Accuracy of Nonenhanced CT vs Contrast-Enhanced CT for Diagnosis of Acute Appendicitis in Adults

BackgroundAcute appendicitis is one of the most common causes of acute abdominal pain requiring emergency intervention. It is often difficult for the clinician to make an accurate diagnosis due to nonspecific and overlapping clinical symptoms. Computed tomography (CT) has become the imaging modality of choice for the evaluation of suspected acute appendicitis. The main purpose of our study was to compare nonenhanced CT (NECT) with contrast-enhanced CT (CECT) for the diagnosis of acute appendicitis.Material and MethodsA total of 140 patients were enrolled in the study. Two abdominal radiologists—masked to both the clinical information and the final diagnosis—retrospectively reviewed the computed tomographic findings and made an imaging diagnosis based on (1) NECT only, (2) CECT only, and (3) both NECT and CECT. With the final diagnosis as the reference standard, the accuracy of each CT technique was estimated.ResultsThe respective sensitivity, specificity, and accuracy for NECT, CECT, and NECT + CECT for the diagnosis of acute appendicitis were 80.7%, 86.7%, and 84.3%; 86.0%, 81.9%, and 83.6%; and, 87.7%, 80.7%, and 83.6%. There was no significant difference in the diagnosis of acute appendicitis among the 3 techniques. In order to make a correct diagnosis, the presence of at least 3 imaging findings for NECT or at least 4 for CECT had the best diagnostic accuracy. We also found that 9.25 mm was the optimal cut-off threshold for the detection of patients with acute appendicitis.ConclusionOur study allowed direct comparison between NECT, CECT, and NECT + CECT combined. There was no difference in the ability of each CT technique for diagnosing patients with acute appendicitis. For a patient whom iodinated contrast media is contraindicated or a patient who has an increased risk of severe adverse reaction, we would encourage the use of NECT because it provides comparable diagnostic accuracy without further exposing such patient to the contrast media.     

The unilateral hyperdense middle cerebral artery: An early CT-sign of embolism or thrombosis

Summary In four patients with acute neurologic deficits non-enhanced CT on admission showed a hyperdense segment of one middle cerebral artery. These patients eventually turned out to have complete infarctions of the middle cerebral artery territory, the high density representing an intravascular clot. Three patients died within a few days and one survived with disabling deficits, so this visualisation of emboli on CT may be considered to be a sign of a poor prognosis.     

Perfusion CT in acute stroke: prediction of vessel recanalization and clinical outcome in intravenous thrombolytic therapy

This study evaluated perfusion computed tomography (PCT) for the prediction of vessel recanalization and clinical outcome in patients undergoing intravenous thrombolysis. Thirty-nine patients with acute ischemic stroke of the middle cerebral artery territory underwent intravenous thrombolysis within 3 h of symptom onset. They all had non-enhanced CT (NECT), PCT, and CT angiography (CTA) before treatment. The Alberta Stroke Program Early Computed Tomography (ASPECT) score was applied to NECT and PCT maps to assess the extent of ischemia. CTA was assessed for the site of vessel occlusion. The National Institute of Health Stroke Scale (NIHSS) score was used for initial clinical assessment. Three-month clinical outcome was assessed using the modified Rankin scale. Vessel recanalization was determined by follow-up ultrasound. Of the PCT maps, a cerebral blood volume (CBV) ASPECT score of >6 versus ≤6 was the best predictor for clinical outcome (odds ratio, 31.43; 95% confidence interval, 3.41–289.58; P < 0.002), and was superior to NIHSS, NECT and CTA. No significant differences in ASPECT scores were found for the prediction of vessel recanalization. ASPECT score applied to PCT maps in acute stroke patients predicts the clinical outcome of intravenous thrombolysis and is superior to both early NECT and clinical parameters. S.P. Kloska and R. Dittrich contributed equally to this work.     

Prospective comparison of helical CT of the abdomen and pelvis without and with oral contrast in assessing acute abdominal pain in adult Emergency Department patients

Purpose This prospective study compares the agreement of nonenhanced helical computed tomography (NECT) with oral contrast-enhanced computed tomography (CECT) in Emergency Department (ED) patients presenting with acute abdominal pain.Materials and methods One hundred eighteen patients presenting to the ED with acute abdominal pain undergoing CT were enrolled over a 13-month period using convenience sampling. Exclusion criteria included acute trauma, pregnancy, unstable patients, and patients suspected of having urinary calculi. Patients were scanned helically using 5-mm collimation before and approximately 90 min after oral contrast administration. Both exams were prospectively interpreted by different attending radiologists in a blinded fashion using an explicit data sheet specifying the presence or absence of 28 parameters relating to various common diagnoses.Results The 118 patients had a mean age of 49 years, a male: female ratio of 7:13, and a median height, weight, and BMI of 166 cm, 80 kg, and 29, respectively. The most common indications for the study included appendicitis (32%) and diverticular disease (12%). Pain maximally localized to the right lower quadrant in 37% and the left lower quadrant in 21%. There were 21 patients that had significant disagreement of interpretations between NECT and CECT resulting in a simple agreement of 79% (95% CI: 70–87%). For specific radiologic parameters, agreement ranged from 77 to 100%. A post hoc agreement analysis was subsequently performed by two radiologists and only five paired scans were identified as discordant between the NECT and CECT. For only one of these patients did both radiologists agree that there was a definite discordant result between the two studies. A final unblinded consensus review demonstrated that much of the disagreement between the interpretations was related to interobserver variation.Conclusion There is 79% simple agreement between NECT and CECT in diagnosing various causes of acute abdominal pain in adult ED patients. Post hoc analysis indicates that a significant portion of the discordance was attributable to interobserver variability. This data suggests that NECT should be considered in adult ED patients presenting with acute abdominal pain.This work was partially presented at the RSNA in Chicago 2004.     

PET/CT in malignant melanoma: contrast-enhanced CT versus plain low-dose CT

Purpose  

The aim of this study was to evaluate the diagnostic value of contrast-enhanced CT (CECT) versus non-enhanced low-dose CT (NECT) in the staging of advanced malignant melanoma with ¹⁸F-fluordeoxyglucose (FDG) positron emission tomography (PET)/CT.     

Double-helical CT pitfall: the native hyperdense basilar artery

PURPOSE: The unenhanced signs of basilar thrombosis at computed tomography (CT) is the hyperdense visualization of the basilar artery due to intravascular thrombosis. In patients who are clinically asymptomatic, hyperdense visualization of the basilar artery can be observed, if scanned with a double helical CT. Purpose of the present study was to evaluate the diagnostic significance of these changes seen at double-helical CT. MATERIAL AND METHOD: Ten patients patients underwent double-helical CT of a portion of the base of the skull. In each case, 5-mm and 10-mm fused slices were obtained. The patency of the visualized vessels was then documented using contrast-enhanced images. RESULTS: The differences in attenuation between the 5-mm and 10-mm fused slices obtained at native examinations were a median 11 HU. Subsequent contrast enhanced studies documented patency of the examined vessels. CONCLUSION: The present data show that the hyperdense basilar artery as a sign of thrombotic occlusion is not valid when thin, fused slices are obtained at double-helical CT.     

“Hyperdense artery sign” in early ischemic stroke: diagnostic value of model-based reconstruction approach in comparison with standard hybrid iterative reconstruction algorithm

Purpose

Hyperdense artery sign is the earliest sign of ischemic stroke on non-enhanced computed tomography and it can be visible long before parenchymal changes. The aim of our study was to compare diagnostic value of model-based iterative reconstruction algorithm (IMR) with that of iterative reconstruction algorithm (iDose4) in identifying hyperdense artery sign.

Methods

We selected 56 consecutive patients suspected for ischemic stroke, who underwent a NCCT and that demonstrated a vessel occlusion at angio-CT or developed ischemic lesion at follow-up CT. Two readers randomly analyzed images of NCCT reconstructed both with iDose4 (4 mm) and IMR (2 mm), reporting presence of hyperdense artery sign (0: no; 1: yes; 2: not sure). They rated image quality on a 4-point scale (1: unacceptable; 4: more than average) and recorded HU values of clot and of normal vessel and measured noise index, CNR and SNR.

Results

Mean values of CTDI, DLP, and ED were respectively of 43 mGy, 819.7 mGy cm, and 1.72 mSv.By analyzing the IMR reconstruction, both readers were able to recognize hyperdense vessel sign in 55/56 patients, while only in 12/56 patients were identified with iDose.IMR obtained better rating of image quality (mean score for IMR 3.32 vs 2.53 for iDose), higher clot density (57.2 vs 46.7 HU), lower noise index (5 vs 2), higher CNR and SNR (respectively 4.2 vs 2 and 16.8 vs 8.5).

Conclusions

Model-based approach significantly increases sensitivity in detecting hyperdense artery sign, offering higher SNR and CNR in brain CT images in comparison with standard hybrid reconstruction algorithm.

     

Relationship between thrombus attenuation and different stroke subtypes

Introduction

More insights in the etiopathogenesis of thrombi could be helpful in the treatment of patients with acute ischemic stroke. The aim of our study was to determine the relationship between presence of a hyperdense vessel sign and thrombus density with different stroke subtypes.

Methods

We included 123 patients with acute ischemic anterior circulation stroke and a visible occlusion on CT-angiography caused by cardioembolism (n?=?53), large artery atherosclerosis (n?=?55), or dissection (n?=?15). Presence or absence of a hyperdense vessel sign was assessed and thrombus density was measured in Hounsfield Units (HU) on non-contrast 1 mm thin slices CT. Subsequently, occurrence of hyperdense vessel sign and thrombus density (absolute HU and rHU (=HU thrombus/HU contralateral)) were related with stroke subtypes.

Results

The presence of hyperdense vessel signs differed significantly among subtypes and was found in 45, 64 and 93 % of patients with cardioembolism, large artery atherosclerosis and dissection, respectively (p?=?0.003). The mean HU and rHU (+95 % CI) of the thrombi in all vessels were respectively 56.1 (53.2–59.0) and 1.39 (1.33–1.45) in cardioembolism, 64.6 (62.2–66.9) and 1.59 (1.54–1.64) in large artery atherosclerosis and 76.4 (73.0–79.8) and 1.88 (1.79–1.97) in dissection (p?<?0.0001). We found the same significant ranking order in the density of thrombi with hyperdense vessel signs (mean HU and rHU (+95 % CI), respectively): cardioembolism 61.3 (57.4–65.3) and 1.49 (57.4–65.3); large artery atherosclerosis 67.3 (64.9–69.7) and 1.65 (1.58–1.71); dissection 76.4 (72.6–80.1) and 1.89 (1.79–1.99, p?<?0.0001).

Conclusion

Presence of a hyperdense vessel sign and thrombus density are related to stroke subtype.     

Effect of contrast material on image noise and radiation dose in adult chest computed tomography using automatic exposure control: a comparative study between 16-, 64- and 128-slice CT

Purpose

To determine the difference in radiation dose between non-enhanced (NECT) and contrast-enhanced (CECT) chest CT examinations contributed by contrast material with different scanner generations with automatic exposure control (AEC).

Methods & materials

Each 42 adult patients received a NECT and CECT of the chest in one session on a 16-, 64- or 128-slice CT scanner with the same scan protocol settings. However, AEC technology (Care Dose 4D, Siemens) underwent upgrades in each of the three scanner generations. DLP, CTDIvol and image noise were compared.

Results

Although absolute differences in image noise were very small and ranged between 10 and 13 HU for NECT and CECT in median, the differences in image noise and dose (DLP: 16-slice:+2.8%; 64-slice:+3.9%; 128-slice:+5.6%) between NECT and CECT were statistically significant in all groups. Image noise and dose parameters were significantly lower in the most recent 128-slice CT generation for both NECT and CECT (DLP: 16-slice:+35.5-39.2%; 64-slice:+6.8-8.5%).

Conclusion

The presence of contrast material lead to an increase in dose for chest examinations in three CT generations with AEC. Although image noise values were significantly higher for CECT, the absolute differences were in a range of 3 HU. This can be regarded as negligible, thus indicating that AEC is able to fulfill its purpose of maintaining image quality. However, technological developments lead to a significant reduction of dose and image noise with the latest CT generation.     

Patient encounter time intervals in the evaluation of emergency department patients requiring abdominopelvic CT: oral contrast versus no contrast

The aim of the study was to assess various time intervals during patient encounters involving unenhanced (NECT) versus oral-contrast-enhanced (CECT) abdominopelvic (A/P) CT performed in the emergency department (ED) on adult patients presenting with acute abdominal pain. Computerized patient order entry and administrative data as well as scans themselves were retrospectively evaluated at a high-volume (107,000 visits per annum) regional medical center urban ED for a period of 30 consecutive days. All adult patients who had CT of abdomen and pelvis for abdominal pain during the 30 days of the study period were included. Data collected included demographic information, time of registration, time of first encounter in the ED, time of CT order, clinical indication for scan, time of scan, time of disposition (i.e., discharge or admit), and final disposition. Patients were excluded if they were less than 16 years old, pregnant, or met criteria for major trauma and evaluation in the trauma suite. Patients were also excluded from analysis if they received more than one scan on the same day (3 patients). Of 183 patients, 102 underwent NECT and 81 CECT. Some of the patients who underwent NECT had urinary colic. Among patients who did not have urinary colic there is a statistically significant difference in the median time intervals between: (1) patient arrival in the ED and evaluation by a physician (NECT 57 min, CECT 84 min, P<0.001); (2) patient exam by the physician and the time the A/P CT was ordered (NECT 35 min, CECT 63 min, P<0.01); (3) receipt of the CT order and the time of the scan (NECT 104 min, CECT 172 min, P<0.001); and (4) time of arrival in ED and disposition (NECT 358 min, CECT 599 min, P<0.001). There are significant time interval differences between CECT and NECT during patient encounters involving adults presenting with abdominal pain to the ED. The differences are greater than the amount of time allotted for opacification of small bowel (90 min). Baseline data such as these may prove useful in assessing the efficacy of scan techniques and improving resource utilization.     

Intravenous contrast medium and renal cyst

There are many reasons for what is apparently a benign renal cyst being hyperdense on computed tomography (CT). A previous intravascular contrast material injection (intravenous urogram or arteriogram) within one to three days is cited as one of the possible causes. This prospective study of 13 patients with renal cyst was designed to investigate such a possibility. None of the patients had a hyperdense renal cyst on delayed CT scan following contrast injection. We conclude that intravenous contrast material is not a cause of hyperdensity of a renal cyst on CT.     

CT demonstration of portal and superior mesenteric vein thrombosis in hepatocellular carcinoma

Three cases of hepatocellular carcinoma in which computed tomography (CT) demonstrated thrombosis of the portal vein are reported. In one patient, extension of the thrombus into the superior mesenteric vein was identified as well. The outstanding CT features of portal vein thrombosis were: (a) enlargement of the vein, (b) intraluminal low density area, and (c) hyperdense peripheral ring due to the enhancement of the venous wall. These findings may be useful in differentiating hepatocellular carcinoma from hepatic metastases.     

Acute appendicitis: diagnostic value of nonenhanced CT with selective use of contrast in routine clinical settings

The purposes of this study were to determine the (1) frequency with which nonenhanced computed tomography (CT) (NECT) permits conclusive diagnosis of acute appendicitis, (2) accuracy of NECT when findings are conclusive, and (3) overall accuracy of a CT protocol consisting of NECT with selective use of contrast. Five hundred and thirty-six patients underwent a NECT protocol with selective use of contrast. Diagnostic accuracy was then determined separately for (1) patients with conclusive initial NECT, (2) patients with inconclusive initial NECT, and (3) all patients. NECT was conclusive on initial interpretation in 404/536 patients and inconclusive in 132/536. Of 132 inconclusive studies, 126 were repeated with contrast (intravenous, oral or rectal). Sensitivity, specificity, and positive and negative predictive value for diagnosis of acute appendicitis were (1) 90%, 96.0%, 84.8%, and 97.4% in patients with conclusive NECT (n = 404); (2) 95.6%, 92.3%, 73%, and 99% in patients with inconclusive NECT followed by repeat CT with contrast; and (3) 91.3%, 95%, 82%, and 98% in all patients. The initial diagnosis of appendicitis may be made by NECT in 75% of patients, with contrast administration reserved for inconclusive NECT studies.     

Hyperdense artery sign on computed tomography in acute ischemic stroke

Despite the advent and growing availability of magnetic resonance imaging, the imaging modality of choice in the acute care of stroke patients in many institutions remains computed tomography. The hyperdense artery sign is the earliest marker of acute ischemic stroke. In this short review, we discuss the pathology, incidence, clinical aspects, imaging findings, significance and future questions that need to be addressed concerning this important sign.     

Enhancement pattern of hepatocellular carcinoma: comparison of real-time contrast-enhanced ultrasound and contrast-enhanced computed tomography

We compared the enhancement pattern of 98 hepatocellular carcinoma nodules in 92 patients on contrast-enhanced ultrasound (CEUS) and contrast-enhanced computed tomography (CECT). Contrast-enhanced ultrasound was performed with SonoVue and a low mechanical index method. In arterial phase, 98 nodules were hyperenhancing on CEUS and 94 on CECT. In portal phase, 82 nodules were hypoenhancing on CEUS and 83 on CECT. Peripheral thin-rim-like enhancement was exhibited in 30 nodules on CEUS and 31 on CECT. Intratumoral vessels were visualized in 94 nodules on CEUS and 36 on CECT.     

Hyperdense gallbladder wall sign: an overlooked sign of acute cholecystitis on unenhanced CT examination

We reviewed the unenhanced computer tomography (CT) scans of 53 patients with surgically proven acute cholecystitis, where 27 patients presented with hyperdense gallbladder wall. To our knowledge, this sign was never reported before. Because mucosa is highly sensitive to ischemia, early mucosal necrosis and hemorrhage may result in CT-detectable high density. Similar episode may also occur in acute cholecystitis. This sign also reflects high probability for acute gangrenous cholecystitis. We suggest that patients with this sign should have urgent treatment.     

Acute portal vein thrombosis

The findings in acute portal vein thrombosis in a patient with chronic calcific pancreatitis and two episodes of pancreatic surgery are described. The diagnosis was made by ultrasound, which showed a dilated portal vein filled with low-level echoes, surrounding hepatic oedema, hypertrophy of the hepatic artery, splenomegaly, collateral vessels and ascites. This was confirmed by computed tomography. The ultrasonic differences in appearance between acute and chronic portal vein thrombosis are discussed, in the context of portal hypertension. The diagnosis of acute portal vein thrombosis should be considered in patients in the appropriate situation who suffer a sudden clinical deterioration with right upper quadrant or abdominal pain. Ultrasound is recommended as the imaging modality of first choice because of the flexibility of its scanning plane and its real time and Doppler capabilities. Computed tomography is valuable in patients with an ileus or heavy pancreatic calcification and for its ability to demonstrate patent vessels on intravenous injection of contrast medium.     

The bull's-eye sign of extracranial cervical aneurysms

Extracranial, cervical aneurysms and arterial thrombosis are uncommon entities. In most cases, they have diagnostic clinical presentations. However, on occasion the history and physical findings do not clearly suggest their presence. In these cases, postcontrast computed tomography scans can aid in rapidly establishing the correct diagnosis by revealing a "bull's-eye" appearance within the mass (vessel lumen). The diagnosis is less difficult to make when the involved vessel is the carotid artery, because this artery is routinely identified on postcontrast computed tomography scans and the lesion can be easily placed along its course. The vascular origin of such a lesion is not usually evident on computed tomography if the process does not lie along the course of a major vessel. In these cases, the bull's-eye sign can establish the diagnosis so that prompt consideration can be given to angiography and therapy.     

Multiple globoid meningiomas associated with craniomandibular fibrous dysplasia: case report

A 20-year-old male with craniomandibular deformity and almost total visual loss of the right eye due to bilateral optic atrophy underwent cerebral nonenhanced computed tomography (NECT) examinations. He had multiple sphenoidal-temporoparietal meningiomas, with adjacent hyperostoses and distant calvarial hyperdense lesions, as well as sclerotic expansion of right mandibular condyle. History, clinical and imaging findings were suggestive of associated fibrous dysplasia (FD), which explained the visual loss due to optic nerve compression through sphenoidal optic foramens. Cranial and mandibular FD and concurrent multiple globoid meningiomas in this case may suggest a mutual influence, which may explain the etiopathogenesis of FD lesions and/or bone hyperdensities adjacent or distant to meningiomas.     

Cross-sectional imaging for diagnosis and clinical outcome prediction of acute basilar artery thrombosis

Basilar artery occlusion is a potentially fatal condition and imaging findings can be subtle. Prompt diagnosis is vital, as recognition may lead to therapeutic recanalization that may improve functional outcome and survival. Furthermore, cross-sectional imaging signs may help predict eventual outcome and, therefore, guide which patients should be subjected to aggressive treatment. Computed tomography (CT) signs include a hyperdense basilar artery that has a high specificity, accuracy, positive and negative predictive value. Evidence regarding the prognostic significance of the hyperdense basilar artery sign is conflicting. Early magnetic resonance imaging (MRI) features include loss of flow void, seen as increased signal intensity within the basilar artery on T2-weigted images and identification of acute thrombus, seen as intermediate signal on T1-weighted images. MRI sequences are more sensitive for early detection of acute ischaemia or infarction, ideally with diffusion-weighted imaging (DWI). Both CT and MR angiography are sensitive for detection of acute thrombus, seen as a filling defect or occlusion. These are the non-invasive imaging techniques of choice to confirm diagnosis, with perhaps the speed and accessibility of CT angiography resulting in this technique being valuable in the acute setting. Several new scoring systems based on arterial segmentation rather than global volume assessment using CT angiography source images and DWI have shown early promise in the prediction of eventual clinical outcome in order to isolate those patients who may benefit from therapeutic recanalization.