OBJECTIVETo develop a virtual navigation mode to enlarge the field of view and decrease the deformation of the visual area.

METHODThe method was implemented in 3 steps. The entire colon was first divided into consecutive sections, and each section was split into two halves by a plane. The virtual camera was finally assigned onto each half of the sections for navigation.

RESULTSAdequate subsections were achieved with this method, which also offer an enlarged field of view for the benefit of focal inspection.

CONCLUSIONThe division navigation mode is suitable for the development of a virtual colonoscopy navigation and diagnosis system.

Colon ; anatomy & histology ; diagnostic imaging ; Colonography, Computed Tomographic ; methods ; Colonoscopy ; methods ; Computer Simulation ; Humans ; Tomography, X-Ray Computed ; methods

The virtual colonoscopy, virtual flattening and virtual splitting method are enhanced by the GPGPU model. The novel virtual eversion method is integrated for fast polyp detection. The experimental result showed that the system and various visualization methods can represent the colon inner-surface clearly and exactly, supporting real-time man-machine interaction. The proposed system is promising in human gastrointestinal cancer and polyp inspection.
Colonic Polyps ; diagnosis ; Colonography, Computed Tomographic ; instrumentation ; methods ; Humans ; Imaging, Three-Dimensional ; Software Design ; Tomography, X-Ray Computed

The proposed automatic section method achieves accurate automatic section on colon outer surface centerline and evert the colon, by calculating the centerline windowed average curvature. The method is validated on CT colon datasets, and experimental results show that the sectioned virtual eversion facilitates colon visualization and analysis.
Colon ; anatomy & histology ; diagnostic imaging ; pathology ; Colonography, Computed Tomographic ; methods ; Humans ; Imaging, Three-Dimensional ; methods ; Phantoms, Imaging ; User-Computer Interface

PURPOSE: Virtual colonoscopy is the most recently developed tool for detecting colorectal cancers and polyps, but its effectiveness is limited. In our study, we compared the result of preoperative virtual colonoscopy to result of preoperative and postoperative colonoscopy. We evaluated also the accuracy of preoperative virtual colonoscopy in patients who had obstructive colorectal cancer that did not allow passage of a colonoscope. METHODS: A total of 164 patients who had undergone preoperative virtual colonoscopy and curative surgery after the diagnosis of a colorectal adenocarcinoma between November 2008 and August 2013 were pooled. We compared the result of conventional colonoscopy with that of virtual colonoscopy in the nonobstructive group and the results of preoperative virtual colonoscopy with that of postoperative colonoscopy performed at 6 months after surgery in the obstructive group. RESULTS: Of the 164 patients, 108 were male and 56 were female patients. The mean age was 62.7 years. The average sensitivity, specificity, and accuracy of virtual colonoscopy for all patients were 31.0%, 67.2%, and 43.8%, respectively. In the nonobstructive group, the average sensitivity, specificity, and accuracy were 36.6%, 66.2%, and 48.0%, respectively, whereas in the obstructive group, they were 2%, 72.4%, and 25.4%. Synchronous cancer was detected via virtual colonoscopy in 4 of the 164 patients. CONCLUSION: Virtual colonoscopy may not be an effective method for the detection of proximal colon polyps, but it can be helpful in determining the therapeutic plan when its results are correlated with the results of other studies.
Adenocarcinoma ; Colon* ; Colonic Polyps ; Colonography, Computed Tomographic* ; Colonoscopes ; Colonoscopy ; Colorectal Neoplasms* ; Diagnosis ; Female ; Humans ; Male ; Methods ; Polyps ; Sensitivity and Specificity

OBJECTIVETo assess the clinical values of CT colonography (CTC) in the diagnosis of colonic polyps.

METHODSForty-two patients who were clinically suspicious of colonic polyps or underwent colonic polyps screening received both CTC and conventional colonoscopy. Sixteen or 64-slice spiral CT and professional imaging processing techniques were used for evaluation. Per-polyp and per-patient results were analyzed. Those by per-polyp were subsequently divided into > or = 10 mm group, 5-10 mm group, and < or = 5 mm group. Sensitivity, positive predictive value (PPV), specificity, negative predictive value (NPV), and accuracy were calculated using statistical method for diagnostic studies, with conventional colonoscopy as a gold standard.

RESULTSNinety and 61 polyps were found by CTC and conventional colonoscopy, respectively. Sensitivity and PPV were 80.3%/55.6% by per-polyp and 100%/92.9%, 93.8%/65.2%, and 68.8%/ 41.5% in the > or = 10 mm group, 5-10 mm group, and < or = 5 mm group, respectively. Sensitivity, PPV, specificity, NPV, and accuracy by per-patient were 97.1%, 89.5%, 42.9%, 75.0%, and 88.1%, respectively.

CONCLUSIONCTC can clearly reveal the morphology of colonic polyps and can be used as a routine monitoring method for the clinical diagnosis of polyps.

Adult ; Aged ; Aged, 80 and over ; Colonic Polyps ; diagnostic imaging ; Colonography, Computed Tomographic ; methods ; Female ; Humans ; Male ; Middle Aged ; Sensitivity and Specificity

Recently, the availability of multidetector-row CT (MDCT) and continuous refinement in three-dimensional (3D) imaging process have greatly expanded the role of CT in evaluating patients with gastrointestinal diseases. MDCT is the latest advancement in CT technology and is now more readily available. This imaging modality can offer full examination of the entire intestinal tract as well as powerful information about the bowel itself and its surrounding structures, which are inherent advantages of CT over conventional barium or optical endoscopic studies. In most cases, MDCT with various 3D technologies can make an easy, rapid, and accurate diagnosis by one-stop imaging, and enables to avoid other examinations. Therefore, knowledge and awareness of valuable clinical applications and proper scan technique of MDCT imaging is essential to achieve the diagnostic goal of one-step imaging.
Barium Sulfate/diagnostic use ; Colonic Neoplasms/diagnosis/radiography ; Colonic Polyps/diagnosis/radiography ; Colonography, Computed Tomographic/instrumentation/*methods ; *Enema ; Humans ; Imaging, Three-Dimensional ; Tomography, Spiral Computed/instrumentation/*methods

Colon cancer is one of the leading causes of cancer-related deaths, while the virtual colonoscopy plays an important role in the early detection of colon cancer. Effective colon segmentation is the basis of virtual colonoscopy. Oral contrast agent can reduce the use of laxatives, but it can to bring some difficulties in the colon segmentation. Because of the partial volume effect, the CT value of air-tagging boundary span a wide range, which are not easily eliminated. We present an effective method of colon segmentation in this paper. Firstly, we used adaptive threshold method to extract air area. Then we segmented tagging region and removed air-tagging boundary by segment region growing method based on statistical information and morphological operation. The experiments showed that the agreement between the results by manual and by orithm segmentation reached 93.4%.
Algorithms ; Colon ; diagnostic imaging ; Colonography, Computed Tomographic ; methods ; Humans ; Pattern Recognition, Automated ; methods ; Radiographic Image Enhancement ; methods ; Radiographic Image Interpretation, Computer-Assisted ; methods

There are many factors affecting the successful performance of CT colonography (CTC). Adequate colonic cleansing and distention, the optimal CT technique and interpretation with using the newest CTC software by a trained reader will help ensure high accuracy for lesion detection. Fecal and fluid tagging may improve the diagnostic accuracy and allow for reduced bowel preparation. Automated carbon dioxide insufflation is more efficient and may be safer for colonic distention as compared to manual room air insufflation. CT scanning should use thin collimation of < or =3 mm with a reconstruction interval of < or =1.5 mm and a low radiation dose. There is not any one correct method for the interpretation of CTC; therefore, readers should be well-versed with both the primary 3D and 2D reviews. Polyps detected at CTC should be measured accurately and reported following the "polyp size-based" patient management system. The time-intensive nature of CTC and the limited resources for training radiologists appear to be the major barriers for implementing CTC in Korea.
Carbon Dioxide/administration & dosage ; Cathartics/therapeutic use ; Colonic Polyps/radiography ; Colonography, Computed Tomographic/*methods ; Contrast Media/administration & dosage ; Diagnosis, Computer-Assisted ; Feces ; Humans ; Imaging, Three-Dimensional ; Insufflation/methods

PURPOSE: We sought to evaluate the clinical usefulness of CT colonography (CTC) after incomplete conventional colonoscopy (CC) for occlusive colorectal cancer (CRC) according to the tumor location. MATERIALS AND METHODS: Seventy-five patients with occlusive CRC underwent subsequent CTC immediately after incomplete CC. Fifty-nine patients had distal CRC and 16 had proximal colon cancer. Experienced radiologists prospectively analyzed the location, length, and TNM staging of the main tumor. The colorectal polyps in the remaining colorectum and additional extraluminal findings were also recorded. Sixty-seven patients underwent colorectal resection. We retrospectively analyzed the surgical outcome and correlated CTC and CC findings. RESULTS: The overall accuracies of tumor staging were: T staging, 86%; N staging (nodal positivity), 70% (80%); and intra-abdominal M staging, 94%. Additional colonic polyps were found in 23 patients. Six synchronous carcinomas were detected (9%); three in the proximal colon and three in the distal colon of occlusion. Clinically significant localization errors at CC were noted in 8 patients (12%, 5 proximal colon cancers and 3 distal CRCs) and were corrected by CTC. After CTC, the surgeons modified the initial surgical plan in 11 cases (16%). CONCLUSION: In occlusive CRC, CTC is not only useful in the evaluation of the proximal bowel, but can also provide surgeons with accurate information about staging and tumor localization. CTC is recommended when endoscopists encounter occlusive CRC, regardless of tumor location.
Adult ; Aged ; Aged, 80 and over ; Colonography, Computed Tomographic/*methods ; Colonoscopy/*methods ; Colorectal Neoplasms/pathology/radiography/*surgery ; Female ; Humans ; Male ; Middle Aged ; Neoplasm Staging ; Reproducibility of Results

OBJECTIVE: To determine the effect of reduced abdominal compression in prone position on ascending colonic movement during supine-to-prone positional change during CT colonography (CTC). MATERIALS AND METHODS: Eighteen consecutive patients who had undergone prone CTC scanning with cushion blocks placed under the chest and hip/thigh to reduce abdominal compression and had confirmed sessile polyps > or = 6 mm in the well-distended, straight, mid-ascending colon, were included. Radial location along the ascending colonic luminal circumference (degrees) was measured for 24 polyps and 54 colonic teniae on supine and prone CTC images. The supine-to-prone change ranging between -180degrees and +180degrees (- and + for internal and external colonic rotations, respectively), was determined. In addition, possible causes of any ascending colonic rotations were explored. RESULTS: Abdominal compression during prone CTC scanning completely disappeared with the use of cushion blocks in 17 of 18 patients. However, some degrees of ascending colonic rotation were still observed, with the radial location changes of -22degrees to 61degrees (median, 13.9degrees) for the polyps and similar degrees for teniae. Fifty-four percent and 56% of polyps and teniae, respectively, showed changes > 10degrees. The radial location change of the polyps was significantly associated with the degree of anterior shift of the small bowel and mesentery (r = 0.722, p < 0.001) and the degree of posterior displacement of the ascending colon (r = 0.566, p = 0.004) during supine-to-prone positional change. CONCLUSION: Ascending colonic rotation upon supine-to-prone positional change during CTC, mostly in the form of external rotation, is not eliminated by removing abdominal compression in prone position.
Aged ; Colon/*pathology/*radiography ; Colonic Polyps/*radiography ; Colonography, Computed Tomographic/*methods ; Female ; Humans ; Male ; Middle Aged ; Movement ; Prone Position/*physiology ; Retrospective Studies ; Rotation