Colon cancer screening with virtual colonoscopy: promise, polyps, politics

Virtual colonoscopy (CT colonography) promises to become a primary method for colorectal cancer screening and return radiologists to a major role in colon cancer prevention. Results from major centers in the United States show accuracy to be comparable to conventional colonoscopy for detection of polyps of significant size--that is, greater than 10 mm--with few false-positives. The advent of virtual colonoscopy has also heightened awareness of the natural history of colonic polyps, particularly in terms of identifying an appropriate target size for detection in colorectal screening programs. Small polyps (<10 mm) are often either hyperplastic on histology or are unlikely to progress to frank cancer in the patient's lifetime and are therefore of little clinical significance for the average adult. Thus, the rationale for detecting and removing each and every colonic polyp regardless of size has come under increasing scrutiny in the context of cost-benefit analysis of various test strategies for colorectal cancer screening. Virtual colonoscopy may allow patients to obtain reliable information about the status of their colonic mucosa noninvasively and thus make a more informed decision as to whether to proceed to conventional colonoscopy for polypectomy.

Periventricular leukomalacia: relationship between lateral ventricular volume on brain MR images and severity of cognitive and motor impairment

PURPOSE

To evaluate the utility of lateral ventricular volume measurements in predicting motor and cognitive impairment severity in children with periventricular leukomalacia (PVL), with or without seizures.

MATERIALS AND METHODS

The charts of children with spastic cerebral palsy and PVL documented on brain magnetic resonance (MR) images were reviewed. Affected children were grouped by motor and cognitive impairment severity and seizure disorder. An age-matched control group was established. Lateral ventricular volumes were measured on two-dimensional T2-weighted spin-echo MR images. Analysis of variance was used to identify significant differences in mean lateral ventricular volume between groups. Paired analyses of differences were performed with the Bonferroni t method.

RESULTS

Thirty-six children (24 boys, 12 girls) with spastic cerebral palsy and PVL and 21 age-matched control subjects (14 boys, seven girls) were identified. Mean lateral ventricular volumes of the moderate and marked motor deficit groups were significantly larger than those of the control and mild motor deficit groups (F = 29.24; alpha = .01). Mean lateral ventricular volumes of all cognitive impairment groups were significantly larger than those of the control and no-cognitive-impairment groups (F = 21.101 alpha = .01). There was no difference in mean lateral ventricular volume between children with PVL with or without seizures.

CONCLUSION

Lateral ventricular volume measurements can be used as quantitative markers of clinical impairment severity and as clinical outcome predictors before formal testing is possible.

A comparison of virtual and conventional colonoscopy for the detection of colorectal polyps

BACKGROUND

Virtual colonoscopy is a new method of imaging the colon in which thin-section, helical computed tomography (CT) is used to generate high-resolution, two-dimensional axial images. Three-dimensional images of the colon simulating those obtained with conventional colonoscopy are then reconstructed off-line. We compared the performance of virtual and conventional colonoscopy for the detection of colorectal polyps.

METHODS

We prospectively studied 100 patients at high risk for colorectal neoplasia (60 men and 40 women; mean age, 62 years). We performed virtual colonoscopy immediately before conventional colonoscopy. We inserted a rectal tube and insufflated the colon with air to the maximal level that the patient could tolerate. We administered 1 mg of glucagon intravenously immediately before CT scanning to minimize the degree of smooth-muscle spasm and peristalsis and to reduce the patient's discomfort.

RESULTS

The entire colon was clearly seen by virtual colonoscopy in 87 patients and by conventional colonoscopy in 89. Fifty-one patients had normal findings on conventional colonoscopy. In the other 49, we identified a total of 115 polyps and 3 carcinomas. Virtual colonoscopy identified all 3 cancers, 20 of 22 polyps that were 10 mm or more in diameter (91 percent), 33 of 40 that were 6 to 9 mm (82 percent), and 29 of 53 that were 5 mm or smaller (55 percent). There were 19 false positive findings of polyps and no false positive findings of cancer. Of the 69 adenomatous polyps, 46 of the 51 that were 6 mm or more in diameter (90 percent) and 12 of the 18 that were 5 mm or smaller (67 percent) were correctly identified by virtual colonoscopy. Although discomfort was not specifically recorded, none of the patients requested that virtual colonoscopy be stopped because of discomfort or pain.

CONCLUSIONS

In a group of patients at high risk for colorectal neoplasia, virtual and conventional colonoscopy had similar efficacy for the detection of polyps that were 6 mm or more in diameter.

Virtual colonoscopy--technique and applications

Virtual colonoscopy is a new method for evaluating the colon which uses thin section computed tomography of the clean air distended colon. The acquired computed tomography data is then subjected to computer manipulation to demonstrate the colonic mucosa. It is a safe, non-invasive, well-tolerated method that has potential as a method of colorectal cancer screening. This review will describe the technique, review preliminary results, and discuss the present and future applications of this technique.

MRI and MRCP in pancreaticobiliary malignancy

Ultrasonography and CT scanning have been the standard techniques for demonstrating pancreatic carcinoma, although MR and more recently even endoscopic ultrasound have shown excellent results. MRCP is a specialized MR technique that shows fluid containing structures in a 2D image display similar to direct ERCP findings. Accuracy of MRCP (sensitivity, specificity) equals or exceeds ERCP for both biliary and pancreatic duct morphology. MRCP does not provide information with regard resectability. MRI can be applied to pancreaticobiliary malignancies as conventional MR, as MR angiography/venography or as MR cholangiopancreatography (MRCP). The technique and applications of each method differ. Although all have been well documented in the literature, their clinical role when compared to other evolving technologies such as helical CT and endoscopic ultrasound is still evolving.

Biliopancreatic malignancy current diagnostic possibilities: an overview

Modern imaging of pancreatic cancer remains a daily challenge both for detection and staging. Helical CT scanning, MRI, and more recently endoscopic ultrasound (EUS) all contribute. Demonstration of local vascular anatomy for assessing resectability is increasingly performed by non-invasive methods such as CT and MR angiography avoiding the need for traditional catheter angiograms. While a variety of primary tumors can occur in the pancreas ductal adenocarcinoma is by far the most important clinically accounting for c.80% of pancreatic neoplasms. Moreover, cancer of the pancreas presents more frequent and complex diagnostic imaging problems than carcinomas of the biliary tract and will form the focus of this discussion.

Occlusive colon carcinoma: virtual colonoscopy in the preoperative evaluation of the proximal colon

PURPOSE

To evaluate the use of preoperative virtual colonoscopy to examine the proximal colon in patients with distal occlusive carcinomas, defined as cancers that cannot be traversed endoscopically.

MATERIALS AND METHODS

Twenty-nine patients with occlusive colorectal carcinomas underwent preoperative virtual colonoscopy with use of a standard protocol. Patients with acute bowel obstruction were excluded. Results of virtual colonoscopy were compared with the findings of preoperative colonoscopy, preoperative barium enema examination, intraoperative colon palpation, histopathologic outcome, and postoperative colonoscopy and barium enema examination, where possible.

RESULTS

Virtual colonoscopy helped identify all 29 occlusive carcinomas and demonstrated two cancers and 24 polyps in the proximal colon. Both synchronous cancers were confirmed intraoperatively and resected. Postoperative conventional colonoscopy in 12 patients confirmed 16 polyps identified at virtual colonoscopy and demonstrated two subcentimeter polyps missed at virtual colonoscopy. Postoperative barium enema examination was performed in two patients and helped confirm two polyps identified at virtual colonoscopy. Virtual colonoscopy successfully demonstrated the proximal colon in 26 of 29 patients examined compared with preoperative barium enema examination, which failed to adequately demonstrate the proximal colon in any patient examined.

CONCLUSION

Virtual colonoscopy is a feasible and useful method for evaluating the entire colon before surgery in patients with occlusive carcinomas.

Colorectal neoplasm detection using virtual colonoscopy: a feasibility study

BACKGROUND

Virtual colonoscopy is a potentially powerful tool for non-invasive colorectal evaluation. In vitro studies have established its accuracy in simulated polyp detection but little data exist regarding its use in clinical practice.

AIMS

To evaluate the ability of virtual colonoscopy to detect colorectal cancers and polyps in patients with endoscopically proven colorectal neoplasms and to correlate the findings of virtual colonoscopy with those of conventional colonoscopy, surgery, and histopathology.

PATIENTS

Thirty eight patients with endoscopic findings suggestive of colorectal carcinoma.

METHODS

Virtual colonoscopy was performed using thin section helical computed tomography (CT) of the abdomen and pelvis after rectal insufflation of room air. Commercially available software was used to generate endoscopic "fly through" examinations of the colon from the CT data. Results were correlated with the findings of conventional colonoscopy and with the surgical and histopathological outcome in each case.

RESULTS

Thirty eight pathologically proven colorectal cancers and 23 adenomatous polyps were present. On virtual colonoscopy, all cancers and all polyps measuring greater than 6 mm in size were identified; there were two false positive reports of polyps. On conventional colonoscopy, there was one false positive report of a malignant sigmoid stricture; four subcentimetre polyps were overlooked. Virtual colonoscopy enabled visualisation of the entire colon in 35 patients; conventional colonoscopy was incomplete in 14 patients. Virtual colonoscopy correctly localised all 38 cancers, compared with 32 using conventional colonoscopy.

CONCLUSION

Virtual colonoscopy is a feasible method for evaluating the colon; it may have role in diagnosis of colorectal cancer and polyps.

Advances in abdominal MR imaging

Major technical advances in MR imaging have led to its wider use in the evaluation of abdominal disease. The principle new pulse sequence is the RARE sequence for T2-weighted imaging. Multishot and breath-hold single-shot RARE techniques are now widely used, and both have performed as well as conventional spin-echo imaging with far shorter acquisition times. The most notable improvements have been in the detection and characterization of hepatic lesions. Two liver-specific contrast agents received FDA approval during 1997: SPIO particles or ferumoxide and mangafodipir trisodium, a hepatocyte-specific agent. Both of these agents provide considerable benefit in the detection and characterization of hepatic lesions. Manganese enhancement has also proved useful in MR imaging of the pancreas, although fat-suppressed T1-weighted imaging with dynamic gadolinium enhancement has also yielded results comparable with those of contrast-enhanced CT. MR hydrography, a generic term for static fluid imaging, is another derivative of RARE fast T2-weighted imaging. MRCP, the best known example of MR hydrography, has been rapidly and widely employed as a primary method for imaging the biliary and pancreatic ducts and has become competitive with ERCP. MR vascular imaging, especially portal venography, has been used for noninvasive imaging of portal venous disease in Budd Chiari disease, before placement of transjugular intrahepatic portosystemic shunts, and for pancreatic cancer staging. Finally, the development of conventional phased-array body coils and endorectal coils has enabled high-quality MR imaging of perirectal disease (including Crohn disease, fistula in ano, and postpartum sphincter dysfunction). Future abdominal applications of MR imaging will involve second-generation MR interventional techniques, including use of open systems, functional or diffusion-weighted imaging exploiting the molecular activity of tissues, and virtual MR endoscopy. Although CT continues to evolve as the premier technique for survey screening of the abdomen, the technical advances in MR imaging have enabled this modality to assume some special nitch roles (in which it adds unique value) in the evaluation of the abdomen. Radiologists can safely assume that there will undoubtedly be much more to come.

MR cholangiopancreatography challenges invasive methods

To gain acceptance, MRCP must accurately visualize both normal and abnormal biliary and pancreatic ducts. Imaging of the non-dilated system remains a technical challenge due to the small caliber of normal ducts. Using either nonbreath-hold or breath-hold techniques, however, the normal common bile duct can be visualized in as many as 98% of patients.

CT colonoscopy of colorectal neoplasms: two-dimensional and three-dimensional virtual-reality techniques with colonoscopic correlation

OBJECTIVE

The aim of this study was to compare the diagnostic accuracy of two-dimensional (2D) CT colonography and three-dimensional (3D) virtual colonoscopy with conventional colonoscopy in patients who have suspected colorectal neoplasms.

SUBJECTS AND METHODS

Twenty patients were studied (eight women and 12 men; mean age, 53 years; range, 42-85 years). All patients had findings on conventional colonoscopy suggestive of colorectal carcinoma and underwent colonic CT within 3 hr of endoscopy. Two-dimensional CT colonography and 3D virtual colonoscopy images were generated from the same data set that was obtained from thin-section helical CT of the abdomen and pelvis after rectal insufflation of room air. Three-dimensional virtual colonoscopy images were obtained by downloading CT data to a workstation equipped with commercially available software. Volume- and perspective-rendering techniques were used to achieve interactive, 3D virtual "fly-through" examinations of the colonic mucosa. The results of 2D CT colonography and 3D virtual colonoscopy were compared with the findings of conventional colonoscopy and correlated with surgical and pathologic outcome where possible.

RESULTS

Twenty masses (defined as intraluminal projections 2 cm or larger in diameter) and 15 polyps (defined as projections smaller than 2 cm in diameter) were identified in our study group. All masses and 14 of 15 polyps were successfully shown on 2D colonography. Three findings of polyps on 2D colonography were false-positive, and one was false-negative. Three-dimensional virtual colonoscopy revealed 19 of 20 masses and 13 of 15 polyps. On conventional colonoscopy, all 20 masses and 13 of 15 polyps were identified, with one false-positive finding of a malignant stricture in a normal colon. Complete examination of the colon was possible in 18 of 20 patients using the 2D technique and in 17 of 20 patients using 3D virtual colonoscopy, whereas conventional colonoscopy showed the entire colon in only 12 of 20 patients.

CONCLUSION

Two-dimensional CT colonography and 3D virtual colonoscopy are complementary and effective techniques for examining the colon in patients with suspected colorectal carcinoma. CT techniques offer several advantages over conventional colonoscopy including the ability to detect abnormalities proximal to obstructing carcinomas, accurate localization of abnormalities within the colon, and good patient tolerance. These CT techniques may play an important role in future diagnosis of colorectal cancer and for screening patients at risk.

MR cholangiopancreatography after unsuccessful or incomplete ERCP

PURPOSE

To assess the value of magnetic resonance (MR) cholangiopancreatography in patients in whom endoscopic retrograde cholangiopancreatography (ERCP) was unsuccessful or did not completely delineate ductal abnormalities.

MATERIALS AND METHODS

MR cholangiopancreatography was performed in 37 consecutive patients because ERCP was unsuccessful (n = 20), postsurgical biliary-enteric anatomy was present (n = 10), or evidence of complete pancreatic duct obstruction was found ar ERCP (n = 7).

RESULTS

MR cholangiopancreatography was successful in all patients. Eleven patients had normal MR findings and required no further intervention. Eight patients has abnormalities that were detected with MR but were followed up clinically. Eleven patients subsequently underwent laparotomy, three underwent therapeutic percutaneous transhepatic cholangiography (PTC), two underwent diagnostic (PTC), and one underwent ultrasound-guided biopsy.

CONCLUSIONS

MR cholangiopancreatography plays an important role in the care of patients in whom ERCP is unsuccessful or incomplete and when technical difficulties can be anticipated.

Magnetic resonance cholangiography: comparison with endoscopic retrograde cholangiopancreatography

BACKGROUND & AIMS

Magnetic resonance cholangiography (MRC) is a noninvasive diagnostic modality capable of producing high-quality images of the biliary tree. The purpose of this study was to determine in a prospective, blinded fashion the sensitivity and specificity of three-dimensional fast spin-echo (3D FSE) MRC for the evaluation of biliary tract abnormalities.

METHODS

Forty-six patients referred for elective direct cholangiography (45 endoscopic retrograde cholangiopancreatography and 1 percutaneous transhepatic cholangiography) were studied prospectively with 3D FSE MRC during a 1-year period. All images were interpreted blindly by two radiologists. The presence of dilatation, strictures, and intraductal abnormalities was recorded. Sensitivity and specificity of 3D FSE MRC were determined using findings on direct cholangiography as the gold standard.

RESULTS

MRC images of diagnostic quality were obtained in 44 (95.7%) of the patients. Sensitivity for the detection of bile duct dilatation (n = 27), biliary strictures (n = 10), and intraductal abnormalities (n = 7) was 96.3%, 90%, and 100%, respectively. In addition, the MRC showed 16 of 17 patients with normal bile ducts (specificity, 94.1%).

CONCLUSIONS

MRC has a very high sensitivity and specificity in the evaluation of the biliary tract. Based on these data, we believe that the efficacy of MRC using 3D FSE is sufficient to warrant its use in the routine diagnosis of biliary tract disease.

Cellular uptake and trafficking of a prototypical magnetic iron oxide label in vitro

RATIONALE AND OBJECTIVES

Target-specific magnetic resonance (MR) contrast agents are being developed to improve the accuracy of MR imaging. The purpose of this study was to determine the mechanism of cell uptake, and modes of intracellular trafficking of a prototypical iron oxide label (RMA) used in the synthesis of some target-specific MR contrast agents.

METHODS

The prototypical agent (RMA) consisted of a dextran-coated monocrystalline iron oxide that was modified with rhodamine (fluorescent label) and opsonized with albumin. Fluorescence microscopy was performed in a phagocytic C6 cell line and in murine bone marrow macrophages. Immunohistochemistry against lysosomal markers was used to confirm the intracellular location of the label.

RESULTS

RMA was identified inside cells after incubation at concentrations as low as 4.0 x 10(-10) M Fe, typically observed with receptor mediated endocytosis and several orders of magnitude lower than that expected with fluid phase pinocytosis. Cell uptake could be inhibited by excess protein but not by dextran. RMA localized initially to tubular and to round intracellular organelles and co-localized with an antibody against a murine lysosomal glycoprotein antibodies (LGP-A) in macrophages. Three days after incubation, RMA was concentrated in perinuclear vesicles, which most likely represent terminal lysosomes where final breakdown appears to occur.

CONCLUSIONS

The mechanism of cellular uptake of a prototypical opsonized iron oxide label is consistent with receptor-mediated endocytosis. Immediately after cell contact, RMA localizes to the lysosomal compartment and at long time points reside in vesicles that by morphology and distribution appear to be terminal lysosomes. Iron oxides therefore demonstrate metabolism via the lysosomal pathway.

MR cholangiopancreatography: efficacy of three-dimensional turbo spin-echo technique

OBJECTIVE

The purpose of this study was to correlate a new three-dimensional turbo spin-echo MR cholangiopancreatography technique with endoscopic cholangiopancreatography or percutaneous cholangiography to determine the efficacy of the new technique for visualizing and diagnosing diseases of the pancreatic and biliary ducts. It was hypothesized that the new technique would provide diagnostic images without prolonged breath holding or a surface coil as required by previous MR techniques.

SUBJECTS AND METHODS

We describe a respiratory-triggered, heavily T2-weighted, three-dimensional, multislab turbo spin-echo sequence for MR cholangiopancreatography. Thirty patients with suspected biliary or pancreatic disease were randomly selected from referrals for endoscopic retrograde cholangiopancreatography. All patients were imaged with the optimized MR technique prior to attempted endoscopic or percutaneous cholangiopancreatography. The MR images were evaluated without additional clinical or radiographic information by consensus opinion of two of the authors for visualization and caliber of the ducts. When the ducts were abnormal, the level and probable cause were categorized as follows: normal, periampullary stricture, localized duct stenosis, multifocal strictures, calculous disease, duct anomalies, and cystic disease. The images obtained by conventional percutaneous or endoscopic cholangiopancreatography were evaluated in the same manner with the exception that additional clinical and radiologic information was provided. The diagnostic categories determined by MR and direct cholangiopancreatography were compared. Patients were included in the analysis only if endoscopic or percutaneous opacification of the biliary or pancreatic ducts was successful.

RESULTS

Diagnostic MR images were obtained in 29 (97%) of 30 patients. Endoscopic or percutaneous cholangiopancreatography was successful in 21 of the 29 patients for the common bile duct and in 17 of the 29 patients for the pancreatic duct. The diagnosis for the common bile duct by the MR technique agreed with the diagnosis by endoscopic or percutaneous cholangiopancreatography in 19 (90%) of 21 patients. For diagnosis of diseases of the pancreatic duct, there was agreement in 15 (88%) of 17 patients.

CONCLUSION

Respiratory-triggered, multislab, three-dimensional turbo spin-echo MR cholangiopancreatography is a noninvasive technique for visualization of the pancreatic and biliary ductal systems. It is capable of providing diagnostic information equivalent to invasive techniques in a large percentage of patients and should be the technique of choice when invasive techniques are incomplete, unsuccessful, or technically difficult.

Pancreatic duct: MR cholangiopancreatography with a three-dimensional fast spin-echo technique

PURPOSE

To determine the role of three-dimensional fast spin-echo magnetic resonance (MR) cholangiopancreatography in the evaluation of the normal and abnormal pancreatic duct.

MATERIALS AND METHODS

A non-breath-hold MR cholangiopancreatographic technique with use of a body coil was compared with direct pancreatography performed with endoscopic retrograde cholangiopancreatography in 37 patients.

RESULTS

MR cholangiopancreatograms of satisfactory quality were obtained in 92% of patients. Sensitivity for detection of pancreatic duct dilatation (n = 15) was 100% and 87% (observers 1 and 2, respectively). Among patients with pancreatic duct strictures (n = 8), 75% of the strictures were detected; there was a single false-positive finding. Specificity for both observers was 69% for the maximum intensity projection reconstructions and increased to 81% with review of the source images. Four of six cases of pancreas divisum (67%) and two cases of pancreatic duct stones were demonstrated. Interobserver agreement was moderate to substantial, as assessed with kappa-analysis.

CONCLUSION

MR cholangiopancreatography can accurately demonstrate the normal pancreatic duct as well as various pancreatic duct abnormalities.

Treatment of pelvic abscesses: value of one-step sonographically guided transrectal needle aspiration and lavage

OBJECTIVE

The percutaneous treatment of pelvic abscesses has traditionally involved the placement of drainage catheters via a transgluteal, transrectal, or transvaginal route. These procedures are painful and prolonged. The goal of this study was to demonstrate the effectiveness of a one-step, single-puncture method for draining pelvic abscesses by use of a transrectal sonographically guided needle for aspiration and lavage instead of a two-step Seldinger technique for catheter placement.

SUBJECTS AND METHODS

Thirty-three pelvic abscesses in 24 patients were drained by use of transrectal ultrasound guidance. All abscesses were initially seen on transrectal sonograms or CT scans and ranged from 2 to 11 cm in diameter. Abscesses were located in the prostate (n = five), seminal vesicles (n = five), pouch of Douglas (n = 21), and interloop (between bowel loops) (n = two). Causes of pouch of Douglas (cul-de-sac) abscesses included appendicitis (n = two), Crohn's disease (n = two), diverticulitis (n = three), trauma (n = six), HIV infection (n = two), complications of sigmoidectomy (n = one), complications of colectomy (n = one), pelvic inflammatory disease (n = two), and severe prostatitis (n = two). Interloop abscesses were attributable to HIV infection (n = one) and lymphoma (n = one). The procedure was performed without a cleansing enema or local anesthesia and required less than 30 min. An 18-gauge needle was inserted transrectally into the abscess cavity under transrectally guided sonography. The fluid collection was completely aspirated, and the cavity was lavaged with saline. Administration of antibiotics for 7-21 days, rather than prolonged catheter drainage, was used to treat residual infection. Resolution was documented after 7 days by sonography or CT examination.

RESULTS

Transrectal aspiration was successful in treating 28 (85%) of the 33 pelvic abscesses in 21 (88%) of the 24 patients. Failure occurred in three patients, two with multiple abscesses and one with an enteric fistula for whom surgical drainage was subsequently required. The volume of aspirates ranged from 5 to 220 ml. There were no complications.

CONCLUSION

Transrectal sonographically guided needle aspiration-lavage offers a one-step method for treating pelvic abscesses that does not require catheter placement or prolonged drainage. The procedure produces minimal discomfort and essentially no complications. Our results show that transrectal sonographically guided needle aspiration combined with antibiotic therapy is an effective treatment for pelvic abscesses.

Dissolution of calcified gallstones. Part II. Evaluation of edetic acid preparations for dissolution of residue after in vitro methyl tert-butyl ether treatment

RATIONALE AND OBJECTIVES

The authors assessed the potential of edetic acid (EDTA) preparations to dissolve the residue of calcified gallstones partially treated with methyl tert-butyl ether (MTBE).

METHODS

Nineteen triplets (57 gallstones) were submitted to dissolution in EDTA, urea-EDTA, and an MTBE control for 48 hours after initial partial dissolution in MTBE for 24 hours. Results were compared with findings at specimen computed tomography and crystallographic analysis. All data were corrected for differences in stone size.

RESULTS

In all three treatment groups (EDTA, urea-EDTA, MTBE), almost identical dissolution outcomes were observed within each triplet. Most triplets that dissolved displayed a laminated or a core-calcification pattern and consisted primarily of cholesterol. Specimens that dissolved poorly in all three groups displayed dense calcifications or thick calcified rims and were classified as pigment stones.

CONCLUSION

Because no statistically significant differences in dissolution were found among the EDTA, urea-EDTA, and MTBE treatments, we conclude that EDTA preparations are not superior to the continued use of MTBE for dissolution of residue after initial MTBE treatment.

Dissolution of calcified gallstones. Part I. Correlation of in vitro dissolution kinetics in methyl tert-butyl ether with patterns of calcification by computed tomography

RATIONALE AND OBJECTIVES

The authors evaluated the relationship between stone computed tomography (CT) attenuation patterns and the kinetics of dissolution with methyl tertbutyl ether (MTBE).

METHODS

Single moderately and heavily calcified gallstones from 40 patients were selected from a gallstone library and classified for pattern of calcification by in vitro CT scan (dense, rim, core, and laminated). Each stone was placed in a 10-mL aliquot of MTBE for 24 hours. Stone residue was blotted dry and weighted at 8, 16, and 24 hours. Results were normalized with respect to stone size.

RESULTS

Only 1 of 40 (4%) specimens dissolved to particulate matter that was smaller than 2 mm. All (6 of 6) stones that were densely calcified showed virtually no dissolution. The rate of gallstone dissolution varied temporally within the rim, core, and laminated stone categories and was related to the composition of the layer exposed to the solvent at any given time.

CONCLUSION

The success and rate of dissolution may be predicted by the pattern of calcification as determined by computed tomography (CT).

Prediction of gallstone composition: synthesis of CT and radiographic features in vitro

PURPOSE

To test a morphoradiographic algorithm designed to predict the composition of gallstones with use of computed tomography (CT) to define calcification patterns.

MATERIALS AND METHODS

Two reviewers retrospectively evaluated the radiographic features of 120 separate in vitro specimens (59 radiopaque and 61 radiolucent), then classified the stones into several categories of composition with the algorithm.

RESULTS

The most useful features for prediction of cholesterol composition were, in order of decreasing importance, stone shape, absence of dense calcification on plain radiographs, overall CT attenuation not higher than that of water, presence of a second generation of smaller stones, and a peripheral cover of calcification detected on CT scans of aging cholesterol stones. The greatest error occurred in distinction between stones with mixed composition (50%-79% cholesterol) and older stones with higher cholesterol content (80%-95% cholesterol).

CONCLUSION

The range of qualitative CT appearances advances the possibility of predicting gallstone composition and potential outcome of nonsurgical treatment.

Liver tumor imaging. Current concepts

With the increasing availability of curative surgical techniques for primary and secondary hepatic neoplasms, the tasks for clinical imaging of patients suspected of having liver cancer have become more exacting. Detection of tumor, differential diagnosis of individual nodules, and mapping the anatomic extensions of malignant disease are now required routinely. The most sensitive imaging techniques are computed tomography and arterial portography and intraoperative sonography, but because of their invasiveness, there are reserved exclusively for cancer staging. For primary screening, magnetic resonance imaging is increasingly preferred over computed tomography because of its superiority in discriminating hemangiomas and cysts from metastases without the need for iodinated contrast material.

Screening for colon cancer: controversies and recommendations

Colorectal cancer is the second most common cause of overall cancer mortality in the United States. This article review pertinent clinical and policy issues, details current colorectal cancer screening concepts, summarizes American College of Radiology achievements to date, and outlines projects in the next phase of the effort.

Accumulation of iron oxide particles around liver metastases during MR imaging

The histologic nature of the bright ring ("peritumoral edema") around some liver metastases on T2-weighted magnetic resonance (MR) images is controversial. In the case reported, particles of the iron oxide contrast agent AMI-25 are retained in the peritumoral zone of a colon cancer metastasis, causing the bright ring to disappear. The location of iron particles in resected specimens could be used systematically to study peritumoral edema.

Percutaneous obliteration of the cystic duct with a holmium:yttrium-aluminum-garnet laser: results of in vitro and animal experiments

OBJECTIVE

The purpose of this study was to investigate the feasibility of using a holmium:yttrium-aluminum-garnet laser to permanently occlude the cystic duct in order to isolate the gallbladder from the biliary-enteric circulation and prevent gallstone formation.

MATERIALS AND METHODS

To determine the optimal laser parameters (power and pulsing rate) for cystic duct thermocoagulation, 20 freshly excised porcine gallbladders with intact cystic ducts underwent low-energy (0.075-0.085 J/pulse) or high-energy (0.20-0.25 J/pulse) thermocoagulation. Histopathologic examination was done to determine the extent of cystic duct injury. After in vitro experiments, percutaneous transcholecystic laser thermocoagulation of the cystic duct was performed on 23 anesthetized domestic pigs (four controls). Cholangiograms immediately after laser thermocoagulation were obtained to assess cystic duct occlusion. Animals were sacrificed for histopathologic correlation immediately after laser thermocoagulation (n = 4), 72 hr later (n = 4), and 6 weeks later (n = 15).

RESULTS

In the in vitro studies, all 10 cystic ducts in the high-energy group were occluded, while only four in the low-energy group were occluded. At histology, all cases in both groups showed circumferential injury to the cystic duct wall without injury to the cystic artery or vein. In the in vitro experiments, the cystic duct was successfully cannulated in 21 (91%) of 23 animals. Cholangiography after thermocoagulation showed occlusion of the cystic duct in 16 (84%) of 19 cases. Immediately after laser thermocoagulation, the cystic duct mucosa was circumferentially destroyed, whereas after 72 hr necrosis of the cystic duct wall and periductal tissues had occurred. By 6 weeks, all pigs had complete cystic duct fibrosis without injury to the common bile duct.

CONCLUSION

Holmium:yttrium-aluminum-garnet laser thermocoagulation of the cystic duct can be performed easily, results in immediate cystic duct occlusion, and leads to permanent fibrous ductal obliteration by 6 weeks.

Percutaneous chemical gallbladder sclerosis after laser-induced cystic duct obliteration: results in an experimental model

OBJECTIVE

Chemical gallbladder sclerosis has been attempted as a way to defunctionalize the gallbladder in patients who have undergone nonsurgical removal of gallstones and who are unable to undergo surgical/laparoscopic cholecystectomy. The purpose of this investigation was threefold: to study an animal model for chemical sclerosis of the gallbladder with 95% ethanol and 3% sodium tetradecyl sulfate, to attempt chemical sclerosis immediately after percutaneous cystic duct obliteration by laser thermocoagulation, and to assess histopathologic changes in the gallbladder after sclerosis.

MATERIALS AND METHODS

Percutaneous cholecystostomy and laser thermocoagulation of the cystic duct was performed in 13 pigs. Eight pigs underwent immediate gallbladder sclerosis with 95% ethanol and 3% sodium tetradecyl sulfate while two pigs received 95% ethanol only. The remaining three pigs served as controls. The cholecystostomy catheter was removed immediately after the procedure. All animals were sacrificed 6 weeks after laser thermocoagulation. Multiple sections through the gallbladder, which included the adjacent liver, the cystic duct, and the common bile duct, were obtained for histologic examination.

RESULTS

At autopsy, the gallbladder in all 10 animals who underwent gallbladder sclerosis was reduced in size compared with controls. In all treated animals, the gallbladder mucosa was denuded; however, in nine of 10 cases reepithelialization had occurred. Complete sclerosis without reepithelialization was achieved in one pig who received both ethanol and sodium tetradecyl sulfate. In the two animals who received ethanol only, the depth of wall necrosis around the gallbladder lumen was less than in those pigs who received both ethanol and sodium tetradecyl sulfate. No pigs showed signs of hepatic necrosis or injury to the common bile duct.

CONCLUSION

Cystic duct laser thermocoagulation allows immediate gallbladder sclerotherapy without injury to the common bile duct. Sclerosis with ethanol and sodium tetradecyl sulfate results in denudation of the gallbladder mucosa. However, a single therapeutic session with immediate removal of the cholecystostomy catheter was inadequate for gallbladder ablation in this model because of reepithelialization.

Liver tumor imaging: current concepts

With the increasing availability of curative surgical techniques for primary and secondary hepatic neoplasms, the tasks for clinical imaging of liver cancer suspects have become more exacting. Detection of tumor, differential diagnosis of individual nodules, and mapping the anatomic extensions of malignant disease are now routinely required. Related and unrelated liver substrate abnormalities such as cavernous hemangioma and focal fatty deposits are often discovered in liver cancer suspects and must be differentiated from metastatic deposits. Moreover, modern imaging methods frequently display tiny subcentimeter nodules which often prove difficult to adequately characterize (micrometastases vs other). The most sensitive imaging techniques are CT after arterial portography and intraoperative ultrasound, but because of their invasiveness, these are reserved exclusively for staging. For primary screening MR imaging is increasingly preferred over CT because of its superiority in discriminating hemangiomas and cysts from metastases without the need for iodinated contrast material.

Iron oxide enhanced MR imaging of the liver and spleen: review of the first five years

Superparamagnetic iron oxide (SPIO) particles are a potent new class of MR contrast agents affording improved detection of hepatic and splenic neoplasms. In this report we review the development of this agent through preclinical studies and early clinical results at Massachusetts General Hospital during a 5 year investigation. SPIO particles are sequestered by normal reticuloendothelial system (RES) phagocytic Kupffer cells but are not retained in tumor tissue. Consequently, there is a five fold increase in T2 relaxation between normal RES tissue and tumor with a comparable advantage in quantitative signal to noise ratio, contrast to noise ratio and lesion detectibility in the liver and spleen at MR imaging. Increased lesion conspicuity can be exploited to decrease threshold size for lesion detection to less than 3 mm. Clinically beneficial effects occur with a variety of mildly T2-weighted spin-echo pulse sequences; gradient-echo techniques show even greater benefit after administration of SPIO. Metabolically, pharmaceutical grade preparations are biodegradable and bioavailable, being rapidly turned over into body iron stores and incorporated into erythrocyte hemoglobin. Early dose escalation clinical trials have identified a probable clinical dose range of 10-20 mumol Fe/kg body weight. SPIO compounds evaluated to date are still investigational in the United States. Newer commercial formulations currently being evaluated may extend clinical safety margins.

Percutaneous contact dissolution of gallstones: complexity of radiologic care

The clinical and technical considerations for successful gallstone dissolution with methyl tert-butyl ether (MTBE) are often underestimated. Patients are selected for MTBE therapy on the basis of a functioning gallbladder without evidence of acute inflammation or calcified stones at plain radiography. A transhepatic route is favored for percutaneous insertion of the cholecystostomy catheter because of the theoretic reduced frequency of bile leakage. MTBE is delivered manually through the catheter in a closed system, with dissolution times of 4-16 hours. After MTBE dissolution, residual debris in the gallbladder is present at follow-up sonography in up to 75% of patients. The high frequency of residual debris, the potential for stone recurrence, and the labor-intensive nature of MTBE therapy make its future uncertain, especially with the advent of laparoscopic cholecystectomy.

Optimal technique for detection of gallstones at injection cholecystography: in vitro analysis

Injection cholecystography is often employed during invasive gallbladder procedures to determine the number of gallstones that are present. The authors undertook this study to define the optimal radiographic technique for performance of injection cholecystography. Condoms filled with 100 mL of contrast medium at four different iodine concentrations (30%, 15%, 7.5%, and 3.8% [wt/vol]) and containing up to five 4-mm-thick gallstones or a single 10-mm-thick gallstone were radiographed in a 20-cm-deep water bath by using four kilovolt peak settings (70, 80, 90, and 100 kVp). Images were read by three radiologists who were blinded to the radiographic technique. significantly (P less than .05) improved Decreasing iodine concentration significantly (P less than .05) improved detection of 4-mm-thick gallstones at a constant kilovolt peak setting. However, increasing the kilovolt peak setting while using the same concentration of contrast medium had no statistically significant influence on gallstone detectability, although radiologists did indicate a preference for the high-kilovolt peak technique. Results of the authors' experiments showed that for detection of small gallstones at injection cholecystography, use of a low-concentration contrast medium and a high kilovolt peak setting is the recommended radiographic technique.

Perfusion characteristics of hepatic cavernous hemangioma using intravenous CT angiography (IVCTA)

Thirty-three patients with 35 proven hepatic cavernous hemangiomas (HCH) were studied with intravenous CT angiography (IVCTA). 15 scans were performed during the first 30 s after bolus (6 ml/s) injection of 50 ml iodinated contrast material. Thereafter 2 scans/min were obtained up to 30 min. Three criteria were utilized at IVCTA to make a specific diagnosis of HCH: (1) detection of an intense mural nodular enhancement in the arterial phase. The density in the nodular region(s) should have a density level similar to that of the aorta or hepatic arteries; (2) well-defined nodular area(s); and (3) centripetally oriented enlargement of the nodular region(s). These criteria were seen in 31 of 35 hemangiomas. In contrast the 'typical' Freeny-Marks criteria were present in only 23 of 35 hemangiomas. The results show that our criteria may provide greater specificity.