Colonoscopía virtual de screening de cáncer colorrectal en pacientes con enfermedad diverticular / Virtual colonoscopy for colorectal cancer screening in patients with diverticular disease

CONTEXTO: El cáncer colorrectal (CCR) es un problema de salud pública en todo el mundo y particularmente em nuestro país, dada su elevada incidencia. En Argentina, según las estimaciones de incidencia del Observatorio Global de Cáncer de la OMS se estimaron 15.692 casos nuevos para el año 2018 en ambos sexos, concentrando el 13% del total de tumores, siendo el segundo cáncer más frecuente, por detrás del cáncer de mama en mujeres y el cáncer de próstata en hombres. En Argentina el CCR es el segundo cáncer de mayor mortalidad (luego del cáncer de pulmón), con más de 7.000 fallecimientos anuales. TECNOLOGÍA: La colonoscopía tomográfica computarizada, también conocida como colonoscopía virtual, fue desarrollada como un método mínimamente invasivo para examinar el colon.5 Se ha sugerido el uso de esta prueba para la detección de anomalías en el colon y el recto como por ejemplo, CCR y pólipos. Esta tecnología implica el uso de tomografía computarizada helicoidal (TC) e imágenes generadas por computadora para producir imágenes bidimensionales y tridimensionales (3D) de alta resolución del colon y el recto. OBJETIVO: El objetivo del presente informe es evaluar la evidencia disponible acerca del desempeño diagnóstico, la eficacia, seguridad y aspectos relacionados a las políticas de cobertura del uso de colonoscopia virtual para screening de CCR en pacientes con enfermedad diverticular. MÉTODOS: Se realizó una búsqueda en las principales bases de datos bibliográficas, en buscadores genéricos de internet, y financiadores de salud. Se priorizó la inclusión de revisiones sistemáticas (RS), ensayos clínicos controlados aleatorizados (ECAs), evaluaciones de tecnologías sanitarias (ETS), evaluaciones económicas, guías de práctica clínica (GPC) y políticas de cobertura de diferentes sistemas de salud. RESULTADOS: Se incluyeron cuatro RS, un ECA, seis GPC, dos informes de ETS, una RS de evaluaciones económicas, y 12 informes de políticas de cobertura de CTC en screening de CCR en pacientes con enfermedad diverticular. CONCLUSIONES: No se encontraron estudios que comparen de forma directa la utilización de colonoscopía virtual por tomografía computarizada contra otros métodos diagnósticos (excluyendo enema de bario de doble contraste) para el screening de cáncer colorrectal en pacientes con enfermedad diverticular. La decisión del método a utilizar podría basarse en consideraciones clínicas y preferencia de los pacientes y cuestiones como la accesibilidad a las diferentes modalidades de cribado. Se encontró evidencia de moderada calidad que sugiere que la colonoscopía virtual tiene uma sensibilidad superior al enema de bario de doble contraste en el screening de cáncer colorrectal em la población general y podría inferirse que también la tendría en pacientes con enfermedad diverticular. Financiadores públicos y privados de países de altos ingresos cubren el uso de colonoscopía virtual en el screening de cáncer colorrectal en pacientes con antecedentes de videocolonoscopía incompleta o en los que la videocolonoscopía se encuentra contraindicada. Esta tecnología no es mencionada en el Programa Médico Obligatorio ni es reintegrada por el Sistema Único de Reintegro de la Argentina. Esta tecnología se encuentra recomendada por guías de práctica clínica como técnica de screening de cáncer colorrectal y en Argentina el Instituto Nacional del Cáncer la recomienda como uma alternativa válida para el tamizaje luego de una videocolonoscopía incompleta.

History, evolution, and current status of radiologic imaging tests for colorectal cancer screening.

Colorectal cancer screening is thought to be an effective tool with which to reduce the mortality from colorectal cancer through early detection and removal of colonic adenomas and early colon cancers. In this article, we review the history, evolution, and current status of imaging tests of the colon-including single-contrast barium enema, double-contrast barium enema, computed tomographic (CT) colonography, and magnetic resonance (MR) colonography-for colorectal cancer screening. Despite its documented value in the detection of colonic polyps, the double-contrast barium enema has largely disappeared as a screening test because it is widely perceived as a labor-intensive, time-consuming, and technically demanding procedure. In the past decade, the barium enema has been supplanted by CT colonography as the major imaging test in colorectal cancer screening in the United States, with MR colonography emerging as another viable option in Europe. Although MR colonography does not require ionizing radiation, the radiation dose for CT colonography has decreased substantially, and regular screening with this technique has a high benefit-to-risk ratio. In recent years, CT colonography has been validated as an effective tool for use in colorectal cancer screening that is increasingly being disseminated.

Flexible sigmoidoscopy does not significantly increase polyp and cancer detection yield when used to supplement CT colonography.

BACKGROUND AND AIMS: Flexible sigmoidoscopy (FS) increases polyp and carcinoma detection in addition to double contrast barium enema (DCBE). However, CT colonography (CTC) is now the preferred technique. Our aim was to explore whether FS increases polyp and carcinoma detection rates when used in addition to CTC. METHODS: Patients who underwent FS and CTC between 2007 and 2009 were included and data were collected from patient records. Yields of polyp, adenoma and carcinoma detection were calculated for FS and CTC. RESULTS: In a cohort of 294 patients, CTC detected 36 patients with carcinomas while FS detected 28. One rectal cancer not seen on CTC was diagnosed by FS. Polyps were seen by CTC in 66 and FS in 45 patients. In 5 patients FS found polyps that were not detected by CTC; 3 of which were small adenomas. FS detected extra adenomas or carcinomas in 1.36% (4/294). Adding FS to CTC neither increased the cancer nor the polyp detection yield significantly. CONCLUSIONS: This first study investigating the use of FS in addition to CTC detected little additional pathology. The routine use of FS as a supplement to CTC for adenoma and carcinoma detection is of questionable utility.

Dose optimisation of double-contrast barium enema examinations.

The purpose of the present work was to optimise the filtration and dose setting for double-contrast barium enema examinations using a Philips MultiDiagnost Eleva FD system. A phantom study was performed prior to a patient study. A CDRAD phantom was used in a study where copper and aluminium filtration, different detector doses and tube potentials were examined. The image quality was evaluated using the software CDRAD Analyser and the phantom dose was determined using the Monte Carlo-based software PCXMC. The original setting [100 % detector dose (660 nGy air kerma) and a total filtration of 3.5 mm Al, at 81 kVp] and two other settings identified by the phantom study (100 % detector dose and additional filtration of 1 mm Al and 0.2 mm Cu as well as 80 % detector dose and added filtration of 1 mm Al and 0.2 mm Cu) were included in the patient study. The patient study included 60 patients and up to 8 images from each patient. Six radiologists performed a visual grading characteristics study to evaluate the image quality. A four-step scale was used to judge the fulfillment of three image quality criteria. No overall statistical significant difference in image quality was found between the three settings (P > 0.05). The decrease in the effective dose for the settings in the patient study was 15 % when filtration was added and 34 % when both filtrations was added and detector dose was reduced. The study indicates that additional filtration of 1 mm Al and 0.2 mm Cu and a decrease in detector dose by 20 % from the original setting can be used in colon examinations with Philips MultiDiagnost Eleva FD to reduce the patient dose by 30 % without significantly affecting the image quality. For 20 exposures, this corresponds to a decrease in the effective dose from 1.6 to 1.1 mSv.

Evaluation of patient dose for barium enemas and CT colonography in Japan.

The objective of this study was to assess patient doses for examinations of the lower digestive tract (barium enemas and CT colonography) in Japan. These doses were evaluated from in-phantom dose measurements using a dosemeter-implanted anthropomorphic phantom and from the knowledge of procedures of these examinations. For barium enemas, the doses, which were the sums of doses for various projections in the procedure, were separately derived for fluoroscopy and for analogue and digital radiography. For CT colonography, the doses were evaluated for the prone and the supine positions, each including the doses by scout imaging, and a single abdominal scan for routine and low-dose set-ups. For barium enemas, maximum local skin doses were less than 100 mGy despite relatively long average fluoroscopy times of 8 min; organ doses ranged from 9-26 mGy in the abdomen. The effective dose of 10.7 mSv for analogue radiography decreased by 12% when digital radiography was used, although more than 80% of the dose was due to fluoroscopy. In routine CT colonography performed using a relatively high mean effective mAs of 119 for the accurate detection of colorectal cancer and extra colonic lesions, organ doses within the primary X-ray beam were between 30 mGy and 44 mGy for paired scans whereas, in a low-dose set-up with an effective mAs of 27, they were approximately 10 mGy. Effective doses for routine and low-dose CT colonography of 23.4 mSv and 5.7 mSv were about double and half of the doses for barium enemas, respectively.

Development of a cathartic-free colorectal cancer screening test using virtual colonoscopy: a feasibility study.

OBJECTIVE: The purpose of our study was to develop a method to subtract barium-labeled stool from the colon using a phantom and to evaluate the performance of the technique in a pilot human population. MATERIALS AND METHODS: A phantom containing 6-mm flat polyps and three types of simulated stool (homogeneous, moderately heterogeneous, and severely heterogeneous) mixed with barium was created, scanned, and tested using three stool subtraction algorithms but no cathartic. Thirty patients with suspected colorectal polyps were studied using stool tagging to determine which was the most effective stool subtraction algorithm. Colonoscopy was the reference standard. Examinations were evaluated blindly using the unsubtracted and 6 weeks later both the unsubtracted and subtracted data sets. RESULTS: A threshold of 200 H and expansion and convolution techniques were the most effective tools for subtracting stool and minimizing artifacts. When applied to the human population, sensitivities using the unsubtracted data sets were 90% (18/20) and 68% (26/38) for polyps > or = 1 cm and > or = 5 mm, respectively. Specificities were 100% (4/4) and 75% (3/4) for polyps > or = 1 cm and > or = 5 mm. For the stool-subtracted data sets, sensitivities were 90% (18/20) and 71% (27/38) for polyps > or = 1 cm and > or = 5 mm. Per patient sensitivities were 88% (15/17) and 77% (20/26) for > or = 1 cm and > or = 5 mm polyps. Specificities were 100% (4/4) for large polyps and 25% (1/4) for smaller polyps. CONCLUSION: Image processing tools combining thresholding, expansion, and convolution were the most useful for stool subtraction. Laxative-free colon examinations using barium for stool labeling can be performed at CT colonography with or without stool subtraction with high accuracy. Further study is warranted.

[Virtual CT colonoscopy and virtual CT barium enema using multidetector-row CT].

CT colonography is a promising technique that provides both multiplanar and endoluminal perspective of the air-filled, distended, cleaned colon. "Virtual colonoscopy" refers to computer-simulated 3D endoscopic visualization of the colonic mucosal surface. Unlike barium enema and conventional colonoscopy, CT colonography can give cross- sectional and endoluminal images of the colon and enables to image extracolic abnormality. CT colonography offers potential advantages over colonoscopy in that it causes little discomfort to the patient, and does not need sedation. It is more accurate in spatial location of lesions and creates no complication. To date, most studies assessing CT colonography have focused in technical development, less aggressive bowel preparation, and computer-aided diagnosis of polyp detection. In the future, CT colonography would be a diagnostic and screening tool for the colorectal polyp and cancer.

Multidetector-row CT of the Gastrointestinal Tract / 대한소화기학회지

Recently, the availability of multidetector-row CT (MDCT) and continuous refinement in three-dimensional (3D) imaging process have greatly expanded the role of CT in evaluating patients with gastrointestinal diseases. MDCT is the latest advancement in CT technology and is now more readily available. This imaging modality can offer full examination of the entire intestinal tract as well as powerful information about the bowel itself and its surrounding structures, which are inherent advantages of CT over conventional barium or optical endoscopic studies. In most cases, MDCT with various 3D technologies can make an easy, rapid, and accurate diagnosis by one-stop imaging, and enables to avoid other examinations. Therefore, knowledge and awareness of valuable clinical applications and proper scan technique of MDCT imaging is essential to achieve the diagnostic goal of one-step imaging.