Vassilios Raptopoulos

Role of virtual computed tomographic colonography in patients with colorectal cancers and obstructing colorectal lesions

PURPOSE: The aim of this study was to assess the ability of computed tomographic colonography to diagnose colorectal masses, stage colorectal cancers, image the proximal colon in obstructing colorectal lesions, and evaluate the anastomoses in patients with previous colorectal surgery. METHODS: We prospectively performed computed tomographic colonography examinations in 34 patients (20 males; mean age, 64.2; range, 19–91 years): 20 patients had colorectal masses (defined at endoscopy as intraluminal masses 2 cm or larger), 7 patients had benign obstructing colorectal strictures, and 7 patients had a prior colorectal resection. Final tumor staging was available in all 16 patients who had colorectal cancers and 15 patients were referred after incomplete colonoscopy. The ability of computed tomographic colonography to stage colorectal cancers, identify synchronous lesions in patients with colorectal masses, and image the proximal colon in patients with obstructing colorectal lesions was assessed. RESULTS: Computed tomographic colonography identified all colorectal masses, but overcalled two masses in patients who were either poorly distended or poorly prepared. Computed tomographic colonography correctly staged 13 of 16 colorectal cancers (81 percent) and detected 16 of 17 (93 percent) synchronous polyps. Computed tomographic colonography overstaged two Dukes Stage A cancers and understaged one Dukes Stage C cancer. A total of 97 percent (87/90) of all colonic segments were adequately visualized at computed tomographic colonography in patients with obstructing colorectal lesions compared with 60 percent (26/42) of segments at barium enema (P<0.01). Colonic anastomoses were visualized in all nine patients, but in one patient, computed tomographic colonography could not distinguish between local tumor recurrence and surgical changes. CONCLUSION: Computed tomographic colonography can accurately identify all colorectal masses but may overcall stool as masses in poorly distended or poorly prepared colons. Computed tomographic colonography has an overall staging accuracy of 81 percent for colorectal cancer and is superior to barium enema in visualizing colonic segments proximal to obstructing colorectal lesions.

Factors associated with conversion to laparotomy in patients undergoing laparoscopic appendectomy.

BACKGROUND Laparoscopic appendectomy (LA) has been increasingly adopted for its advantages over the open technique, but there is a possibility of conversion to open appendectomy (OA) if complications occur or the extent of inflammation prohibits successful dissection. This study aimed to identify the preoperative predictors for conversion from laparoscopic to open appendectomy. STUDY DESIGN Medical records of 705 consecutive patients who underwent surgery for suspected appendicitis were reviewed retrospectively. LA was attempted in 595 patients by 25 different surgeons. Factors evaluated were age, gender, body mass index, previous abdominal surgery, previous appendicitis attack, pain, nausea, vomiting, fever, duration of symptoms, local or diffuse tenderness, leukocyte count and surgeons experience in LA. RESULTS Conversion to OA occurred in 58 patients (9.7%). The most common reason for conversion was dense adhesions due to inflammation, followed by localized perforation and diffuse peritonitis. Based on 261 patients evaluated by CT scan preoperatively, significant factors in the final multivariate analysis associated with conversion to OA were age > or = 65 [Odds ratio (OR) = 3.78, 95% CI:1.11-12.84], diffuse tenderness on physical examination (OR = 11.32, 95% CI: 1.32-96.62), and a surgeon with less experience in LA (< or = 10 operations, OR = 3.38, 95% CI:1.02-11.17). The presence of significant fat stranding associated with fluid accumulation, inflammatory mass or localized abscess in CT scan also significantly increased the possibility of conversion (OR = 5.60, 95% CI:2.48-12.65). CONCLUSIONS Identifying the potential factors for conversion preoperatively may assist the surgeons in making decisions concerning the management of patients with appendicitis and in the judicious use of LA.

CT and MRI in Diseases of the Aorta

OBJECTIVE This review focuses on the role of CT and MRI in the diagnosis, follow-up, and surgical planning of aortic aneurysms and acute aortic syndromes, including aortic dissection, intramural hematoma, and penetrating aortic ulcer. It also provides a systematic approach to the definition, causes, natural history, and imaging principles of these diseases. CONCLUSION An understanding of the pathophysiology, natural history, and imaging features is the key to successful diagnosis and appropriate management of patients with these aortic diseases.

Perfusion MDCT Enables Early Detection of Therapeutic Response to Antiangiogenic Therapy

OBJECTIVE The objective of our study was to determine whether perfusion CT can be used to detect early changes in therapeutic response to antiangiogenic therapy in an animal tumor model. MATERIALS AND METHODS Twenty-five rats implanted with R3230 mammary adenocarcinoma (diameter, 1.2-2.0 cm) randomly received 7.5 or 30 mg/kg of an antiangiogenic agent, sorafenib, by daily gavage for 4 (n = 4), 9 (n = 9), or 14 (n = 5) days. Seven untreated animals served as a control group. Perfusion MDCT was performed at days 0, 4, 9, and 14 with 0.4 mL of ioversol (350 mg/mL) and included four 5-mm slices covering the entire tumor volume. Changes in tumor growth were determined by volumetric analysis of CT data. Serial changes in tumor volume and blood flow were assessed and correlated with pathology findings. RESULTS All control tumors grew larger (from 2.0 +/- 0.7 cm(3) at day 0 to 5.9 +/- 1.0 cm(3) at day 14), whereas all treated tumors shrank (from 2.5 +/- 1.1 to 2.1 +/- 1.0 cm(3)), with a statistically significant rate of growth or shrinkage in both groups (p < 0.05). Although perfusion in the control tumors changed little from day 0 to day 14 (day 0, 18.1 +/- 9.2 mL/min/100 g; day 4, 15.8 +/- 5.6; day 9, 21.7 +/- 12.2; day 14, 27.7 +/- 34), in the sorafenib group, the mean blood flow was significantly lower at day 4 (5.2 +/- 3.2 mL/min/100 g, 77% decrease), day 9 (6.4 +/- 4.0 mL/min/100 g, 66% decrease), and day 14 (6.3 +/- 5.2 mL/min/100 g, 83% decrease) compared with day 0 (23.8 +/- 11.6 mL/min/100 g) (p < 0.05). Poor correlation was seen between changes in blood flow and tumor volume for days 0-9 (r(2) = 0.34), 4-9 (r(2) = 0.0004), and 9-14 (r(2) = 0.16). However, when comparing day 4 images with days 9 and 14 images, seven of 14 (50%) sorafenib-treated tumors had focal areas of new perfusion that correlated with areas of histopathologic viability despite the fact that these tumors were shrinking in size from day 4 onward (day 4, 2.18 +/- 0.8 cm(3); day 9, 1.98 +/- 0.8 cm(3)). CONCLUSION Perfusion MDCT can detect focal blood flow changes even when the tumor is shrinking, possibly indicating early reversal of tumor responsiveness to antiangiogenic therapy. Given that changes in tumor volume after antiangiogenic therapy do not necessarily correlate with true treatment response, physiologic imaging of tumor perfusion may be necessary.

Spectral CT with Metal Artifacts Reduction Software for Improvement of Tumor Visibility in the Vicinity of Gold Fiducial Markers

PURPOSE To evaluate spectral computed tomography (CT) with metal artifacts reduction software (MARS) for reduction of metal artifacts associated with gold fiducial seeds. MATERIALS AND METHODS Thirteen consecutive patients with 37 fiducial seeds implanted for radiation therapy of abdominal lesions were included in this HIPAA-compliant, institutional review board-approved prospective study. Six patients were women (46%) and seven were men (54%). The mean age was 61.1 years (median, 58 years; range, 29-78 years). Spectral imaging was used for arterial phase CT. Images were reconstructed with and without MARS in axial, coronal, and sagittal planes. Two radiologists independently reviewed reconstructions and selected the best image, graded the visibility of the tumor, and assessed the amount of artifacts in all planes. A linear-weighted κ statistic and Wilcoxon signed-rank test were used to assess interobserver variability. Histogram analysis with the Kolmogorov-Smirnov test was used for objective evaluation of artifacts reduction. RESULTS Fiducial seeds were placed in pancreas (n = 5), liver (n = 7), periportal lymph nodes (n = 1), and gallbladder bed (n = 1). MARS-reconstructed images received a better grade than those with standard reconstruction in 60% and 65% of patients by the first and second radiologist, respectively. Tumor visibility was graded higher with standard versus MARS reconstruction (grade, 3.7 ± 1.0 vs 2.8 ± 1.1; P = .001). Reduction of blooming was noted on MARS-reconstructed images (P = .01). Amount of artifacts, for both any and near field, was significantly smaller on sagittal and coronal MARS-reconstructed images than on standard reconstructions (P < .001 for all comparisons). Far-field artifacts were more prominent on axial MARS-reconstructed images than on standard reconstructions (P < .01). Linear-weighted κ statistic showed moderate to perfect agreement between radiologists. CT number distribution was narrower with MARS than with standard reconstruction in 35 of 37 patients (P < .001). CONCLUSION Spectral CT with use of MARS improved tumor visibility in the vicinity of gold fiducial seeds.

Multislice CT angiography

Abstract.The introduction of multislice CT into clinical radiology constitutes a quantum leap that significantly widens the scope of vascular CT imaging. The advances over conventional spiral CT have been quantitative, mainly in terms of increased image acquisition speed which provides unprecedented volume coverage and spatial resolution. Moreover, significant technical innovations, such as cardiac scanning capabilities, have brought about a qualitative shift towards applications that were thought to be beyond the scope of CT imaging. This way multislice CT offers a wealth of new opportunities for quickly and accurately diagnosing suspected vascular disease in all organ systems; however, as we move towards faster and faster image acquisition techniques, we are also facing new challenges that require development of novel strategies in order to take full advantage of the increased capabilities of multislice CT in its current form and future generations of CT scanners.

Split-bolus spectral multidetector CT of the pancreas: assessment of radiation dose and tumor conspicuity.

PURPOSE To assess tumor conspicuity and radiation dose with a new multidetector computed tomography (CT) protocol for pancreatic imaging that combines spectral CT and split-bolus injection. MATERIALS AND METHODS This study was approved by the institutional review board and compliant with HIPAA. The requirement for informed consent was waived. One hundred sixty-three consecutive patients referred for possible pancreatic mass underwent CT with either a standard or split-bolus spectral CT protocol depending on scanner availability. Split-bolus spectral CT (CT unit with spectral imaging) combines pancreatic and portal venous phases in a single scan: 70 seconds before CT, 100 mL of contrast material is injected for the portal venous phase followed approximately 35 seconds later by injection of 40 mL of contrast material to boost the pancreatic phase. Bolus tracking after the second bolus initiates scanning 15 seconds after aorta enhancement reaches 280 HU. Images were reconstructed at 60 and 77 keV. The standard protocol (64-detector row unit) included unenhanced and pancreatic and portal venous phase imaging, with a single contrast material injection timed with bolus tracking 15 seconds after aortic enhancement of 300 HU for the pancreatic phase and 32 seconds later for the portal venous phase. Tumor conspicuity (difference in attenuation between tumor and pancreatic parenchyma) and contrast-to-noise ratio (CNR) were determined. Attenuation of aorta, main portal vein, and liver were measured. Patient size and per-examination radiation dose were recorded. The heteroscedastic t test, Fisher exact test, and Mann-Whitney test were used for statistical analysis. RESULTS There were no significant differences in age, weight, and body mass index between patients in the standard CT (46 of 80 patients had lesions) and split-bolus spectral CT (39 of 83 patients had lesions) groups; however, there were significantly more women in the split-bolus group (P = .02). Tumor conspicuity and CNR were higher with the 60-keV split-bolus protocol (89.1 HU ± 56.6 and 8.8 ± 6.2, respectively) than with the pancreatic or portal venous phase of the standard protocol (43.5 HU ± 28.4 and 4.5 ± 3.0, and 51.5 HU ± 30.3 and 5.6 ± 4.0, respectively; P < .01 for all comparisons). Dose-length product was 1112 mGy · cm ± 437 with the standard protocol and 633 mGy · cm ± 105 with the split-bolus protocol (P < .001). CONCLUSION Split-bolus spectral multidetector CT resulted in vascular, liver, and pancreatic attenuation and tumor conspicuity equal to or greater than that with multiphase CT, with a 43% reduction in radiation dose.

Is CT angiography sufficient for prediction of resectability of periampullary neoplasms

The optimal preoperative evaluation of periampullary neoplasms remains controversial. The aim of this study was to analyze the accuracy of helical computed tomography (CT) and CT angiography with three-dimensional reconstruction in predicting resectability. Between March 1996 and May 1999, a total of 100 patients with periampullary neoplasms were prospectively staged by helical CT and CT angiography with three-dimensional reconstruction. Vascular involvement was graded from 0 to 4, with grade 0 representing no vascular involvement and grade 4 total encasement of either the superior mesenteric vein or artery. Patients with grade 4 lesions were considered unresectable. Sixty-eight patients underwent surgical exploration with intent to perform a pancreaticoduodenectomy. Forty-four lesions were grade 0, five were grade 1, eight were grade 2, and 11 were grade 3. Resectability for grades 0 to 3 was 96%, l00%, 50%, and 9%, respectively, for an overall resectability rate of 76%. Resectability in patients with vascular encroachment (grade 2) is usually determined by the extent of local disease rather than the presence of extrapancreatic disease. Resection is rarely possible in patients with evidence of vascular encasement (grade 3). Additional imaging modalities such as diagnostic laparoscopy are superfluous in patients with no evidence of local vascular involvement on CT angiography (grades 0 and 1) because of the high resectability rate and infrequency of unsuspected distant metastatic deposits.

Dose Reduction in Computed Tomographic Angiography of Pregnant Patients With Suspected Acute Pulmonary Embolism

Purpose: The aim of this study was to quantify the effect of a reduced-dose pulmonary computed tomographic (CT) angiography protocol on radiation dose and image quality in pregnant patients as compared with a standard protocol. Materials and Methods: Twenty-six pregnant women with suspected pulmonary embolism underwent reduced-dose CT angiography (200 mA and 100 kV, from the aortic arch to the diaphragm). The matched control group standard protocol was 400 mA, 120 kilovolt (peak), and the entire thorax. The CT dose index, dose-length product, effective dose, image quality, and signal-to-noise ratio were assessed and compared with the Wilcoxon rank sum test result. Results: The CT dose index, mean dose-length product, and calculated effective dose were lower in the pregnancy group than in the controls: mean (SD), 5.21 (1.54) mGy versus 20.86 (5.59) mGy; 105.65 (39.77) mGy cm versus 575.71 (154.86) mGy cm, and 1.79 (0.676) msv versus 9.787 (2.63) msv, respectively (P < 0.0001). Quality scores of segmental (P = 0.266) and subsegmental (P = 0.207) arteries and arterial attenuation (P = 0.443) were similar. Conclusions: In pregnant patients with suspected pulmonary embolism, combined reduction of kilovoltage and milliampere-second settings and z-axis coverage results in a substantial reduction of radiation dose while maintaining diagnostic imaging quality.

Liver regeneration after living adult right lobe transplantation

AbstractBackground: The purpose of this study was to describe liver regeneration in patients undergoing living-adult liver transplantation. Methods: This prospective study included 10 donors and eight recipients who had a total of 65 computed tomographic (CT) scans. All patients had preoperative CT (n = 18), and follow-up CT scans (n = 47) were obtained for up to 14 months after transplantation. Liver and spleen volumes were measured by hand tracing each organ on the axial portal venous phase images. Results: Both donors and recipients showed immediate increases in liver volume. However, liver regeneration was significantly faster and reached a higher peak in recipients than in donors. Splenic volume in donors demonstrated an initial increase followed by a decline, reaching the preoperative volume after 1 year. Splenic volume in recipients demonstrated immediate decline postoperatively. Conclusion: Restoration of liver volume occurred rapidly after transplantation, but followed different patterns in donors and recipients. Deviation from these patterns warrants further investigation.