CT colonoscopy of colorectal neoplasms: two-dimensional and three-dimensional virtual-reality techniques with colonoscopic correlation

OBJECTIVE: The aim of this study was to compare the diagnostic accuracy of two-dimensional (2D) CT colonography and three-dimensional (3D) virtual colonoscopy with conventional colonoscopy in patients who have suspected colorectal neoplasms. SUBJECTS AND METHODS: Twenty patients were studied (eight women and 12 men; mean age, 53 years; range, 42-85 years). All patients had findings on conventional colonoscopy suggestive of colorectal carcinoma and underwent colonic CT within 3 hr of endoscopy. Two-dimensional CT colonography and 3D virtual colonoscopy images were generated from the same data set that was obtained from thin-section helical CT of the abdomen and pelvis after rectal insufflation of room air. Three-dimensional virtual colonoscopy images were obtained by downloading CT data to a workstation equipped with commercially available software. Volume- and perspective-rendering techniques were used to achieve interactive, 3D virtual "fly-through" examinations of the colonic mucosa. The results of 2D CT colonography and 3D virtual colonoscopy were compared with the findings of conventional colonoscopy and correlated with surgical and pathologic outcome where possible. RESULTS: Twenty masses (defined as intraluminal projections 2 cm or larger in diameter) and 15 polyps (defined as projections smaller than 2 cm in diameter) were identified in our study group. All masses and 14 of 15 polyps were successfully shown on 2D colonography. Three findings of polyps on 2D colonography were false-positive, and one was false-negative. Three-dimensional virtual colonoscopy revealed 19 of 20 masses and 13 of 15 polyps. On conventional colonoscopy, all 20 masses and 13 of 15 polyps were identified, with one false-positive finding of a malignant stricture in a normal colon. Complete examination of the colon was possible in 18 of 20 patients using the 2D technique and in 17 of 20 patients using 3D virtual colonoscopy, whereas conventional colonoscopy showed the entire colon in only 12 of 20 patients. CONCLUSION: Two-dimensional CT colonography and 3D virtual colonoscopy are complementary and effective techniques for examining the colon in patients with suspected colorectal carcinoma. CT techniques offer several advantages over conventional colonoscopy including the ability to detect abnormalities proximal to obstructing carcinomas, accurate localization of abnormalities within the colon, and good patient tolerance. These CT techniques may play an important role in future diagnosis of colorectal cancer and for screening patients at risk.     

Virtual and three-dimensional bronchoscopy with spiral and electron beam computed tomography

PURPOSE: To compare spiral computed tomography (CT) and electron-beam CT (EBT) for 3D and virtual CT-bronchoscopy. MATERIALS AND METHODS: 17 patients with various disorders of the tracheobronchial system were examined using fiberoptic bronchoscopy, spiral CT and EBT. 3D images were reconstructed from CT data sets using automated segmentation based on volume-growing methods. Surface-rendered, volume-rendered, and hybrid reconstructions were visualized in real time using a data helmet. RESULTS: All data sets could be processed to high-quality three-dimensional (3D) and virtual reconstructions. The reduction of motion artifacts due to shorter scan times made EBT data sets better suited for automated segmentation and less susceptible to motion artifacts. 3D and virtual reconstructions did not increase the diagnostic sensitivity of CT compared to axial reconstructions alone. CONCLUSIONS: Shorter scan times of CT imaging yield higher-quality 3D and virtual reconstructions. Modern reconstruction techniques are valuable visualization tools for select indications and are the prerequisite for future developments in computer-aided medicine.     

The genomic organization of the genes for human lipopolysaccharide binding protein (LBP) and bactericidal permeability increasing protein (BPI) is highly conserved

PURPOSE: The authors evaluated computed tomographic (CT) virtual colography for the detection of simulated polyps under ideal conditions, as well as the effects on lesion conspicuity of (a) collimation, (b) table pitch, and (c) orientation of the colon lumen with respect to the gantry. MATERIALS AND METHODS: Pig colon was resected and cleansed, and polyps with diameters of 3, 7, and 10 mm were created. Each specimen was scanned with collimation of 5 and 7 mm and table pitch of 1.0, 1.6, and 2.0 at angles of 0 degrees, 45 degrees, and 90 degrees to the gantry. The initial two-dimensional (2D) images were reconstructed at 1-mm intervals (2D reconstructions), from which three-dimensional (3D) virtual colography images were generated. Polyp conspicuity on the initial and reconstructed 2D images and the 3D reconstructions was evaluated on a three-point scale: 0 = polyp not depicted, 1 = polyp faintly depicted, and 2 = polyp clearly depicted. RESULTS: The 10-mm-diameter polyp was clearly depicted (grade 2 conspicuity) on every initial and reconstructed 2D image and 3D reconstruction without regard to collimation, table pitch, or angle to the gantry. The 7-mm-diameter polyp was clearly depicted (grade 2 conspicuity) on every initial and reconstructed 2D image, but conspicuity on 3D reconstructions varied as the imaging parameters varied. The 3-mm-diameter polyp was faintly depicted (grade 1 conspicuity) on the initial and reconstructed 2D images and 3D reconstructions, but conspicuity varied on the 3D reconstructions as the imaging parameters varied. CONCLUSION: CT virtual colography helped detection of small mucosal polyps regardless of the angle of the colon lumen to the gantry at which they were obtained.     

Radiation exposure during CT examination of thorax and abdomen. Comparison of sequential, spiral and electron beam computed tomography

Comparison of radiation exposure applied by different types of CT scanners for the investigation of the chest and abdomen. Determination of radiation exposure applied by multi-phase spiral CT. Estimation of the dose in air in the system axis of the scanner, the CT dose index (CTDI) and the effective dose for electron beam tomography (EBT) and two conventional CT scanners (sequence, SEQ; spiral, SCT). For EBT, dose in system axis for investigation of the abdomen was above 50 mGy. Effective dose for investigation of the chest and abdomen was higher with EBT (11 and 26 mSv, respectively) than with conventional CT (SEQ, 4 and 20 mSv; SCT, 2 and 7 mSv). The effective dose for a biphasic investigation (liver 5 mSv, kidney 4 mSv) was below, for a triphasic investigation (liver 7 mSv) above the effective dose of the investigation of the abdomen (6 mSv). Investigation of the abdomen with the EBT should only be performed for certain indications. With spiral CT, effective dose is much lower than with EBT.     

Visualization of colorectal polyps with spiral CT colography: evaluation of processing parameters with perspective volume rendering

PURPOSE: To evaluate two key processing steps for detection of colon polyps with spiral computed tomographic (CT) colography with perspective volume rendering (PVR): image reconstruction and opacity assignment of the attenuation data. MATERIALS AND METHODS: Spiral CT was performed in 10 patients with known polyps confirmed at colonoscopy, and detailed quantitative analyses were performed of data obtained in four. First, anatomic fidelity of three-dimensional (3D) images generated from two-dimensional (2D) source images with equal voxel dimensions (87%-90% overlap) was compared with 3D images generated from 2D source images with unequal voxel dimensions (0%-80% overlap). Next, the relative dimensions of colorectal polyps to adjacent structures were evaluated for various opacity threshold settings. Then, step and sigmoidal opacity functions were compared with respect to image smoothness and edge sharpness. RESULTS: PVR images generated after interpolation of image data reconstructed with at least 60% overlap were equivalent in image quality to PVR images generated from source images with equal voxel dimensions. Relative polyp-to-haustral fold dimensions demonstrated substantial distortions with opacity thresholds below -700 HU. The 3D PVR images generated with the sigmoidal opacity function were significantly smoother than those generated with the step opacity function (paired t test, P < .02), with small differences noted in edge sharpness. CONCLUSION: Use of highly overlapping source images (87%-90%) was not necessary to generate 3D PVR images of colorectal polyps. Image artifacts were suppressed with use of an appropriate opacity threshold and a sigmoidal opacity function without substantial loss in edge sharpness.     

Virtual colonoscopy with magnetic resonance imaging: in vitro evaluation of a new concept

BACKGROUND & AIMS: Screening for colonic polyps is desirable. A new concept based on cross-sectional and endoscopic analysis of a magnetic resonance (MR) data set is presented. METHODS: Ex vivo autopsy colonic specimens, containing artificially placed polyps, were obtained and filled with a gadolinium-containing solution. Forty-four thin-section MR images were obtained in a 1.5-T MR scanner in 28 seconds. A three-dimensional endoscopic fly-through of these images was rendered. Fly-throughs and two-dimensional cross-sectional images were analyzed by two observers for the presence of polyps. RESULTS: The average sensitivity and specificity for the detection of polyps based on three-dimensional endoscopic MR colon imaging were 87% and 96%, respectively. Analysis of cross-sectional images showed an overall sensitivity and specificity of merely 57% and 84%, respectively. The difference in the interpretation of three-dimensional MR colonoscopy and two-dimensional cross-sections was statistically significant (P < 0.001). With three-dimensional MR colonoscopy, overall sensitivity for detection of polyps measuring < or =5 mm in length and diameter was 70%; for larger polyps, it increased to 95% (P < 0.01). CONCLUSIONS: The feasibility of an MR-based endoluminal assessment of the colon is shown. Minimal invasiveness, lack of radiation exposure, and high in vitro diagnostic accuracy warrant further investigation of this novel concept.     

Evaluation of image quality using 1 : 1 pitch and 1.5 : 1 pitch helical CT in children: a comparative study

OBJECTIVE: The objective of this study was to compare the quality of 1 : 1 and 1.5 : 1 pitch helical contrast-enhanced thoracic and abdominal CT images in children who cannot cooperate for breath holding. MATERIALS AND METHODS: This is a retrospective study of 33 contrast-enhanced CT examinations in 11 children of 0-4 years of age. All children had an initial CT study using 1 : 1 pitch helical scanning followed over the next 6-36 months by one to four CT examinations with 1.5 : 1 pitch. Radiation dose with the two techniques was measured with a pencil ionization chamber. RESULTS: The two techniques provided comparable overall image quality. There was 33 % less radiation dose with 1.5 : 1 pitch helical scanning. CONCLUSION: The 1.5 : 1 pitch helical CT provides comparable quality images and a smaller radiation dose than 1 : 1 pitch in examining children aged 0-4 years.     

A prospective evaluation of the safety and efficacy of methohexital in the emergency department

OBJECTIVE: Knowledge of a possible correlation between distal polyps found at screening sigmoidoscopy and proximal colonic lesions is important for deciding whether to perform total colonoscopy or not. PATIENTS: A prospective analysis of 2439 consecutive patients with colorectal polyps. Of these, 304 were asymptomatic subjects who underwent complete colonoscopy for screening and were found to have adenomatous or hyperplastic polyps in the distal colorectum. RESULTS: Ten (15%) out of 65 patients with distal hyperplastic polyps only and 86 (36%) out of 239 with distal adenomatous polyps were found to have adenomatous polyps in the proximal colon as well (P < 0.001). The frequency of synchronous proximal adenomas in patients with small (< or = 5 mm) or large distal adenomas (> 5 mm) was comparable (37% and 35%, respectively). However, patients with small distal adenomas had significantly smaller proximal adenomas (P = 0.004) containing less villous component (P = 0.017) than those with large distal adenomas. Neither the patient's age nor the presence of multiple distal adenomas increased the prevalence of proximal adenomas. CONCLUSION: Hyperplastic polyps found on rectosigmoidoscopy do not indicate a need for a complete colorectal examination, as 15% of patients with distal hyperplastic polyps will have proximal adenomatous polyps, a figure that is comparable with that of asymptomatic patients having no distal polyps, either hyperplastic or adenomatous. When only small distal adenomas are found at screening sigmoidoscopy in asymptomatic persons the decision to do a total colonoscopy should be based on individual considerations, as in such cases only small polyps are to be expected in the proximal colon.     

Laparoscopic inguinal hernia repair by an intraperitoneal onlay mesh technique using expanded PTFE: a prospective study

BACKGROUND: Colonoscopy is the gold standard for the detection of colon polyps and cancers, but failed detections can occur and the reasons are incompletely understood. METHODS: During a retrospective evaluation of the sensitivity of barium enema and colonoscopy in 20 Indiana Hospitals, we encountered 47 cases of colorectal cancer in which a colonoscopy performed within 3 years of the diagnosis had not detected the cancer. Cases were reviewed for location of tumor, extenuating factors, pathologic features, delay in diagnosis from failed detection, and who performed the examination. RESULTS: Failed detection was more likely when colonoscopy was performed by a nongastroenterologist than a gastroenterologist (odds ratio 5:36, 95% CI [2.94,9.77]). Twenty-seven cancers were "missed," and 20 were estimated to be not reached. However, the location of missed tumors and a general absence of adequate documentation of cecal intubation suggested that some cecal and ascending colon cancers recorded as missed may actually have been not reached. Variation in sensitivity among gastroenterologists suggested that meticulous examination is also important in maximizing sensitivity. CONCLUSIONS: These cases suggest several factors that might improve the quality and sensitivity of colonoscopy: (1) examiners should receive adequate training, (2) cecal intubation rates should be high, (3) cecal intubation should be verified by specific landmarks in all cases, (4) failure to reach the cecum should be followed by prompt barium enema, and (5) meticulous examination would appear to improve sensitivity for cancer detection.     

Possibility of different cancer development between the proximal and distal colon: comparison of the distribution between adenomatous polyps and cancer

BACKGROUND/AIM: The aim of this study was to compare the distribution of adenomatous polyps with that of cancer in the colon by using adenomatous polyps removed by colonoscopy. METHODOLOGY: 1223 adenomatous polyps removed by an endoscopic polypectomy were compared with 226 colon cancers with regard to their distribution, size and age. RESULTS: With patients over 65 years of age, the incidence of adenomatous polyps was lower in the proximal colon than in the distal colon, however, the incidence of cancer was higher in the proximal colon than in the distal colon (p<0.05). The distribution of adenomatous polyps according to size was also significantly different between the proximal and distal colon (p<0.05). CONCLUSION: These results thus suggest that some difference may exist in cancer development between the proximal and distal colon.     

Evidence for inverse agonism of SR141716A at human recombinant cannabinoid CB1 and CB2 receptors

OBJECTIVES: We studied the clinical spectrum, histology, and malignant potential of colonic polyps in Indian children (< or =12 yr). METHODS: Two hundred thirty-six children with colonic polyps were studied from January 1991 to October 1996. They were evaluated clinically and colonoscopic polypectomy was done. Children with five or more juvenile polyps were labeled as having juvenile polyposis and serial colonoscopic polypectomies were done every 3 wk. Colectomy was performed when there were intractable symptoms or clearing of the polyps by colonoscopy was not possible. Histological examination of the polyps was done. Follow-up colonoscopy was done in children with juvenile polyposis only. RESULTS: The mean age of these children was 6.12 +/- 2.7 yr, with a male preponderance (3.5:1). Rectal bleeding of a mean duration of 14 +/- 16 months was the presenting symptom in 98.7%. Solitary polyps were seen in 76%, multiple polyps in 16.5%, and juvenile polyposis in 7% (n = 17) of the children. A majority (93%) of the polyps were juvenile and 85% were rectosigmoid in location. Adenomatous changes, seen in 11%, were more common in juvenile polyposis (59%) than in juvenile polyps (5%). Among those with juvenile polyposis, colon clearance was achieved in eight, six required colectomy for intractable symptoms, and three were still on the polypectomy program. Polyps recurred in 5% of children with juvenile polyps and 37.5% of those with juvenile polyposis. CONCLUSIONS: Juvenile polyps remain the most common colonic polyps in children. A significant number of cases of polyps are multiple and proximally located, which emphasizes the need for total colonoscopy in all. Juvenile polyps should be removed even if asymptomatic because of their neoplastic potential. Colonoscopic polypectomy is effective even in juvenile polyposis. Surveillance colonoscopy is required in juvenile polyposis only.     

Diagnosis of pulmonary embolism with spiral and electron-beam CT

PURPOSE: To compare spiral (SCT) and electron-beam CT (EBT) for the diagnosis of pulmonary embolism (PE). MATERIALS AND METHODS: From June 1997 to June 1998 188 patients with suspected acute or chronic thromboembolism of the pulmonary arteries were examined. A total of 108 patients were scanned using SCT and 80 patients using EBT. On each scanner two different scan protocols were evaluated. RESULTS: PE was diagnosed in 38 patients using EBT and in 49 patients using SCT. Especially with EBT, isolated peripheral emboli could be confidently diagnosed. When EBT and SCT were compared for the analysis of peripheral pulmonary arteries, some paracardiac segmental and subsegmental vessels were significantly better analyzable with EB. Additional or diseases other than PE were diagnosed in 112 patients. Other diagnoses included bronchial carcinoma and aortic dissection. CONCLUSIONS: Advanced CT scanning techniques allow the highly accurate diagnosis of central and peripheral PE. Other potentially life-threatening underlying diseases are also readily recognized.     

Significance of CT in the detection of regional lymph node metastases in colorectal carcinoma

PURPOSE: For preoperative staging of colorectal cancer a CT scan is frequently performed. This report examines the sensitivity of CT for regional lymph node metastasis of colorectal cancer using different criteria. MATERIALS AND METHODS: Preoperative CT scans of 153 patients with colorectal cancer were analyzed using different criteria for N1. The results were then compared to the postoperative histological findings. RESULTS: For N1 = lymph nodes (LN) > 1 cm the sensitivity was 47%. For N1 = LN > 1 cm or an increased number of LN < 1 cm the sensitivity was 71%. In patients with a primary tumor seen on CT, sensitivity rose to 87%. DISCUSSION: Evidence of regional nodal metastatic disease is only relevant for rectal cancer, colon polyps, and for locally excised tumors when considering present surgical concepts for the treatment of colorectal cancer. In these cases CT analysis using the broadened criteria for N1 proposes a valuable argument regarding possible preoperative radiotherapy or an operative revision.     

A normal initial colonoscopy after age 50 does not predict a polyp-free status for life

OBJECTIVES: The prevalence of colon polyps increases with age in the general population. It is unknown whether a lack of adenomatous polyps determined at one time point after the age of 50 is predictive of a subsequent low risk of polyp development. METHODS: Twenty-nine patients between ages 50 and 70 who had no prior history of polyps and had a normal colonoscopy at least 5 yr previously were recruited for follow-up colonoscopy to evaluate the incidence of neoplastic disease in this presumably low-risk group. RESULTS: The incidence of adenomatous polyps after a mean of 5.74 yr was 41.4% (95% confidence interval: 23.5-61.1%). A total of 20 adenomatous polyps were found in 12 patients. Seven polyps were 5 mm or more in size. CONCLUSIONS: We conclude that in patients with no history of colonic neoplasia who are 50 yr old, or older, the finding of a normal colonoscopy does not predict diminished risk of neoplasia.     

Comparative effects of staphylokinase and alteplase in rabbit bleeding time models

BACKGROUND: The pathogenesis of bleeding associated with thrombolytic therapy remains largely unknown, although spontaneous bleeding appears to correlate with bleeding time prolongation. Here, the comparative effects on cuticle bleeding times (CBT) and ear puncture bleeding times (EBT) of recombinant staphylokinase (Sak) and alteplase (recombinant tissue-type plasminogen activator, rt-PA) at equivalent doses, alone and in combination with aspirin and heparin, were studied in rabbits. METHODS AND RESULTS: Groups of 4 to 9 rabbits were allocated to one of the 8 following intravenous infusions: saline; aspirin 15 mg/kg and heparin - 100 IU/kg bolus and 10 IU/kg infusion over one hour; 1.5 mg/kg rt-PA; 1.5 mg/kg rt-PA plus aspirin and heparin; 4.5 mg/kg rt-PA; 0.5 mg/kg Sak; 0.5 mg/kg Sak plus aspirin and heparin and 1.5 mg/kg Sak. Bleeding times were determined 30 and 15 min before and 5, 15, 30 and 60 min after the administration over one min of saline, rt-PA or Sak, by simultaneously severing a nail cuticle (CBT) and by puncturing the ear (EBT). Bleeding times were unaffected by saline and by both doses of Sak in monotherapy. Heparin-aspirin and low dose rt-PA significantly lengthened EBT but not CBT. Both CBT and EBT were significantly prolonged (to a mean of > 4 times pretreatment at 5 min) after high-dose rt-PA and after the combined administration of heparin and aspirin with either Sak or tr-PA. rt-PA provoked significantly longer bleeding than Sak in the CBT (p = 0.001; mean estimated difference = 23 min), but not in the EBT. rt-PA but not Sak degraded plasma fibrinogen dose-dependently. CBT correlated inversely with fibrinogen (r= -0.66, p=0.001) but EBT did not. CONCLUSION: At equivalent doses Sak displays a significantly higher fibrin specificity and prolongs bleeding time less than rt-PA, particularly in the nail cuticle bleeding time model in which larger vessels are injured that require fibrinogen for hemostasis.     

Splenic rupture: an unusual complication of colonoscopy

Splenic rupture is an uncommon complication of colonoscopy. A high index of suspicion is a crucial factor in the prompt diagnosis of this rare but potentially fatal complication. We report a case of splenic rupture diagnosed 3 days after a colonoscopy and requiring splenectomy. We also reviewed 17 reported cases of splenic rupture after colonoscopy, including our case. The presumed mechanisms of splenic rupture during colonoscopy are direct trauma to the spleen, excessive splenocolic ligament traction, and decrease in the relative mobility between the spleen and the colon. Of the 17 cases reviewed, 10 had polypectomy and/or biopsy performed during colonoscopy. Other probable risk factors are identified and tabulated. The hemodynamic status of the patient is the primary factor used to determine the therapeutic option. Computed tomographic (CT) scan of the abdomen reliably demonstrates well-contained splenic laceration and subcapsular hematoma, and differentiates these splenic complications from perisplenic clot and hemoperitoneum. Thus, CT scan may help decide which patients may be managed operatively or nonoperatively. Splenectomy is the operative procedure of choice for splenic rupture after colonoscopy. Conservative management includes broad spectrum antibiotics, intravenous fluids, blood transfusion, and close hemodynamic monitoring. The factors mandating further evaluation of persistent abdominal pain after colonoscopy are hemodynamic instability, clinical features of acute abdomen, leukocytosis, and/or acute anemia. The onset of abdominal pain associated with one or more of these critical factors is usually within 24 h after colonoscopy. An emergent CT scan of the abdomen is the modality of choice to further evaluate these clinical features, but intestinal perforation and external bleeding must first be excluded.     

Azoxymethane-induced colon tumors and aberrant crypt foci in mice of different genetic susceptibility

INTRODUCTION: Virtual endoscopy is a new 3D technique which permits to depict the inner surface of anatomic cavities. We report our experience in the study of the nasal cavity and paranasal sinuses. MATERIAL AND METHODS: CT examinations of the maxillofacial region were obtained using 1.5 or 3.0 mm slices, 1.5 or 3.0 mm table feed, 120 kV, 140 mA, 2 s scan time, standard and high resolution algorithms for bony structures and a field of view of 14-16 cm. The images were transferred on a workstation and processed with the Navigator virtual endoscopy software (General Electric). A threshold value ranging -300 to -550 UH was applied. RESULTS: We report a series of virtual images of the nasal cavity which includes rhinopharynx vault, torius tubarius, choanae, turbinates, tubal orifice and osteomeatal complex. Moreover, images of frontal sinus and tear duct, of polyps and fracture of maxillary sinus are also presented. 3D virtual endoscopy provides a clear visualization of the anatomic structures of the nasal cavity and sinuses. The images are similar to those of conventional endoscopy. Moreover virtual endoscopy visualizes the paranasal sinuses, which are not accessible at conventional endoscopy. The main limitations of this new technique are the arbitrary choice of the threshold value and the homogenization of different tissue densities, which reduces the contrast resolution. CONCLUSIONS: Virtual endoscopy can presently be considered a complementary technique of the standard axial and coronal CT examination. It provides an effective demonstration of the anatomy of these structures and shows areas which are difficult to visualize with conventional endoscopy. This technique could be of help in didactical activity; its clinical application has to be verified.     

Electron-beam computed tomography: preliminary experiences in the Netherlands]

The difference between computer tomography (CT) and electron beam tomography (EBT) is that for CT the x-ray tube rotates in a ring round the patient, and for EBT the x-ray beam rotates itself. As a result, with EBT the speed of making images is not limited by the mechanical rotation of the tube, and 16 images can be made per second. An EBT scan of a whole thorax takes 9 seconds. Specific application areas are fast moving organs and patients who cannot remain in one position for long, e.g. children and intensive care patients. Research is being conducted into the possibilities of this non-invasive technique for the demonstration of coronary artery lesions, pulmonary embolism, pulmonary metastases and dynamic examination of the major respiratory tract. Costs of an EBT scan currently amount to Dfl. 450.--but they will probably decrease as this imaging system is developed further. The exposure to radiation is about the same as that caused by a (spiral) CT.     

CT colonography with three-dimensional problem solving for detection of colonic polyps

OBJECTIVE: We performed CT colonography in patients referred for conventional colonoscopy, interpreted the axial images, and used commercially available software to reconstruct endoluminal perspective views to differentiate polyps from folds. SUBJECTS AND METHODS: We prospectively examined 44 patients (27 men and 17 women; mean age, 58 years old) with CT colonography by interpreting the axial images and using three-dimensional rendering for problem solving only. The CT scans were interpreted by two radiologists who were unaware of patients' histories as revealed by colonoscopic findings. The findings on colonography were compared with those of conventional colonoscopy to determine sensitivity, specificity, time spent on interpretation, and confidence of interpretation. RESULTS: Colonoscopy showed normal findings in 28 patients and 22 polyps in the remaining 16 patients. Six polyps were 8 mm or larger, three were 5-7 mm, and 13 were 5 mm or smaller. The findings of the two observers revealed an overall sensitivity of 50% and 38%, respectively, and a specificity of 93% and 86%, respectively. Sensitivity for polyps larger than 8 mm was 83% and specificity was 100% for both observers. The average amount of time spent on interpretation was 28 min 30 sec (range, 14-65 min). Both observers used the endoluminal view for differentiating folds from polyps in 23 (52%) of 44 patients, which had only minimal impact on interpretation time. CONCLUSION: CT colonography can be performed and the images interpreted using currently available hardware and software by initially using the axial images to search for polyps of significant size. Endoluminal views should be used only when necessary to help distinguish normal folds from fixed raised lesions that are suggestive of polyps.     

Multiple colon tumors. Diagnosis and follow-up of 450 patients with colorectal carcinoma

OBJECTIVE: Failure to diagnose synchronous tumors leads to errors in patient treatment and prognosis. The existence of metachronous tumors requires strict patient follow-up to ensure early identification of the second tumor. The present study evaluates the results obtained in the application of a structured procedure for the diagnosis and follow-up of multiple colorectal carcinoma. MATERIALS AND METHODS: A structured procedure was used to follow for 5 years a group of 12 patients with multiple colorectal tumors (7 synchronous and 5 metachronous) of a series of 450 colorectal neoplasms. RESULTS: Six synchronous tumors were diagnosed preoperatively and one intraoperative. Of the 5 metachronous neoplasms, 4 strictly adhered to the follow-up protocol, as a result of which the second tumor was detected at an early stage. The remaining case involved no follow-up, and the second tumor was diagnosed in an advanced stage as a result of bowel occlusion. The left colon was predominantly involved; polyps were detected in 9 cases, while two patients had 3 malignancies detected by histopathological study. COMMENTS: We emphasize the need for a full evaluation of the colon in all patients with colorectal carcinoma. In the case of incomplete preoperative evaluation, intraoperative colonoscopy is to be considered; if this is not feasible it should be performed one month after surgery. A structured follow-up procedure permits the early detection of these tumors, there by improving patient prognosis.