Impact of multislice CT on imaging of acute abdominal disease

Tertiary survey ultrasound has no diagnostic benefit in trauma patients without abdominal injuries on standardised initial whole-body computed tomography

PURPOSE

The aim of our study was to evaluate the impact of a routine tertiary survey ultrasound (US) on patient management in major trauma patients without trauma-related abdominal findings on standardised initial whole-body CT (WBCT).

METHODS

In this retrospective study, all WBCT scans acquired in major trauma patients between 07/2017 and 12/2019 at a university hospital and level I trauma centre were screened. 1,024 patients were included in the final analysis. Results of tertiary survey US and patient information (demographic data, trauma mechanism, imaging findings, clinical course, medical history, and anticoagulative medication) were collected and analysed.

RESULTS

Routine tertiary survey US revealed new abdominal findings in six out of 1,024 patients (0.6%). None of the patients had to undergo surgery or minimally invasive intervention, nor did any of the patients die as a result of abdominal injuries. Additional abdominal imaging after tertiary survey US was ordered in 39 patients (38 US, 1 US + CT). None of these patients required further treatment for abdominal injuries.

CONCLUSIONS

Routine tertiary survey US after inconspicuous standardised initial WBCT did not change clinical outcome for abdominal trauma patients.

Influence of multiplanar reformations on low-contrast performance in thin-collimated multidetector computed tomography

OBJECTIVES

: To analyze the influence of multiplanar reformations of thin-collimated multidetector computed tomography datasets on low-contrast performance.

MATERIALS AND METHODS

: A low-contrast phantom simulating focal hypodense lesions (-20 HU object contrast) was scanned on a 64-slice spiral CT scanner at 4 different dose levels (25 mAs, 50 mAs, 100 mAs, 200 mAs, and no dose modulation). Other scanner parameters were as follows: tube voltage = 120 kVp, rotation time = 0.8 s, reconstructed slice thickness = 0.625 mm, reconstruction interval = 0.5 mm, reconstruction kernel = standard. Coronal reformations were created using the open-source software OsiriX. A sliding-thin-slab (STS) averaging algorithm was applied to each axial and each reformatted dataset with an increasing slab thickness from 1 to 20 slices. The low-contrast performance of all datasets was calculated semiautomatically using a reader-independent, statistical approach and is expressed as the visibility index. The results were analyzed for differences between the coronal reformations and the original axial datasets. In addition, the statistical approach used herein was validated against a reader study.

RESULTS

: The visibility index of the coronal reformatted datasets over all lesion sizes was inferior when compared with the original axial datasets and reached 75.4% (±11.7%), 79.9% (±16.3%), 79.4% (±5.5%), and 93.7% (±14.6%) for dose levels of 25, 50, 100, and 200 mAs, respectively. The overall mean low-contrast performance was 82.1% of the axial dataset (P < 0.05, except for 200 mAs). The deterioration of low-contrast performance was inversely correlated with lesion size (R = 0.91). The use of the STS averaging algorithm significantly improved image quality for all datasets (112.6%-180.2%) with the beneficial effect being stronger for the coronal reformations. There was no statistically significant difference in the evaluation of low-contrast performance between the statistical approach and the ready study.

CONCLUSION

: Coronal reformations of thin-collimated multidetector computed tomography datasets show a significant reduction of low-contrast performance when compared with the original axial dataset, especially in high noise data. The use of an STS averaging algorithm had a significant benefit for both, coronal and axial orientations. The effect was more pronounced with coronal reformations and should be routinely applied to improve image quality.

Diagnosing small hepatic cysts on multidetector CT: an additional merit of thinner coronal reformations

Objective

We wanted to validate the additional merit of the thinner coronal reformation images from multidetector CT (MDCT) for making the diagnosis of hepatic cysts.

Materials and Methods

For the 90 benign hepatic cysts confirmed on MRI, the transverse (5-mm thickness) and additional coronal (2-mm thickness) reformation images from MDCT were compared with each other in terms of the Hounsfield units (HUs) and the size of each hepatic cyst.

Results

The attenuations (mean: 17.2 HUs, standard deviation: ± 14.4) on the thinner coronal images were significantly lower than those (mean: 40.7 HUs; standard deviation: ± 20.6) on the thicker transverse images for the small hepatic cysts (≤ 10 mm on the transverse image, p < 0.01). Twenty-three (79%) of the 29 cysts between 5 mm and 10 mm and 21 (51%) of 41 lesions up to 5 mm showed a mean HU value of 20 or less on the coronal reformation images.

Conclusion

By reducing the partial volume effect, routine coronal reformation of MDCT with a thinner section thickness can provide another merit for making a confidential diagnosis of many small sub-centimeter hepatic cysts, and these small cysts are not easily characterized on the conventional transverse images.

[Multidetector computed tomography in abdominal emergencies]

Abdominal emergencies encompass traumatic events in the region of the abdomen as well as the clinical term acute abdomen. Multidetector CT (MDCT) represents one of the most important imaging modalities for detection and correct diagnosis in such abdominal emergencies. Based on the acquired data MDCT allows a stable imaging of the abdomen in an extremely short time even in critically ill patients. Multiplanar reconstructions can be created based on the high resolution data allowing an impressive visualization of the pathology. In this review article the most important abdominal pathologies of the abdomen diagnosed by MDCT are presented with special emphasis on the liver, bile ducts, spleen and kidneys as well as the gastro-intestinal tract. Additionally, MDCT imaging of the individual organ regions will be dealt with in detail.

Four-section multidetector computed tomographic imaging of bowel obstruction: usefulness of axial and coronal plane combined reading

OBJECTIVE

To compare the diagnostic performance of axial and coronal views in multidetector-row computed tomography (MDCT) of patients with small-bowel obstruction (SBO) or large-bowel obstruction (LBO).

MATERIALS AND METHODS

Among 157 patients with clinical and radiographic findings of BO, 73 patients, who underwent MDCT and were found to have surgically proven SBO (49/73) or LBO (24/73), were retrospectively evaluated. Portal-enhanced MDCT was performed using 4 x 2.5-mm collimation; 3-mm-thick axial images were reconstructed with 2 mm of increment. Coronal views were reformatted using 3-mm-thick sections with 1 mm of increment. Three radiologists analyzed axial (session A), coronal (session B), and axial plus coronal images (session C) to identify the site, cause, and type of BO. To correlate surgical findings and MDCT results, the bowel was divided into duodenum, oral jejunum, aboral jejunum, oral ileum, aboral ileum, cecum/ascending colon, transverse colon, descending colon, and sigmoid colon/rectum. The mean diagnostic accuracy and the mean confidence score of each reader and each reading session were calculated.

RESULTS

The diagnostic accuracy of axial images was higher than that of coronal views (P = 0.014) in SBO, whereas no significant differences were found in LBO. The definition of the SBO cause was correctly assessed in 45 of 49 patients during session A, in 40 of 49 during session B, and in 45 of 49 during session C. In patients with LBO, the cause was correctly assessed in 21 of 24 patients during session A and in 22 of 24 patients during sessions B and C. All readers interpreted axial plus coronal images with a significantly higher confidence level than axial or coronal views alone, either for the detection of the site (P = 0.002) or for the identification of the cause (P < 0.001) of SBO and LBO.

CONCLUSION

The MDCT allowed accurate detection of the site and the cause of obstruction. In SBO, axial images yielded a higher diagnostic accuracy than coronal views, whereas in LBO, no differences were found between axial and coronal planes. The reading of axial plus coronal views significantly improved diagnostic confidence.

Value of automated coronal reformations from 64-section multidetector row computerized tomography in the diagnosis of urinary stone disease

PURPOSE

We determined the value of automated coronal reformation using 64-detector computerized tomography for the detection of urinary stones.

MATERIALS AND METHODS

A total of 72 patients underwent unenhanced 64-detector computerized tomography to diagnose urinary stones. Two radiologists independently reviewed coronal reformations and axial images at separate reading sessions. The stone detection rate, reader confidence and interpretation time per radiologist were recorded. Two radiologists reviewed coronal and axial images in consensus and served as the reference standard.

RESULTS

A total of 175 stones were diagnosed by consensus. Using coronal reformations 162 stones (92.6%) were detected by reader 1 and 157 (89.7%) were detected by reader 2. Using axial images 157 stones (90.3%) were detected by reader 1 and 155 (88.6%) were detected by reader 2. The reading time of coronal reformations was significantly shorter than that of axial images for each reader (p <0.01). Using coronal imaging to complement axial imaging 12 additional stones were detected and 23 were diagnosed with increased confidence by reader 1, while an additional 15 were detected and 8 were diagnosed with increased confidence by reader 2. The mean size of stones detected with coronal reformations alone was significantly smaller than that of the total stones. Excellent interobserver agreement was noted for coronal reformations and axial images (kappa coefficient: 0.91 and 0.904, respectively).

CONCLUSIONS

Review of automated coronal reformations allows equally accurate and more rapid detection of urinary stones compared with axial images alone. In addition, coronal reformation of 64-detector computerized tomography adds value when used in conjunction with axial data sets.

MDCT diagnosis of appendicitis using only coronal reformations

The purpose of this study was to assess the feasibility of diagnosing appendicitis based on coronal reformations without the aid of transverse images. Abdominal and pelvic computed tomography (CT) scans of 53 patients (27 with appendicitis and 26 without appendicitis) were reviewed. All scans were obtained using a four-slice multi-detector row CT. The radiologists were not aware of the final diagnosis. Cases were reviewed for the visualization of the appendix and presence of appendicitis. All images were reviewed on picture archiving and communication systems. There were no false positives for diagnosing appendicitis when using either the transverse or coronal reformations. Appendicitis was not seen on the coronal images in one case, and there were no false negatives when transverse reformations alone were used. This difference was not statistically significant (p < 0.0001 for both modes of display). The sensitivity for diagnosing appendicitis based on the coronal images alone was 96%, the specificity was 100%, and the accuracy was 98%. Coronal reformations decreased the number of images reviewed by 19%. CT diagnosis of appendicitis based on the coronal images is accurate.

Direct visualization of perforation sites in patients with a non-traumatic free pneumoperitoneum: added diagnostic value of thin transverse slices and coronal and sagittal reformations for multi-detector CT

The incremental diagnostic value of adding 1.25-mm slices and coronal and sagittal reformatting to 5-mm axial reconstructions for direct visualization of the perforation site in patients with non-traumatic free pneumoperitoneum was assessed. Forty patients with non-traumatic bowel perforation and free pneumoperitoneum underwent computed tomography (CT). The perforation was gastroduodenal in 18 patients and involved the small or large bowel in 22 patients. Transverse scans were reconstructed with 5-mm thick sections at 5-mm intervals and 1.25-mm-thick sections at 1.25-mm intervals. The second data set was reformatted coronally and sagittaly with 3-mm-thick sections at 3-mm intervals. Three independent blinded readers interpreted 5-mm transverse scans, then combined 1.25-mm and 5-mm-transverse scans, and then combined transverse, coronal and sagittal scans. The rate of identification of the perforation site ranged from 43% to 53% with the combined axial, sagittal and coronal scans, from 28% to 48% with the 1.25- and 5-mm transverse scans, and from 5% to 20% only with the 5-mm thick transverse scans. The agreement between readers was significantly higher with thin slices and reformatting. The use of 1.25-mm axial slices and reformations intrinsically contained more useful diagnostic information than 5-mm axial slices alone for diagnosis of the perforation site in patients with pneumoperitoneum.

Abdominal Pain: Coronal Reformations from Isotropic Voxels with 16-Section CT—Reader Lesion Detection and Interpretation Time

PURPOSE

To retrospectively assess if reader detection of intraabdominal pathologic findings on coronal reformations from isotropic voxels at 16-section computed tomography (CT) was similar to reader detection on transverse scans.

MATERIALS AND METHODS

The institutional review board approved this HIPAA-compliant study, and a waiver of informed consent was obtained. Twenty-nine consecutive patients (12 men, 17 women; mean age, 48 years; age range, 21-93 years) with abdominal pain underwent 16-section CT with coronal reformations. Eight independent readers reviewed randomized scans (transverse and coronal) and identified pathologic findings in multiple organ systems. Timing for each interpretation was recorded. One month later, readers reviewed the scan reformatted in the other imaging plane. Agreement between transverse and coronal scans was measured by using Cohen kappa coefficients.

RESULTS

Agreement was moderate to near perfect between transverse and coronal interpretations for intraabdominal anatomic and pathologic findings (kappa=0.59-1.00). For transverse interpretations, more thoracic pathologic findings were noted than for coronal interpretations; for coronal interpretations, more lymph nodes were noted than for transverse interpretations. Mean transverse interpretation time was 4.9 minutes+/-1.1 (standard deviation) (range, 2.9-6.5 minutes); mean coronal interpretation time was 5.1 minutes+/-0.8 (range, 3.3-6.7 minutes). For each reader, there was no statistically significant difference in interpretation time between transverse and coronal scans (P=.06).

CONCLUSION

With regard to the presence of intraabdominal pathologic findings, coronal reformations from isotropic voxels are similar to transverse scans in terms of interpretation time and reader agreement.

Small-bowel obstruction: coronal reformations from isotropic voxels at 16-section multi-detector row CT

PURPOSE

To retrospectively assess the added value of coronal reformations of the abdomen and pelvis from isotropic voxels by using 16-section multi-detector row computed tomography (CT) for the diagnosis of small-bowel obstruction (SBO).

MATERIALS AND METHODS

This HIPAA-compliant study was approved by the institutional review board of this medical center with a waiver of informed consent. One hundred consecutive patients (40 men and 60 women; mean age, 55 years) suspected of having SBO and abdominal pain underwent 16-section multi-detector row CT with coronal reformations. Twenty-nine patients had a final diagnosis of SBO, and 71 patients did not. Three independent readers blinded to the diagnosis interpreted the CT scout scan, then transverse scans alone, and then transverse plus coronal scans for the presence of SBO and abnormal wall enhancement. Confidence was scored with a 1-5 scale (1 = absent, 5 = present).

RESULTS

Mean sensitivity and specificity of CT scout alone, transverse CT alone, and transverse plus coronal CT for the diagnosis of SBO were 88% and 86%, 87% and 87%, and 87% and 90%, respectively (not significant). In patients without SBO, transverse plus coronal CT enhanced confidence in the exclusion of SBO (P = .01). In patients with SBO, transverse plus coronal CT enhanced confidence in the diagnosis of SBO and identification of abnormal wall enhancement (P = .01).

CONCLUSION

Transverse 16-section multi-detector row CT data sets are an excellent test for the diagnosis of SBO, while the addition of coronal reformations obtained from these isotropic data sets adds confidence to the diagnosis and exclusion of SBO.

Renal Multidector Row CT

Multidetector row CT is the most recent advance in CT technology. An increased number of detector rows and more powerful x-ray tubes result in faster scanning time, increased volume coverage, and improved spatial and temporal resolution. MDCT technology allows superior image quality, decreased examination time, and the ability to perform complex multiphase vascular and three-dimensional examinations.

[Acute abdomen]

Acute abdomen is not a disease entity on its own but describes a critical state of the patient which can be caused by numerous diseases. The surgeon and internist have to apply an interdisciplinary approach to enable a rapid decision on whether immediate laparotomy is mandatory. Few appropriate diagnostic procedures support decision making. In many cases there is an indication for immediate surgery, such as perforated gastric or duodenal ulcer, acute appendicitis, diverticulitis, ruptured aortic aneurysm, mechanic ileus, infarction of the mesenteric artery. This review is mainly focused on diseases which may present as acute abdomen but for which surgery is usually not indicated, such as acute pancreatitis. Furthermore, one also has to consider rare diseases in which laparotomy would clearly be a mistake, such as acute intermittent porphyria or intestinal pseudo-obstruction.

Multi-detector computed tomography of acute abdomen

Acute abdominal pain is one of the most common causes for referrals to the emergency department. The sudden onset of severe abdominal pain characterising the "acute abdomen" requires rapid and accurate identification of a potentially life-threatening abdominal pathology to provide a timely referral to the appropriate physician. While the physical examination and laboratory investigations are often non-specific, computed tomography (CT) has evolved as the first-line imaging modality in patients with an acute abdomen. Because the new multi-detector CT (MDCT) scanner generations provide increased speed, greater volume coverage and thinner slices, the acceptance of CT for abdominal imaging has increased rapidly. The goal of this article is to discuss the role of MDCT in the diagnostic work-up of acute abdominal pain.

Acute appendicitis: added diagnostic value of coronal reformations from isotropic voxels at multi-detector row CT

PURPOSE

To assess retrospectively the added value of coronal reformations from isotropic voxels obtained with 16-section multi-detector row computed tomography (CT) of the abdomen and pelvis in patients with suspected acute appendicitis.

MATERIALS AND METHODS

This study was approved by the institutional review board, and informed consent was waived. One hundred consecutive patients (21 men, 79 women; mean age, 38 years) with suspected appendicitis underwent 16-section multi-detector row CT (section thickness, 0.625 mm; pitch, 1.75; table speed, 35 mm/sec [17.5 mm per rotation, two rotations]; and gantry speed, 0.5 second per rotation), with coronal reformations. Twenty-four patients had appendicitis; 76 did not. Protocol included 150 mL oral iopamidol administered at 3 mL/sec. Transverse scans were reconstructed with 5-mm-thick sections at 5-mm intervals and 0.625-mm-thick sections at 0.625-mm intervals. The second data set was reformatted coronally, with 3-mm-thick sections at 5-mm intervals. Three independent blinded readers interpreted transverse scans alone and then coronal scans; confidence in visualization of any portion of appendix, entire appendix, wall thickening, distention, inflammation, fluid, and appendicitis was scored with 1-5 scale. Sensitivity and specificity were determined for each reader and compared by means of signed rank test. Agreement between readers was determined with kappa statistic. Differences in mean confidence ratings for each finding were determined with Wilcoxon signed rank test.

RESULTS

Mean sensitivity and specificity for all three readers together were 96% and 95% for transverse reformations alone and 95% and 94% for combined transverse and coronal reformations (not significant), respectively. Visualization rates for portion or all of appendix were higher for combined transverse and coronal reformations than for transverse reformations alone (higher mean confidence scores: 0.23 higher [P < .009] and 0.51 higher [P < .001], respectively). In patients without appendicitis, transverse and coronal reformations together enhanced confidence in exclusion of wall thickening, distention, and fluid (lower confidence scores: 0.21 lower [P < .001], 0.17 lower [P < .01], 1.00 lower [P < .001], respectively). Combined transverse and coronal reformations enhanced confidence in identification of appendix in mean of 57 patients. Combined transverse and coronal scans helped exclude appendicitis in mean of 38 patients and aided diagnosis of it in 15.

CONCLUSION

Sixteen-section multi-detector row CT transverse and coronal reformations are equally sensitive and specific for diagnosis of appendicitis. Coronal reformations improve confidence in visualization of appendix (whether diseased or normal) and in diagnosis or exclusion of appendicitis.

Valeur du scanner dans l’occlusion mécanique de l’intestin grêle

Small bowel obstruction is a leading cause of admission in surgical and emergency units. During the last two decades, the classical philosophy of "never let the sun set or rise on small-bowel obstruction" has been succeeded by a new management based especially on the cause and the severity of the obstruction. It most often allows a correct choice between medical therapy and surgery using laparotomy or laparoscopy. This changing attitude is still in progress and is mainly related to the high accuracy of computed tomography. This review will discuss the semiology and value of computed tomography compared with clinical examination and other imaging modalities.