High-attenuation mediastinal masses on unenhanced CT

On unenhanced CT scans, a variety of mediastinal masses contain areas with attenuation values higher than the attenuation value of the chest wall musculature. The increased attenuation may be diffuse or focal and may be a result of calcium deposition, high iodine content, or areas of acute hemorrhage. This report illustrates the gamut of high-attenuation mediastinal masses seen on unenhanced CT. Masses that are of high attenuation only on IV contrast-enhanced images (e.g., aberrant vessels) are not included.     

Pheochromocytoma: detection by unenhanced CT

During a 2 1/2-year period, 10 patients with suspected pheochromocytoma were evaluated by unenhanced computed tomography (CT). Six adrenal masses, one hyperplastic adrenal gland, and two extraadrenal retroperitoneal masses were detected in seven patients; CT of the adrenals and retroperitoneum was normal in three patients. Scintigraphy with iodine-131 metaiodobenzylguanidine (131I-MIBG) was performed in nine of the 10 patients and corroborated the CT findings in all cases. In the three patients with normal CT and 131I-MIBG scintigraphic findings, follow-up assays of serum catecholamines were normal. In six of the seven patients with abnormal CT scans, surgical and pathologic confirmation was obtained; one patient was lost to follow-up after her CT scan. Unenhanced CT is recommended as the initial localizing procedure in patients with suspected pheochromocytoma, thereby avoiding the small but finite risk of hypertensive crisis associated with intravenous injection of urographic contrast medium.     

Normal ureter size on unenhanced helical CT

OBJECTIVE: Unenhanced helical CT is the imaging method of choice when evaluating patients with acute flank pain and suspected ureterolithiasis. In addition to directly identifying stones in the lumen of the ureter, CT secondary signs of obstruction such as ureteral dilatation are frequently present and can be helpful in establishing a diagnosis. The purposes of this study were to define ureteral dilatation on unenhanced helical CT and determine the range of normal ureter size. MATERIALS AND METHODS: We retrospectively reviewed the unenhanced helical CT studies of 212 consecutive patients with acute flank pain whose CT scans showed acute ureterolithiasis. The size of the ureter was determined on the asymptomatic side as well as on the obstructed side. Mean ureteral diameter was determined as the largest transverse dimension along the course of the ureter beginning 1-2 cm below the ureteropelvic junction. RESULTS: The mean size of ureters on the asymptomatic side was 1.8 mm with a standard deviation (SD) of 0.9 mm. The mean size of ureters on the obstructed side was 7 mm with an SD of 3.2 mm. In 96% of patients, the ureter diameter on the asymptomatic side was 3 mm or smaller. CONCLUSION: Three millimeters should be considered the upper limit of normal size for nonobstructed ureters on unenhanced helical CT.     

Dual-energy CT of the brain: Comparison between DECT angiography-derived virtual unenhanced images and true unenhanced images in the detection of intracranial haemorrhage

Objective

To evaluate the diagnostic performance of virtual non-contrast (VNC) images in detecting intracranial haemorrhages (ICHs).

Methods

Sixty-seven consecutive patients with and 67 without ICH who underwent unenhanced brain CT and DECT angiography were included. Two radiologists independently evaluated VNC and true non-contrast (TNC) images for ICH presence and type. Inter-observer agreement for VNC and TNC image evaluation was calculated. Sensitivity and specificity of VNC images for ICH detection were calculated using Fisher’s exact test. VNC and TNC images were compared for ICH extent (qualitatively and quantitatively) and conspicuity assessment.

Results

On TNC images 116 different haemorrhages were detected in 67 patients. Inter-observer agreement ranged from 0.98–1.00 for TNC images and from 0.86–1.00 for VNC images. VNC sensitivity ranged from 0.90–1, according to the different ICH types, and specificity from 0.97–1. Qualitatively, ICH extent was underestimated on VNC images in 11.9% of cases. Haemorrhage volume did not show statistically significant differences between VNC and TNC images. Mean haemorrhage conspicuity was significantly lower on VNC images than on TNC images for both readers (p?<?0.001).

Conclusion

VNC images are accurate for ICH detection. Haemorrhages are less conspicuous on VNC images and their extent may be underestimated.

Key points

? VNC images represent a reproducible tool for detecting ICH.? ICH can be identified on VNC images with high sensitivity and specificity.? Intracranial haemorrhages are less conspicuous on VNC images than on TNC images.? Intracranial haemorrhages extent may be underestimated on VNC images.

     

Spontaneous intracranial hypotension: use of unenhanced MRI

We report a case of spontaneous intracranial hypotension diagnosed with unenhanced cranial MRI, showing laminar subdural fluid and engorgement of the hypophysis and perisellar sinuses. Cerebrospinal fluid pressure was low. MRI was normal after resolution of symptoms. Prior reports emphasise the enhancing pachymeninges seen in this syndrome. We maintain that, when subdural collections and perisellar engorgement are detected on unenhanced MRI in the proper clinical setting, contrast enhancement may not be necessary for the diagnosis. Received: 23 June 1999 Accepted: 13 August 1999     

The value of unenhanced scans in differentiating lesions producing ring enhancement

Ring enhancement with contrast material is a nonspecific computed tomographic finding seen in a variety of lesions, including benign and malignant neoplasms, inflammation, infarction, and hematoma. This lack of specificity is especially troublesome in the differentiation of self-limiting disorders (infarction and hematoma) from progressive processes (tumor or abscess) potentially requiring surgical treatment. To determine whether more specific diagnoses were possible, 115 cases with ring lesions were retrospectively evaluated for the usefulness of precontrast scan features. The presence or absence of a complete ring proved useful. A complete ring on unenhanced scans effectively excluded self-limiting processes; it was seen in none of 18 infarcts or 11 hematomas. A complete ring on unenhanced scans occurred in 37 of 65 neoplasms, and was more common in metastatic disease (2:1) than in gliomas. A complete ring on unenhanced computed tomography was also seen in four of 15 pyogenic abscesses.     

Volume rendering of tendon-bone relationships using unenhanced CT

OBJECTIVE: Clinically, three-dimensional CT of the extremities is most often used to display bony anatomy. However, by combining unenhanced CT with volume-rendering computer graphics, visualization of relationships between bone and soft-tissue structures such as muscle tendon is also possible. The aims of this study were to quantify CT attenuation values of peripheral tendon, muscle, and bone on unenhanced CT and to develop custom opacity transforms on the basis of the attenuation measurements to effectively depict tendon-muscle-bone relationships. CONCLUSION: The mean attenuation of peripheral tendon ( approximately 100 H) is distinctly higher than that of muscle ( approximately 60 H) enabling high-quality volume rendering of muscle-tendon-bone relationships with unenhanced CT. High-frequency (bone) CT reconstruction algorithms commonly used for extremity CT produce approximately twofold higher image noise and inferior three-dimensional renderings compared with those based on less noisy standard or soft-tissue reconstruction algorithms. These concepts can be used to uniquely reveal tendon-muscle-bone relationships for clinical, scientific, and educational purposes.     

多层螺旋CT平扫对急性腹部创伤的诊断价值

目的:进一步认识16层螺旋CT平扫在急性腹部创伤中的诊断价值.方法:990例急性腹部创伤患者,在未口服对比剂情况下行16层螺旋CT平扫,分析其CT影像表现.CT扫描后123例行剖腹术,18例经介入治疗,665例经过1次以上CT随访.把CT初诊结果与手术及随访结果进行比较,观察CT平扫发现急性腹部创伤的敏感性、特异性.结果:990例腹部创伤患者中,首诊阴性病例703例,阳性病例287例,其中实质性脏器损伤238例,空腔脏器损伤7例,实质性脏器损伤合并空腔脏器损伤19例,23例仅见腹腔积液.与手术及随访结果比较,发现实质脏器损伤的假阳性9例,假阴性2例;空腔脏器损伤的假阳性3例,假阴性5例.实质性脏器损伤的敏感性为99.2%,特异性为98.8%;空腔脏器损伤的敏感性为82.1%,特异性99.7%.结论:多层螺旋CT对急性腹部创伤有较高诊断价值,对实质性脏器损伤的发现具有很高的敏感性、特异性,对于空腔脏器损伤诊断的敏感性相对较低.     

胸部非增强CT评价贫血的准确性

目的探讨心腔血液CT值与血红蛋白（Hb）浓度的关系，评价胸部非增强cT诊断贫血的准确性。方法胸部（心脏）非增强螺旋CT扫描患者92例，分别测量左心室血液及室间隔的CT密度，测量患者血液中Hb的浓度，计算血液与室间隔CT密度比，分析各因素之间的相关性。结果血液的CT密度与Hb浓度呈正相关（r=0．571，P=0．000）；血液与室间隔的CT密度比与Hb浓度也呈正相关（r=0．650，P=0．000）。该密度比男性〈90％、女性〈87％则提示患者贫血。结论左心室血液与室间隔的CT密度比可作为判断患者是否贫血的较可靠指标。     

Demonstration of nerve roots on unenhanced computed tomographic scans

Small foci of high attenuation are seen within the subarachnoid space on high resolution axial transverse computed tomography (CT) of the lumbar spine. By use of reformatted images in oblique planes, these foci form linear structures of high attenuation corresponding to the nerve roots of the cauda equina. Unenhanced CT is therefore capable of demonstrating the nerves of the cauda equina in selected cases.     

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.     

Fluctuations in eGFR in relation to unenhanced and enhanced MRI and CT outpatients

Objective

To study fluctuations in estimated glomerular filtration rate (eGFR) in relation to contrast medium (CM) enhanced magnetic resonance imaging (MRI) and computed tomography (CT) compared to control groups in outpatients.

Materials and methods

eGFR was determined right before the imaging procedure and three days later at the department or at the patient's home. The iodine-based and gadolinium-based contrast media were the same as used for all other examinations at the department.

Results

A total of 716 patients completed the study. There was a statistically significant, but not clinically relevant rise in eGFR after three days in all four groups. The average eGFR variation was 4.8 ml/min/1.73 m². There were large variations in eGFR between the two measurements in 45.8% of the patients as they had a change greater than ±10 ml/min/1.73 m². Only three patients fulfilled the contrast-induced nephropathy (CIN) requirement when the definition s-creatinine ≥44 μmol/l (0.5 mg/dl) was used.

Conclusions

eGFR in outpatients undergoing MRI or CT did vary independently of whether the patient received contrast or not. The findings probably reflect the natural variations in s-creatinine levels. This should be taken into consideration when CIN is studied.     

Detection of ingested cocaine-filled packets--diagnostic value of unenhanced CT

PURPOSE: Emergency departments are facing nowadays an increasing number of illegal drug-related health problems, associated with medicolegal and/or social consequences. Body stuffers are street cocaine dealers, who either store wrapped packets of drugs in their rectum or hastily swallow them, prompted by fear of police's arrest. These packets can be life threatening in case of leakage. We evaluate the diagnostic value of unenhanced multidetector CT (MDCT) for detection of cocaine-filled packets (CFP) ingested by body stuffers in a phantom model. MATERIALS AND METHODS: Our phantom simulated normal bowel contents in which a varying number of true and false CFP were randomly mixed. Both only differ in radiological density. During 18 different reading sessions, four radiologists independently evaluated the presence and number of true and false CFP. Interobserver agreement, sensitivity, specificity, positive and negative predictive value were calculated. RESULTS: Interobserver agreement for detection of any packets, for visualization of true, and false CFP was good (kappa=0.63, 0.74 and 0.58, respectively). Sensitivity, specificity, positive and negative predictive value for detection of any packets was 95.6%, 100%, 100% and 62.5%, respectively; for visualization of the true CFP 86.5%, 100%, 100% and 77.6%, respectively; and for the false packets 98.1%, 65%, 88.6% and 87.5%, respectively. CONCLUSION: Unenhanced MDCT without bowel preparation is a fast, reliable and easily reproducible imaging modality for the immediate detection of ingested CFP, thus facilitating medicolegal management of body stuffers.