Quantitative colorectal cancer perfusion measurement by multidetector-row CT: does greater tumour coverage improve measurement reproducibility?

The purpose of this study was to determine if greater z-axis tumour coverage improves the reproducibility of quantitative colorectal cancer perfusion measurements using CT. A 65 s perfusion study was acquired following intravenous contrast administration in 10 patients with proven colorectal cancer using a four-detector row scanner. This was repeated within 48 h using identical technical parameters to allow reproducibility assessment. Quantitative tumour blood volume, blood flow, mean transit time and permeability measurements were determined using commercially available software (Perfusion 3.0; GE Healthcare, Waukesha, WI) for data obtained from a 5 mm z-axis tumour coverage, and from a 20 mm z-axis tumour coverage. Measurement reproducibility was assessed using Bland-Altman statistics, for a 5 mm z-axis tumour coverage, and 20 mm z-axis tumour coverage, respectively. The mean difference (95% limits of agreement) for blood volume, blood flow, mean transit time and permeability were 0.04 (-2.50 to +2.43) ml/100 g tissue; +8.80 (-50.5 to +68.0) ml/100 g tissue/min; -0.99 (-8.19 to +6.20) seconds; and +1.20 (-5.42 to +7.83) ml/100 g tissue/min, respectively, for a 5 mm coverage, and -0.04 (-2.61 to +2.53) ml/100 g tissue; +7.40 (-50.3 to +65.0) ml/100 g tissue/min; -2.46 (-12.61 to +7.69) seconds; and -0.23 (-8.31 to +7.85) ml/100 g tissue/min, respectively, for a 20 mm coverage, indicating similar levels of agreement. In conclusion, increasing z-axis coverage does not improve reproducibility of quantitative colorectal cancer perfusion measurements.

Comparison of radiologists' confidence in excluding significant colorectal neoplasia with multidetector-row CT colonography compared with double contrast barium enema.

The aim of this study was to compare the confidence of experienced radiologists in excluding colonic neoplasia with CT colonography (CTC) compared with barium enema. 78 patients (median age 70 years, range 61-87 years, 44 women) underwent same day CTC and barium enema. Two radiologists experienced in reporting barium enema assessed whether the examination had excluded a polyp 6 mm or greater as "yes", "probably" or "no" for each of 6 colonic segments. Two different radiologists experienced in CTC independently performed the same assessment on the CT datasets. Responses were compared using a paired exact test. Formal barium enema and CT reports were compared with any endoscopic examination performed within 1 year. Studies reporting polyps 6 mm+ in patients not subsequently undergoing endoscopy were reviewed by two independent observers. Radiologists stated they had confidently excluded a significant lesion in 314 (71%) and 382 (86%) of 444 segments with barium enema and CTC, respectively (p<0.001). Confidence was significantly higher with CTC in the in the descending and ascending colon (p = 0.02 and p<0.001, respectively), and caecum (p<0.001). 22 patients underwent some form of endoscopy. Of five patients with proven colorectal neoplasia (including two with cancer), CTC and barium enema correctly identified five and three, respectively. In 56 patients not undergoing endoscopy, CTC reported 17 polyps 6 mm+, of which 16 were retrospectively classified as definite or probable. 11 could not be identified on the barium enema, even in retrospect. Confidence in excluding polyps 6 mm or larger is significantly greater with CT colonography particularly in the proximal colon.

Intra-individual comparison of patient acceptability of multidetector-row CT colonography and double-contrast barium enema.

AIMS: To compare the subjective acceptability of CT colonography in comparison with barium enema in older symptomatic patients, and to ascertain preferences for future colonic investigation. MATERIALS AND METHODS: The study population comprised 78 persons aged 60 years or over with symptoms suggestive of colorectal neoplasia, who underwent CT colonography followed the same day by barium enema. A 25-point questionnaire was administered after each procedure and an additional follow-up questionnaire a week later. Responses were compared using Wilcoxon matched pairs testing, Mann-Whitney test statistics and binomial exact testing. RESULTS: Participants suffered less physical discomfort during CT colonography (p = 0.03) and overall satisfaction was greater compared with barium enema (p = 0.03). On follow-up, respondents reported significantly better tolerance of CT colonography (p = 0.002), and were less prepared to undergo barium enema again (p < 0.001). Of 52 subjects expressing an opinion, all preferred CT to barium enema. CONCLUSION: Patient satisfaction was higher with CT colonography than barium enema. CT colonography caused significantly less physical discomfort and was overwhelmingly preferred by patients.

Multidetector-row CT duodenography in familial adenomatous polyposis: a pilot study.

AIM: To investigate the feasibility of using multidetector-row computed tomography (CT) duodenography to stage duodenal polyposis in patients with familial adenomatous polyposis. MATERIALS AND METHODS: Six patients underwent multidetector-row CT duodenography before upper gastrointestinal endoscopy. A single-blinded radiologist used a surface shaded three-dimensional endoluminal fly though and two-dimensional axial and multiplanar reformats to assign a score for maximum polyp size and number based on the Spigelman classification. Comparison was made with the corresponding Spigelman scores obtained from subsequent endoscopy. RESULTS: CT duodenography was technically successful in five of six patients. The CT derived Spigelman score based on maximum polyp size was accurate in all five patients. The CT derived Spigelman score based on polyp number was accurate in only two cases: Polyp number was overestimated in one patient and underestimated in a further two. In retrospect, fine carpeting of tiny duodenal polyps was poorly visualized with CT. CONCLUSIONS: CT duodenography is technically feasible and accurately predicts maximum polyp size but CT estimates of polyp number are relatively inaccurate. CT duodenography potentially has a useful role for duodenal surveillance in those patients intolerant of conventional endoscopy.

Local radiological staging of rectal cancer.

Rectal cancer is a common malignancy with a highly variable outcome. Local recurrence is dependent upon tumour stage and surgical technique. The role of pre-operative imaging is to determine which patients may be safely managed by surgery alone and which need additional therapy in order to facilitate surgery and improve outcome. This decision depends on the distinction between those with early and advanced disease. While trans-rectal ultrasound has traditionally been used to answer this question, a role for magnetic resonance imaging (MRI) is increasingly argued. This review will focus on the treatment options for rectal cancer and the clinical questions that subsequently arise for the radiologist to answer.

CT colonography practice in the UK: a national survey.

AIM: To determine the provision of computed tomography (CT) colonography in UK radiology departments. MATERIALS AND METHODS: A questionnaire relating to the availability of CT colonography, barriers to implementation, clinical indications, technique, and practitioners was posted to clinical directors of UK radiology departments. RESULTS: One hundred and thirty-eight departments responded. Fifty (36%) offered CT colonography in day-to-day clinical practice. Of those that did not, 68 of 87 (64%) cited limited scanner capacity as the main barrier. Of the 50 departments offering a service, 39 (78%) offered CT after incomplete colonoscopy, 36 (72%), after failed barium enema, and 37 (74%) as an alternative to barium enema. Of those offering a service, the number of studies performed varied between one per month (38%) to more than one per day (8%). Total experience varied between 20 or fewer studies (28%) to more than 300 (12%). Full bowel preparation was common (92%), as was dual positioning (90%). Colonography was interpreted by radiologists with a subspecialty interest in gastrointestinal imaging in 64% of centres offering a service. CONCLUSION: CT colonography is widely available in the UK, with approximately one-third of responders offering a service. Experience and throughput varies considerably. Limited CT scanner capacity is the major barrier to further dissemination.

Use of multidetector-row CT colonography for detection of colorectal neoplasia in patients referred via the Department of Health "2-Week-wait" initiative.

AIM: Patients referred under the Department of Health 2-week wait initiative with symptoms of colorectal cancer frequently undergo whole-colon examination. We investigated the use of computed tomography (CT) colonography as an alternative to colonoscopy in this scenario. MATERIALS AND METHODS: Fifty-four consecutive patients, referred via the 2-week wait initiative and scheduled for colonoscopy, consented to undergo multidetector CT colonography immediately before endoscopy. The site and morphology of any polyp or cancer detected by CT was noted and comparison made with subsequent colonoscopy. RESULTS: Colonoscopy detected polyps or cancer in 29 patients (53.7%). CT colonography prospectively detected 18 of 41 (44%) polyps of 1-5 mm, three of four (75%) polyps of 6-9 mm, four of four (100%) polyps 10 mm or larger, and five of six (83%) cancers. The missed cancer occurred early in the series and was a perceptive error. The overall sensitivity, specificity, positive predictive value and negative predictive value of CT colonography for cancer and polyps 10 mm or greater on a per patient basis were 90, 100, 100 and 98%, respectively. CT detected one renal cancer and one colonic cancer, initially missed due to incomplete colonoscopy. CONCLUSION: CT colonography is a robust technique for investigation of symptomatic patients. The learning curve must be overcome for optimal performance.

Potential clinical implications of direction of a trans-sphincteric anal fistula track.

BACKGROUND: The longitudinal direction of a trans-sphincteric anal fistula track through the anal sphincter complex may have implications regarding fistulotomy. METHODS: The angle of the track of trans-sphincteric fistulas relative to the longitudinal axis of the anal canal was measured before operation by means of magnetic resonance imaging (MRI) in 46 patients. This was compared with the findings at operation. RESULTS: The track passed cranially as well as laterally at an acute angle (less than 90 degrees ) in 23 patients while it passed either transversely or caudally at an obtuse angle (90 degrees or more) in the remaining 23. The internal opening was significantly higher in relation to the dentate line (above in eight patients, at the dentate line in 14 and below in one patient) when the track was acute than when it was obtuse (above in one, at the dentate line in 17 and below in five patients) (P = 0.004). The fistula track crossed the sphincter at a median angle of 35 degrees, 95 degrees and 132 degrees from internal openings sited above, at and below dentate line level respectively (P = 0.002). CONCLUSION: Fistula tracks passed cranially and laterally through the sphincter complex in half of these patients, and were most acutely angled on MRI when internal openings were situated above the dentate line. Preoperative MRI might alert surgeons to the potential hazard of fistulotomy being more extensive than anticipated from simple palpation of the level of the internal opening.

Optimizing bowel preparation for multidetector row CT colonography: effect of Citramag and Picolax.

AIM: To compare the adequacy and acceptability of Picolax and Citramag bowel cleansing agents for CT colonography. MATERIALS AND METHODS: Multidetector row CT colonography was performed in 124 subjects; 43 had been prepared with Picolax and 81 with Citramag. Datasets were assessed for retained fluid and solid residue, and overall adequacy of segmental visualization. Preparation acceptability was also assessed. RESULTS: There was significantly less retained fluid with Picolax. The odds of being in the next higher category for retained fluid when using Picolax were 0.33 (CI: 0.22-0.50, p<0.0001) when compared with Citramag, for all segments combined. However there was significantly more retained solid residue with Picolax. The odds of being in the next higher category for retained residue when using Picolax were 2.44 (CI: 1.41-4.24, p=0.002) when compared with Citramag, for all segments combined. There was no significant difference with respect to overall segmental visualization: the odds of a segment being adequately visualized when using Picolax were 1.52 (CI: 0.88-2.65, p=0.14) when compared with Citramag. There was no significant difference with respect to acceptability. CONCLUSION: Picolax results in a significantly drier colon than Citramag and associated with more retained residue. We found Picolax the more suitable preparation for CT colonography.

Magnetic resonance imaging for primary fistula in ano.

BACKGROUND: This was a prospective study designed to determine the therapeutic impact of magnetic resonance imaging (MRI) in primary fistula in ano, and to assess its effect on outcome. METHODS: Thirty patients with suspected primary fistula in ano underwent preoperative MRI, and the findings were revealed during surgery following examination under anaesthesia (EUA). Any effect on operative approach was noted. Outcome was assessed at a median of 12 months. RESULTS: Two patients had sinuses, one had no sepsis and 27 had fistulas: five superficial, seven intersphincteric, 14 trans-sphincteric and one suprasphincteric. MRI and EUA agreed in 15 patients and MRI findings altered the surgical approach in a further three (10 per cent); two of the latter patients were believed to have a sinus at EUA, which MRI correctly identified as a fistula, allowing definitive treatment. The therapeutic impact of MRI was therefore 10 per cent. Persisting disagreement between MRI and EUA in 12 patients mostly related to minor discrepancies in classification. Only one patient required further unplanned surgery, which was for skin-bridging rather than any new sepsis. CONCLUSION: In experienced hands, MRI has a therapeutic impact of 10 per cent for primary fistula in ano, precipitating surgery that is likely to reduce recurrence in a small, but important, proportion of patients.

CT colonography: methods, pathology and pitfalls.

Computed tomography colonography (CTC) is a relatively new technique that is currently challenging more established methods of large bowel imaging. Several workers have suggested CTC surpasses the barium enema and approaches conventional endoscopy for detection of colorectal neoplasia. Accurate diagnosis relies on technically good studies, the main aim of which is adequate bowel cleansing and distension. Furthermore, the learning curve is steep and normal colonic anatomy has to be re-learned in a CT context. This review aims to describe the technique, revise the imaging features of both normal and pathological colon, and to highlight potential diagnostic pitfalls and their avoidance.

Endocoil magnetic resonance imaging quantification of external anal sphincter atrophy.

BACKGROUND: Anal function depends on the integrity and quality of the sphincter muscles. The diagnosis of external anal sphincter atrophy on endocoil magnetic resonography has been associated with poor outcome from sphincter repair, although the imaging criteria for atrophy remain unclear. METHODS: Women with intact sphincters on endosonography and either normal (more than 60 cm H(2)O) (n = 9) or low (n = 16) squeeze pressures had endocoil magnetic resonography and electromyography. The area and fat content of the external anal sphincter and puborectalis were measured on mid-coronal magnetic resonography and images were graded as showing normal, intermediate or advanced atrophy. The definition of the external anal sphincter on endosonography and the thickness of the internal anal sphincter were also assessed. RESULTS: Women with a normal anal squeeze pressure had a larger external anal sphincter cross-sectional area (mean(s.d.) 240(56) versus 193(62) mm(2); P = 0.01) with a lower mean fat content (mean(s.d.) 23(4) versus 30(6) per cent; P < 0.001) than those with low squeeze pressures. There was an overall correlation between squeeze pressure, cross-sectional area (r = 0.32, P = 0.02) and fat content (r = - 0.51, P < 0.001). Patients with a thin (less than 2 mm) internal anal sphincter and/or a poorly defined external sphincter on endosonography were more likely to have atrophy (positive predictive value 74 per cent). CONCLUSION: : Potential endosonographic markers for external anal sphincter atrophy are suggested, and a visual scale for endocoil magnetic resonographic assessment has been validated.

Pelvic floor imaging.

A greater awareness of the therapies now available for pelvic floor dysfunction has increased demand for specialized imaging of this region. Some of the techniques required are available at relatively few centers, and the purpose of this review is to introduce the emerging subspecialty of pelvic floor imaging to a more general readership. Pelvic floor anatomy is complex and is being unraveled by means of magnetic resonance (MR) imaging. This is discussed in detail by using a global, rather than a compartmentalized, anatomic approach. The physiology of normal urinary and anal function and the routine clinical tests applied to them are outlined. The imaging techniques involved include MR imaging, endosonography, and fluoroscopy. The main investigations include video urodynamic imaging, evacuation proctography, dynamic cystoproctography, dynamic MR imaging of the pelvic floor, and endoluminal imaging of the anal sphincters with MR imaging and ultrasonography. These are described in detail, and their role with regard to the main pathologic conditions of the pelvic floor--urinary and anal incontinence, constipation, and prolapse--are discussed.

Transvaginal ultrasound examination of women with and without pelvic venous congestion.

AIM: To determine if transvaginal ultrasound, including power Doppler examination, can distinguish between women with and without pelvic congestion. MATERIALS AND METHODS: Thirty-six women with pelvic congestion were prospectively examined using transvaginal ultrasonography and standard uterine and ovarian measurements made. Additionally, planimetric measurements of each ovary were taken using an image analysis program to determine the cross-sectional area of ovarian stroma and follicles, if any. Power Doppler images of adnexal vessels were obtained and planimetric estimates of surface area calculated. A congestion score was assigned to each patient, based on vein number, diameter and morphology on grey-scale scanning. Identical measurements were obtained from 19 asymptomatic women and results compared. RESULTS: There was no significant difference between women with pelvic congestion and controls with respect to power Doppler or grey-scale images of adnexal vessels, or congestion score. However, women with pelvic congestion had significantly larger and multicystic ovaries when compared to controls. CONCLUSIONS: Transvaginal ultrasound measurements of adnexal vasculature, including power Doppler measurements, cannot reliably distinguish women with pelvic congestion from controls. However, ultrasound may remain useful for diagnosis of pelvic congestion, predominantly because it is able to visualize multi-cystic ovaries in these patients.

Gender differences in the longitudinal pressure profile of the anal canal related to anatomical structure as demonstrated on three-dimensional anal endosonography.

BACKGROUND: Anal canal squeeze pressure is assumed to be due to external sphincter contraction, but the contribution of other muscles has not been explored. METHODS: Ten male and ten nulliparous female asymptomatic subjects had three-dimensional anal endosonography and manometry. Incremental squeeze pressures at 0. 5-cm intervals, expressed as a percentage of the maximum pressure recorded anywhere in the canal, were related to the following anatomical levels: puborectalis, overlap between external anal sphincter (EAS) and puborectalis, external and internal anal sphincters, and external anal sphincter only. Levels were determined by coronal and sagittal endosonographic reconstructions. RESULTS: Puborectalis was the same length in men and women (median 23.9 versus 27.1 mm) but represented a greater proportion of the anal canal in women (45 versus 61 per cent; P = 0.02). At the level of puborectalis alone, the pressure generated as a proportion of maximum anal canal pressure was 71 (range 32-100) per cent in men and 62 (range 32-100) per cent in women. At the level of the EAS alone, the pressure was 60 (4-98) per cent in men and 82 (41-100) per cent in women; where the external sphincter was overlapped by puborectalis, the pressure was 98 (60-100) per cent in men and 75 (47-100) per cent in women. CONCLUSION: Maximal anal canal squeeze pressure is found where the puborectalis overlaps the EAS. This segment represents a significant proportion of anal canal length in women.

Dynamic MR imaging of the pelvic floor in asymptomatic subjects.

OBJECTIVE: Dynamic MR imaging may be used as an alternative to dynamic cystoproctography for the evaluation of pelvic floor prolapse and configuration. MR criteria for normality are derived from proctographic studies because no large MR study of asymptomatic individuals has been performed. Our study aimed to define the normal range of dynamic pelvic MR appearances in a large group of asymptomatic individuals. SUBJECTS AND METHODS: Fifty healthy adult volunteers (25 men and 25 women; age range, 20-66 years; mean age, 34 years) were prospectively recruited and examined using dynamic MR imaging. All subjects were interviewed and established as healthy using a validated questionnaire. Axial, coronal, and sagittal MR imaging was performed at rest and during maximum pelvic strain using a static 1.0-T unit and a fast-field-echo sequence, providing 10 slices in 31 sec. Standardized measurements of pelvic configuration were taken, and rest and strain imaging were compared to determine the range of normal appearances. RESULTS: Three women developed a cystocele during maximum pelvic strain, two of whom also showed grade 1 uterocervical prolapse, which was also seen in another woman. Three men showed posterior pelvic floor descent in excess of 3 cm during straining. No rectocele, enterocele, rectal prolapse, or perineal hernia was seen in any subject. CONCLUSION: The normal range of pelvic organ descent in asymptomatic subjects seen on dynamic MR imaging included cystocele, uterocervical prolapse, and excessive anorectal junction descent. Although we encountered pelvic prolapse in seven volunteers, it was infrequent and low grade, suggesting that criteria for abnormality derived from proctography are generally applicable to MR imaging.

Three-dimensional endoanal sonography in assessing anal canal injury.

BACKGROUND: Instrument design limits endosonography of the anal canal to the axial plane, with no capability for longitudinal imaging or measurement. Using three-dimensional reconstructions, the relationship between the radial and linear extent of an anal sphincter tear has been explored, and sex differences in anal canal and sphincter length have been established. METHODS: Three-dimensional reconstructions were performed in 20 controls and 24 patients with faecal incontinence found to have 25 external and five internal sphincter defects. The radial and linear extent of any sphincter tear was measured. In controls the length of the sphincters was compared with the total anal canal length, and the maximum and mean internal sphincter thickness was compared. RESULTS: The radial angle of an internal or external sphincter defect was significantly related to its length (R2 = 96.8 per cent and R2 = 84.4 per cent respectively; both P < 0.001). The anal canal was longer in men than in women (mean(s.d.) 32.6(5.3) versus 25.1(3.4) mm; P < 0.001). The internal anal sphincter was also longer in men (25.6(6.3) versus 19.8(4.0) mm; P < 0.02), but the mean internal sphincter length as a percentage of total anal canal length did not differ (78.3 versus 78.7 per cent; P not significant). The anterior external anal sphincter was longer in men than in women (32.6(5.3) versus 15.3(2.8) mm; P < 0.001), and formed a greater percentage of total anal canal length (100 versus 62.9 per cent; P < 0.001). CONCLUSION: Multiplanar imaging has revealed a direct relationship between the length of a sphincter tear and its radial extent as shown on axial scanning. Marked sex differences in sphincter configuration have been demonstrated. In women the shorter anterior sphincter length highlights the risk of complete sphincter disruption with extensive tears.

Intraobserver and interobserver agreement in anal endosonography.

BACKGROUND: The aim of this study was to determine intraobserver and interobserver agreement for sonographic measurements of anal canal structures using anal endosonography (AES), and to determine interobserver agreement for the diagnosis of anal sphincter disruption. METHODS: Fifty-one consecutive patients referred for AES for the investigation of possible sphincter abnormality were examined. Studies were reviewed by two observers who measured anal canal structures at defined levels and locations, and recorded an opinion on sphincter integrity. Repeated measurements made by each observer were compared to determine intraobserver agreement, and measurements and diagnoses were compared between observers to determine interobserver agreement. RESULTS: Intraobserver agreement was better than interobserver agreement for measurements of anal canal structures. Interobserver limits of agreement for external sphincter measurements spanned 5 mm, whereas those for the internal sphincter spanned 1.5 mm. Interobserver agreement for diagnosis of sphincter disruption and internal sphincter echogenicity was very good (kappa = 0.80 and 0.74 respectively). CONCLUSION: The limits of agreement for intraobserver and interobserver measurements of anal canal structures on AES have been defined. Interobserver assessment of sphincter disruption is very good.