CT detection of hepatic and splenic injuries: usefulness of liver window settings

Minimising the impact of errors in the interpretation of CT images for surveillance and evaluation of therapy in cancer

Radiological error is inevitable and usually multifactorial. Error can be secondary to radiologist-specific causes, including cognitive and perceptive errors or ambiguity of report, or system-related causes, including inadequate, misleading, or incorrect clinical information, poor imaging technique, excessive workload, and poor working conditions. In this paper, we discuss a systematic approach to reduce errors in oncological radiology reporting, thus reducing risk to the patient. Rather than attempt to discuss all types of error, we concentrate on the most important and commonly occurring errors that we have encountered over 20 years of practice, based on weekly discrepancy reviews of our practice and independent reviews of clinical and research imaging from other institutions. This review focuses on computed tomography (CT) reporting for staging, surveillance, and response assessment of cancer patients, but the messages apply to all imaging methods.

Optimization of window settings for virtual monoenergetic imaging in dual-energy CT of the liver: A multi-reader evaluation of standard monoenergetic and advanced imaged-based monoenergetic datasets

OBJECTIVES

To evaluate optimal window settings for display of virtual monoenergetic reconstructions in third-generation dual-source, dual-energy computed tomography (DECT) of the liver.

METHODS

Twenty-nine subjects were prospectively evaluated with DECT in arterial (AP) and portal venous (PVP) phases. Three reconstructed datasets were calculated: standard linearly-blended (LB120), 70-keV standard virtual monoenergetic (M70), and 50-keV advanced image-based virtual monoenergetic (M50+). Two readers assessed optimal window settings (width and level, W/L), establishing a mean for each reconstruction which was used for a blinded assessment of liver lesions.

RESULTS

The optimal W/L for M50+ were significantly higher for both AP (W=429.3 ± 44.6 HU, L=129.4 ± 9.7 HU) and PVP (W=376.1 ± 14.2HU, L=146.6 ± 7.0 HU) than for LB120 (AP, W=215.9 ± 16.9 HU, L=82.3 ± 9.4 HU) (PVP, W=173.4 ± 8.9 HU, L=69.3 ± 6.0 HU) and M70 (AP, W=247.1 ± 22.2 HU, L=72.9 ± 6.8 HU) (PVP, W=232.0 ± 27.9 HU, L=91.6 ± 14.4 HU). Use of the optimal window setting for M50+ vs. LB120 resulted in higher sensitivity (AP, 100% vs. 86%; PVP, 96% vs. 63%).

CONCLUSIONS

Application of dedicated window settings results in improved liver lesion detection rates in advanced image-based virtual monoenergetic DECT when customized for arterial and portal venous phases.

The value of "liver windows" settings in the detection of small renal cell carcinomas on unenhanced computed tomography

OBJECTIVE

To assess if "liver window" settings improve the conspicuity of small renal cell carcinomas (RCC).

METHODS

Patients were analysed from our institution's pathology-confirmed RCC database that included the following: (1) stage T1a RCCs, (2) an unenhanced computed tomography (CT) abdomen performed ≤ 6 months before histologic diagnosis, and (3) age ≥ 17 years. Patients with multiple tumours, prior nephrectomy, von Hippel-Lindau disease, and polycystic kidney disease were excluded. The unenhanced CT was analysed, and the tumour locations were confirmed by using corresponding contrast-enhanced CT or magnetic resonance imaging studies. Representative single-slice axial, coronal, and sagittal unenhanced CT images were acquired in "soft tissue windows" (width, 400 Hounsfield unit (HU); level, 40 HU) and liver windows (width, 150 HU; level, 88 HU). In addition, single-slice axial, coronal, and sagittal unenhanced CT images of nontumourous renal tissue (obtained from the same cases) were acquired in soft tissue windows and liver windows. These data sets were randomized, unpaired, and were presented independently to 3 blinded radiologists for analysis. The presence or absence of suspicious findings for tumour was scored on a 5-point confidence scale.

RESULTS

Eighty-three of 415 patients met the study criteria. Receiver operating characteristics (ROC) analysis, t test analysis, and kappa analysis were used. ROC analysis showed statistically superior diagnostic performance for liver windows compared with soft tissue windows (area under the curve of 0.923 vs 0.879; P = .0002). Kappa statistics showed "good" vs "moderate" agreement between readers for liver windows compared with soft tissue windows.

CONCLUSION

Use of liver windows settings improves the detection of small RCCs on the unenhanced CT.

Vascular emergencies in liver trauma

The use of CT in the diagnosis and management of liver trauma is responsible for the shift from routine surgical versus non-surgical treatment in the management of traumatic liver injuries, even when they are of high grade. The main cause of complication and of death in liver trauma is related to vascular injury. The goal of this review focussed on the vascular complications of liver trauma is to describe the elementary lesions shown by CT in liver trauma including laceration, parenchymal hematoma and contusions, partial devascularisation, subcapsular hematomas, hemoperitoneum, active bleeding, pseudoaneurysm of the hepatic artery, bile leak, and periportal oedema, to illustrate the possible pitfalls in CT diagnosis of liver trauma and to underline the key-points which may absolutely be present in a CT report of liver trauma. Then we will remind the grading system based on the CT features and we will analyze the interest and limitations of such grading systems. Last we will discuss the diagnostic strategy at the early phase in patients with suspected liver trauma according to their clinical conditions and underline the conditions of arterial embolization, and then we will discuss the diagnosis strategy at the delayed phase according to the suspected complications.

Transcatheter arterial embolization in the management of hemobilia

BACKGROUND

This retrospective analysis evaluated the clinical and radiologic results of transcatheter arterial embolization (TAE) in the treatment of significant hemobilia. The imaging findings, embolization technique, complications, and efficacy are described.

METHODS

Thirty-two consecutive patients (21 male, 11 female, age range 8-61 years) who were referred to the radiology department for severe or recurrent hemobilia were treated by TAE. Causes of hemobilia were liver trauma (n = 19; iatrogenic in six and road traffic accident in 13), vasculitis (n = 6), vascular malformations (n = 2), and hepatobiliary tumors (n = 5). Iatrogenic liver trauma was secondary to cholecystectomy in those six patients. Four of five hepatobiliary tumors were inoperable malignant tumors and one was a giant cavernous hemangioma. Arterial embolization was done after placing appropriate catheters as close as possible to the bleeding site. Embolizing materials used were Gelfoam, polyvinyl alcohol particles or steel coils, alone or in combination. Postembolization angiography was performed in all cases to confirm adequacy of embolization. Follow-up color Doppler ultrasound and contrast-enhanced computed tomography was done in all patients.

RESULTS

Ultrasonic, computed tomographic, and angiographic appearances of significant hemobilia were assessed. Angiogram showed the cause of bleeding in all cases. Three patients with liver trauma due to accidents required repeat embolization. Eight patients required surgery due to failed embolization (continuous or repeat bleeding in four patients, involvement of the large extrahepatic portion of hepatic artery in two, and coexisting solid organ injuries in two). Severity of hemobilia did not correlate with grade of liver injury. All 13 patients with blunt hepatic trauma showed the cause of hemobilia in the right lobe. No patient with traumatic hemobilia showed an identifiable cause in the left lobe. There were no clinically significant side effects or complications associated with TAE except one gallbladder infarction, which was noted at surgery, and cholecystectomy was performed with excision of the hepatic artery aneurysm.

CONCLUSION

TAE is a safe and effective interventional radiologic procedure in the nonoperative management of patients who have significant hemobilia.

CT Depiction of Pulmonary Emboli: Display Window Settings

PURPOSE

To compare computed tomographic (CT) window settings selected by radiologists with those determined by using two alternative approaches for depiction of pulmonary emboli (PE).

MATERIALS AND METHODS

Institutional review board approval was obtained; informed consent was not required. This study was compliant with the Health Insurance Portability and Accountability Act. Twenty-five clinical chest CT studies were obtained with a standardized PE protocol and retrospectively evaluated by five chest and two body CT radiologists. Of these studies, 13 were positive for PE, and 12 were negative. At the main pulmonary artery (PA), mean attenuations (MPA) and standard deviations (SDPA) were measured. Initially, images were displayed with a standard mediastinal window setting (window width, W = 400 HU; window center, C = 30 HU), and each observer adjusted the setting to a personally preferred setting (eg, "personal") for PE detection. Images displayed at this setting were compared in a side-by-side fashion with the "modified" (W = MPA + 2 . SDPA, C = W/2) and "double-half" (W = 2 . MPA, C = MPA/2) window setting. Each observer rated images from 1 (ie, most preferred) to 3 (ie, least preferred). For quantitative analysis, window width and center value of each setting were divided by corresponding MPA to compute a width ratio and a center ratio. Window settings and ratings were compared with repeated-measures analysis of variance, paired t tests, and Wilcoxon signed-rank tests.

RESULTS

Ratings for all three types of window settings were significantly different (P < .001). Observers preferred their personal settings the most and the modified settings the least. Mean ratios for the seven observers were 1.68 +/- 0.20 for window width and 0.47 +/- 0.08 for window center. Window width ratios for all settings were significantly different from each other (P < .001). Window center ratios were significantly higher for the modified setting than for the double-half setting (P = .013). Values for mean PA attenuation were correlated with window width ratios for six (86%) observers (mean r2 value = 0.29 +/- 0.19, P < or = .03) and with window center ratios for four (57%) observers (mean r2 value = 0.16 +/- 0.14, P < or = .02), thus indicating a trend of setting window width and window center higher when contrast enhancement is lower and vice versa.

CONCLUSION

On average, observers selected CT window settings for PE detection at a window width of slightly less than twice the mean PA attenuation and at a window center of about half the mean PA attenuation. Observers tended to use larger window widths and centers as the degree of PA enhancement was lower.

Haemobilia 2 weeks after a low thoracic stab wound

BACKGROUND

Haemobilia occurs in only 1.2-5% of patients with accidental liver trauma. We describe an unusual case 2 weeks after penetrating thoracic injury.

CASE OUTLINE

A 27-year-old man underwent laparotomy for hepatic bleeding after a low thoracic stab wound. Two weeks later rectal blood loss occurred. CT scan and angiography revealed intrahepatic contrast extravasation at the previous stab wound site. Coils were successfully placed into two branches of the right hepatic artery.

DISCUSSION

Haemobilia should be considered in patients presenting with gastrointestinal blood loss after liver injury. It is diagnosed with angiography and preferably treated by embolisation.

Haemobilia

BACKGROUND

This review aims to establish whether increased use of invasive procedures and the trend toward conservative management of major trauma has resulted in an increased incidence of haemobilia.

METHOD

A Medline (http://igm.nlm.nih.gov/)-based search of the English language literature from January 1996 to December 1999 inclusive was performed using the keywords haemobilia, hemobilia, haematobilia and hematobilia. The presentation, aetiology, investigation, management and outcome of 222 cases were reviewed.

RESULTS

Two-thirds of cases were iatrogenic while accidental trauma accounted for 5 per cent. Haemobilia may be major, constituting life-threatening haemorrhage, or minor; it may present many weeks after the initial injury. Diagnosis is most commonly confirmed by angiography. Management is aimed at stopping bleeding and relieving biliary obstruction; 43 per cent of cases were managed conservatively and 36 per cent were managed by transarterial embolization (TAE). Surgery was indicated when laparotomy was performed for other reasons and for failed TAE. The mortality rate was 5 per cent.

CONCLUSIONS

Although the incidence of iatrogenic haemobilia has risen considerably, the bleeding is often minor and can be managed conservatively. When more urgent intervention is required, TAE is usually the treatment of choice. There is no evidence that the conservative management of accidental liver trauma increases the risk of haemobilia.