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Perry J Pickhardt

Publications and source records attributed to Perry J Pickhardt.

At least 19 recordsLinked to original sources
PubMed2007

Extracolonic tumors of the gastrointestinal tract detected incidentally at screening CT colonography.

PURPOSE: The aim of this article is to report our experience with incidental detection of extracolonic tumors of the gastrointestinal tract identified prospectively at screening CT colonography. METHODS: A total of 2014 patients (1097 females, 917 males; mean age, 56.9 years) underwent primary CT colonography evaluation at our institution over an 18-month period. Following cathartic preparation and colonic distention, supine and prone multidetector CT scans were obtained with thin-collimation low-dose technique without intravenous contrast. We reviewed our database for lesions of the extracolonic gastrointestinal tract that were detected during the prospective reading. RESULTS: Focal extracolonic gastrointestinal tract lesions were prospectively detected in 10 (0.5 percent) of 2014 patients (8 females; 2 males; mean age, 58.5 years). All patients were asymptomatic. Tumor locations included ileum (n = 3), stomach (n = 3), jejunum (n = 2), and appendix (n = 2). Mean tumor size was 2.2 (range, 0.8-3.4) cm. Lesions in eight patients were subsequently confirmed by conventional or capsule endoscopy and/or by intravenous contrast-enhanced CT. Seven lesions were surgically excised and one was removed at endoscopy; two patients with lipomas did not undergo further evaluation or treatment. Final diagnoses were benign in all cases and included lipoma (n = 3), small-bowel hamartoma (n = 2), appendiceal mucinous cystadenoma (n = 2), gastric leiomyoma (n = 1), small-bowel lymphangioma (n = 1), and gastric fundic gland polyp (n = 1). CONCLUSIONS: Incidental extracolonic tumors of the gastrointestinal tract detected at screening CT colonography were all asymptomatic and benign but often prompted more invasive workup. Although the incidence of these tumors was relatively low, widespread population screening with CT colonography would result in new surgical referrals for these findings.

Aged↗
PubMed2006

The cost-effectiveness of CT colonography in screening for colorectal neoplasia.

BACKGROUND: We examined the cost-effectiveness of 2- and 3-dimensional computerized tomography (CT) colonography as a screening test for colorectal neoplasia. METHODS: We created a Markov model of the natural history of colorectal cancer. Effectiveness of screening was based upon the diagnostic accuracy of tests in detecting polyps and cancer. RESULTS: CT colonography every 5 or 10 yr was effective and cost-effective relative to no screening. Optical colonoscopy dominates 2-dimensional CT colonography done every 5 or 10 yr. Optical colonoscopy is weakly dominant over 3-dimensional CT colonography done every 10 yr. 3-D CT colonography done every 5 yr is more effective than optical colonoscopy every 10 yr, but costs an incremental 156,000 dollars per life-year gained. Sensitivity analyses show that test costs, accuracy, and adherence are critical determinants of incremental cost-effectiveness. 3-D CT colonography every 5 yr is a dominant strategy if optical colonoscopy costs 1.6 times more than CT colonography. However, optical colonoscopy is a dominant strategy if the sensitivity of CT colonography for 1 cm adenomas is 83% or lower. CONCLUSIONS: CT colonography is an effective screening test for colorectal neoplasia. However, it is more expensive and generally less effective than optical colonoscopy. CT colonography can be reasonably cost-effective when the diagnostic accuracy of CT colonography is high, as with primary 3-dimensional technology, and if costs are about 60% of those of optical colonoscopy. Overall, CT colonography technology will need to improve its accuracy and reliability to be a cost-effective screening option.

Aged↗
PubMed2006

CT colonography with computer-aided polyp detection: volume and attenuation thresholds to reduce false-positive findings owing to the ileocecal valve.

PURPOSE: To retrospectively identify volume and average attenuation thresholds for differentiating between ileocecal valve (ICV) and polyp at computed tomographic (CT) colonography with computer-aided detection (CAD). MATERIALS AND METHODS: Informed consent (with consent for future retrospective research) and institutional review board (IRB) approval were obtained for the original prospective study. This retrospective study had IRB approval, as well, and was HIPAA-compliant. A total of 496 patients were selected from a larger screening population. CT colonographic images from 394 patients (227 men, 167 women; mean age, 58.0 years; range, 40-79 years) were used as a training set, and images from 102 patients (76 men, 26 women; mean age, 59.8 years; range, 46-79 years) were used as a test set. A series of 2742 volume and attenuation thresholds, for which segmented findings both larger in volume and lower in average attenuation were labeled as ICVs and remaining findings were labeled polyps, were applied to the training set to determine settings with 100% sensitivity for polyp detection and the highest specificity for ICV detection. The optimal settings were then applied to the test set. Significance was assessed with the Fisher exact test, and 95% confidence intervals (CIs) were computed for sensitivity and specificity. RESULTS: A total of 386 ICVs and 67 adenomatous polyps from the training set and 102 ICVs and 138 adenomatous polyps from the test set could be segmented with a three-dimensional segmentation algorithm. When supine and prone images were counted individually, 746 nonunique ICVs from the training set and 191 from the test set were segmentable. In the training set, a volume of 600 mm(3) and an attenuation of 36 HU provided 100% sensitivity (67 polyps; 95% CI: 93%, 100%) and the optimal 83% specificity (618 of 746 ICVs; 95% CI: 80%, 85%). When applied to the test set, this combination provided 97% sensitivity (134 of 138 polyps; 95% CI: 92%, 99%) and 84% specificity (160 of 191 ICVs; 95% CI: 78%, 89%). Differences in sensitivity and specificity in the detection of polyps between the sets were not significant. CONCLUSION: Volume and average CT attenuation thresholds can help differentiate most ICVs from true polyps.

Adult↗
PubMed2006

Screening for colorectal neoplasia with CT colonography: initial experience from the 1st year of coverage by third-party payers.

PURPOSE: To evaluate our experience in the 1st year of computed tomographic (CT) colonography screening since the initiation of local third-party payer coverage. MATERIALS AND METHODS: This HIPAA-compliant study was approved by the institutional review board, and informed consent was waived. Over a 1-year period that ended on April 27, 2005, 1110 consecutive adults (585 women, 525 men; mean age, 58.1 years) underwent primary CT colonography screening. More than 99% were covered by managed care agreements. CT colonographic interpretation was performed with primary three-dimensional polyp detection, and the final results were issued within 2 hours. Patients with large (> or =10-mm) polyps were referred for same-day optical colonoscopy, and patients with medium-sized (6-9-mm) lesions had the option of immediate optical colonoscopy or short-term CT colonography surveillance. RESULTS: Large colorectal polyps were identified at CT colonography in 43 (3.9%) of 1110 patients. Medium-sized lesions were identified in 77 (6.9%) patients, 31 (40%) of whom chose optical colonoscopy and 46 (60%) of whom chose CT colonography surveillance. Concordant lesions were identified in 65 of 71 patients who underwent subsequent optical colonoscopy (positive predictive value, 91.5%). Sixty-one (86%) of 71 optical colonoscopic procedures were performed on the same day as CT colonography, thereby avoiding the need for repeat bowel preparation. The actual endoscopic referral rate for positive findings at CT colonography was 6.4% (71 of 1110 patients). The demand for CT colonography screening from primary care physicians and their patients increased throughout the study period. CONCLUSION: As a primary colorectal screening tool, CT colonography covered by third-party payers has an acceptably low endoscopic referral rate and a high concordance of positive findings at optical colonoscopy.

Chi-Square Distribution↗
PubMed2006

Diagnostic performance of primary 3-dimensional computed tomography colonography in the setting of colonic diverticular disease.

BACKGROUND & AIMS: Colonic diverticular disease (CDD) is a leading cause of nondiagnostic segmental evaluation at computed tomography colonography (CTC). The primary goal of this study was to evaluate the impact of CDD on polyp detection at primary 3-dimensional (3D) CTC. METHODS: The study group consisted of 280 asymptomatic average-risk adults (mean age, 58.1 y; 167 men, 113 women). All patients underwent CTC followed by same-day optical colonoscopy with segmental unblinding (reference standard). Primary 3D endoluminal evaluation with 2-dimensional correlation was used for initial polyp detection at CTC. Without knowledge of polyp findings, all colonic segments were reviewed for the presence of CDD and graded as absent, minimal, moderate, or extensive disease. RESULTS: Moderate or extensive CDD was present in 271 (12.1%) of 2240 colonic segments and 142 (50.7%) of 280 patients. CTC performance for polyps 6 mm or larger in the presence and absence of moderate-extensive CDD was as follows: by-segment sensitivity of 90.3% (28/31) and 79.4% (123/155); by-patient sensitivity of 86.5% (64/74) and 83.1% (54/65); by-segment specificity of 97.1% (233/240) and 97.7% (1772/1814); by-patient specificity of 83.8% (57/68) and 83.6% (61/73); by-segment positive predictive value of 80.0% (28/35) and 74.5% (123/165); by-patient positive predictive value of 85.3% (64/75) and 81.8% (64/66); by-segment negative predictive value of 98.7% (233/236) and 98.2% (1172/1804); and by-patient negative predictive value of 85.1% (57/67) and 84.7% (61/72), respectively (not significant, P > or = .15). CONCLUSIONS: CDD was common in this asymptomatic screening population, but its presence did not degrade the diagnostic performance of primary 3D CTC for polyp detection.

Adenocarcinoma↗
PubMed2006

Surface visualization at 3D endoluminal CT colonography: degree of coverage and implications for polyp detection.

BACKGROUND & AIMS: Effective colonoscopic screening for polyps, whether by optical or virtual means, requires adequate visualization of the entire colonic surface. The purpose of this study was to assess prospectively the degree of surface coverage at 3-dimensional (3D) endoluminal computed tomography colonography (CTC) after retrograde fly-through, combined retrograde-antegrade fly-through, and review of remaining missed regions. METHODS: The study group consisted of 223 asymptomatic adults (mean age, 57.8 +/- 7.2 y; 111 men, 112 women) undergoing primary CTC screening. CTC studies were interpreted by experienced readers using a primary 3D approach. The CTC software system that was used continually tracks the percentage of endoluminal surface visualized. The degree of coverage was assessed prospectively after retrograde and combined retrograde-antegrade navigation. The added effect of reviewing missed regions was also assessed prospectively. RESULTS: The mean surface coverage after only retrograde 3D endoluminal fly-through from rectum to cecum was 76.6% +/- 4.8% (range, 63%-92%); coverage was 80% or less in 181 (81.2%) patients. Antegrade navigation back to the rectum increased the overall coverage to 94.1% +/- 2.3% (range, 84%-99%; P < .0001). A review of missed regions 300 mm(2) or larger increased coverage to 97.9% +/- 1.1% (range, 93%-99%; P < .0001) and added 21.4 +/- 11.4 seconds to the interpretation time (range, 3-67 s). CONCLUSIONS: Combined bidirectional retrograde and antegrade 3D navigation, supplemented by rapid review of missed regions, effectively covers the entire evaluable surface at CTC. Unidirectional retrograde 3D fly-through typically excludes 20% or more of the endoluminal surface, which may provide insight into potential limitations at optical colonoscopy.

Aged↗
PubMed2006

Hybrid segmentation of colon filled with air and opacified fluid for CT colonography.

Reliable segmentation of the colon is a requirement for three-dimensional visualization programs and automatic detection of polyps on computed tomography (CT) colonography. There is an evolving clinical consensus that giving patients positive oral contrast to tag out remnants of stool and residual fluids is mandatory. The presence of positive oral contrast in the colon adds an additional challenge for colonic segmentation but ultimately is beneficial to the patient because the enhanced fluid helps reveal polyps in otherwise hidden areas. Therefore, we developed a new segmentation procedure which can handle both air- and fluid-filled parts of the colon. The procedure organizes individual air- and fluid-filled regions into a graph that enables identification and removal of undesired leakage outside the colon. In addition, the procedure provides a risk assessment of possible leakage to assist the user prior to the tedious task of visual verification. The proposed hybrid algorithm uses modified region growing, fuzzy connectedness and level set segmentation. We tested our algorithm on 160 CT colonography scans containing 183 known polyps. All 183 polyps were in segmented regions. In addition, visual inspection of 24 CT colonography scans demonstrated good performance of our procedure: the reconstructed colonic wall appeared smooth even at the interface between air and fluid and there were no leaked regions.

Air↗
PubMed2006

Polyps: linear and volumetric measurement at CT colonography.

PURPOSE: To retrospectively determine which of several computed tomographic (CT) colonography-based polyp measurements is most compatible with the linear measurement at optical colonoscopy and which is best for assessing change in polyp size. MATERIALS AND METHODS: This HIPAA-compliant study had institutional review board approval; informed consent was obtained. Prone and supine CT colonography with same-day optical colonoscopy was performed in 216 patients (147 men and 69 women; age range, 46-79 years; mean age, 59.2 years) with 338 polyps detected at CT colonography. Polyp size was measured with three linear measurements and two volume measurements. One linear measurement and one volume measurement were performed by using automated segmentation; remaining measurements were performed manually. Compatibility with linear size at optical colonoscopy and measurement reproducibility were assessed three ways: variation from size measurement at optical colonoscopy, change between prone and supine scans, and variability between observers. Confidence analysis assessed the ability of each measurement to identify polyps with an optical colonoscopy measurement of 1 cm or greater. RESULTS: Two hundred fifty-one segmentable polyps were present on both supine and prone scans. Linear polyp diameter manually measured on a three-dimensional endoluminally viewed surface (L(M3D)) indicated with 95% confidence that a polyp measured as 0.8 cm or smaller was less than 1.0 cm at optical colonoscopy. Prone and supine polyp size difference was smallest for L(M3D) and the linear diameter computed from manual and automated volume measurements, with interquartile ranges smaller than or equal to 0.3, 0.2, and 0.5 cm, respectively. Interobserver and intraobserver variability was smallest for linear polyp diameter measurements on a two-dimensional display, with a mean percentage difference of 2.8% (95% Bland-Altman limits of agreement: -17.8%, 23.4%) and 5.0% (95% Bland-Altman limits of agreement: -28.3%, 38.3%), respectively. CONCLUSION: L(M3D) best approximated polyp size measurements at optical colonoscopy. Linear diameter calculated from automated volume measurements showed the smallest variation between supine and prone scans while avoiding observer variability and may be best for assessing polyp size changes with serial examinations.

Adult↗
PubMed2006

Extracolonic findings identified in asymptomatic adults at screening CT colonography.

OBJECTIVE: The purpose of this article is to demonstrate the wide variety of extracolonic findings that may be encountered at screening CT colonography (CTC) in asymptomatic adults as well as to discuss the pertinent issues regarding the detection of potential abnormalities in a healthy population. CONCLUSION: Regardless of whether extracolonic evaluation resulting from CTC screening is viewed as a net benefit or liability, it is an unavoidable responsibility that must be handled with care by the interpreting radiologist. Although many potential abnormalities may be questioned, the pretest probability of clinically relevant disease is quite low in average-risk asymptomatic adults, which may influence subsequent management decisions.

Adult↗
PubMed2006

Patient-controlled room air insufflation versus automated carbon dioxide delivery for CT colonography.

OBJECTIVE: Our objective was to prospectively compare colonic distention and patient comfort at screening CT colonography (CTC) with patient-controlled room air (RA) insufflation versus automated carbon dioxide (CO2) delivery. SUBJECTS AND METHODS: Two hundred eight adults undergoing CTC were randomized to RA or CO2 (104 per method). Colonic distention was prospectively assessed by segment using a 4-point scale (1 = optimal, 2 = adequate, 3 = inadequate, 4 = collapsed). Adequacy of combined supine/prone segmental evaluation was also recorded. Patients provided discomfort ratings on a 0-10 scale (0-1 = none/insignificant, 2-3 = minimal, 4-6 = intermediate, 7-10 = significant) before, during, and after the procedure. RESULTS: No significant differences in segmental distention were observed in the prone position between techniques. In the supine position, CO2 resulted in significantly greater distention in the sigmoid, descending, and transverse segments (p < 0.01). After combined supine/prone assessment, two/104 (1.9%) and three/104 (2.9%) patients were judged to have an inadequately evaluated segment on RA and CO2, respectively (four sigmoid, one transverse). Mean discomfort scores for RA and CO2 were 3.97 and 5.08 during the examination (p < 0.01); 0.91 and 0.42 immediately after (p < 0.01); 0.51 and 0.25 15 min later (p < 0.05); and 0.15 and 0.04 2 hours later (p < 0.01), respectively. During active distention, 19 (18.3%) and 33 (31.7%) patients reported significant transient discomfort with RA and CO2, respectively (p < 0.05). Beyond 15 min, only two (1.9%) patients with RA and no patients with CO2 had a discomfort level higher than 3. CONCLUSION: Although patient-controlled RA insufflation and automated CO2 delivery each resulted in negligible postprocedure discomfort and reliable colonic distention, CO2 was better for both categories.

Air↗
PubMed2006

Polyp volume versus linear size measurements at CT colonography: implications for noninvasive surveillance of unresected colorectal lesions.

OBJECTIVE: Proposed surveillance of unresected medium-sized (6.0-9.9 mm) polyps will require reliable detection of small incremental changes. The purpose of this study was to assess the reproducibility of linear versus volume measurements of polyp size at CT colonography (CTC) and to correlate results with a hemispheric model. MATERIALS AND METHODS: The study group consisted of 30 polyps on supine and prone CTC data sets. Measurements were performed separately by two experienced radiologists using the same CTC system (Vitrea 2), resulting in 120 linear and volume measurements. Linear size was defined as the longest dimension among the 2D multiplanar reconstruction views. Semiautomated volume determination required manual tracing of polyp boundaries on 2D multiplanar reconstruction views. The relative error between reviewers 1 and 2 was defined as 100 x (/D1 - D2/)/D(ave) for linear size (D) and as 100 x (/V1 - V2)/V(ave) for volume (V), where ave is average. RESULTS: The mean relative error for linear size and volume measurement was 10.4% +/- 10.7% and 16.9% +/- 13.2%, respectively. Median linear size and volume of polyps were 9.4 mm and 270 mm3, respectively. CTC-derived volumes for medium-sized polyps closely approximated hemispheric volume (V = (pi/12) x D(b), where b =3.13, r2 = 0.90). Small incremental changes in hemispheric size result in a 3:1 relative change in volume versus diameter, such that a 1-mm diameter change in a medium-sized hemispheric polyp results in a relative change in linear size and volume ranging from approximately 11-18% and 31-53%, respectively. CONCLUSION: Because changes in polyp volume are amplified compared with linear dimension, volume measurement rather than diameter measurement will better allow detection of small incremental changes in polyp size using CTC.

Colonic Polyps↗
PubMed2005

Microcomputed tomography colonography for polyp detection in an in vivo mouse tumor model.

This study was initiated to evaluate the efficacy of negative contrast-enhanced microcomputed tomography (microCT) colonography for the noninvasive detection of colonic tumors in living mice. After colonic preparation, 20 anesthetized congenic mice were scanned with high-resolution microCT. Images were displayed by using commercial visualization software and interpreted by two gastrointestinal radiologists, who were unaware of tumor prevalence and findings at gross pathology. Two-dimensional multiplanar images were assessed by using a five-point scale to distinguish colonic tumors (polyps) from fecal pellets (5 = definitely a tumor, 4 = probably a tumor, 3 = indeterminate, 2 = probably not a tumor, 1 = definitely not a tumor). Gross pathologic evaluation of excised mouse colons served as the reference standard. Data analysis included dichotomizing results, with 1-2 indicating no tumor and 3-5 indicating tumor and also receiver operator characteristic curve analysis with area under the curve for threshold-independent assessment. A total of 41 colonic polyps in 18 of the 20 mice were identified at gross examination on necropsy, of which 30 measured 2-5 mm and 11 measured <2 mm in size. The pooled per-polyp sensitivity for lesions >2 mm was 93.3% (56/60). The pooled per-mouse sensitivity for polyps >2 mm was 97.1% (33/34). Pooled specificity for distinguishing fecal pellets from tumor was 98.5% (65/66). The combined area under the curve from receiver operator characteristic curve analysis was 0.810 +/- 0.038 (95% confidence interval, 0.730-0.890). These findings indicate that accurate noninvasive longitudinal monitoring of colon tumor progression or response to various therapies is now technically feasible in live mice by using this microCT colonography method.

Animals↗
PubMed2005

Virtual colonoscopy: issues related to primary screening.

Virtual colonoscopy (VC) is a minimally invasive CT examination that has continued to rapidly evolve and improve as a diagnostic screening tool. Current state-of-the-art VC technique has already been shown to be highly effective for screening at the University of Wisconsin. Although more widespread implementation of VC screening faces multiple challenges and barriers, these are all greatly overshadowed by the immediate need for increased patient compliance in effective colorectal screening programs. Given the wide availability of CT and the favorable safety profile compared with optical colonoscopy, VC holds significant potential for addressing a very important yet preventable public health concern. This paper will briefly address some of the major issues related to the general application of VC for colorectal screening, such as diagnostic performance, development of an acceptable screening algorithm, and several technique-related issues.

Algorithms↗
PubMed2005

Automated seed placement for colon segmentation in computed tomography colonography.

RATIONALE AND OBJECTIVE: To present an algorithm to automatically locate seeds for colon segmentation in computed tomography colonography (CTC). MATERIALS AND METHODS: The algorithm automatically locates two points (seeds) inside the colon lumen. Because of their high distention and fixed anatomic position, we focus on the cecum and rectum for automatic seed placement. We use two-dimensional morphological operators that find pockets of colonic air of sufficient size. For the rectum, we search within an inferiorly and centrally located CT slice. For the cecum, we search in a group of CT slices in the middle of the scanned volume on the patient's right side. We applied our automated algorithm to segment the colon in 292 consecutive cases of CTC (146 prone, 146 supine). RESULTS: After automated seed placement, 83.2% (243 of 292) of the colons were segmented completely and 9.6% (28 of 292) were segmented partially. The unsegmented colon parts were present in datasets where the colon was collapsed in more than one place or because seeds could not be placed in regions filled with fluid. In the remaining 7.2% (21 of 292) of cases, the automatic segmentation leaked outside the colon because of a limitation of the contrast-enhanced fluid detection algorithm. CONCLUSION: Fully automatic seed placement for colonic segmentation is feasible in the majority of cases without seeding of undesired extracolonic air.

Adult↗