil were 78%, 93%, 86% and 89%; for specificity 63%, 78%, 77% and 79%; and for accuracy 73%, 87%, 82% and 84%, respectively. In determining the nodal involvement by tumour the sensitivity values for CT, ES, MRI and MRI with endorectal coil 52%, 71%, 65% and 82%; for specificity 78%, 76%, 80% and 83%; and for accuracy 66%, 74%, 74% and 82%, respectively. MRI with an endorectal coil is the single investigation that most accurately predicts pathological stage in rectal cancer. Accepted: 14 October 1999     

Prediction of tumor biological characteristics in different colorectal cancer liver metastasis animal models using 18F-FDG and 18F-FLT

Background: Positron emission tomography(PET) is a noninvasive method to characterize different metabolic activities of tumors, providing information for staging, prognosis, and therapeutic response of patients with cancer. The aim of this study was to evaluate the feasibility of~(18)F-fludeoxyglucose(~(18)F-FDG) and 3'-deoxy-3'-~(18)F-fluorothymidine(~(18)F-FLT) PET in predicting tumor biological characteristics of colorectal cancer liver metastasis.Methods: The uptake rate of~(18)F-FDG and~(18)F-FLT in SW480 and SW620 cells was measured via an in vitro cell uptake assay. The region of interest was drawn over the tumor and liver to calculate the maximum standardized uptake value ratio(tumor/liver) from PET images in liver metastasis model. The correlation between tracer uptake in liver metastases and VEGF, Ki67 and CD44 expression was evaluated by linear regression.Results: Compared to SW620 tumor-bearing mice, SW480 tumor-bearing mice presented a higher rate of liver metastases. The uptake rate of~(18)F-FDG in SW480 and SW620 cells was 6.07% ± 1.19% and2.82% ± 0.15%, respectively(t = 4.69, P = 0.04); that of~(18)F-FLT was 24.81% ± 0.45% and 15.57% ± 0.66%, respectively(t = 19.99, P 0.001). Micro-PET scan showed that all parameters of FLT were significantly higher in SW480 tumors than those in SW620 tumors. A moderate relationship was detected between metastases in the liver and~(18)F-FLT uptake in primary tumors(r = 0.73, P = 0.0019).~(18)F-FLT uptake was also positively correlated with the expression of CD44 in liver metastases(r = 0.81, P = 0.0049).Conclusions: The uptake of~(18)F-FLT in metastatic tumor reflects different biological behaviors of colon cancer cells.~(18)F-FLT can be used to evaluate the metastatic potential of colorectal cancer in nude mice.     

Macro-regenerative nodules in biliary atresia： CT/MRI findings and their pathological relations

AIM： To describe the radiological findings of a macro-regenerative nodule （MRN） in the liver of pretransplantation biliary atresia （BA） patients and to correlate it with histological findings.
METHODS： Between August 1990 and November 2007, 144 BA patients underwent liver transplantation （LT） at our institution. The pre-transplantation computer tomograghy （CT） and magnetic resonance imaging （MRI） findings were reviewed and correlated with the post-transplantation pathological findings.
RESULTS： Nine tumor lesions in 7 patients were diagnosed in explanted livers. The post-transplantation pathological findings showed that all the lesions were MRNs without malignant features. No small nodule was detected by either MRI or CT. Of the 8 detectable lesions, 6 （75%） were in the central part of the liver, 5 （63%） were larger than 5 cm, 5 （63%） had intratumor tubular structures, 3 （38%） showed enhancing fibrous septa, 3 （38%） had arterial enhancement in CT, one （13%） showed enhancement in MRI, and one （13%） had internal calcifications.
CONCLUSION： Although varied in radiological appearance, MRN can be differentiated from hepatocellular carcinoma （HCC） in most of BA patients awaiting LT. The presence of an arterial-enhancing nodule does not imply that LT is withheld solely on the basis of presumed malignancy by imaging studies. Liver biopsy may be required in aid of diagnostic imaging to exclude malignancy.