Percutaneous treatment of common bile duct stones: results and complications in 110 consecutive patients.

BACKGROUND/AIMS: Choledocholithiasis is a common complication of cholecystolithiasis, occurring in 15-20% of patients who have gallbladder stones. Endoscopic retrograde cholangio-pancreatography is the standard treatment. When this is not possible or not feasible, percutaneous transhepatic stone removal is an alternative treatment. In this retrospective study, we analyze 110 patients who were treated with percutaneous transhepatic removal of Common Bile Duct (CBD) stones. PATIENTS AND METHODS: Between March 1998 and September 2013 110 patients (61 men, 49 women; aged 14-96, mean age 69.7 years) with confirmed bile duct stones were included. PTC was done using ultrasound and fluoroscopy. Balloon dilatation of the papilla was done with 8-12 mm balloons. If stone size exceeded 10 mm, mechanical lithotripsy was performed. Stones were then removed by percutaneous extraction or evacuation into the duodenum. RESULTS: In 104 patients (104/110; 94.5%) total stone clearance of the CBD was achieved. A total of 12 complications occurred (10.9%), graded with the Clavien-Dindo scale as IVa, IVb, and V, respectively; hypoxia requiring resuscitation, sepsis and death due to ongoing cholangiosepsis (n = 1, 4, 1). Minor complications I, II, and IIIa included: small liver abscess, pleural empyema, transient hemobilia and mild fever (n = 1, 1, 2, 2). CONCLUSION: Percutaneous removal of CBD stones is an effective alternative treatment, when endoscopic treatment is contra-indicated, fails or is not feasible. It is effective, has a low complication rate and using deep sedation potentially requires only a very limited number of treatment sessions.

Diagnostic value of CT-colonography as compared to colonoscopy in an asymptomatic screening population: a meta-analysis.

OBJECTIVES: Previous meta-analyses on CT-colonography included both average and high risk individuals, which may overestimate the diagnostic value in screening. A meta-analysis was performed to obtain the value of CT-colonography for screening. METHODS: A search was performed using PubMed, Embase and Cochrane. Article selection and critical appraisal was done by two reviewers. INCLUSION CRITERIA: prospective, randomized trials or cohort studies comparing CT-colonography with colonoscopy (≥50 participants), ≥95% average risk participants ≥50 years. Study characteristics and 2 × 2 contingency Tables were recorded. Sensitivity and specificity estimates were calculated per patient and per polyp (≥6 mm, ≥10 mm), using univariate and bivariate analyses. RESULTS: Five of 1,021 studies identified were included, including 4,086 participants (<1% high risk). I(2)-values showed substantial heterogeneity, especially for 6-9 mm polyps and adenomas: 68.1% vs. 78.6% (sensitivity per patient). Estimated sensitivities for patients with polyps or adenomas ≥ 6 mm were 75.9% and 82.9%, corresponding specificities 94.6% and 91.4%. Estimated sensitivities for patients with polyps or adenomas ≥ 10 mm were 83.3% and 87.9%, corresponding specificities 98.7% and 97.6%. Estimated sensitivities per polyp for advanced adenomas ≥ 6 mm and ≥ 10 mm were 83.9% and 83.8%. CONCLUSION: Compared to colonoscopy, CT-colonography has a high sensitivity for adenomas ≥ 10 mm. For (advanced) adenomas ≥ 6 mm sensitivity is somewhat lower.

The pivotal role of cardiac computed tomography angiogram and 18F-fluorodeoxyglucose positron emission tomography-computed tomography in the diagnosis of right sided endocarditis: a case report.

BACKGROUND: Infective endocarditis (IE) poses many clinical and diagnostic challenges. Echocardiography is regarded as the imaging modality of choice for the diagnosis of IE, and plays a key role in both the diagnosis and management of endocarditis. We report on a case in which one could have overlooked an endocarditis of a pulmonary homograft if one had relied on echocardiography alone. CASE SUMMARY: A 38-year-old man presented with intermittent fever and fatigue for 1 month. He had undergone a Ross procedure for a bicuspid aortic valve stenosis at the age of 17 years. At the age of 36 years a valve-sparing aortic root replacement was performed because of aortic root dilatation. Besides a systolic murmur 3/6 noted at the left sternal border, physical examination was normal. Multiple blood cultures grew Streptococcus mitis. Both transthoracic and transoesophageal echocardiogram could not detect any signs of endocarditis. As endocarditis can be overlooked due to reverberations and acoustic shadowing, we performed 18F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) and cardiac computed tomography angiogram (cardiac CTA). Both imaging modalities showed large vegetations attached to the pulmonary homograft. DISCUSSION: Endocarditis poses diagnostic challenges. While echocardiography is the cornerstone of imaging, one may overlook a pulmonary homograft endocarditis due to reverberations and acoustic shadowing. Therefore, if clinical suspicion of endocarditis is strong, one should consider additional imaging by means of cardiac CTA and/or 18F-fluorodeoxyglucose positron emission tomography-computed tomography imaging to assess valves in pulmonary position, especially in those whom have had prior surgical intervention at this location.

Image quality and patient acceptance of four regimens with different amounts of mild laxatives for CT colonography.

OBJECTIVE: The purpose of our study was to prospectively evaluate image quality and patient acceptance of CT colonography (CTC) with fecal tagging using different levels of catharsis. SUBJECTS AND METHODS: Forty consecutive increased-risk patients were randomized. Group 1 received orally 20 mg of bisacodyl, group 2 received 30 mg of bisacodyl, group 3 received 20 mg of bisacodyl and 8.2 g of magnesium citrate, and group 4 received 30 mg of bisacodyl and 16.4 g of magnesium citrate. All patients used a 2-day low-fiber diet and received diatrizoate meglumine and barium for fecal tagging. One reviewer blindly scored subjective image quality (fecal tagging, amount of residual feces [liquid or solid], luminal distention, and image readability) on a 5- to 6-point scale using a 2D review technique. The mean and SD of attenuation of tagging were measured as well as the relative SD as a measure of homogeneity. Furthermore, patient acceptance (burden related to diarrhea, abdominal pain, flatulence, and overall burden) was evaluated. Ordinal regression, generalized estimating equations, and parametric and nonparametric tests were used for analysis. RESULTS: Image readability was evaluated as good or excellent in all examinations except one in group 2 (nondiagnostic) and two in group 3 (moderate). Group 2 contained more feces than group 4 (p = 0.04). With regard to mean attenuation and homogeneity of tagging, no significant differences were observed between groups. Group 4 experienced more severe diarrhea than groups 1 and 2 and higher overall burden than groups 1 and 3 (p < 0.042). CONCLUSION: The mildest preparation with 20 mg of bisacodyl provided good image quality of CTC images. Increasing the amount of laxatives did not improve image quality or tagging characteristics but was associated with a lower patient acceptance.

Performance of radiographers in the evaluation of CT colonographic images.

OBJECTIVE: The purpose of this study was to compare the accuracy of radiographers with that of radiologists in the interpretation of CT colonographic images. MATERIALS AND METHODS: Four observers (a radiologist, a radiologist in training, and two radiographers) evaluated 145 data sets using a primary 3D approach. The radiographers were part of our CT colonography work group and underwent training that consisted of 20 cases. The reference standard was optical colonoscopy with second-look colonoscopy for discrepant lesions > or = 10 mm in diameter. Mean sensitivities per patient and per polyp stratified for size (any size, > or = 6 mm, and > or = 10 mm) was determined for the radiologists and radiographers. Specificity was determined on a per-patient basis. RESULTS: At colonoscopy in 86 of 145 patients, a total of 317 polyps were found (60 polyps > or = 6 mm in 26 patients and 31 polyps > or = 10 mm in 18 patients). No statistically significant differences were found in detection rates between radiologists and radiographers. Sensitivities for patients with a lesion of any size (66% for radiologists vs 65% for radiographers), > or = 6 mm (81% vs 87%), and > or = 10 mm (both 78%) were similar for all observers. On a per-polyp basis, detection rates were equivalent regardless of polyp size (47% vs 40%), for lesions > or = 6 mm (71% vs 65%), and for lesions > or = 10 mm (69% vs 66%). Mean specificities were similar among patients without lesions (31% vs 30%), patients without lesions > or = 6 mm (71% vs 67%), and patients without lesions > or = 10 mm (93% vs 93%). CONCLUSION: Radiographers with training in CT colonographic evaluation achieved sensitivity and specificity in polyp detection comparable with that of radiologists. Radiographers can be considered reviewers in the evaluation of CT colonographic images.

Computed tomography colonography: current issues.

OBJECTIVE: Direct and indirect evidence supports the concept of screening for adenomas and early stage colorectal cancer in reducing the incidence and disease-specific mortality. Controversy remains as to the appropriateness of and preferred methods for screening an asymptomatic population. METHODS: Review of computed tomography (CT) colonography based on the literature and personal experience. RESULTS AND CONCLUSIONS: Current discrepancies in the data on accuracy and patient acceptance of CT colonography reflect differences in the performance and evaluation of this examination. Before CT colonography can be implemented in colorectal cancer screening, factors that cause this variability must be elucidated. Studies in which high-resolution scanning, three-dimensional review methods and an enhanced colonoscopic reference are used achieve an accuracy that is similar to colonoscopy. At the same time the evidence that ultra-low radiation dose CT colonography is feasible is mounting, a development that dramatically reduces one of the largest obstacles for large-scale application of this technique.

Colonography by computed tomography.

Computed tomographic colonography ('virtual colonoscopy') has shown promising results in the detection of large (> or = 10 mm) polyps in populations with a high prevalence of polyps. Recent studies in low prevalence populations, however, show variable results in sensitivity, ranging from 55% to 94% for the detection of patients with polyps measuring 10 mm or longer. Therefore questions have been raised about computed tomographic colonography as a screening method, probably the most valuable use of this technique. This article describes possible causes of these remarkable differences as well as advances in computed tomographic colonography.

Admission blood glucose level as risk indicator of death after myocardial infarction in patients with and without diabetes mellitus.

BACKGROUND: High admission blood glucose levels after acute myocardial infarction (AMI) are common and associated with an increased risk of death in subjects with and without known diabetes. Recent data indicate a high prevalence of abnormal glucose metabolism in patients with unknown diabetes at the time of AMI. We investigated the predictive value of admission blood glucose levels after AMI for long-term prognosis in patients with and without previously diagnosed diabetes mellitus, particularly in those with unknown diabetes but with blood glucose levels in the diabetic range. METHODS: In a retrospective study with prospective follow-up, 846 patients (737 without and 109 with known diabetes) were eligible for follow-up during a median of 50 months (range, 0-93 months). RESULTS: During follow-up, 208 nondiabetic patients (28.2%) and 47 diabetic patients (43.1%) died (P =.002). An increase of 18 mg/dL (1 mmol/L) in glucose level was associated with a 4% increase of mortality risk in nondiabetic patients and 5% in diabetic patients (both P<.05). Of the 737 previously nondiabetic subjects, 101 had admission blood glucose levels of 200 mg/dL (11.1 mmol/L) or more, and mortality in these patients was comparable to that in patients who had established diabetes (42.6% vs 43.1%). CONCLUSIONS: Admission blood glucose level after AMI is an independent predictor of long-term mortality in patients with and without known diabetes. Subjects with unknown diabetes and admission glucose levels of 200 mg/dL (11.1 mmol/L) or more after AMI have mortality rates comparable to those of subjects with established diabetes. Admission blood glucose level may serve to identify subjects at high long-term mortality risk, in particular among those with unknown diabetes.

Magnetic resonance colonography with limited bowel preparation: a comparison of three strategies.

PURPOSE: To prospectively compare three strategies of magnetic resonance colonography (MRC) with fecal tagging. MATERIALS AND METHODS: Three strategies were compared: (S1) gadolinium as oral tagging agent and a gadolinium-water mixture for rectal filling (bright lumen), (S2) oral barium and water rectally, and (S3) oral barium and air rectally. In S2 and S3 (both dark lumen) gadolinium was injected intravenously. Three-dimensional (3D) T1-weighted and two-dimensional (2D) T2-weighted sequences were used. Two observers scored diagnostic confidence and image quality (contrast, homogeneity, artifacts), analyzed by chi-squared and Fisher's exact test. Patient experience and preference were determined by questionnaire (Mann-Whitney test). RESULTS: A total of 45 patients were included, 15 were randomly assigned per strategy. Diagnostic confidence of S1 and S3 is significantly better than for S2. S1 has the additional advantage of showing significantly better contrast between bowel wall and lumen, and showing significantly better homogeneity on both T1- and T2-weighted sequences, but with significantly more artifacts on the T1-weighted sequences. S3 showed significantly better contrast and homogeneity than S2 on the T2-weighted sequences. Bowel preparation of S1 was rated significantly better. Patient preference was comparable. CONCLUSION: Image quality was best using the bright lumen strategy or the dark lumen strategy using air for rectal filling. Although bowel preparation was rated best using the bright lumen strategy, patient preference was comparable.

Feasibility study of computed tomography colonography using limited bowel preparation at normal and low-dose levels study.

The purpose was to evaluate low-dose CT colonography without cathartic cleansing in terms of image quality, polyp visualization and patient acceptance. Sixty-one patients scheduled for colonoscopy started a low-fiber diet, lactulose and amidotrizoic-acid for fecal tagging 2 days prior to the CT scan (standard dose, 5.8-8.2 mSv). The original raw data of 51 patients were modified and reconstructed at simulated 2.3 and 0.7 mSv levels. Two observers evaluated the standard dose scan regarding image quality and polyps. A third evaluated the presence of polyps at all three mSv levels in a blinded prospective way. All observers were blinded to the reference standard: colonoscopy. At three times patients were given questionnaires relating to their experiences and preference. Image quality was sufficient in all patients, but significantly lower in the cecum, sigmoid and rectum. The two observers correctly identified respectively 10/15 (67%) and 9/15 (60%) polyps > or =10 mm, with 5 and 8 false-positive lesions (standard dose scan). Dose reduction down to 0.7 mSv was not associated with significant changes in diagnostic value (polyps > or =10 mm). Eighty percent of patients preferred CT colonography and 13% preferred colonoscopy (P<0.001). CT colonography without cleansing is preferred to colonoscopy and shows sufficient image quality and moderate sensitivity, without impaired diagnostic value at dose-levels as low as 0.7 mSv.

A comparison of primary two- and three-dimensional methods to review CT colonography.

The aim of our study was to compare primary three-dimensional (3D) and primary two-dimensional (2D) review methods for CT colonography with regard to polyp detection and perceptive errors. CT colonography studies of 77 patients were read twice by three reviewers, first with a primary 3D method and then with a primary 2D method. Mean numbers of true and false positives, patient sensitivity and specificity and perceptive errors were calculated with colonoscopy as a reference standard. A perceptive error was made if a polyp was not detected by all reviewers. Mean sensitivity for large (> or = 10 mm) polyps for primary 3D and 2D review was 81% (14.7/18) and 70%(12.7/18), respectively (p-values > or = 0.25). Mean numbers of large false positives for primary 3D and 2D were 8.3 and 5.3, respectively. With primary 3D and 2D review 1 and 6 perceptive errors, respectively, were made in 18 large polyps (p = 0.06). For medium-sized (6-9 mm) polyps these values were for primary 3D and 2D, respectively: mean sensitivity: 67%(11.3/17) and 61%(10.3/17; p-values > or = 0.45), number of false positives: 33.3 and 15.6, and perceptive errors : 4 and 6 (p = 0.53). No significant differences were found in the detection of large and medium-sized polyps between primary 3D and 2D review.

MR colonography with limited bowel preparation compared with optical colonoscopy in patients at increased risk for colorectal cancer.

PURPOSE: To prospectively evaluate the diagnostic performance of magnetic resonance (MR) colonography by using limited bowel preparation in patients with polyps of 10 mm or larger in diameter in a population at increased risk for colorectal cancer, with optical colonoscopy as the reference standard. MATERIALS AND METHODS: The institutional review boards of all three hospitals approved the study. All patients provided written informed consent. In this multicenter study, patients undergoing colonoscopy because of a personal or family history of colorectal cancer or adenomatous polyps were included. Two blinded observers independently evaluated T1- and T2-weighted MR colonographic images obtained with limited bowel preparation (bright-lumen fecal tagging) for the presence of polyps. The limited bowel preparation consisted of a low-fiber diet, with ingestion of lactulose and an oral gadolinium-based contrast agent (with all three major meals) starting 48 hours prior to imaging. Results were verified with colonoscopic outcomes. Patient sensitivity, patient specificity, polyp sensitivity, and interobserver agreement for lesions of 10 mm or larger were calculated for both observers individually and combined. RESULTS: Two hundred patients (mean age, 58 years; 128 male patients) were included; 41 patients had coexistent symptoms. At colonoscopy, 12 patients had 22 polyps of 10 mm or larger. Per-patient sensitivity was 58% (seven of 12) for observer 1, 67% (eight of 12) for observer 2, and 75% (nine of 12) for both observers combined for polyps of 10 mm or larger. Per-patient specificity was 95% (178 of 188) for observer 1, 97% (183 of 188) for observer 2, and 93% (175 of 188) for both observers combined. Per-polyp sensitivity was 55% (12 of 22) for observer 1, 50% (11 of 22) for observer 2, and 77% (17 of 22) for both observers combined. Interobserver agreement was 93% for identification of patients with lesions of 10 mm or larger. CONCLUSION: In patients at increased risk for colorectal cancer, specificity of MR colonography by using limited bowel preparation was high, but sensitivity was modest.

MR colonography with limited bowel preparation: patient acceptance compared with that of full-preparation colonoscopy.

PURPOSE: To prospectively evaluate participants' experience and preference of magnetic resonance (MR) colonography with limited bowel preparation compared with full-preparation colonoscopy in participants at increased risk for colorectal cancer. MATERIALS AND METHODS: This study had institutional review board approval; all participants gave written informed consent. In this multicenter study, consecutive participants undergoing conventional colonoscopy because of a personal or family history of colorectal cancer or adenomatous polyps underwent MR colonography 2 weeks prior to colonoscopy. They all followed a low-fiber diet and were given lactulose and an oral contrast agent (fecal tagging with gadolinium) 2 days before colonography. Before imaging, spasmolytics were administered intravenously, and a water-gadolinium chelate mixture was administered rectally for distention of the colon. Breath-hold T1- and T2-weighted sequences were performed in the prone and supine positions. Participant experience in terms of, for example, pain and burden was determined by using a five-point scale and was evaluated with a Wilcoxon signed rank test; participant preference was determined by using a seven-point scale and was evaluated with the chi2 statistic after dichotomizing. RESULTS: Two hundred nine participants (77 women, 132 men; mean age, 58 years; range, 23-84 years) were included. One hundred forty-eight participants received sedatives (midazolam) and/or analgesics (fentanyl) during colonoscopy. Participants rated the MR colonography bowel preparation as less burdensome (P<.001) compared with the colonoscopy bowel preparation (10% and 71% of participants rated the respective examinations moderately to extremely burdensome). Participants also experienced less pain at MR colonography (P<.001) and found MR colonography less burdensome (P<.001). Immediately after both examinations, 69% of participants preferred MR colonography, 22% preferred colonoscopy, and 9% were indifferent (P<.001, 69% vs 22%). After 5 weeks, 65% preferred MR colonography and 26% preferred colonoscopy (P<.001). CONCLUSION: Participants preferred MR colonography without extensive cleansing to colonoscopy immediately after both examinations and 5 weeks later. Experience of the bowel preparation and of the procedure was rated better.

Effective radiation doses in CT colonography: results of an inventory among research institutions.

The purpose of this study was to estimate the effective dose that is currently used in CT colonography using scan parameters that were collected for this purpose, and to investigate trends in time. PubMed was systematically searched from 1996 until January 2004 for studies investigating CT colonography. Research institutions were contacted and asked for their current scan protocol. Thirty-six institutions published 74 studies. Twenty-eight of the 36 institutions provided their current protocol. The median effective dose in 2004 was 5.1 mSv (range 1.2-11.7 mSv) per position. Most institutions (93%) scan in both the supine and prone positions. The median mAs value was 67 mAs (range 20-200), median collimation was 2.5 mm (range 0.75-5). From 1996 until 2004 a significant decrease in mAs and collimation (P=0.006, P<0.0001, respectively) was observed, while institutions that used a multislice scanner increased (P<0.0001). The effective dose remained constant (P=0.76). In 2004 the median effective dose for a complete CT colonography was 10.2 mSv. Despite the increasing use of multislice scanners, which are slightly less dose-efficient, the median effective dose remained approximately constant between 1996 and 2004. This is mainly caused by the use of lower mAs settings.

CT colonography and colonoscopy: assessment of patient preference in a 5-week follow-up study.

PURPOSE: To prospectively evaluate short- and midterm patient preference of computed tomographic (CT) colonography relative to colonoscopy in patients at increased risk for colorectal cancer and to elucidate determinants of preference. MATERIALS AND METHODS: Consecutive patients at increased risk for colorectal cancer underwent CT colonography prior to scheduled colonoscopy. Patient experience and preference were assessed both directly after the examinations and 5 weeks after the examinations. Differences in pain, embarrassment, discomfort, and preference were assessed with the Wilcoxon signed rank sum test or a binomial test. Potential determinants of preference were investigated with logistic regression analyses. RESULTS: Data for 249 patients were included. Fewer patients experienced severe or extreme pain during CT colonography (seven [3%] of 245) than during colonoscopy (81 [34%] of 241) (P < .001). Directly after both examinations, 168 (71%) of 236 patients preferred CT colonography; 5 weeks later, 141 (61%) of 233 patients preferred CT colonography (P < .001). Initially, a painful colonoscopy examination (odds ratio, 0.17; 95% confidence interval [CI]: 0.08, 0.38) was a determinant of CT colonography preference. Similarly, a painful (odds ratio, 3.70; 95% CI: 1.54, 8.92) or an embarrassing (odds ratio, 4.46; 95% CI: 1.18, 16.88) CT colonography examination was a determinant of colonoscopy preference. After 5 weeks, the presence of polyps emerged as a determinant of colonoscopy preference (odds ratio, 1.94; 95% CI: 1.02, 3.70), while the role of experiences waned. CONCLUSION: Patients preferred CT colonography to colonoscopy; however, this preference decreased in time, while outcome considerations gradually replaced temporary experiences of inconvenience.

Computed tomographic colonography compared with colonoscopy in patients at increased risk for colorectal cancer.

BACKGROUND & AIMS: To date, computed tomographic (CT) colonography has been compared with an imperfect test, colonoscopy, and has been mainly assessed in patients with positive screening test results or symptoms. Therefore, the available data may not apply to screening of patients with a personal or family history of colorectal polyps or cancer (increased risk). We prospectively investigated the ability of CT colonography to identify individuals with large (>or=10 mm) colorectal polyps in consecutive patients at increased risk for colorectal cancer. METHODS: A total of 249 consecutive patients at increased risk for colorectal cancer underwent CT colonography before colonoscopy. Two reviewers interpreted CT colonography examinations independently. Sensitivity, specificity, and predictive values were determined after meticulous matching of CT colonography with colonoscopy. Unexplained large false-positive findings were verified with a second-look colonoscopy. RESULTS: In total, 31 patients (12%) had 48 large polyps at colonoscopy. This included 8 patients with 8 large polyps that were overlooked initially and detected at the second-look colonoscopy. In 6 of 8 patients, the missed polyp was the only large lesion. With CT colonography, 84% of patients (26/31) with large polyp(s) were identified, paired for a specificity of 92% (200-201/218). Positive and negative predictive values were 59%-60% (26/43-44) and 98% (200-201/205-206), respectively. CT colonography detected 75%-77% (36-37/48) of large polyps, with 9 of the missed lesions being flat. CONCLUSIONS: CT colonography and colonoscopy have a similar ability to identify individuals with large polyps in patients at increased risk for colorectal cancer. The large proportion of missed flat lesions warrants further study.

Three-dimensional display modes for CT colonography: conventional 3D virtual colonoscopy versus unfolded cube projection.

The authors compared a conventional two-directional three-dimensional (3D) display for computed tomography (CT) colonography with an alternative method they developed on the basis of time efficiency and surface visibility. With the conventional technique, 3D ante- and retrograde cine loops were obtained (hereafter, conventional 3D). With the alternative method, six projections were obtained at 90 degrees viewing angles (unfolded cube display). Mean evaluation time per patient with the conventional 3D display was significantly longer than that with the unfolded cube display. With the conventional 3D method, 93.8% of the colon surface came into view; with the unfolded cube method, 99.5% of the colon surface came into view. Sensitivity and specificity were not significantly different between the two methods. Agreements between observers were kappa = 0.605 for conventional 3D display and kappa = 0.692 for unfolded cube display. Consequently, the latter method enhances the 3D endoluminal display with improved time efficiency and higher surface visibility.

CT colonography: feasibility of substantial dose reduction--comparison of medium to very low doses in identical patients.

In a feasibility study, the authors compared polyp detection and interobserver variability at computed tomographic (CT) colonography in 15 patients with doses ranging from medium to very low (12.00-0.05 mSv). At levels down to 2% of the medium dose, the mean detection of polyps 5 mm or larger remained at least 74%, while the number of false-positive results decreased and the interobserver agreement remained constant. Initial observations indicate that it is feasible to reduce the radiation dose required for CT colonography. Further studies are needed, however, to investigate the clinical value of very low-dose CT colonography.

CT colonography at different radiation dose levels: feasibility of dose reduction.

PURPOSE: To investigate the sensitivity and specificity of polyp detection and the image quality of computed tomographic (CT) colonography at different radiation dose levels and to study effective doses reported in literature on CT colonography. MATERIALS AND METHODS: CT colonography and colonoscopy were performed with 100 mAs in 50 consecutive patients at high risk for colorectal cancer; 50- and 30-mAs CT colonographic examinations were simulated with controlled addition of noise to raw transmission measurements. One radiologist randomly evaluated all original and simulated images for the presence of polyps and scored image quality. Differences in image quality were assessed with the Wilcoxon rank test. Scan protocols from the literature and recent (unpublished) updates were collected. RESULTS: In nine of 10 patients with polyps 5 mm in diameter or larger (sensitivity, 90%) and in seven of 17 patients with polyps smaller than 5 mm, polyps were correctly identified with CT colonography at all dose levels. Specificity for patients without polyps 5 mm or larger was 53%-60% at all dose levels and for patients without any polyps was 26% (at 100 and 50 mAs) and 48% (at 30 mAs). Image quality decreased significantly as the dose level decreased. The median effective doses (supine and prone positions) calculated from protocols reported in the literature and updates were 7.8 and 8.8 mSv, respectively. CONCLUSION: Although image quality decreases significantly at 30 mAs (3.6 mSv), polyp detection remains unimpaired. The median dose for CT colonography at institutions that perform CT colonographic research is currently 8.8 mSv.