CAD techniques, challenges, and controversies in computed tomographic colonography

Computer-aided diagnosis (CAD) for computed tomographic colonography (CTC) automatically detects the locations of suspicious polyps and masses on CTC and provides radiologists with a second opinion. CAD has the potential to increase radiologists' diagnostic performance in the detection of polyps and masses and to decrease variability of the diagnostic accuracy among readers without significantly increasing the reading time. Technical developments have advanced CAD substantially during the past several years, and a fundamental scheme for the detection of polyps has been established. The most recent CAD systems based on this scheme produce a clinically acceptable high sensitivity and a low false-positive rate. However, CAD for CTC is still under active development, and the technology needs to be improved further. This report describes the expected benefits, the current fundamental scheme, the key techniques used for detection of polyps and masses on CTC, the current detection performance, as well as the pitfalls, challenges, controversies, and the future of CAD.

Diagnostic performance of virtual colonoscopy

The most important diagnostic performance of virtual colonoscopy is the ability to detect colorectal polyps. However, its diagnostic value for evaluation of patients undergoing incomplete colonoscopy and the ability to detect unsuspected extracolonic findings are also important diagnostic features. Because of important differences between published patient populations, a meta-analysis combining data from different studies would not provide a reliable statistic. The by-patient sensitivity for patients with polyps 10 mm and larger ranges from 75% to 100% in most series and was 100% in the two largest series published to date. By-polyp sensitivity for polyps 10 mm and larger ranges from 50% to 100% and was 89-90% in the two largest series. Detailed data on smaller polyps are summarized. Virtual colonoscopy is an excellent test for evaluation of patients with incomplete colonoscopies. The incidence of significant extracolonic findings is 7-13%.

Automated segmentation of colonic walls for computerized detection of polyps in CT colonography

PURPOSE

A new method for fully automated segmentation of the colonic walls in volumetric CT data was developed for limitation of the search space in computerized detection of polyps.

METHOD

For reliable segmentation, an anatomy-oriented approach was used, in which several anatomical structures are segmented in addition to the colon for utilization of their properties.

RESULTS

The segmentation method was validated by use of 14 data sets, consisting of cases positive for colonic polyps. We found that the segmented colonic walls included all of the polyps. A subjective rating of the results was performed based on several criteria for visualization of anatomic detail of the colonic wall and mucosal surface. Except for a few cases in which insufflation of the colon was insufficient, all of the results included >95% of the colonic walls.

CONCLUSION

This method for colonic wall segmentation is reliable and the segmentation results are applicable in both visualization of the colon and computer-aided diagnosis in the detection of polyps in CT colonography.

Tumor size on computed tomography scans: is one measurement enough?

BACKGROUND

Bidimensional tumor measurements are used routinely as surrogates for tumor volume. The purpose this study was to determine whether there is any added benefit in bidimensional or tridimensional measurements over a unidimensional measurement.

METHODS

Sixty-nine colorectal hepatic metastases on 19 computed tomography scans (1-8 lesions per scan) from 9 patients were analyzed. Five patients contributed 2-4 scans each (mean, 3 scans). The standard volume of these lesions was determined by the "summation of areas" technique. The maximum axial dimension, the product of the greatest axial dimensions, and several volume estimates (based on the volumes of a sphere, an ellipsoid, and a cube) each were correlated with the standard volume.

RESULTS

The maximum axial dimension and the product of the greatest axial dimensions correlated equally with tumor volume (correlation coefficient = 0.93). Surrogate measures based on the equations for a sphere and an ellipsoid underestimated tumor volume, whereas the equation for a cube overestimated volume.

CONCLUSIONS

When reporting tumor size, there is no significant added benefit in reporting bidimensional or tridimensional measurements over the maximum axial dimension.

Virtual colonoscopy: a novel imaging modality for colorectal cancer

Advances in computed tomography (CT) technology and computer capabilities have contributed to the development of a new imaging modality for colorectal lesions called CT colonography or virtual colonoscopy. Virtual colonoscopy is a rapid, minimally invasive scan of the cleansed and distended colon. Early work has demonstrated that this test is safe and well tolerated, and that it may be sensitive and specific enough to identify most significant precancerous or cancerous lesions. A number of technical and practical problems remain before virtual colonoscopy can be applied at a population level.

Role of chest CT in the follow-up of ovarian adenocarcinoma

OBJECTIVE

We describe the prevalence of metastatic chest disease in ovarian adenocarcinoma as seen on CT. We sought to determine whether routine chest CT added any pertinent information to the follow-up examination of patients with ovarian adenocarcinoma.

MATERIALS AND METHODS

Retrospective review of our tumor registry yielded 96 patients with ovarian adenocarcinoma who had only a single primary malignancy and at least one CT scan of the chest, abdomen, and pelvis. CT scans were reviewed to assess the presence of metastatic chest disease in relation to disease activity in the abdomen and pelvis. Chest CT findings were correlated with the physical examination findings and CA-125 levels and were reviewed in consultation with a gynecologic oncologist to select only those patients with chest abnormalities attributable to metastatic disease.

RESULTS

A total of 266 CT scans were obtained. Forty (41.7%) of the 96 patients had abnormalities attributable to metastatic chest disease on one or more scans. In the absence of disease progression in the abdomen and pelvis, chest disease progression was seen in only six (2.7%) of the 226 follow-up CT scans. Five of the six patients had rising CA-125 levels.

CONCLUSION

Correlation of the findings of abdominal and pelvic CT with the physical findings and the CA-125 levels serves as effective follow-up in patients with ovarian adenocarcinoma. The contribution of additional chest CT in these patients is small.

Portal and mesenteric venous calcification in patients with advanced cirrhosis

OBJECTIVE

The incidence of calcification in the portal and mesenteric venous system was studied in patients with advanced cirrhosis undergoing evaluation for liver transplantation. The significance of portal and mesenteric calcification on liver transplantation was also investigated.

CONCLUSION

An 11% incidence of portal and mesenteric venous calcification was found in patients with cirrhosis, which was much higher than anticipated. Two (29%) of seven patients who had calcification present on CT and underwent liver transplantation died at surgery as a result of portal venous thrombosis. Thus, venous calcification seen on CT is a significant finding in patients undergoing liver transplantation.

Collateral pathways in superior vena caval obstruction as seen on CT

PURPOSE

Collateral venous pathways occurring with superior vena cava (SVC) obstruction were examined based on CT scans obtained from the thoracic inlet to the pubic symphysis. Similarities and variations from the prior classification scheme were analyzed.

METHOD

A retrospective review of our database resulted in a cohort comprising 21 CT scans from 19 patients. The location and frequency of each collateral pathway and the level of the SVC obstruction were tabulated. An accepted classification scheme was applied to the collateral patterns in each case. Additional and atypical features were noted.

RESULTS

Fifteen common collateral veins were found that could be grouped into one to four collateral pathways. Unusual shunts, including hepatic parenchymal and pulmonary pathways, were found. Thirteen cases (62%) varied from the standard classification owing to different occlusion levels or presence of other collaterals. No statistically significant relationship between the level of occlusion and the number of collateral pathway groups was found. The most common abdominal collateral veins were those along the liver surface (52.3% of cases), although 18 patients (94.7%) had at least one collateral vein visible in the abdomen.

CONCLUSION

The spectrum of venous collateral formations as seen on thoracoabdominal CT scans often includes collaterals at or below the level of the diaphragm, including intrahepatic shunts. Many collateral patterns found in this series could not be classified with the existent classification scheme.

Comparative viewing modalities for CT cystography

BACKGROUND

To define the speed and accuracy of two different reconstructive techniques using computed tomography (CT) cystography for the detection and measurement of urinary bladder masses and determine the overall ease of use.

METHODS

Ten patients scheduled for cystoscopy for the evaluation of hematuria or bladder masses were studied by means of thin-section CT of the air-distended bladder. Two techniques were employed by two radiologists to blindly interpret the data: conventional two-dimensional data with interactive three-dimensional problem solving (2D3DPS) and surface-shaded display (SSD) three-dimensional images. The results were compared with the data from cystoscopy.

RESULTS

Twenty-two (100%) of 22 masses detected on cystoscopy were visualized using the reconstructive techniques. Both modalities were shown to have high accuracy, but only the 2D3DPS had a sensitivity and specificity of 100% for both observers at the patient-level diagnosis. The sensitivities for detecting individual masses for the two observers were 100% and 64% for 2D3DPS and 64% and 70% for SSD.

CONCLUSION

Both methods used to display the CT data had a high sensitivity and specificity for masses, but only the 2D3DPS had a sensitivity and specificity of 100% at the patient-level diagnosis, thus making it a feasible imaging modality for cystography. It was also preferred overall for ease of use, high accuracy, and relative low cost.

Efficacy and safety of mangafodipir trisodium (MnDPDP) injection for hepatic MRI in adults: results of the U.S. Multicenter phase III clinical trials. Efficacy of early imaging

The efficacy of contrast-enhanced magnetic resonance imaging (MRI) for detecting and characterizing, or excluding, hepatic masses was assessed in 404 patients, following the intravenous administration of mangafodipir trisodium (MnDPDP) injection, a hepatic MRI contrast agent. An initial contrast-enhanced computed tomography (CT) examination was followed by unenhanced MRI, injection of MnDPDP (5 micromol/kg IV), and enhanced MRI at 15 minutes post injection. Agreement of the radiologic diagnoses with the patients' final diagnoses was higher for enhanced MRI and for the combined unenhanced and enhanced MRI evaluations than for unenhanced MRI alone or enhanced CT using the clinical diagnosis as the gold standard. Mangafodipir-enhanced MRI uniquely provided additional diagnostic information in 48% of the patients, and patient management was consequently altered in 6% of the patients. MnDPDP-enhanced MRI was comparable or superior to unenhanced MRI and enhanced CT for the detection, classification, and diagnosis of focal liver lesions in patients with known or suspected focal liver disease.

CT colonography: the next colon screening examination?

Computed tomographic (CT) colonography is a new-generation technique for detecting colorectal neoplasms by using volumetric CT data combined with specialized imaging software. Patient examinations require full colonic preparation, insufflation, and data acquisition with the patient in the supine and prone positions. Current CT technology allows a single image of the colon to be acquired in as little as 20 seconds with a minimum of patient discomfort. Specialized computer software for interpretation usually combines transverse, multiplanar reformation, and three-dimensional endoluminal images for the optimal visualization of the colon and rectum. As of the time this article was written, CT colonography was competitive as a full structural colonic examination for the detection of polyps and cancer. To the authors' knowledge, no study results have yet been reported in a screening population. The unique capabilities of CT colonography include the display of the proximal colon that is inaccessible at colonoscopy because of obstructing colonic lesions or because of incomplete endoscopic examinations and the assessment of extracolonic abdominal and pelvic organs. This abdominopelvic survey potential provides radiologists with an opportunity to discover other potentially life-threatening, asymptomatic conditions. Further technologic developments and validation studies are in progress. CT colonography is an exciting and promising technique with an enormous potential for colorectal screening in the future.

Safety and efficacy of mangafodipir trisodium (MnDPDP) injection for hepatic MRI in adults: results of the U.S. multicenter phase III clinical trials (safety)

The short-term safety of mangafodipir trisodium (MnDPDP) injection was studied in 546 adults with known or suspected focal liver lesions. An initial contrast-enhanced computed tomography examination was followed by unenhanced magnetic resonance imaging (MRI), injection of MnDPDP (5 micromol/kg), and enhanced MRI. Adverse events were reported for 23% of the patients; most were mild to moderate in intensity, did not require treatment, and were not drug related. The most commonly reported adverse events were nausea (7%) and headache (4%). The incidence of serious adverse events was low (nine events in six patients) and not drug related. Injection-associated discomfort was reported for 69% of the patients, and the most commonly reported discomforts included heat (49%) and flushing (33%). Changes in laboratory values and vital signs were generally transient, were not clinically significant, and did not require treatment. There were no clinically significant short-term risks from exposure to MnDPDP.

Automated calculation of the centerline of the human colon on CT images

RATIONALE AND OBJECTIVES

This article presents an evaluation of an automated technique for determining the colon centerline with computed tomographic (CT) data sets.

MATERIALS AND METHODS

The technique proceeds as follows. After indication of a voxel in the rectum, voxels corresponding to air were segmented. Points along the colon centerline were estimated on the basis of centers of mass of grown voxels. A second segmentation and centerline calculation was initiated at the cecum. These two centerlines were then averaged. The resulting average was refined by using lumen data obtained perpendicular to the average centerline. The accuracy of the technique was investigated with simulation phantoms. The technique was also evaluated for 40 clinical colon cases. Calculated centerline points were compared with those indicated by radiologists for a randomly selected clinical case.

RESULTS

In the simulation studies, the calculated centerline points were, on average, within 2.5 mm of the true centerlines but differed by up to 4 mm in regions of deep folds or sharp turns. In the clinical colon study, 40% of the centerlines were computed with a single seed point and 25% with two seed points. Average centerlines were computed in 1 minute. The root mean square difference between the computed centerline points and those indicated by the radiologists was 4-5 mm (comparable to interobserver variations).

CONCLUSION

Accurate centerlines can be determined from colon CT data with this automated technique.

CT findings after laparoscopic repair of ventral hernia

OBJECTIVE

We describe CT findings after laparoscopic repair of ventral hernia with emphasis on formation of postoperative fluid collections that can mimic recurrent bowel herniation or infected postoperative fluid collections.

CONCLUSION

The porous property of the mesh used in laparoscopic repair of ventral hernia allows reaccumulation of fluid in the existing hernia sac or spaces in the subcutaneous tissues that can be created by laparoscopic manipulation. These fluid collections should be expected and are differentiated from infected fluid collections or hernia recurrence by clinical presentation, laboratory data, and lack of ancillary features associated with true hernia such as presence of hernia sac, herniated mesentery, or bowel obstruction.

CT colonography with three-dimensional problem solving for detection of colonic polyps

OBJECTIVE

We performed CT colonography in patients referred for conventional colonoscopy, interpreted the axial images, and used commercially available software to reconstruct endoluminal perspective views to differentiate polyps from folds.

SUBJECTS AND METHODS

We prospectively examined 44 patients (27 men and 17 women; mean age, 58 years old) with CT colonography by interpreting the axial images and using three-dimensional rendering for problem solving only. The CT scans were interpreted by two radiologists who were unaware of patients' histories as revealed by colonoscopic findings. The findings on colonography were compared with those of conventional colonoscopy to determine sensitivity, specificity, time spent on interpretation, and confidence of interpretation.

RESULTS

Colonoscopy showed normal findings in 28 patients and 22 polyps in the remaining 16 patients. Six polyps were 8 mm or larger, three were 5-7 mm, and 13 were 5 mm or smaller. The findings of the two observers revealed an overall sensitivity of 50% and 38%, respectively, and a specificity of 93% and 86%, respectively. Sensitivity for polyps larger than 8 mm was 83% and specificity was 100% for both observers. The average amount of time spent on interpretation was 28 min 30 sec (range, 14-65 min). Both observers used the endoluminal view for differentiating folds from polyps in 23 (52%) of 44 patients, which had only minimal impact on interpretation time.

CONCLUSION

CT colonography can be performed and the images interpreted using currently available hardware and software by initially using the axial images to search for polyps of significant size. Endoluminal views should be used only when necessary to help distinguish normal folds from fixed raised lesions that are suggestive of polyps.

Helical CT examination of potential kidney donors

OBJECTIVE

The purpose of our study was to evaluate helical CT using axial, coronal, and three-dimensional (3D) reconstruction in the examination of potential kidney donors and to compare the results with angiography and surgery when possible. We also reviewed previously published reports.

SUBJECTS AND METHODS

Thirty-six patients underwent unenhanced and enhanced helical CT (3-mm collimation, 150-170 ml of i.v. contrast material injected at 4 ml/sec; pitch 1.5; 17-sec scan delay) with coronal and 3D shaded-surface-display reconstructions made from 1.5-mm overlapping reconstructions. All CT scans were interpreted independently of each other by two observers unaware of other findings. A third observer, who was aware of other findings, also interpreted the images. Results were compared with angiography (24 cases) and surgery (24 cases). Our results are compared with those of other investigators.

RESULTS

Axial CT was the best method for detecting accessory arteries (24%) and early branching (10%); it also detected relevant venous and ureteral anatomy and incidental findings. The coronal and 3D images rarely added information that resulted in changed patient treatment. CT findings were concordant with those of digital angiography in 89% of kidneys and were 98% concordant with surgery.

CONCLUSION

Helical CT can show arterial, venous, and ureteral anatomy and can also show important incidental findings. If only helical CT is used, a few small accessory vessels and an occasional renal artery stenosis may be missed. Axial images are generally diagnostic and may be supplemented by multiplanar and 3D images read concurrently.

Imaging of pancreatic transplantation using portal venous and enteric exocrine drainage

OBJECTIVE

We describe the normal radiologic appearance of pancreatic allografts transplanted using portal venous drainage with enteric drainage of exocrine secretions. We also describe the radiologic appearance of postsurgical complications.

MATERIALS AND METHODS

Of 56 patients who received pancreatic transplants using the portal-enteric technique, 24 patients subsequently required radiologic examination for suspected complications involving the pancreatic allograft. Twenty-three patients underwent CT scanning; a total of 58 CT scans were obtained. Nine abdominal sonograms were obtained in five patients, and one patient underwent angiography. The radiologic appearance of each transplant and the complications were analyzed retrospectively and correlated with the clinical course.

RESULTS

The most common indications for CT scanning were fever, elevated levels of serum amylase, and evaluation or follow-up of fluid collections. CT showed the normal and abnormal anatomy of the allograft. Abnormal findings seen in the 58 CT scans included fat stranding (30 scans), ascites (21 scans), peripancreatic fluid or pseudocyst (13 scans), and heterogeneity of the allograft (five scans). One patient had pancreatic infarction with pneumatosis and pneumoperitoneum. The allograft was obscured by bowel gas on three sonograms. Four sonograms showed no abnormalities (one Doppler sonogram showed the arterial supply and venous drainage), and one sonogram showed a pseudocyst. In the one patient who underwent angiography, imaging showed no arterial blood flow to the transplant.

CONCLUSION

Pancreatic transplantation with portal venous drainage and enteric drainage of exocrine secretions and the complications of such transplantation were revealed with CT, sonography, and angiography. Knowledge of normal anatomic configuration will allow proper interpretation of normal and abnormal findings.

CT imaging in adults with neurofibromatosis-1: frequent asymptomatic plexiform lesions

OBJECTIVE

The authors examined the incidence and radiologic characteristics of plexiform neurofibromas in neurofibromatosis-1 (NF-1) to define a cohort at greatest risk for malignant nerve-sheath tumors.

BACKGROUND

Plexiform neurofibromas are a frequent complication of NF-1. They can impair function, produce disfigurement, and be the site for the development of malignant nerve-sheath tumors. The incidence and natural history of plexiform neurofibromas is unknown.

METHODS

CT imaging of the chest, abdomen, and pelvis was performed in 91 of 125 consecutive adults (age, > or = 16 years) with NF-1.

RESULTS

Twenty percent of patients had plexiform neurofibromas of the chest in the paraspinal, mediastinal, or supraclavicular area. Approximately 40% of patients had abnormal abdominal/pelvic scans. The paraspinal, sacral plexus, sciatic notch, and perirectal regions were the most common sites. Most plexiform neurofibromas were asymptomatic. Imaging also revealed a number of tumors, including malignant nerve-sheath tumors, adrenal tumors, carcinoids, and schwannomas.

CONCLUSIONS

The frequency of plexiform lesions and other tumors in NF-1 indicates that clinicians should monitor young adults carefully; however, imaging characteristics alone cannot reliably distinguish benign from malignant lesions.

Primary non-Hodgkin's splenic lymphoma

OBJECTIVES

To describe the imaging, clinical and pathological features of primary splenic lymphoma using a strict definition.

METHODS

Of 21 cases, plain films were available in nine, sonograms in 10 and CT in 16. We categorized the spleen as either normal, enlarged with no focal defects (type 1), studded with miliary masses (type 2), containing multifocal masses of varying size (1-10 cm) (type 3) or containing a solitary large mass >5 cm without (type 4A) or with (type 4B) central hypodensity/anechoic areas.

RESULTS

Clinical presentations were left upper quadrant pain, weight loss and/or fever. One case was found incidentally on CT. Fourteen were type 4A, three type 4B, four type 3 and none were type 1 or 2. Nine of 10 cases were hypoechoic. In 11/12 cases with enhanced scans, the lesions are hypodense relative to the splenic parenchyma, and in one case, the lesion was necrotic. Rim enhancement was seen in one case.

CONCLUSION

Primary splenic lymphoma usually presents as a mass or masses rather than with splenomegaly alone. Splenectomy may be required for diagnosis.

Small simulated polyps in pig colon: sensitivity of CT virtual colography

PURPOSE

The authors evaluated computed tomographic (CT) virtual colography for the detection of simulated polyps under ideal conditions, as well as the effects on lesion conspicuity of (a) collimation, (b) table pitch, and (c) orientation of the colon lumen with respect to the gantry.

MATERIALS AND METHODS

Pig colon was resected and cleansed, and polyps with diameters of 3, 7, and 10 mm were created. Each specimen was scanned with collimation of 5 and 7 mm and table pitch of 1.0, 1.6, and 2.0 at angles of 0 degrees, 45 degrees, and 90 degrees to the gantry. The initial two-dimensional (2D) images were reconstructed at 1-mm intervals (2D reconstructions), from which three-dimensional (3D) virtual colography images were generated. Polyp conspicuity on the initial and reconstructed 2D images and the 3D reconstructions was evaluated on a three-point scale: 0 = polyp not depicted, 1 = polyp faintly depicted, and 2 = polyp clearly depicted.

RESULTS

The 10-mm-diameter polyp was clearly depicted (grade 2 conspicuity) on every initial and reconstructed 2D image and 3D reconstruction without regard to collimation, table pitch, or angle to the gantry. The 7-mm-diameter polyp was clearly depicted (grade 2 conspicuity) on every initial and reconstructed 2D image, but conspicuity on 3D reconstructions varied as the imaging parameters varied. The 3-mm-diameter polyp was faintly depicted (grade 1 conspicuity) on the initial and reconstructed 2D images and 3D reconstructions, but conspicuity varied on the 3D reconstructions as the imaging parameters varied.

CONCLUSION

CT virtual colography helped detection of small mucosal polyps regardless of the angle of the colon lumen to the gantry at which they were obtained.

Islet cell tumors of the pancreas: pathologic-imaging correlation among size, necrosis and cysts, calcification, malignant behavior, and functional status

OBJECTIVE

The purpose of our study was to correlate the imaging and pathologic features of islet cell tumors with regard to tumor size, necrosis and cysts, calcification, malignant behavior, and functional status.

MATERIALS AND METHODS

We retrospectively reviewed the clinical, pathologic, and imaging features of all 133 cases of pathologically proved islet cell tumors of the pancreas seen at the Armed Forces Institute of Pathology. Clinical data, including the patients' symptoms and serologic characteristics, were used to distinguish hyperfunctioning tumors (those causing symptoms related to elevated serum polypeptide levels) from nonhyperfunctioning tumors; hyperfunctioning tumors were divided further into insulin-producing and non-insulin-producing types. All patients had at least one cross-sectional imaging study, including CT (n = 118), sonography (n = 42), or MR imaging (n = 22). Clinical, pathologic, and imaging features were evaluated and correlated with tumor size, necrosis and cysts, calcification, local invasion, vascular invasion, metastases, and functional status.

RESULTS

Islet cell tumors with areas of necrosis or cystic change found pathologically and on imaging studies (56/133) were larger (8.4 cm in mean transverse diameter) than homogeneous solid lesions (2.9 cm in mean transverse diameter) and were predominantly non-insulin producing (48/56) and nonhyperfunctioning (36/56). Of the 43 insulinomas, 35 were small (2.2 cm in mean transverse diameter), solid, and homogeneous. Larger size also was associated with calcification and malignant behavior, including local invasion, vascular invasion, and distant metastases.

CONCLUSION

Our findings show that cystic and necrotic islet cell tumors are usually non-insulin-producing and nonhyperfunctioning neoplasms and larger than the typically solid and small insulinomas. Calcification, local invasion, vascular invasion, and metastatic disease are more commonly seen with larger neoplasms.

CT findings of regression in intraabdominal desmoplastic small-cell tumor

We report the computed tomographic (CT) findings in a patient with intraabdominal desmoplastic small-cell tumor before and after 10 weeks of chemotherapy. This tumor is a rare, frequently fatal neoplasm of the peritoneum, seen predominantly in young males. Initial CT demonstrated large intraperitoneal masses, hepatic metastases, retroperitoneal and right axillary lymphadenopathy, ascites, and pleural effusion. Follow-up CT showed marked decrease of the main tumor bulk and complete regression in the axillary nodes.

Colorectal carcinoma in young patients: CT detection of an atypical pattern of recurrence

Colonic adenocarcinoma is an uncommon but aggressive neoplasm in patients under the age of 40. The goals of this study were to evaluate the utility of computed tomography (CT) in preoperative staging and detection of postoperative recurrences in young patients with colon cancer and to evaluate the pattern of recurrent disease. We reviewed 51 cases of adenocarcinoma in patients aged 40 years and younger. CT preoperatively staged 21 (72%) of 29 patients correctly and had a 100% positive predictive value for metastatic disease. Recurrent disease occurred in 23 (76%) of 30 nonstage D patients with at least 2 years of disease-free follow-up. CT accurately detected 21 (91%) of 23 cases of recurrent disease. Local recurrences were detected in 20 (87%) of 23 patients. Isolated local disease was the most frequent pattern of recurrence, seen in 17 (74%) of 23 patients. Hepatic metastases were rare and occurred in nine (13%) of 51 patients. Young patients with colon cancer have an increased prevalence of isolated local recurrences and decreased rate of hepatic metastases than the older population. In order to detect early, and therefore resectable recurrent disease, CT examinations should be obtained early and often in the postoperative period.

Hodgkin's disease of the gastrointestinal tract

Hodgkin's disease (HD) is rarely considered in the differential diagnosis of gastrointestinal (GI) disorders. We report eight cases of GI HD. The patients, ages 16-64, all with stage IV disease of varied histologic subtypes and GI symptoms including pain, upper or lower GI bleeding and/or obstruction. There was diffuse gastric fold thickening in one case, a large submucosal mass along the proximal greater curvature in another case, and a large ulcerating mass along the lesser curvature in the third case. Two cases of jejunal disease manifested as either a short or long segment of luminal narrowing with prominent mucosal nodularity. Another case exhibited a short area of complete mucosal destruction, irregular cavitation and intraluminal filling defect. In one additional case there was diffuse jejunal nodularity. Colonic involvement (two cases) presented as a solitary polypoid mass in transverse colon in one patient and severe narrowing of the descending colon with adjacent mesenteric mass on CT in another. We conclude that although rare in Hodgkin's disease, GI involvement should be considered, particularly in patients with stage IV disease.

Prevalence and duration of postoperative pneumoperitoneum: sensitivity of CT vs left lateral decubitus radiography

OBJECTIVE

The purpose of this study was to evaluate the prevalence, location, and duration of pneumoperitoneum in postoperative patients and to compare the sensitivities of CT and left lateral decubitus radiography in the detection of postoperative pneumoperitoneum.

SUBJECTS AND METHODS

Twenty-seven CT scans and 27 abdominal radiographs with the patient in the left lateral decubitus position were obtained prospectively in 17 patients after uncomplicated abdominal surgery. Fifteen patients were examined 3 days after surgery and 12 were examined 6 days after surgery. The studies were evaluated in a blinded fashion for the presence, location, and volume of free air. The presence of air on the radiographs and the presence and quantity of air on the CT scans were correlated with each subject's surgical procedure, age, sex, and body habitus.

RESULTS

Pneumoperitoneum was seen on 13 (87%) of 15 CT scans and eight (53%) of 15 radiographs obtained 3 days after surgery and on six (50%) of 12 CT scans and one (8%) of 12 radiographs obtained 6 days after surgery. The calculated volume of free air seen on the CT scans ranged from 0.3 to 5.8 ml. Sixty-two percent of collections by volume were located in the midline/parahepatic space, 22% in the pelvis, and 16% in the mesentery. Radiographs showed pneumoperitoneum in only nine (47%) of 19 examinations in which the corresponding CT scans showed free air. Findings on radiographs were false-negative in seven (87%) of eight obese patients in whom pneumoperitoneum was detected on CT scans.

CONCLUSION

The prevalence of pneumoperitoneum in the postoperative period based on CT findings is greater than that previously reported. Small amounts of pneumoperitoneum frequently collect along the anterior abdominal wall in two preferential spaces, the pararectus and midrectus recesses. The results of this study show that CT is significantly more sensitive than plain radiography for detecting small amounts of free intraperitoneal air in postoperative patients. Radiography is particularly insensitive for imaging obese and heavy patients.

The radiologic evaluation of acute abdominal pain of intestinal origin. A clinical approach

The patient with acute abdominal pain presents the attending physician with a wide and varied gamut of diagnostic possibilities. Prompt and accurate diagnosis is essential for the proper care and management of these acutely ill patients. Diagnostic radiology is often an integral part of the emergent evaluation of these patients. This article focuses on some of the key plain-film findings in the patients suffering from acute abdominal pain of intestinal causes and reviews the radiologic evaluation of several major abdominal conditions such as acute appendicitis, diverticulitis, inflammatory bowel disease, bowel ischemia, and infarction.

Calcified intrahepatic portal vein thrombus: distinction from intrahepatic choledocholithiasis

In a case of calcified intrahepatic portal vein thrombus CT demonstrated a branching calcified intrahepatic mass with peripheral enhancement following dynamic bolus contrast medium administration. The distinction from intrahepatic choledocholithiasis was made with normal cholangiography. Calcified portal vein thrombus should be considered an unusual cause of branching calcified intrahepatic mass on CT.

Radiology of the esophagus

Plain films, esophagrams, and cross-sectional imaging studies have important roles in evaluating patients with suspected esophageal disease. The strengths and weaknesses of each technique are described in this article. The salient radiographic features of various inflammatory and neoplastic conditions of the esophagus are also described, with emphasis on the value of high-quality triphasic esophagography.

Polypoid and pseudopolypoid manifestations of inflammatory bowel disease

The polypoid manifestations of the idiopathic inflammatory bowel diseases (ulcerative colitis and Crohn disease) are often confusing. Inflammatory polyps project above the level of the surrounding mucosa. Pseudopolyposis (in ulcerative colitis) or a cobblestone appearance (in Crohn disease) results when extensive ulceration develops and only scattered islands of relatively normal mucosa remain; thus, the ulcerated areas may be falsely perceived as the baseline and the islands as polyps. Postinflammatory (filiform) polyps--fingerlike projections of submucosa covered by mucosa on all sides--reflect healing of undermined mucosal and submucosal remnants and ulcers and are almost always multiple. Patients with ulcerative colitis or Crohn disease are at increased risk for developing adenocarcinoma. Occasionally, dysplasia occurs as a polypoid lesion. Dysplasia of the colon (mucosal atypia) is a histologic marker highly associated with adenocarcinoma. Because differentiating adenocarcinoma and dysplasia from inflammatory or postinflammatory polyps is sometimes difficult or impossible, endoscopy and biopsy are usually recommended for definitive diagnosis of suspicious lesions.

US-guided percutaneous laser ablation of liver tissue in a chronic pig model

The authors evaluated the safety of ultrasound (US)-guided percutaneous ablation of liver tissue using a neodymium-yttrium-aluminum-garnet (Nd:YAG) laser fiber placed through a skinny needle. The US appearance of the lesion was correlated with the pathologic findings in 19 pigs killed at 1-7 weeks. A 20-gauge needle was percutaneously placed in the liver, and a fiber with a 0.5-cm cladding-stripped tip was inserted. The Nd:YAG laser was fired for 6 minutes at 1-4 W. The early sonographic appearance was recorded, and the US appearance before the pigs were killed was correlated with the gross and histopathologic findings. There were no cases of abdominal bleeding or infection. Mild transient changes in liver function were seen. An initial strong echogenic focus decreased slightly in echogenicity for 10 minutes and then stabilized. Over 1-7 weeks, the 1-cm-diameter lesion decreased in size and developed an echogenic rim that correlated with a peripheral zone of inflammatory repair around a small central cavity and zone of necrosis. US-guided laser ablation of liver tissue is safe in this pig model, and the US appearance corresponds to a process of repair and removal of necrotic liver tissue.

Animal model for fluoroscopically guided laser application in the biliary tree

The purpose of this project was to develop an animal model for a fluoroscopically guided application of the contact neodymium-yttrium aluminum garnet (Nd-YAG) laser in the bile duct and identify the factors affecting the extent of damage to the duct wall. This model permits cholangiographic visualization of the duct during laser application. Laser damage is limited by using contact probes and firing the laser while slowly pulling the probe proximally into the duct. Sixteen common bile duct laser burns were produced in 14 dogs. Power settings of 8-25 W were used. The tension of the contact probe along the duct wall, termed "wall tension," was varied through intraoperative manipulation in order to mimic a variety of ductal geometries that might be encountered in clinical use. The authors produced duct damage ranging from a superficial burn to perforation. Power and wall tension were the most important factors in determining the depth and circumference of damage, and the use of 15 W or less did not perforate the duct.

Cronkhite-Canada syndrome: radiologic features

We report 6 cases of Cronkhite-Canada syndrome, analyze the patterns of involvement, and review the literature on this entity. There were 4 women and 2 men, with an average age of 58 years. The stomach was diseased diffusely in 5 and focally (distally) in 1. Small bowel polyps were detected in 4 patients. Patterns of involvement were classified as (a) innumerable small polyps carpeting large areas, (b) scattered varying-size polyps, and (c) sparse involvement with few small polyps. There was concordance of patterns between the stomach and colon in 5 of the 6 patients.

Colorectal hemangioma: radiologic findings

The authors correlated radiographs with the clinical and histologic data of 12 patients with colorectal hemangioma. All patients presented with rectal bleeding, which was chronic in seven. Phleboliths were also visible in seven cases, which correlated with chronic bleeding in five. On barium studies, three masses were soft and three produced rigid narrowing. The atypical features of rigid luminal narrowing, which might mimic a carcinoma, and hypovascularity correlated with chronic bleeding or visible phleboliths, which suggest the correct diagnosis of colorectal hemangioma.

Tumors of the small intestine with little or no malignant predisposition: a review of the literature and report of 56 cases

Benign small bowel tumors are rare. If those with malignant potential are excluded, a small group of truly benign lesions remains. Fifty-six cases of these small bowel tumors were analyzed for clinical data, pathologic diagnosis, number, size, location, and radiologic appearance. Lesions included lipoma, myoepithelial hamartoma, Peutz-Jeghers hamartoma, neurogenic tumors (including gangliocytic paraganglioma), Brunner's gland abnormalities, and inflammatory fibroid polyp. Location, number, and radiographic morphology can be helpful in reaching a more specific diagnosis. Age of patient and size of tumor may be helpful in the differential diagnosis; however, sex of the patient and clinical symptoms are not.

Mesenteric and omental cysts: histologic classification with imaging correlation

Forty-one cases of mesenteric and omental cysts are reported. Histologically, several specific types could be distinguished: lymphangioma, 19 cases; nonpancreatic pseudocyst, 11 cases; enteric duplication cyst, six cases; mesothelial cyst, three cases; and enteric cyst, two cases. A lymphangioma is usually a multiloculated cyst located in the mesentery that shows no discernible wall on computed tomography (CT) and may have characteristics of fat on CT and magnetic resonance imaging. Abnormalities in the small bowel mucosa were frequently noted on barium studies. A nonpancreatic pseudocyst is usually a unilocular or multilocular cyst located in either the mesentery or the omentum, with abundant debris sonographically and an enhancing wall on CT. An enteric duplication cyst is a unilocular cyst with an enhancing wall on CT. Mesothelial and enteric cysts are anechoic, thin-walled cysts. Emphasis is placed on the importance of identifying lymphangioma, which is more difficult to manage than the other forms of mesenteric and omental cysts.

Hepatoblastoma: radiologic-pathologic correlation in 50 cases

Fifty cases of hepatoblastoma were reviewed. Virtually all patients were infants or young children with hepatomegaly or a mass. Calcification seen on 11 of 20 radiographs was often in a pattern of small chunks, and eight of these correlated with osteoid formation in histologically mixed hepatoblastomas. Angiography generally showed tumor vascularity, sometimes with a spoke-wheel pattern. Suggestion of tumor nodularity or lobulation on sonography or computed tomography (CT) correlated with the gross appearance. The tumor was usually echogenic and occasionally had small hypoechoic or anechoic areas representing necrosis or hemorrhage. On CT it was usually hypodense, with minimal if any enhancement. The calcification pattern and demonstration of tumor lobulation with septation may help differentiate hepatoblastoma from other liver neoplasms in infants and children under 5 years of age.

Nodular regenerative hyperplasia of the liver: clinical and radiologic observations

This report describes 21 cases of nodular regenerative hyperplasia (NRH) and its clinical and radiologic features. NRH of the liver is an established pathologic entity that should not be confused with focal nodular hyperplasia, hepatocellular adenoma, or the regenerative nodules associated with cirrhosis. Correct diagnosis will prevent an unnecessary hepatic lobectomy should NRH be mistaken for hepatocellular adenoma. Unlike focal nodular hyperplasia, NRH may bleed, may be associated with portal hypertension in one-half of cases, and is often associated with a systemic disease such as a myelo- or lymphoproliferative disorder. Correct diagnosis is important because the prognosis in patients with NRH and portal hypertension is better than that in patients with portal hypertension due to cirrhosis. Radiologically, multiple nodules, large masses, or an apparently normal liver (containing nodules less than 0.5 cm in diameter) were visible. The nodules may take up technetium sulfur colloid and have variable echogenicity on sonography. They are often hypodense on CT without significant enhancement. The nodules may fill from the periphery on angiography, are vascular, and sometimes contain small hypovascular areas due to hemorrhage. A large nodule may rupture and cause hemoperitoneum. These findings may resemble some features of focal nodular hyperplasia, hepatocellular adenoma, or metastases. NRH is probably underdiagnosed owing to a lack of recognition of the entity and limited sampling of liver tissue by needle biopsy. Scintigraphy, sonography, and CT of the liver should be performed in cases of idiopathic portal hypertension to detect NRH. In cases with compatible findings, multiple needle biopsies or a laparoscopically guided needle biopsy or wedge liver biopsy should be recommended for definitive diagnosis.

Natural history of the obstructed rabbit appendix: observations with radiography, sonography, and CT

Chronic (1-3 months' duration) appendiceal obstruction was induced in 11 rabbits to assess the pathologic consequences and to study the associated radiologic, sonographic, and CT findings. Three pathologic/radiologic groups resulted with approximately equal frequency. In group A, the abscess was characterized by inflammatory cells in the lumen and wall of the appendix without mucin production. Calcification was shown radiographically, and sonography showed an anechoic or complex pattern. Group B, the "mixed response," was characterized by an intact hyperplastic mucosa, mucin secretion, and inflammatory debris in the lumen. Occasional calcification was present radiographically, and sonography showed a complex or hypoechoic pattern. In group C, true mucoceles had an intact hyperplastic mucosa, a mucin-filled lumen, and minimal inflammation. These were anechoic on sonography except for mobile foci of inflammatory debris. Chronic obstruction of the appendix results in a spectrum of pathologic responses with varying degrees of either inflammation and mucosal destruction or mucosal hyperplasia and mucin secretion. An abscess results when infection overwhelms the host's inflammatory responses. If the bacteria are destroyed by these defenses, a mucocele forms. An intermediate situation occurs when there is a mixed response with chronic inflammatory changes and an intact mucosa. This finding supports the existence of chronic appendicitis in humans.

Hemangioma of the spleen: radiologic-pathologic correlation in ten cases

Ten cases of hemangioma of the spleen were reviewed. Plain abdominal radiographs and scintigrams are helpful in specifying the splenic location. Calcification, either central punctate or peripheral curvilinear, can be detected on radiographs or computed tomographic (CT) scans. The spectrum form solid to cystic change observed in the pathologic specimens is reflected in analogous patterns on CT scans and sonograms: predominantly solid mass; mass with cystic spaces. The angiographic findings are nonspecific. It is possible to suggest the diagnosis of hemangioma of the spleen when an asymptomatic patient presents with a discrete splenic mass, particularly if there is evidence of calcification and cystic change within the lesion.

Undifferentiated (embryonal) sarcoma of the liver: radiologic-pathologic correlation

Undifferentiated (embryonal) sarcoma (UES) is an uncommon malignant mesenchymal hepatic tumor that occurs in older children and young adults. Fourteen cases are correlated with radiologic and pathologic findings. Radiologic findings reflect the spectrum of solid to cystic appearances observed in the gross specimens. Sonography typically demonstrates a large mass that may be predominantly solid with many small anechoic spaces or may be cystic. Computed tomography reveals a hypodense mass with hyperdense septa of variable thickness and a dense peripheral rim corresponding to the fibrous pseudocapsule of the tumor. Angiographically, UES is usually hypovascular with tumoral vessels, although hypervascular and avascular patterns occur. Prognosis of UES is poor, with a median survival of less than 1 year. Radiologists should be familiar with this malignant tumor since it may present as a large cystic hepatic mass, suggestive of a benign lesion.

Nonparasitic splenic cysts: a report of 52 cases with radiologic-pathologic correlation

We reviewed 52 cases of splenic cysts on file at the Armed Forces Institute of Pathology. There were 24 true (epidermoid) and 28 false (posttraumatic) cysts. The history and clinical presentations, including pain, splenomegaly, or mass, were similar in both groups. Radiologic manifestations included splenomegaly and the occasional identification of a distinct mass by conventional radiography even in the absence of calcification. The lesions produced a photopenic defect on nuclear scintigraphy and were avascular on angiography. Sonography and CT demonstrated a cystic lesion with occasional septations, wall trabeculation, and low-level internal echoes. Three false cysts demonstrated solid and cystic components on sonography and CT, corresponding to organizing hematoma within the cyst. Splenomegaly or a splenic mass of a predominantly cystic nature with no clinical evidence of echinococcus suggests the diagnosis of splenic cyst. Reliable radiologic distinction between true or false splenic cyst does not seem possible. Complex mass may represent a "transition" between hematoma and false splenic cyst.