Suspected ureteral colic: primary helical CT versus selective helical CT after unenhanced radiography and sonography.

OBJECTIVE: The purpose of this study was to compare the accuracy of unenhanced helical CT with combined sonography and unenhanced radiography in patients with acute flank pain suggestive of ureteral colic. SUBJECTS AND METHODS: From January 1997 to December 1999, 181 consecutive patients with acute flank pain underwent unenhanced radiography, sonography, and unenhanced helical CT (protocol A). From January 2000 to December 2000, 96 consecutive patients arriving at the emergency department with acute flank pain were alternately submitted either to primary unenhanced helical CT (protocol B, 48 patients) or to unenhanced radiography and sonography with the addition of helical CT in unclear cases (protocol C, 48 patients). RESULTS: When compared with the diagnostic accuracy for ureterolithiasis of the combined sonography and radiography in the same group of subjects (protocol A), CT had a greater sensitivity (92% vs 77%), negative predictive value (87% vs 68%), and overall accuracy (94% vs 83%). Among patients who underwent primary CT (protocol B), we found three false-negatives (all with spontaneous stone passage) and no false-positives. Among patients initially examined with unenhanced radiography and sonography (protocol C), we found one false-positive (leading to patient admission and needless repeated radiographic and sonographic studies) and six false-negatives (all followed by an uncomplicated course and spontaneous passage); CT depicted four of these stones but did not result in change in treatment. Fourteen percent of the patients in protocol C required invasive treatment, but combined sonography and radiography showed stones and hydronephrosis in all these patients. CONCLUSION: Unenhanced CT was the most accurate modality for determining the presence of ureterolithiasis. The combination of abdominal radiography and sonography, however, yielded comparable results with no clinically important misdiagnoses and thus can be used as an alternative when CT resources are limited.     

Sensitivity of CT scout radiography and abdominal radiography for revealing ureteral calculi on helical CT: implications for radiologic follow-up

OBJECTIVE: We compared the sensitivity of CT scout radiography with that of abdominal radiography in revealing ureteral calculi on unenhanced helical CT. MATERIALS AND METHODS: Over a 6-month period, patients presenting to the emergency department with acute flank pain were examined with standard abdominal radiography and unenhanced helical CT, which included CT scout radiography. In 60 patients in whom a diagnosis of ureteral calculus was made, CT scout radiographs and abdominal radiographs were examined by two interpreters who assessed whether stones could be visualized. All CT scout radiographs were viewed on a workstation using optimized window settings. RESULTS: CT scout radiography and abdominal radiography revealed 28 (47%) and 36 (60%) of 60 ureteral calculi, respectively. All ureteral calculi that appeared on CT scout radiography also appeared on abdominal radiography. However, eight calculi that were visible on abdominal radiography were not visible on CT scout radiography. CT scout radiography and abdominal radiography revealed 28% and 46% of 39 calculi less than or equal to 3 mm in diameter, respectively. For 21 calculi larger than 3 mm, the sensitivity of CT scout radiography and abdominal radiography was 81% and 86%, respectively. CONCLUSION: Abdominal radiography is more sensitive than CT scout radiography in revealing ureteral calculi; however, some calculi revealed on unenhanced helical CT cannot be seen on either abdominal radiography or CT scout radiography. Ureteral calculi not visible on either study can only be followed, when necessary, with unenhanced helical CT.     

Diagnostic value of unenhanced helical CT in adult patients with suspected acute appendicitis

Clinical diagnosis of appendicitis is usually made on the basis of history, physical examination and laboratory studies. Approximately 30-45% of patients with suspected appendicitis present with atypical clinical and laboratory findings. Recently graded compression ultrasound and thin section unenhanced helical CT have been used to establish diagnosis for patients with suspected acute appendicitis. The purpose of this study was to determine the diagnostic accuracy of thin section unenhanced helical CT protocol in adult patients with suspected acute appendicitis. CT scans obtained when patients presented with right lower quadrant pain and the clinical impression was equivocal for appendicitis were evaluated. Of 296 patients referred for CT, 123 patients subsequently underwent surgery. Appendicitis had been correctly predicted in 104 of 108 patients surgically proven to have appendicitis. Unenhanced helical CT in the diagnosis of acute appendicitis had a sensitivity of 96%, specificity of 98%, positive predictive value of 97% and negative predictive value of 98%. If no definite inflammatory changes are detected, on the basis of our experience we recommend that the patient be monitored clinically, and that thin section unenhanced helical CT is the optimal technique to detect acute appendicitis in adult patients.     

Spiral computerized tomography without perfusion of contrast media as first line investigation in patients with renal colic

INTRODUCTION: We investigated the diagnostic accuracy of unenhanced helical CT in the detection of stones in patients with suspected renal colic from ureteral stones and compared CT findings with the results of plain abdominal film and US. MATERIAL AND METHODS: We reviewed the findings relative to 80 patients (age range 24-75) who came to our observation to the Emergency Department with acute flank pain. All patients had been examined with plain abdominal radiography, US and unenhanced helical CT. RESULTS: While abdominal radiography showed the presence of radiopaque stones in 38 patients only (47.5%), US demonstrated ureter dilatation in 72 patients and detected stones in 36 of them (45%). Helical CT performed best, depicting a stone in 72 patients (90%), with high sensitivity and specificity. Mean stone size was 3 mm, with 7 mm-1 mm range. The biggest stones were seen in 3 cases and the smallest ones in 34. In 8 patients with no signs of stones we found other extraurinary conditions, namely pancreatitis, diverticula, renal cancer. We also found a case of urinary tract infection. CONCLUSIONS: Thanks to its short execution time and accuracy, helical CT makes the examination of choice in patients with acute flank pain due to renal colic. It is also a most valuable tool in the differential diagnosis of other pathological causes of pain such as abdominal or pelvic masses and inflammatory conditions.     

Diagnosis of acute appendicitis with unenhanced helical CT: a study of 130 patients

The aim of this study was to determine the sensitivity, specificity, and diagnostic accuracy of helical computed tomography (CT) without oral, intravenous, or rectal administration of contrast material in confirming the diagnosis of acute appendicitis in patients with suggestive clinical and laboratory findings. One hundred and thirty patients with suspected acute appendicitis underwent an unenhanced helical CT scan. Scans were obtained in a single breath-hold from the level of umbilicus to the pubic symphysis using a 5-mm collimation. Oral, intravenous, or rectal contrast materials were not used. The criteria for diagnosis of acute appendicitis included an enlarged diameter of appendix more than 6 mm with associated periappendiceal inflammation. The results yielded a sensitivity of 94.7%, a specificity of 91.7%, an accuracy of 93.8%, a positive predictive value of 96.7%, and a negative predictive value of 86.8%. Unenhanced helical CT accurately diagnoses acute appendicitis, and it protects the patients from unnecessary further time-consuming diagnostic procedures, the risks associated with contrast material administration, and unnecessary surgical interventions. Electronic Publication     

Trends in the use of unenhanced helical CT for acute urinary colic

OBJECTIVE: Unenhanced helical CT for urolithiasis detection is a limited CT examination that was designed specifically for the detection of urolithiasis. The purpose of this study was to repeat a prior study to assess whether clinicians had broadened the indications and changed the yield and findings of unenhanced helical CT. MATERIALS AND METHODS: One hundred consecutive patients with suspected renal colic or flank pain referred for unenhanced helical CT were selected for this study. We reviewed the original radiographic reports for each patient and recorded the presence of ureteral calculi. Other urinary abnormalities and extraurinary lesions were also recorded and compared with the results of the previous study. RESULTS: In this study, 56% of the patients who underwent unenhanced helical CT had symptoms of urinary colic, and 44% of patients had unspecified flank pain, compared with 100% of patients with symptoms of urinary colic 1 year earlier. The sensitivity and specificity of unenhanced helical CT in detecting ureteral calculi were 96% and 99%, respectively. Ureteral calculi were identified in only 28% of the patients versus 49% of patients (p < .01) 1 year earlier. Extraurinary lesions were identified in 45% of the patients versus 16% (p < .01) 1 year before. CONCLUSION: As clinicians developed familiarity with this technique, the indications for performance of unenhanced helical CT were expanded with a consequent reduction in the rate of detection of stone disease and identification of an increased number of extraurinary lesions, which suggests a demand for emergency abdominal CT studies.     

Acute nontraumatic abdominal pain in adult patients: abdominal radiography compared with CT evaluation

PURPOSE: To compare the diagnostic yield of abdominal radiography with that of computed tomography (CT) in adult patients presenting to the emergency department with nontraumatic abdominal pain. MATERIALS AND METHODS: Records of 1,000 consecutive patients presenting to the emergency department with acute abdominal pain from April to June 1998 were retrospectively reviewed. A total of 871 patients underwent abdominal radiography, and 188 underwent abdominal CT. The report interpretations of the abdominal radiographs and CT scans were divided into normal, nonspecific, and abnormal categories. Final discharge diagnoses were compared with the interpretations of the imaging examination results, and sensitivities and specificities of each modality were calculated and compared. RESULTS: Interpretation of abdominal radiographs was nonspecific in 588 (68%) of 871 patients, normal in 200 (23%), and abnormal in 83 (10%). The highest sensitivity of abdominal radiography was 90% for intraabdominal foreign body and 49% for bowel obstruction. Abdominal radiography had 0% sensitivity for appendicitis, pyelonephritis, pancreatitis, and diverticulitis. Sensitivities of abdominal CT were highest for bowel obstruction and urolithiasis at 75% and 68%, respectively. CONCLUSION: Abdominal radiographs are not sensitive in the evaluation of adult patients presenting to the emergency department with nontraumatic abdominal pain.     

Comparison of CT and sonography in the diagnosis of acute appendicitis: a blinded prospective study

OBJECTIVE: Our objective was to compare the accuracy of CT and sonography in a general community teaching hospital for the diagnosis of acute appendicitis in patients with suspected acute appendicitis. SUBJECTS AND METHODS. In this prospective study, 199 consecutive patients with clinical signs and symptoms of acute appendicitis were examined with sonography (graded compression technique) and CT (focused unenhanced single-detector helical CT [5-mm section thickness]. CT was performed from the L2 vertebral body to the pubic symphysis, and no patients were given oral, rectal, or IV contrast medium. The primary sonographic criterion for diagnosing acute appendicitis was an incompressible appendix with a transverse outer diameter of 6 mm or larger with incompressible periappendicular inflamed fat with or without an appendicolith. The primary CT criterion for diagnosing acute appendicitis was the identification of an appendix with a transverse outer diameter of 6 mm or larger with associated periappendiceal inflammatory changes. The results, independently reported, were correlated with surgical and histopathologic findings. RESULTS: One hundred thirty-two patients had acute appendicitis at surgery, and 67 patients did not. The sensitivity of CT and sonography was 76% and 79%, respectively; the specificity was 83% and 78%; the accuracy was 78% and 78%; the positive predictive value was 90% and 87%; and the negative predictive value was 64% and 65%. CONCLUSION: Unenhanced focused single-detector helical CT and graded compression sonography performed in a general community teaching hospital by both body imaging radiologists and general radiology staff members have a similar accuracy for the diagnosis of acute appendicitis.     

Comparing the diagnostic performance of MRI versus CT in the evaluation of acute nontraumatic abdominal pain during pregnancy

The objectives of this study were to document the utilization of MRI compared with CT in pregnant patients presenting with acute nontraumatic abdominal pain at our institution and to compare the diagnostic performance of the two modalities. A retrospective review identified all pregnant patients at our institution who had MRI or CT exams of the abdomen and/or pelvis for acute nontraumatic abdominal pain over a 3-year period from January 2008 through December 2010. The imaging diagnoses were compared with pathologic data or operative findings as the primary reference standard or with clinical follow-up and laboratory data as the secondary reference standard. Patients without surgically proven diagnoses were followed clinically until delivery, when possible. Ninety-four pregnant patients were included in this study: 61 MRI exams were performed in 57 patients, 44 CT exams were performed in 43 patients (including six patients who had both), and 72 patients (77?%) had ultrasound prior to cross-sectional imaging, with the appendix specifically assessed in 25 patients but visualized in only two of them. Of 61 MRI exams, 24 were considered positive for imaging diagnoses, 33 were negative, and 4 were equivocal. Of 44 CT exams, 24 were positive and 20 were negative. The test characteristics for MRI and CT in the diagnosis of acute abdominal pain were as follows: sensitivity 91 and 88?%, specificity 85 and 90?%, positive predictive value 81 and 91?%, negative predictive value 94 and 8 5?%, and diagnostic accuracy 88 and 88?%, respectively. Differences were not statistically significant (p value?=?1). The majority of MRIs (34/61?=?56?%) were read by emergency radiologists. MRI and CT performed equally well in the evaluation of acute nontraumatic abdominal pain during pregnancy. Given its lack of ionizing radiation, MRI may be preferable. Given that the majority of MRIs were read by radiologists specializing in emergency imaging, this is a technique that emergency radiologists should be comfortable interpreting.     

Unenhanced helical CT: the “unbeatable” emergency examination for acute flank pain

Unenhanced helical CT has made the excretory urogram virtually obsolete in the evaluation of patients presenting to the emergency department with acute flank pain. A case is presented demonstrating yet another advantage of unenhanced helical CT: that of unmasking the clever malingerer who feigns renal colic in order to obtain controlled drugs.     

Acute abdominal pain in children: usefulness of three-view abdominal radiographs in the emergency department

Diagnostic imaging is often an integral component in the workup of a pediatric patient with acute abdominal pain. The purpose of this study was to compare the diagnostic value of a three-view acute abdominal series (AAS) with that of a single supine view (SSV) in children with acute abdominal pain. All subjects aged ≤18 years that underwent an emergency three-view AAS examination for acute abdominal pain at a single urban hospital system were included. Retrospective evaluation of radiological diagnosis, number of radiological images, further imaging, management, and clinical outcomes was performed. “Positive” AAS studies were compared with corresponding SSV images for direct comparison of diagnostic value. Standard nonparametric statistical evaluation was performed. Five hundred forty-one AAS studies were included in the study. Greater than three radiographs were acquired in 29 % (153/541) of the subjects. Two hundred ninety-nine out of 541 AAS studies included a technically adequate SSV of the abdomen and pelvis. Most AAS examinations were categorized as negative (n = 485; 90 %). Of the 56 examinations initially classified as positive, there was no significant statistical difference between diagnostic accuracy between the AAS and SSV on retrospective evaluation. For pediatric subjects with nontraumatic acute abdominal pain, the yield of conventional radiographic study is exceedingly low. If required, a technically adequate single supine anteroposterior (AP) view of the abdomen and pelvis is sufficient for initial radiographic evaluation while reducing unnecessary radiation exposure to the patient.     

Diagnosing acute appendicitis using a nonoral contrast CT protocol in patients with a BMI of less than 25

The objective of this study was to compare the accuracy for the diagnosis of appendicitis in patients presenting to the emergency department (ED) with acute, nontraumatic abdominal pain and a body mass index (BMI) of less than 25 before and after the implementation of a nonoral contrast computed tomography (CT) protocol with intravenous contrast. The IRB approved this HIPAA-compliant retrospective study; informed consent was waived. This study included 736 adult patients with a BMI of less than 25 presenting to our ED with acute, nontraumatic abdominal pain over two distinct 6-month time periods. An oral and intravenous contrast-enhanced protocol was utilized in the first cohort (group A), and an intravenous contrast-enhanced protocol without oral contrast was utilized in the second cohort (group B). Three abdominal fellowship-trained readers retrospectively reviewed all CT studies and electronic medical records, including surgical/pathology reports that served as reference standards. Group A consisted of 359 patients; 41 patients had surgically proven appendicitis. The sensitivity and specificity of the readers for diagnosing appendicitis in group A ranged from 95.2–100 and 98.1–99.5 %, respectively. Group B consisted of 372 patients; 39 had surgically proven appendicitis. The sensitivity and specificity of the readers in group B ranged from 92.0–100 and 98.6–100 %, respectively. There were no statistically significant differences in sensitivity or specificity for CT scans performed in groups A and B. In patients with a BMI of less than 25, an intravenous contrast-enhanced CT protocol without oral contrast demonstrates similar accuracy to an intravenous contrast-enhanced protocol with oral contrast for diagnosing acute appendicitis.     

Nontraumatic abdominal emergencies: acute abdominal pain: diagnostic strategies

Common causes of acute abdominal pain include appendicitis, cholecystitis, bowel obstruction, urinary colic, perforated peptic ulcer, pancreatitis, diverticulitis, and nonspecific, nonsurgical abdominal pain. The topographic classification of acute abdominal pain (pain in one of the four abdominal quadrants, diffuse abdominal pain, flank or epigastric pain) facilitates the choice of the imaging technique. The initial radiological evaluation often consists of plain abdominal radiography, despite significant diagnostic limitations. The traditional indications for plain films--bowel obstruction, pneumoperitoneum, and the search of ureteral calculi--are questioned by helical computed tomography (CT). Although ultrasonography (US) is in many centers the modality of choice for imaging the gallbladder and the pelvis in children and women of reproductive age, CT is considered to be one of the most valued tools for triaging patients with acute abdominal pain. CT is particularly beneficial in patients with marked obesity, unclear US findings, bowel obstruction, and multiple lesions. The introduction of multidetector row CT (MDCT) has further enhanced the utility of CT in imaging patients with acute abdominal pain.     

Accuracy of nonfocused helical CT for the diagnosis of acute appendicitis: a 5-year review

OBJECTIVE: The clinical usefulness of routine, nonfocused helical CT was evaluated in diagnosing acute appendicitis or providing an alternative diagnosis in patients presenting to the emergency department with acute lower abdominal pain. MATERIALS AND METHODS: We reviewed CT reports and clinical records of 650 consecutive adult patients who presented between January 1996 and December 2000 with right lower quadrant pain or lower abdominal pain and clinical findings suggestive of appendicitis. Helical CT was performed with oral contrast material in 610 cases (93.8%) and IV contrast in 572 cases (88.0%). Both vascular and enteric contrast media were administered in 544 cases (83.7%). Rectal contrast material was administered in 52 cases (8.0%). The abdomen was helically scanned from the dome of the diaphragm to the iliac crests with a collimation of 7 mm, from the iliac crests to the acetabular roof at a 5-mm collimation, from the acetabular roof to the symphysis pubis with a collimation of 5-10 mm. The surgical or clinical record was used for follow-up. RESULTS: Of the 650 patients, 552 (84.9%) had adequate clinical follow-up. There were 137 true-positive, eight false-positive, five false-negative, and 402 true-negative cases. The sensitivity, specificity, and accuracy of nonfocused helical CT were 96.5%, 98.0%, 97.6%, respectively. The positive and negative predictive values were 94.5% and 98.8%, respectively. In patients without acute appendicitis, CT suggested an alternative diagnosis, which clinically explained the patient's acute abdominal pain in 266 patients (66.2%). CONCLUSION: Nonfocused helical CT was highly accurate in diagnosing acute appendicitis or suggesting an alternative diagnosis in patients with acute lower abdominal pain or right lower quadrant pain.     

Helical CT of diaphragmatic rupture caused by blunt trauma

OBJECTIVE: The purpose of this study was to determine the diagnostic sensitivity and specificity of helical CT with sagittal and coronal reformatted images in detecting diaphragmatic rupture after blunt trauma. MATERIALS AND METHODS: Chest and abdominal helical CT scans obtained in 41 patients with suspected diaphragmatic injury after major blunt trauma were reviewed by three observers who were unaware of surgical findings. Coronal and sagittal reformatted images were reviewed for each patient as well. Findings consistent with diaphragmatic injury, such as waistlike constriction of abdominal viscera (i.e., the "collar sign"), intrathoracic herniation of abdominal contents, and diaphragmatic discontinuity were recorded. Sensitivity and specificity of helical CT were calculated on the basis of surgical findings and clinical follow-up. RESULTS: Helical CT was performed preoperatively in 23 patients with diaphragmatic rupture (left, n = 17; right, n = 5; bilateral, n = 1). An additional 18 patients underwent helical CT to further evaluate suspicious findings seen on chest radiography at admission and were found to have an intact diaphragm. Sensitivity for detecting left-sided diaphragmatic rupture was 78% and specificity was 100%. Sensitivity for the detection of right-sided diaphragmatic rupture was 50% and specificity was 100%. The most common CT finding of diaphragmatic rupture was the collar sign, identified in 15 patients (sensitivity, 63%; specificity, 100%). Diaphragmatic discontinuity was seen in four patients. CONCLUSION: Helical CT, especially with the aid of reformatted images, is useful in the diagnosis of acute diaphragmatic rupture after blunt trauma. Helical CT can be used to detect 78% of left-sided and 50% of right-sided injuries.     

Abdominal radiography after CT reveals urinary calculi: a method to predict usefulness of abdominal radiography on the basis of size and CT attenuation of calculi

OBJECTIVE: The purpose of this study was to determine if the radiographic visibility of urinary tract calculi could be predicted on the basis of CT features. MATERIALS AND METHODS: The images of 26 patients whose urinary tract calculi were revealed on unenhanced helical CT and who also underwent digital abdominal radiography were retrospectively reviewed. CT features studied included size and CT attenuation of the calculi. These CT findings were correlated with the ability to detect the same calculi with radiography. RESULTS: Forty-nine urinary tract calculi were detected with unenhanced helical CT in 26 patients. Twenty-six (53%) calculi were visible on radiography. Most (79%) calculi larger than 5 mm were detectable with radiography (p < 0.01). One (8%) of 13 calculi with CT attenuation below 200 H was detectable on radiographs. Ninety-five percent (21/22) of calculi with CT attenuation exceeding 300 H were visible on radiographs (p < 0.0001). The one remaining calculus was obscured by overlying anatomy. CONCLUSION: Radiographic surveillance of urinary tract calculi detected with CT may not be useful if the calculi have a CT attenuation below 200 H. Most calculi larger than 5 mm and nearly all calculi with a CT attenuation exceeding 300 H can be seen on abdominal radiographs.     

Is unenhanced CT sufficient for evaluation of acute abdominal pain?

Background: To determine whether intravenous contrast improves the ability of radiologists to establish the cause of acute abdominal pain after nondiagnostic or normal unenhanced CT. Methods: Out of 164 consecutive emergency department patients presenting with less than 48 h of nontraumatic, acute abdominal pain, a confident diagnosis for cause of pain was made prospectively in 71/164 (43%) patients on these unenhanced scans by the monitoring radiologist. In the other 93 patients, our study sample, intravenous contrast-enhanced CT was obtained. At a later date, retrospectively, two experienced abdominal CT radiologists independently evaluated unenhanced CT scans alone for potential causes of pain and diagnostic confidence level on a 1–3 scale. At least 2 weeks later, intravenous enhanced and unenhanced scans were read side-by-side for the same assessment. Results: There was no significant difference in diagnostic confidence levels comparing unenhanced CT alone (2.59) vs. intravenous enhanced and unenhanced CT together (2.64). Chi-square analysis found no significant difference in finding a cause for pain when intravenous contrast was added compared to the initial unenhanced scan alone. Conclusions: Intravenous contrast did not significantly improve the ability of CT to establish a cause of abdominal pain after a negative or nondiagnostic unenhanced CT.     

Thrombus imaging in acute ischaemic stroke using thin-slice unenhanced CT: comparison of conventional sequential CT and helical CT

Objectives

Thin-slice helical unenhanced CT can be used for thrombus imaging but increases radiation exposure. Conventional sequential images obtained by multidetector CT can be reconstructed into thin-slice images. The purpose of this study was to evaluate if conventional sequential unenhanced CT images can replace helical unenhanced CT for thrombus imaging.

Methods

Fifty consecutive patients with acute ischaemic stroke underwent both 5-mm conventional sequential unenhanced CT and helical unenhanced CT. Each of the sequential and helical unenhanced CT images was subsequently reconstructed into four 1.25-mm images. Thrombus volumes and HU were measured semi-automatically using both types of unenhanced CT. Thrombus HU ratio (rHU) was calculated using the HU of the contralateral segment. The intraclass correlation coefficient (ICC) and Bland–Altman plots were used to assess measurement agreement.

Results

The mean rHUs were 1.47?±?0.17 for sequential unenhanced CT and 1.47?±?0.18 helical unenhanced CT (P?=?0.542). The mean thrombus volumes were 124.25?±?125.65?mm³ and 117.84?±?124.32?mm³ on sequential and helical unenhanced CT images, respectively (P?=?0.063). Measurement agreement between thrombus volumes from the two unenhanced CT images was high (ICC?=?0.981).

Conclusions

Thin-slice unenhanced CT images reconstructed from 5-mm sequential images can replace helical unenhanced CT for thrombus imaging in acute ischaemic stroke.

Key Points

? Unenhanced CT is used to evaluate intra-arterial thrombus. ? Thrombus HU and volume measurements using sequential or helical CT are comparable. ? Conventional sequential images can replace helical CT for thrombus imaging. ? Radiation dose for thrombus imaging can be reduced using sequential CT.     

The role of aortic wall CT attenuation measurements for the diagnosis of acute aortic syndromes

Objectives

To determine if measurements of aortic wall attenuation can improve the CT diagnosis of acute aortic syndromes.

Methods

CT reports from a ten year period were searched for acute aortic syndromes (AAS). Studies with both an unenhanced and a contrast enhanced (CTA) series that had resulted in the diagnosis of intramural hematoma (IMH) were reviewed. Diagnoses were confirmed by medical records. The attenuation of aortic wall abnormalities was measured. The observed attenuation threshold was validated using studies from 39 new subjects with a variety of aortic conditions.

Results

The term “aortic dissection” was identified in 1206, and IMH in 124 patients’ reports. IMH was confirmed in 31 patients, 21 of whom had both unenhanced and contrast enhanced images. All 21 had pathologic CTA findings, and no CTA with IMH was normal. Attenuation of the aortic wall was greater than 45 HUs on the CTA images in all patients with IMH. When this threshold was applied to the new group, sensitivity for diagnosing AAS was 100% (19/19), and specificity 94% (16/17). Addition of unenhanced images did not improve accuracy.

Conclusions

Measurements of aortic wall attenuation in CTA have a high negative predictive value for the diagnosis of acute aortic syndromes.     

Acute abdomen: Added diagnostic value of coronal reformations with 64-slice multidetector row computed tomography

RATIONALE AND OBJECTIVES: We sought to assess retrospectively the added value of coronal reformations from isotropic voxels obtained with 64-slice multidetector row computed tomography (CT) of the acute abdomen. MATERIALS AND METHODS: This retrospective study was approved by the institutional review board and informed consent was waived. Multidetector helical 64-section CT (section thickness, 0.6 mm; pitch 1.75; table speed 35 mm/sec) was performed in 100 patients (60 women and 40 men; age range, 9-/+85 years; mean age, 45.2 years) with acute nontraumatic abdominal pain who had been referred from the emergency department. Axial images were reconstructed with 5-mm-thick sections at 5-mm intervals. The second data set was reformatted coronally, with 3-mm-thick sections at 3-mm intervals. Four independent, blinded readers with various level of training interpreted first the axial scans alone and then followed immediately by the coronal scans. Confidence in the visualization of anatomy and pathology was scored on a 5-point scale. The final diagnosis was determined by surgical and pathologic reports and by clinical follow-up in those who did not undergo surgery. RESULTS: Based upon the individual patient's clinical history and other comorbid factors, 92 patients received intravenous contrast and 90 patients received oral contrast. In 45 patients, no CT abnormalities were detected for an explanation of the abdominal pain. Mean sensitivity and specificity of axial CT alone were 92.5% and 91%, respectively. No significant differences in sensitivity and specificity were observed for the use of combined axial and coronal images. For the most inexperienced reader, the coronal reformations were helpful in 95% of cases, while for the most experienced reader, the coronal reformations were helpful in 35% of the cases. The coronal images were deemed helpful in an average of 62.3% of the cases for the four readers. However, diagnosing subtle pathology in the abdominal wall was difficult on coronal reformations alone. Overall, coronal reformations improved diagnostic confidence and interobserver agreement over axial images alone for visualization of normal abdominal structures and in the diagnosis of abdominal pathology. CONCLUSION: Axial and coronal reformations of 64-section multidetector row CT have equal sensitivity and specificity for the diagnosis of acute abdominal pathology. However, coronal reformations improved the diagnostic confidence for all readers but most significantly for the least experienced. Therefore, radiology departments with residents should consider routinely generating coronal images in patients with acute abdominal pain.