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Abstract
AIM To evaluate the value of prone imaging in computed tomography pneumocolon. MATERIALS AND METHODS In the U.K., patients commonly undergo computed tomography (CT) pneumocolon in the supine position alone. A prospective analysis of both supine and prone CT images was performed. The degree of distension and the presence/absence of fluid/faecal residue were documented. RESULTS Twenty-five patients were examined in total. In all cases, all five segments of the colon were well visualized on combined assessment of supine/prone images. Diagnostic distension was obtained in all five segments of the bowel in 69% of cases in the prone position, but in only 24% of patients in the supine position. The rectum and sigmoid colon were well distended in 100 and 88%, respectively, on prone CT, but in only 58 and 35% of cases, respectively, on supine CT. Problems encountered by fluid/faecal residue were eliminated on prone CT. CONCLUSION Adjunctive prone pelvic CT should be performed in all patients undergoing CT pneumocolon unless the supine images can be fully reviewed and shown to be satisfactory before the patient leaves the CT department. If a single positional sequence is to be performed, then prone CT is the position of choice.
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Affiliation(s)
- A A Yong
- Department of Diagnostic Radiology, Central Middlesex Hospital, London, U.K
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152
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Morrin MM, Farrell RJ, Kruskal JB, Reynolds K, McGee JB, Raptopoulos V. Utility of intravenously administered contrast material at CT colonography. Radiology 2000; 217:765-71. [PMID: 11110941 DOI: 10.1148/radiology.217.3.r00nv42765] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
PURPOSE To determine if intravenously administered contrast material improves overall reader confidence in the assessment of the colon, large-bowel wall conspicuity, and diagnostic accuracy in the detection of colorectal polyps and cancers at computed tomographic (CT) colonography. MATERIALS AND METHODS Two hundred patients underwent CT colonography in both supine and prone positions. A five-point scale was used to assess the effect of contrast enhancement on overall reader confidence and bowel wall conspicuity. Eighty-one patients underwent CT colonography with complete colonoscopic or surgical correlation; diagnostic accuracy was compared in 48 patients who received contrast material and 33 who did not. RESULTS Bowel preparation was ideal in 38 (19%) of 200 patients. Enhanced prone CT images had significantly better scores for reader confidence (4.9 +/- 0.1 vs 4.6 +/- 0.1, P: <.005) and bowel wall conspicuity (4.6 +/- 0.2 vs 4.2 +/- 0.2, P: <.005) compared with those of nonenhanced prone images despite no significant difference in bowel distention (3.8 +/- 0.2 vs 3.9 +/- 0. 1, P: =.8). Enhancement significantly improved the ability to depict medium (6-9-mm) polyps (75% vs 58%, P: <.05). Three large (10-19-mm) polyps were detected only with contrast enhancement; two remained submerged despite dual positioning. CONCLUSION The use of intravenously administered contrast material significantly improved reader confidence in the assessment of bowel wall conspicuity and the ability of CT colonography to depict medium polyps in suboptimally prepared colons.
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Affiliation(s)
- M M Morrin
- Departments of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave, Boston MA 02215, USA.
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153
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Miao YM, Amin Z, Healy J, Burn P, Murugan N, Westaby D, Allen-Mersh TG. A prospective single centre study comparing computed tomography pneumocolon against colonoscopy in the detection of colorectal neoplasms. Gut 2000; 47:832-7. [PMID: 11076883 PMCID: PMC1728155 DOI: 10.1136/gut.47.6.832] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
BACKGROUND AND AIMS To determine the sensitivity and specificity of computed tomography (CT) pneumocolon in the detection of colorectal neoplasms. METHODS A total of 201 consecutive patients with colorectal symptoms or requiring surveillance for colorectal neoplasms underwent both conventional colonoscopy and CT pneumocolon. RESULTS On conventional colonoscopy 13 invasive colorectal carcinomas were detected in 13 patients, and 118 polyps in 63 patients (14 polyps were > or =1 cm in diameter, 25 were 6-9 mm, and 79 were < or =5 mm). CT pneumocolon detected all 13 cancers, two false positive cancers, but only 20 polyps (seven were > or =1 cm). This resulted in a sensitivity of 100% (95% confidence interval (CI) 87-100%) and specificity of 99% (95% CI 97-100%) for detection of invasive carcinoma, and a sensitivity of 73% (95% CI 56-90%) and specificity of 94% (95% CI 91-98%) for detection of invasive carcinoma and/or > or =1 cm polyps. CT pneumocolon also identified invasive carcinoma not seen at colonoscopy because of incomplete examination in three patients, and detected metastases in six colorectal carcinoma patients and extracolonic carcinoma in a further seven patients. CONCLUSIONS CT pneumocolon had a high sensitivity and specificity for detection of invasive colorectal carcinoma but not colorectal polyps. CT pneumocolon may be suitable for initial investigation of patients with symptoms of colorectal malignancy.
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Affiliation(s)
- Y M Miao
- Department of Gastroenterology, Chelsea and Westminster Hospital, London, UK
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154
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Mendelson RM, Foster NM, Edwards JT, Wood CJ, Rosenberg MS, Forbes GM. Virtual colonoscopy compared with conventional colonoscopy: a developing technology. Med J Aust 2000; 173:472-5. [PMID: 11149303 DOI: 10.5694/j.1326-5377.2000.tb139298.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
AIM To determine the accuracy of computed tomography colography (virtual colonoscopy) in detecting colorectal polyps and colorectal cancer. DESIGN Blinded comparison of virtual colonoscopy (initially supine-only scans and later supine plus prone scans) with the criterion standard of conventional colonoscopy. SUBJECTS AND SETTING 100 patients aged 55 years or over referred to a public teaching hospital for colonoscopy, July 1997 to January 2000, because of colonic symptoms or a family history of bowel cancer. MAIN OUTCOME MEASURES Presence and size of polyps and other lesions; certainty of polyp identification on virtual colonoscopy (on 100-point visual analogue scale); sensitivity and predictive values of virtual colonoscopy. RESULTS Conventional colonoscopy identifed 121 polyps in 47 patients; 28 of these polyps, in 19 patients, were identified by virtual colonoscopy. Sensitivity of virtual colonoscopy for detecting polyps (using supine plus prone scans) was 73% for polyps with diameter > or = 10 mm (95% CI, 39%-94%) and 19% for smaller polyps (95% CI, 10%-31%) (P < 0.001); corresponding figures for supine-only scans were 57% (95% CI, 18%-90%) and 11% (95% CI, 4%-24%), respectively. Ten polyps identified at virtual colonoscopy were considered false-positive findings (8%). The value of finding a polyp on virtual colonoscopy (with thresholds of 5 mm for diameter and 30 points for certainty score) was assessed as a predictor of finding a polyp (diameter > 5 mm) on conventional colonoscopy. Positive and negative predictive values were 88% and 89%, respectively, for supine plus prone scans. CONCLUSION Although virtual colonoscopy shows potential as a diagnostic tool for colorectal neoplasia, it is currently not sufficiently sensitive for widespread use.
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Affiliation(s)
- R M Mendelson
- Department of Diagnostic and Interventional Radiology, Royal Perth Hospital, WA.
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155
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Abstract
Computed tomography (CT) represents the preferred imaging modality for imaging the large bowel when virtual endoscopic reconstructions are desired. Using the spiral acquisition technique, it has become possible to scan the entire abdomen within a single breathhold, however, slice thicknesses of 5 mm or more are necessary should the breathhold not last longer than 30-40 s. With the advent of multislice CT, contiguous 1-mm slices can be obtained through the entire abdomen while even shortening the breathhold to 25-30 s. The improved speed and spatial resolution of multislice CT results in remarkably sharp virtual reconstructions allowing detection of polyps with sizes less than 3 mm. The disadvantages must still be considered including a dataset consisting of up to 800 images representing a new challenge for postprocessing hard- and software.
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Affiliation(s)
- P Rogalla
- Department of Radiology, Charité Hospital, Humboldt-Universität zu Berlin, Schumannstr. 20/21, 10098, Berlin, Germany.
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156
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Hagspiel KD, Altes TA, Mugler JP, Spellman MJ, Mata JF, Tustison NJ, Brookeman JR. MR virtual colonography using hyperpolarized (3)He as an endoluminal contrast agent: demonstration of feasibility. Magn Reson Med 2000; 44:813-6. [PMID: 11064418 DOI: 10.1002/1522-2594(200011)44:5<813::aid-mrm21>3.0.co;2-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Hyperpolarized gas MR virtual colonography was performed in plastic phantoms and in the dog colon. (3)He was laser polarized in a prototype commercial system. 2D and 3D gradient echo sequences were used to image the noble gas-filled structures. The hyperpolarized (3)He within the plastic tube and colon lumen produced high signal, providing excellent contrast from the surrounding structures. The virtual colonoscopic analysis of the canine dataset allowed visualization of the colonic features and the colonic wall from inside the colon. (3)He colonoscopy is a novel technique to visualize the colon with MRI with the application of an inert gaseous endoluminal contrast agent.
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Affiliation(s)
- K D Hagspiel
- Department of Radiology, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA.
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157
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Fletcher JG, Johnson CD. Computed tomographic colonography: current and future status for colorectal cancer screening. Semin Roentgenol 2000; 35:385-93. [PMID: 11060924 DOI: 10.1053/sroe.2000.17756] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- J G Fletcher
- Department of Diagnostic Radiology, Mayo Clinic, Rochester, MN 55905, USA
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158
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Affiliation(s)
- P M McMahon
- Department of Radiology, Massachusetts General Hospital, Boston 02114, USA
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159
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Whiting BR, McFarland EG, Brink JA. Influence of image acquisition parameters on CT artifacts and polyp depiction in spiral CT colonography: in vitro evaluation. Radiology 2000; 217:165-72. [PMID: 11012440 DOI: 10.1148/radiology.217.1.r00oc13165] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To quantify the effects of spiral computed tomographic (CT) acquisition parameters on the magnitude of three-dimensional (3D) rippling artifacts and polyp depiction. MATERIALS AND METHODS An in vitro colon phantom was constructed with air-filled acrylic cylinders that contained synthetic polyps of 3-13 mm. The phantom was submerged in fluid and positioned at four angles of inclination relative to the z axis. Image data were acquired at collimation and pitch combinations of 3 mm and 1.67 and 5 mm and 1.6, respectively. Rippling artifacts were quantified by measuring the longitudinal variation of in-plane phantom edge width, and the influence of these artifacts on the depiction of pedunculated and sessile polyps was assessed qualitatively. RESULTS The in-plane magnitude of the rippling artifact was a function of the angle of inclination relative to the longitudinal axis and the table increment. The through-plane periodicity of the artifact was equal to one-half the table increment. CONCLUSION The table increment and angle of inclination of the surface of the object relative to the z axis determine the periodicity and magnitude of the rippling artifact at 3D spiral CT colonography. Although the depiction of small pedunculated polyps was not compromised, some sessile polyps were degraded by the artifact.
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Affiliation(s)
- B R Whiting
- Electronic Radiology Lab, and Abdominal Imaging Section, Mallinckrodt Institute of Radiology, 510 S Kingshighway Blvd, St Louis, MO 63110, USA.
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160
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Schoenfelder D, Debatin JF. The role of MR colonography for colorectal cancer screening. Semin Roentgenol 2000; 35:394-403. [PMID: 11060925 DOI: 10.1053/sroe.2000.17762] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- D Schoenfelder
- Department of Diagnostic Radiology, University Hospital Essen, Germany
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161
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Fletcher JG, Johnson CD, Welch TJ, MacCarty RL, Ahlquist DA, Reed JE, Harmsen WS, Wilson LA. Optimization of CT colonography technique: prospective trial in 180 patients. Radiology 2000; 216:704-11. [PMID: 10966698 DOI: 10.1148/radiology.216.3.r00au41704] [Citation(s) in RCA: 274] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
PURPOSE To assess the added benefits of prone positioning in addition to supine positioning and oral iodinated contrast medium for help in the detection of colonic polyps at computed tomographic (CT) colonography. MATERIALS AND METHODS CT colonography was performed in prone and supine positions in 180 patients with polyps or risk factors for colonic neoplasia. Patients were randomly assigned to receive a standard bowel preparation or a standard preparation plus oral iodinated contrast medium. One radiologist interpreted supine images alone, and another analyzed supine and prone images. All patients subsequently underwent colonoscopy. RESULTS At colonoscopy, 121 large (> or =1-cm-diameter) polyps and 142 smaller (0.5-0.9-cm) polyps were identified. Prone positioning resulted in increased sensitivity for identification of patients with large (> or =1-cm) polyps (increase from 70% to 85%, P: =.004) and of patients with polyps 0.5 cm or larger (increase from 75% to 88%, P: <.005), with no change in specificity. Use of oral contrast medium did not significantly improve polyp detection even in the subset of patients in whom colonic fluid attenuation was markedly increased. CONCLUSION Acquisition and review of supine and prone CT colonographic images significantly improves the ability to identify patients with polyps 0.5 cm in diameter or larger. Administration of oral iodinated contrast medium does not significantly improve polyp detection.
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Affiliation(s)
- J G Fletcher
- Department of Diagnostic Radiology, Mayo Clinic and Mayo Foundation, Rochester, MN 55905, USA.
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162
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Saar B, Heverhagen JT, Obst T, Berthold LD, Kopp I, Klose KJ, Wagner HJ. Magnetic resonance colonography and virtual magnetic resonance colonoscopy with the 1.0-T system: a feasibility study. Invest Radiol 2000; 35:521-6. [PMID: 10981995 DOI: 10.1097/00004424-200009000-00001] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
RATIONALE AND OBJECTIVES An ex vivo study and a clinical, prospective, patient study were undertaken to evaluate the feasibility of magnetic resonance (MR) colonography with a 1.0-T system. METHODS An ex vivo colon model was scanned. A cleaned pig colon was prepared with six simulated sessile polyps (diameters of 4-12 mm) and one simulated pedunculated polyp (diameter of 5 mm). Subsequently, five patients (aged 39-81 years; four women, one man) were examined with MR colonography, immediately followed by endoscopic colonoscopy. After preparation for colonoscopy, the colon was filled with a Gd-DTPA/water solution (1:100). A breath-hold 3D gradient-echo sequence was acquired in both the prone and supine positions and after intravenous Gd-DTPA administration. Images were analyzed interactively by using multiplanar projections, maximum-intensity projection, and a virtual endoscopic view. The MR results were compared with the findings of the fiberoptic endoscopy. RESULTS All seven simulated lesions of the colon model could be detected by MR imaging. In one patient, an advanced colon cancer as well as an additional small polyp was depicted. In the other four patients, single polyps with a diameter of 1 to 2.5 cm and a large adenoma were visualized by MR colonography. Contrast enhancement of the polyps was noted only after subtraction. CONCLUSIONS The 1.0-T system is feasible for MR colonography. Reduced requirements for hardware could contribute to establish the novel technique as a screening method for colorectal polyps.
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Affiliation(s)
- B Saar
- Department of Radiology, University Hospital Rechts der Isar, Technische Universitaet of Munich, Germany.
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163
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Luboldt W, Bauerfeind P, Wildermuth S, Marincek B, Fried M, Debatin JF. Colonic masses: detection with MR colonography. Radiology 2000; 216:383-8. [PMID: 10924558 DOI: 10.1148/radiology.216.2.r00au11383] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
PURPOSE To assess magnetic resonance (MR) colonography as a method for detection of colorectal masses, with conventional colonoscopy as the reference standard. MATERIALS AND METHODS MR colonography was performed in 132 patients referred for colonoscopy because of the possible presence of a mass. After rectal filling with a gadopentetate dimeglumine and water enema, T1-weighted three-dimensional gradient-echo MR studies were acquired with the patient in the prone and supine positions. Water-sensitive single-shot fast spin-echo MR images were also obtained. Surface-rendered virtual endoscopic endoluminal views, orthogonal sections in three planes, and water-sensitive MR images were interactively assessed for presence of colorectal masses by two radiologists. RESULTS MR colonography was well tolerated without sedation or analgesia. MR image quality was sufficient for diagnosis in 127 (96%) patients. Most small (</=5-mm-diameter) masses were overlooked at MR colonography, but 19 of 31 6-10-mm lesions and 26 of 27 large (>10-mm) lesions were correctly identified. For these large masses, MR colonography had a sensitivity of 93%, specificity of 99%, positive predictive value of 92%, and negative predictive value of 98% for detection of masses. CONCLUSION MR colonography is a promising modality for help in detecting colorectal mass lesions larger than 10 mm in diameter.
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Affiliation(s)
- W Luboldt
- Institute of Diagnostic Radiology, University Hospital Zurich, Switzerland
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164
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Abstract
Computed tomographic (CT) colonography is a new-generation technique for detecting colorectal neoplasms by using volumetric CT data combined with specialized imaging software. Patient examinations require full colonic preparation, insufflation, and data acquisition with the patient in the supine and prone positions. Current CT technology allows a single image of the colon to be acquired in as little as 20 seconds with a minimum of patient discomfort. Specialized computer software for interpretation usually combines transverse, multiplanar reformation, and three-dimensional endoluminal images for the optimal visualization of the colon and rectum. As of the time this article was written, CT colonography was competitive as a full structural colonic examination for the detection of polyps and cancer. To the authors' knowledge, no study results have yet been reported in a screening population. The unique capabilities of CT colonography include the display of the proximal colon that is inaccessible at colonoscopy because of obstructing colonic lesions or because of incomplete endoscopic examinations and the assessment of extracolonic abdominal and pelvic organs. This abdominopelvic survey potential provides radiologists with an opportunity to discover other potentially life-threatening, asymptomatic conditions. Further technologic developments and validation studies are in progress. CT colonography is an exciting and promising technique with an enormous potential for colorectal screening in the future.
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Affiliation(s)
- C D Johnson
- Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
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165
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Summers RM, Beaulieu CF, Pusanik LM, Malley JD, Jeffrey RB, Glazer DI, Napel S. Automated polyp detector for CT colonography: feasibility study. Radiology 2000; 216:284-90. [PMID: 10887263 DOI: 10.1148/radiology.216.1.r00jl43284] [Citation(s) in RCA: 171] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
An abdominal computed tomographic scan was modified by inserting 10 simulated colonic polyps with use of methods that closely mimic the attenuation, noise, and polyp-colon wall interface of naturally occurring polyps. A shape-based polyp detector successfully located six of the 10 polyps. When settings that enhanced the edge profile of polyps were chosen, eight of 10 polyps were detected. There were no false-positive detections. Shape analysis is technically feasible and is a promising approach to automated polyp detection.
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Affiliation(s)
- R M Summers
- Department of Diagnostic Radiology, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bldg 10, Rm 1C660, 10 Center Dr MSC 1182, Bethesda, MD 20892-1182, USA.
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166
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Macari M, Milano A, Lavelle M, Berman P, Megibow AJ. Comparison of time-efficient CT colonography with two- and three-dimensional colonic evaluation for detecting colorectal polyps. AJR Am J Roentgenol 2000; 174:1543-9. [PMID: 10845478 DOI: 10.2214/ajr.174.6.1741543] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
OBJECTIVE We compared the findings of time-efficient CT colonography with complete two-dimensional (2D) and three-dimensional (3D) CT colonography and conventional colonoscopy in detecting colorectal polyps. SUBJECTS AND METHODS Forty-two patients undergoing colonoscopy screening were examined with CT colonography before endoscopy. Data were examined following one of two methods. In method 1, axial 2D data sets were examined in a cine mode. If findings were suggestive of abnormality, focal areas were examined with 3D CT colonography. In method 2, data sets were examined exactly as in method 1, and subsequent to that review, data sets were examined with simultaneous 3D "fly-through" CT colonography (surface-rendered images) and multiplanar reformatted images. The time required to examine CT colonography using each technique was recorded and abnormal findings were documented. Results of methods 1 and 2 were compared with findings on colonoscopy. RESULTS Colonoscopy detected 16 polyps in 13 patients (polyp size, 2-10 mm). Ten polyps measured 5 mm or less, five measured between 6 and 9 mm, and one measured 10 mm or more. Using method 1, two of 10 polyps measuring less than 5 mm, three of five polyps measuring between 6 and 9 mm, and one polyp measuring 10 mm were detected. We noted no false-positive polyps. Average evaluation time was 16 min. With method 2, the same polyps were seen as with method 1. No additional polyps were detected, and the average evaluation time was 40 min. CONCLUSION Axial 2D CT colonography can be performed quickly and is comparable with complete 2D and 3D CT colonography in detecting colorectal polyps.
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Affiliation(s)
- M Macari
- Department of Radiology, New York University Medical Center, NY 10016, USA
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167
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Ferrucci JT. CT colonography for colorectal cancer screening: lessons from mammography. AJR Am J Roentgenol 2000; 174:1539-41. [PMID: 10845477 DOI: 10.2214/ajr.174.6.1741539] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- J T Ferrucci
- Department of Radiology, Boston University School of Medicine, Boston Medical Center, MA 02118, USA
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168
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Rex DK, Johnson DA, Lieberman DA, Burt RW, Sonnenberg A. Colorectal cancer prevention 2000: screening recommendations of the American College of Gastroenterology. American College of Gastroenterology. Am J Gastroenterol 2000; 95:868-77. [PMID: 10763931 DOI: 10.1111/j.1572-0241.2000.02059.x] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- D K Rex
- Indiana University Hospital, Indianapolis 46202, USA
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169
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170
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Abstract
Since modern imaging modalities deliver huge amounts of data, which cannot be assessed easily, the visualization techniques are utilized to emphasize the structures of interest. To compare them, the different visualization techniques (maximum intensity projection, multiplanar reformations, shaded surface display and volume rendering) are regressed to a common ground whereby their strengths and weaknesses can be revealed. Additionally, medical image analysis can detect anatomical objects in volumetric data sets and provides their descriptions for further use. Usually, segmentation plays a crucial roll in that process. There are many segmentation methods which can be categorized in boundary-based and content-based ones. The extraction of anatomical objects also allows their quantification. Image analysis and visualization do not squeeze more information out of a data volume, but they provide different ways to look at it. As in real life, this alone may enlarge the insight.
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Affiliation(s)
- M Blank
- Institute of Medical Physics, University of Erlangen-Nuremberg, Krankenhausstr. 12, 91054, Erlangen, Germany.
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171
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Paik DS, Beaulieu CF, Jeffrey RB, Karadi CA, Napel S. Visualization modes for CT colonography using cylindrical and planar map projections. J Comput Assist Tomogr 2000; 24:179-88. [PMID: 10752876 DOI: 10.1097/00004728-200003000-00001] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE The purpose of this study was to demonstrate the limitations to the effectiveness of CT colonography, colloquially called virtual colonoscopy (VC), for detecting polyps in the colon and to describe a new technique, map projection CT colonography using Mercator projection and stereographic projection, that overcomes these limitations. METHOD In one experiment, data sets from nine patients undergoing CT colonography were analyzed to determine the percentage of the mucosal surface visible in various visualization modes as a function of field of view (FOV). In another experiment, 40 digitally synthesized polyps of various sizes (10, 7, 5, and 3.5 mm) were randomly inserted into four copies of one patient data set. Both Mercator and stereographic projections were used to visualize the surface of the colon of each data set. The sensitivity and positive predictive value (PPV) were calculated and compared with the results of an earlier study of visualization modes using the same CT colonography data. RESULTS The percentage of mucosal surface visualized by VC increases with greater FOV but only approaches that of map projection VC (98.8%) at a distorting, very high FOV. For both readers and polyp sizes of > or =7 mm, sensitivity for Mercator projection (87.5%) and stereographic projection (82.5%) was significantly greater (p < 0.05) than for viewing axial slices (62.5%), and Mercator projection was significantly more sensitive than VC (67.5%). Mercator and stereographic projection had PPVs of 75.4 and 78.9%, respectively. CONCLUSION The sensitivity of conventional CT colonography is limited by the percentage of the mucosal surface seen. Map projection CT colonography overcomes this problem and provides a more sensitive method with a high PPV for detecting polyps than other methods currently being investigated.
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Affiliation(s)
- D S Paik
- Stanford Medical Informatics, Stanford University School of Medicine, CA 94305-5488, USA
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172
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Morrin MM, Farrell RJ, Raptopoulos V, McGee JB, Bleday R, Kruskal JB. Role of virtual computed tomographic colonography in patients with colorectal cancers and obstructing colorectal lesions. Dis Colon Rectum 2000; 43:303-11. [PMID: 10733110 DOI: 10.1007/bf02258293] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
PURPOSE The aim of this study was to assess the ability of computed tomographic colonography to diagnose colorectal masses, stage colorectal cancers, image the proximal colon in obstructing colorectal lesions, and evaluate the anastomoses in patients with previous colorectal surgery. METHODS We prospectively performed computed tomographic colonography examinations in 34 patients (20 males; mean age, 64.2; range, 19-91 years): 20 patients had colorectal masses (defined at endoscopy as intraluminal masses 2 cm or larger), 7 patients had benign obstructing colorectal strictures, and 7 patients had a prior colorectal resection. Final tumor staging was available in all 16 patients who had colorectal cancers and 15 patients were referred after incomplete colonoscopy. The ability of computed tomographic colonography to stage colorectal cancers, identify synchronous lesions in patients with colorectal masses, and image the proximal colon in patients with obstructing colorectal lesions was assessed. RESULTS Computed tomographic colonography identified all colorectal masses, but overcalled two masses in patients who were either poorly distended or poorly prepared. Computed tomographic colonography correctly staged 13 of 16 colorectal cancers (81 percent) and detected 16 of 17 (93 percent) synchronous polyps. Computed tomographic colonography over-staged two Dukes Stage A cancers and understaged one Dukes Stage C cancer. A total of 97 percent (87/90) of all colonic segments were adequately visualized at computed tomographic colonography in patients with obstructing colorectal lesions compared with 60 percent (26/42) of segments at barium enema (P < 0.01). Colonic anastomoses were visualized in all nine patients, but in one patient, computed tomographic colonography could not distinguish between local tumor recurrence and surgical changes. CONCLUSION Computed tomographic colonography can accurately identify all colorectal masses but may overcall stool as masses in poorly distended or poorly prepared colons. Computed tomographic colonography has an overall staging accuracy of 81 percent for colorectal cancer and is superior to barium enema in visualizing colonic segments proximal to obstructing colorectal lesions.
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Affiliation(s)
- M M Morrin
- Department of Radiology, and Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA
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173
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Affiliation(s)
- G W Stevenson
- Department of Radiology, McMaster University, Hamilton, Ontario, Canada.
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174
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Abstract
Herein, the authors (a) review the status of the specialty; (b) report and analyze the various areas in which progress has occurred, namely, conventional radiology and picture archiving and communication systems (or PACS), ultrasonography, computed tomography, magnetic resonance imaging, interventional radiology, and nuclear medicine; and (c) discuss the problems radiology faces as it enters the new millennium. The problems are those facing medicine as a whole, as well as those threatening the future of radiology. These include the following: Will there be a need for radiologists in the future? Will radiology be too costly to be affordable? How can turf wars and fragmentation be solved? Possible remedies are suggested. Positive aspects are discussed in the light of the challenge to demonstrate value. Medical imaging is entering the new millennium with a solid record of recent advances in digital, cross-sectional, and interventional radiology. These advances have made the specialty indispensable in the treatment of patients. Careful statesmanship will be needed to solve the many problems that face medicine as a whole and radiology in particular.
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Affiliation(s)
- A R Margulis
- University Advancement and Planning, University of California at San Francisco, 94118, USA
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175
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176
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Fenlon HM, Nunes DP, Schroy PC, Barish MA, Clarke PD, Ferrucci JT. A comparison of virtual and conventional colonoscopy for the detection of colorectal polyps. N Engl J Med 1999; 341:1496-503. [PMID: 10559450 DOI: 10.1056/nejm199911113412003] [Citation(s) in RCA: 549] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
BACKGROUND Virtual colonoscopy is a new method of imaging the colon in which thin-section, helical computed tomography (CT) is used to generate high-resolution, two-dimensional axial images. Three-dimensional images of the colon simulating those obtained with conventional colonoscopy are then reconstructed off-line. We compared the performance of virtual and conventional colonoscopy for the detection of colorectal polyps. METHODS We prospectively studied 100 patients at high risk for colorectal neoplasia (60 men and 40 women; mean age, 62 years). We performed virtual colonoscopy immediately before conventional colonoscopy. We inserted a rectal tube and insufflated the colon with air to the maximal level that the patient could tolerate. We administered 1 mg of glucagon intravenously immediately before CT scanning to minimize the degree of smooth-muscle spasm and peristalsis and to reduce the patient's discomfort. RESULTS The entire colon was clearly seen by virtual colonoscopy in 87 patients and by conventional colonoscopy in 89. Fifty-one patients had normal findings on conventional colonoscopy. In the other 49, we identified a total of 115 polyps and 3 carcinomas. Virtual colonoscopy identified all 3 cancers, 20 of 22 polyps that were 10 mm or more in diameter (91 percent), 33 of 40 that were 6 to 9 mm (82 percent), and 29 of 53 that were 5 mm or smaller (55 percent). There were 19 false positive findings of polyps and no false positive findings of cancer. Of the 69 adenomatous polyps, 46 of the 51 that were 6 mm or more in diameter (90 percent) and 12 of the 18 that were 5 mm or smaller (67 percent) were correctly identified by virtual colonoscopy. Although discomfort was not specifically recorded, none of the patients requested that virtual colonoscopy be stopped because of discomfort or pain. CONCLUSIONS In a group of patients at high risk for colorectal neoplasia, virtual and conventional colonoscopy had similar efficacy for the detection of polyps that were 6 mm or more in diameter.
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Affiliation(s)
- H M Fenlon
- Department of Radiology, Boston University School of Medicine, Boston Medical Center, MA 02118, USA
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177
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Affiliation(s)
- S Halligan
- Intestinal Imaging Centre, St Mark's Hospital, Harrow HA1 3UJ.
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178
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Morrin MM, Farrell RJ, Kruskal JB, LaMont JT. Virtual colonoscopy: a kinder, gentler colorectal cancer screening test? Lancet 1999; 354:1048-9. [PMID: 10509490 DOI: 10.1016/s0140-6736(99)00302-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- M M Morrin
- Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
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179
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Weishaupt D, Patak MA, Froehlich J, Ruehm SG, Debatin JF. Faecal tagging to avoid colonic cleansing before MRI colonography. Lancet 1999; 354:835-6. [PMID: 10485732 DOI: 10.1016/s0140-6736(99)80020-8] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Colonic cleansing is unpleasant and has low acceptance by patients. We show the feasibility of faecal tagging, which obviates the need for colonic cleansing, in conjunction with internal magnetic resonance imaging colonography.
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180
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Ahlquist DA, Johnson CD. Screening by CT colonography: too early to pass judgment on a nascent technology. Gastrointest Endosc 1999; 50:437-40. [PMID: 10462676 DOI: 10.1053/ge.1999.v50.99617] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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181
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Abstract
Since modern imaging modalities deliver huge amounts of data the visualization techniques utilized must emphasize the structures of interest. To compare them, the different visualization techniques are regressed to a common ground whereby their strengths and weaknesses can be revealed. Perspective, lighting, color and motion support the real world look and feel. Virtual 3D techniques allow the observer to move through 3D images of anatomy almost in real time. In virtual cisternoscopy this concept is applied to 3D data of the head to reveal a closer look at the cerebral vessels. The more realistic presentation of the 3D data allows for higher efficiency.
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Affiliation(s)
- M Blank
- Institute of Medical Physics, University of Erlangen-Nuremberg, Erlangen, Germany.
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182
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Rex DK, Vining D, Kopecky KK. An initial experience with screening for colon polyps using spiral CT with and without CT colography (virtual colonoscopy). Gastrointest Endosc 1999; 50:309-13. [PMID: 10462648 DOI: 10.1053/ge.1999.v50.97776] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND Computed tomographic (CT) colography (virtual colonoscopy) is a new imaging method for detection of colon polyps and cancer. OBJECTIVE To evaluate the sensitivity of CT colography for polyp detection in a population without symptoms that included persons without colon neoplasia and with radiologists blinded to colonoscopic findings. METHODS Forty-six persons without symptoms underwent spiral CT followed by same-day colonoscopy with subsequent inspection of two-dimensional axial CT images, interactive multiplanar images, and surfaced and volume-rendered images of the colon (three-dimensional CT colography). RESULTS Three-dimensional CT colography was superior to two-dimensional axial imaging for detection of colon polyps. Three-dimensional CT colography depicted 1 of 4 (25%) adenomas 2 cm in diameter or larger, 6 of 10 (60%) adenomas 1 to 1.9 cm, 6 of 14 (43%) 6 to 9 mm, and 7 of 65 (11%) 5 mm in diameter or smaller. Three-dimensional CT colography showed a polyp that might have led to colonoscopy in 3 of 4 (75%) patients whose largest adenoma was 2 cm or larger, 5 of 6 (83%) patients with largest adenoma 1 to 1.9 cm, 3 of 7 (43%) patients with largest adenoma 6 to 9 mm, and 4 of 16 patients (25%) with largest adenoma 5 mm or smaller. Large, flat adenomas of the right colon were difficult to identify with three-dimensional CT colography. The specificity of three-dimensional CT colography for patients with adenomas 1 cm in diameter or larger was 89%. Examination of patients with missed adenomas after unblinding indicated that meticulous bowel preparation and adequate distention are critical to accurate interpretation. Perceptual errors were common. CONCLUSIONS CT colography as performed in this study is not adequate as a colorectal cancer screening test. Several technical factors that appear critical to accurate performance of CT colography are defined.
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Affiliation(s)
- D K Rex
- Department of Medicine, Indiana University School of Medicine, Indianapolis, USA
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183
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Sonnenberg A, Delcò F, Bauerfeind P. Is virtual colonoscopy a cost-effective option to screen for colorectal cancer? Am J Gastroenterol 1999; 94:2268-74. [PMID: 10445561 DOI: 10.1111/j.1572-0241.1999.01304.x] [Citation(s) in RCA: 139] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Computed tomography (CT) or magnetic resonance (MR) colonography is a new technique that uses data generated from CT or MR imaging to create two- and three-dimensional scans of the colon. It has been advocated to become the new primary technique of screening for colorectal cancer. The economic feasibility of such recommendation, however, has not yet been evaluated. METHODS The cost-effectiveness of two screening strategies using CT colonography or conventional colonoscopy was compared by computer models based on a Markov process. We supposed that a hypothetical population of 100,000 subjects aged 50 yr undergoes a screening procedure every 10 yr. Suspicious findings of CT colonography are worked-up by colonoscopy. After polypectomy, colonoscopy is repeated every 3 yr until no adenomatous polyps are found. RESULTS Under baseline conditions, screening by CT colonography costs $24,586 per life-year saved, compared with $20,930 spent on colonoscopy screening. The incremental cost-effectiveness ratios comparing CT colonography to no screening and colonoscopy to CT colonography were $11,484 and $10,408, respectively. Screening by colonoscopy remains more cost-effective even if the sensitivity and specificity of CT colonography both rise to 100%. For the two screening procedures to become similarly cost-effective, CT colonoscopy needs to be associated with an initial compliance rate 15-20% better or procedural costs 54% less than colonoscopy. CONCLUSIONS To become cost-effective and be able to compete with colonoscopy in screening for colorectal cancer, CT or MR colonography would need be offered at a very low price or result in compliance rates much better than those associated with colonoscopy.
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Affiliation(s)
- A Sonnenberg
- The Department of Veterans Affairs Medical Center and The University of New Mexico, Albuquerque, USA
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184
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TAKEBAYASHI SHIGEO, HOSAKA MASAHIKO, TAKASE KAZUNORI, KUBOTA NOBUYOSHI, KISHIDA TAKESHI, MATSUBARA SHO. COMPUTERIZED TOMOGRAPHY NEPHROSCOPIC IMAGES OF RENAL PELVIC CARCINOMA. J Urol 1999. [DOI: 10.1016/s0022-5347(05)68548-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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185
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Abstract
Over the last 10 years, spiral CT has become the optimal method of performing all CT within the abdomen and pelvis. Not only has the technique improved the quality of individual examinations, it has also opened up many new diagnostic possibilities which are currently being evaluated and compared with the concurrent advances in ultrasound and MRI. These new diagnostic possibilities are discussed in this review article. So too are the economic advantages of the shorter data-acquisition times which also make the examination much better tolerated by the patient.
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Affiliation(s)
- A El Sherif
- Department of Radiology, Addenbrooke's Hospital and the University of Cambridge, UK
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186
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Beaulieu CF, Jeffrey RB, Karadi C, Paik DS, Napel S. Display modes for CT colonography. Part II. Blinded comparison of axial CT and virtual endoscopic and panoramic endoscopic volume-rendered studies. Radiology 1999; 212:203-12. [PMID: 10405743 DOI: 10.1148/radiology.212.1.r99jl17203] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To determine the sensitivity of radiologist observers for detecting colonic polyps by using three different data review (display) modes for computed tomographic (CT) colonography, or "virtual colonoscopy." MATERIALS AND METHODS CT colonographic data in a patient with a normal colon were used as base data for insertion of digitally synthesized polyps. Forty such polyps (3.5, 5, 7, and 10 mm in diameter) were randomly inserted in four copies of the base data. Axial CT studies, volume-rendered virtual endoscopic movies, and studies from a three-dimensional mode termed "panoramic endoscopy" were reviewed blindly and independently by two radiologists. RESULTS Detection improved with increasing polyp size. Trends in sensitivity were dependent on whether all inserted lesions or only visible lesions were considered, because modes differed in how completely the colonic surface was depicted. For both reviewers and all polyps 7 mm or larger, panoramic endoscopy resulted in significantly greater sensitivity (90%) than did virtual endoscopy (68%, P = .014). For visible lesions only, the sensitivities were 85%, 81%, and 60% for one reader and 65%, 62%, and 28% for the other for virtual endoscopy, panoramic endoscopy, and axial CT, respectively. Three-dimensional displays were more sensitive than two-dimensional displays (P < .05). CONCLUSION The sensitivity of panoramic endoscopy is higher than that of virtual endoscopy, because the former displays more of the colonic surface. Higher sensitivities for three-dimensional displays may justify the additional computation and review time.
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Affiliation(s)
- C F Beaulieu
- Department of Radiology, Stanford University School of Medicine, CA 94305, USA.
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187
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Karadi C, Beaulieu CF, Jeffrey RB, Paik DS, Napel S. Display modes for CT colonography. Part I. Synthesis and insertion of polyps into patient CT data. Radiology 1999; 212:195-201. [PMID: 10405742 DOI: 10.1148/radiology.212.1.r99jl25195] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To develop and validate a method for the insertion of digitally synthesized polyps into computed tomographic (CT) images of the human colon for use as ground truth for evaluation of virtual colonoscopy. MATERIALS AND METHODS Spiral CT simulator software was used to generate 10 synthetic polyps in various configurations. Additional software was developed to insert these polyps into volume CT scans. Ten polyps in eight patients were selected for comparison. Three radiologists evaluated whether two-dimensional (2D) CT images and three-dimensional (3D) volume-rendered CT images showed synthetic or real polyps. RESULTS Edge-response profiles and noise of simulated polyps matched those of native polyps. Frequency distributions of reviewers' responses were not significantly different for synthetic versus real polyps in either 3D or 2D images. Responses were clustered around the response of "unsure" if lesions were real or synthetic. Receiver operating characteristic curves had areas of 0.54 (95% CI = 0.39, 0.68) for 3D and 0.39 (95% CI = 0.25, 0.53) for 2D images, which were not significantly different from random guessing (P = .70 and .28 for 3D and 2D images, respectively). CONCLUSION Synthetic polyps were indistinguishable from real polyps. This method can be used to generate ground truth experimental data for comparison of CT colonographic display and detection methods.
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Affiliation(s)
- C Karadi
- Department of Medicine, Stanford University School of Medicine, CA 94305-5488, USA
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188
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Samara Y, Fiebich M, Dachman AH, Kuniyoshi JK, Doi K, Hoffmann KR. Automated calculation of the centerline of the human colon on CT images. Acad Radiol 1999; 6:352-9. [PMID: 10376066 DOI: 10.1016/s1076-6332(99)80230-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
RATIONALE AND OBJECTIVES This article presents an evaluation of an automated technique for determining the colon centerline with computed tomographic (CT) data sets. MATERIALS AND METHODS The technique proceeds as follows. After indication of a voxel in the rectum, voxels corresponding to air were segmented. Points along the colon centerline were estimated on the basis of centers of mass of grown voxels. A second segmentation and centerline calculation was initiated at the cecum. These two centerlines were then averaged. The resulting average was refined by using lumen data obtained perpendicular to the average centerline. The accuracy of the technique was investigated with simulation phantoms. The technique was also evaluated for 40 clinical colon cases. Calculated centerline points were compared with those indicated by radiologists for a randomly selected clinical case. RESULTS In the simulation studies, the calculated centerline points were, on average, within 2.5 mm of the true centerlines but differed by up to 4 mm in regions of deep folds or sharp turns. In the clinical colon study, 40% of the centerlines were computed with a single seed point and 25% with two seed points. Average centerlines were computed in 1 minute. The root mean square difference between the computed centerline points and those indicated by the radiologists was 4-5 mm (comparable to interobserver variations). CONCLUSION Accurate centerlines can be determined from colon CT data with this automated technique.
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Affiliation(s)
- Y Samara
- Department of Radiology, University of Chicago, IL 60637, USA
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189
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Ott DJ. Noninvasive "colonoscopy"--fact or fiction? Am J Gastroenterol 1999; 94:1104-6. [PMID: 10201496 DOI: 10.1111/j.1572-0241.1999.1104a.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- D J Ott
- Department of Radiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
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190
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Johnson CD, Ahlquist DA. Computed tomography colonography (virtual colonoscopy): a new method for colorectal screening. Gut 1999; 44:301-5. [PMID: 10026308 PMCID: PMC1727417 DOI: 10.1136/gut.44.3.301] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- C D Johnson
- Department of Diagnostic Radiology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA
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191
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Abstract
Virtual colonoscopy (VC) is an evolving technique that combines volume scanning and computer visualization methods to enable minimally invasive and effective colorectal cancer screening. Although VC offers significant clinical and public health advantages over conventional endoscopic screening, several issues confront VC's emergence into the medical marketplace.
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Affiliation(s)
- D J Vining
- Department of Radiology, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1088, USA
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192
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Stoll E, Stern C, Stucki P, Wildermuth S. A new filtering algorithm for medical magnetic resonance and computer tomography images. J Digit Imaging 1999; 12:23-8. [PMID: 10036664 PMCID: PMC3452428 DOI: 10.1007/bf03168623] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Inner views of tubular structures based on computer tomography (CT) and magnetic resonance (MR) data sets may be created by virtual endoscopy. After a preliminary segmentation procedure for selecting the organ to be represented, the virtual endoscopy is a new postprocessing technique using surface or volume rendering of the data sets. In the case of surface rendering, the segmentation is based on a grey level thresholding technique. To avoid artifacts owing to the noise created in the imaging process, and to restore spurious resolution degradations, a robust Wiener filter was applied. This filter working in Fourier space approximates the noise spectrum by a simple function that is proportional to the square root of the signal amplitude. Thus, only points with tiny amplitudes consisting mostly of noise are suppressed. Further artifacts are avoided by the correct selection of the threshold range. Afterwards, the lumen and the inner walls of the tubular structures are well represented and allow one to distinguish between harmless fluctuations and medically significant structures.
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Affiliation(s)
- E Stoll
- Physics Institute, University of Zurich, Switzerland
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193
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Abstract
Computed tomography (CT) and magnetic resonance (MR) colography (virtual colonoscopy) are new techniques being developed for the purpose of imaging colorectal polyps and cancer. Limited data are available regarding the performance characteristics of either technique, particularly MR. Initial reports suggest that the sensitivity of CT and MR colography for patients with adenomas > or = 1 cm ranges from 75-90%, and decreases precipitously for smaller polyps. Very early data suggest that the specificity for patient with large adenomas is around 90%, but for patients with adenomas in the 5-9 mm range has been as low as 65%. This review discusses currently available published and abstracted data on CT and MR colography and discusses the real and potential advantages and disadvantages of CT and MR colography compared to current colonic imaging methods. The review discusses problems that must be overcome in order for CT or MR colography to be demonstrated as practical tests, and suggests guidelines for the performance of clinical trials testing the performance characteristics of these methods.
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Affiliation(s)
- D K Rex
- Indiana University School of Medicine and Indiana University Hospital, Indianapolis 46202, USA
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194
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Dachman AH, Kuniyoshi JK, Boyle CM, Samara Y, Hoffmann KR, Rubin DT, Hanan I. CT colonography with three-dimensional problem solving for detection of colonic polyps. AJR Am J Roentgenol 1998; 171:989-95. [PMID: 9762982 DOI: 10.2214/ajr.171.4.9762982] [Citation(s) in RCA: 211] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
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.
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Affiliation(s)
- A H Dachman
- Department of Radiology, The University of Chicago Hospitals, IL 60637, USA
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195
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Beaulieu CF, Napel S, Daniel BL, Ch'en IY, Rubin GD, Johnstone IM, Jeffrey RB. Detection of colonic polyps in a phantom model: implications for virtual colonoscopy data acquisition. J Comput Assist Tomogr 1998; 22:656-63. [PMID: 9676463 DOI: 10.1097/00004728-199807000-00028] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE Virtual colonoscopy is a new method of colon examination in which computer-aided 3D visualization of spiral CT simulates fiberoptic colonoscopy. We used a colon phantom containing various-sized spheres to determine the influence of CT acquisition parameters on lesion detectability and sizing. METHOD Spherical plastic beads with diameters of 2.5, 4, 6, 8 and 10 mm were randomly attached to the inner wall of segments of plastic tubing. Groups of three sealed tubes were scanned at 3/1, 3/2, 5/1 collimation (mm)/pitch settings in orientations perpendicular and parallel to the scanner gantry. For each acquisition, image sets were reconstructed at intervals from 0.5 to 5.0 mm. Two blinded reviewers assessed transverse cross-sections of the phantoms for bead detection, using source CT images for images for acquisitions obtained with the tubes oriented perpendicular to the gantry and using orthogonal reformatted images for scans oriented parallel to the gantry. RESULTS Detection of beads of > or = 4 mm was 100% for both tube orientations and for all collimator/pitch settings and reconstruction intervals. For the 2.5 mm beads, detection decreased to 78-94% for 5 mm collimation/pitch 2 scans when the phantom sections were oriented parallel to the gantry (p = 0.01). Apparent elongation of beads in the slice direction occurred as the collimation and pitch increased. The majority of the elongation (approximately 75%) was attributable to changing the collimator from 3 to 5 mm, with the remainder of the elongation due to doubling the pitch from 1 to 2. CONCLUSION CT scanning at 5 mm collimation and up to pitch 2 is adequate for detection of high contrast lesions as small as 4 mm in this model. However, lesion size and geometry are less accurately depicted than at narrower collimation and lower pitch settings.
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Affiliation(s)
- C F Beaulieu
- Department of Radiology, Stanford University Medical Center, CA 94305, USA
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