Detection and characterisation of liver metastases

Modern liver imaging of cancer patients requires an imaging modality that is not only highly sensitive in detecting lesions but also provides reliable characterisation of lesions and thus allows differentiation of metastases from frequently found benign lesions. Conventional ultrasound (US) has a relatively poor sensitivity and specificity for imaging liver metastases and US used to be inferior to CT and MRI mainly due to a lack of contrast agents. This has changed with the advent of microbubble contrast agents for US. The use of recent contrast agents such as SonoVue (Bracco, Italy) combined with low mechanical index contrast-specific imaging techniques such as Contrast Pulse Sequencing provides dynamic real time imaging of focal liver lesions in the arterial, portal venous and delayed phase. This improves lesion detection and characterisation. To investigate the benefit of SonoVue for detecting liver metastases we studied 40 cancer patients with liver lesions on reference imaging (CT or MRI), 37 of them had metastases. The mean number of reference confirmed metastases per patient increased from 1.85+/-1.79 on conventional ultrasound to 2.73+/-2.50 post SonoVue (p < 0.05). CEUS showed more individual metastases than baseline in 12 (34%) patients. Using CT or MRI as the reference, the mean sensitivity to individual metastases increased from 69% on baseline US to 90% post contrast (p < 0.0005). The role of SonoVue in characterisation of focal liver lesions was evaluated in 63 patients. One lesion was studied per patient. Based on standardised dynamic enhancement criteria for each lesion type, the number of correctly diagnosed lesions improved from 41 (65%) on baseline US to 58 (92%) post contrast (p < 0.001). On CEUS all 27 metastases were correctly diagnosed, while baseline US misinterpreted 2 of these. The number of correctly diagnosed benign lesions (n = 28) increased from 12 (43%) on baseline to 25 (89%) post SonoVue. In conclusion, detection and characterisation of focal liver lesions by US are markedly improved by the use of SonoVue. Contrast agents add a new dimension to sonography allowing it to rival CT and MRI, especially for lesion characterisation.

Becken-Bein-CT-Angiographie mit der 16-Zeilen-Multislice-Technik: Kontrastmittel-Enhancement und Bildqualität unter Einsatz eines standardisierten Untersuchungsprotokolls

PURPOSE

To assess the degree of enhancement and image quality of 16-slice multidetector CT angiography (MDCTA) of pelvic and lower limb arteries with a monophasic contrast medium injection protocol.

MATERIALS AND METHODS

Fifty patients underwent a CT angiography of the pelvic and lower limb arteries using the following parameters: collimation 16 x 1.5 mm, rotation time 0.5 s, table feed 40 mm/sec, slice thickness 2 mm, reconstruction interval 1.2 mm, 100 ml Iomeprol 400 + 60 ml normal saline, flow rate 4 ml/s, bolus tracking (threshold of 250 DeltaHU in aorta). Arterial enhancement was measured in all arterial segments. Maximum intensity projections (MIP) together with axial images were reviewed by two radiologists (consensus). If the results were inconclusive for stenosis, additional curved multiplanar reformations (MPR) were performed.

RESULTS

The mean arterial enhancement values were aorta: 314 +/- 69, pelvis: 342 +/- 105, thigh: 347 +/- 139, calf: 231 +/- 109 DeltaHU. The image quality was judged as excellent in 346 (77.6 %), adequate in 76 (17 %), and inadequate in 24 (5.4 %, all but one in calf and foot) of 446 arterial territories. An override of the contrast bolus below the knee occurred in 2 patients rendering the calf arteries nondiagnostic. Venous enhancement occurred in 13 patients but this compromised the diagnostic assessment in only one case. Additional MPRs were required accurately to assess stenoses in 22 of 200 arterial levels in 16 patients with marked arterial calcifications.

CONCLUSION

16-slice MDCTA with a monophasic contrast bolus of Iomeprol 400 provided good arterial enhancement and diagnostic image quality in 94.6 % of the depicted arterial segments. The majority (67 %) of nondiagnostic segments were below the ankle. MPRs were required in patients with marked calcification for accurate assessment of stenosis.

Die Rolle der Ganzkörper-Spiral-CT bei der Primärdiagnostik polytraumatisierter Patienten - Vergleich mit konventioneller Radiographie und Abdomensonographie

PURPOSE

To evaluate the role of routine "whole body spiral CT"in the primary work-up of polytrauma patients for injuries of the thorax, abdomen and spine, and to compare the results with those of conventional radiography of the chest and spine and abdominal ultrasound.

MATERIALS AND METHODS

Fifty consecutive polytrauma patients underwent contrast-enhanced single slice spiral CT (5 mm collimation) from the vertex to the floor of the pelvis as part of the primary work-up after emergency room admission. Overlapping high resolution sections and sagittal reformations of the spine were obtained. Reports of additional chest radiographs (n=43), abdominal ultrasound examinations(n = 47) and spine radiographs (n = 36) performed in the emergency room were available for retrospective comparison. The "final diagnoses," which served as the standard of reference, were taken from the patients' records using all information that be-came available until discharge or death, such as findings from further imaging, surgery and autopsy.

RESULTS

CT showed 109(97%) of 112 thoracic and abdominal soft-tissue injuries. Relevant injuries missed were an early splenic laceration and an early pelvic hematoma, both of which became clinically apparent several hours later. There were 4 false positive CT findings. Conventional chest radiography demonstrated only 20% of thoracic and sonography 22% of abdominal injuries. Chest radiography and sonography produced 2 false-positive findings each. CT showed 66 (87%) of 76 vertebral fractures including all 19 unstable ones.CT missed 5 anterior vertebral body and 5 spinous/transverse process fractures. Conventional radiography found 71 % of vertebral fractures including only 50 % of the unstable ones.

CONCLUSION

Routine performance of whole body spiral CT as part of the primary work-up of polytrauma patients provides a fast and comprehensive survey and detects almost all soft tissue injuries of the chest and abdomen. It is clearly superior to chest radiography and abdominal sonography. All spinal injuries relevant for the acute management were also seen on CT, but not on conventional radiography.

Liver metastases in cancer: detection with contrast-enhanced ultrasonography

In patients with known or suspected malignancy, ultrasonography (US) is often the first choice for liver imaging because of its widespread availability and low cost. Compared with contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI), the sensitivity of conventional US for detecting hepatic metastases is relatively poor. The advent of microbubble contrast agents changed this situation. Sensitivity and specificity increased substantially with the use of these contrast agents and contrast-specific imaging modes in recent years. Currently, numerous US imaging methods exist, based on Doppler techniques or harmonic imaging. They exploit the complex nonlinear behavior of microbubbles in a sound field to achieve marked augmentation of the US signal. Although microbubble contrast agents are essentially blood pool agents, some have a hepatosplenic specific late phase. Imaging during this late phase is particularly useful for improving the detection of malignant liver lesions and allows US to perform similarly to spiral CT as shown by recent studies. In addition, this late phase imaging is very helpful for lesion characterization. Low mechanical index imaging with the newer perfluor agents permits real-time imaging of the dynamic contrast behavior during the arterial, portal venous, and late phases and is particularly helpful for lesion characterization. The use of US for hemodynamic studies of the liver transit time may detect blood flow changes induced by micrometastases even before they become visible on imaging. In this field of functional imaging, further research is required to achieve conclusive results, which are not yet available.

[Ultrasound contrast agents]

Ultrasound contrast agents consist of tiny gas bubbles encapsulated by a stabilising membrane or shell. When combined with recent contrast-specific ultrasound techniques, they provide substantial enhancement of vessels and solid organs. The clinical use and the diagnostic value of ultrasound contrast agents are in principle comparable to those of contrast agents for CT and MRI. They add an additional dimension of information to sonography, which results in considerable improvement of diagnostic accuracy in many cases. This paper reviews the physicochemical properties of various microbubble contrast agents, discusses non-linear bubble behaviour and contrast-specific imaging techniques. An overview of the most important radiological clinical applications in the liver, kidney and spleen is given.

Double contrast MRI of thermally ablated liver metastases

PURPOSE

To investigate the ability of double contrast MRI (enhancement with iron oxide and gadopentetate dimeglumine) to increase the difference in contrast between various tissues after thermal ablation of liver metastases.

MATERIALS AND METHODS

12 patients were imaged after MR-guided laser-induced thermotherapy (LITT). Imaging was performed with a 1.5T MR system. Nonenhanced, iron oxide-enhanced and double contrast images were acquired using T (1)-weighted GRE and T (2)-weighted TSE sequences. Iron oxide imaging was performed 10 min after injection of 1.4 ml ferucarbotran (Resovist(R), Schering AG Berlin, Germany) and double contrast imaging 60 sec after the additional injection of 0.1 mmol/kg body weight gadopentetate dimeglumine (Magnevist(R), Schering AG Berlin, Germany). Qualitative and quantitative assessment was performed on induced necroses, residual or recurrent tumor tissue and metastatic tissue untreated at the time of the study.

RESULTS

Iron oxide-enhanced T (1) GRE images demonstrated the highest contrast between ablated hyperintense tissue and iron accumulating and resultant hypointense liver parenchyma. Due to Gd enhancement, double contrast T (1)-weighted GRE images displayed the highest change in signal intensity in vital tumor tissue compared to ablated tissue and iron oxide accumulating liver parenchyma (p < 0.01).

CONCLUSIONS

First observations indicate that LITT of hepatic metastases can be better followed with double contrast MRI, which displays increased contrast due to Gd enhancement of perfused tumor tissue and signal intensity loss in iron oxide accumulating hepatic parenchyma. Induced necrosis does not change its signal intensity at all after injection of iron oxide and Gd-containing contrast media.

[Feasibility and optimization of the combined injection of contrast medium and normal saline with a single-syringe CT injection system]

PURPOSE

To optimize the technique of injecting contrast medium followed by saline flush with a single-syringe CT injection system.

MATERIALS AND METHODS

A CT injection system with a single syringe was filled with 100 ml of contrast medium (Iopromide 300 or Iomeprol 400) and 50 ml of normal saline solution. The following variables were evaluated: filling sequence, filling rate, syringe position during filling, ejection rate and delay before ejection. In consecutive portions of 10 ml, the whole volume was continuously ejected into test tubes that were subjected to CT densitometry on these test tubes. Each experiment was performed three times.

RESULTS

Filling the syringe first with saline solution and subsequently with contrast medium resulted in no substantial mixing, whereas filling in the reverse order caused noticeable mixing of both solutions. Manual filling at a rate < or = 1 ml/s gave the best results. At faster filling rates (4 ml/s, 10 ml/s), substantial mixing of contrast agent and saline solution was observed. The separation of the two liquids was optimal when the syringe nozzle was pointed downward. Ejection rate (3 ml/s, 4 ml/s) and time delay between filling and ejection (0 min, 10 min) did not influence the distribution of density. The maximum iodine concentration using this approach was 235 mg/ml for Iopromide 300 and 327 mg/ml for Iomeprol 400. This indicates a reduction of the maximum iodine concentration of up to 28 % even when using the optimal technique for controlling mixing of both liquids.

CONCLUSION

Manual filling of the CT injection syringe with saline solution followed by contrast media with the syringe nozzle pointed downward provides the best separation between contrast medium and normal saline solution but reduces the maximum iodine concentration by up to 28 %. For examinations requiring a high iodine concentration, such as CT-angiography, an iodine concentration of 400 mg/ml should be selected for the combined injection of contrast medium and normal saline solution with a single-syringe CT injection system.

[Characterization of focal liver lesions with contrast-enhanced low MI real time ultrasound and SonoVue]

PURPOSE

SonoVue is a new microbubble ultrasound contrast agent that for the first time allows continuous real time examination during the different phases of contrast enhancement using low transmission power, expressed as mechanical index (MI). This study investigates whether low MI real time phase inversion imaging with SonoVue can improve the characterization of focal liver lesions in comparison to unenhanced sonography and power Doppler sonography.

MATERIALS AND METHODS

Sixty-three patients with 35 malignant and 28 benign liver lesions were studied with unenhanced ultrasound (US) including B-mode and power Doppler, followed by contrast-enhanced al MI (0.1 - 0.3) real time phase inversion US during arterial, portal-venous and delayed liver phase (> 2 min after injection). Findings of the scans obtained before and after administration of contrast agent were compared with each other and with reference examinations (biopsy, MRI, CT or intraoperative US).

RESULTS

The number of correctly diagnosed lesions increased from 41 (65%) without contrast agent to 58 (92%) with contrast agent (p < 0.001). The differentiation of malignant from benign lesions improved from 43 (68 %) to 60 (95 %, p < 0.001). After administration of the contrast agent, all 35 malignant lesions were correctly recognized and 3 of the 28 benign lesions were misclassified. All 27 metastases showed little or no enhancement on portal-venous and delayed phase imaging, independent of their arterial features. All 6 hepatocellular carcinomas (HCC) enhanced markedly during arterial phase and 5 showed less contrast uptake than normal liver in the late phase. Ten of 11 hemangioma displayed arterial peripheral nodular enhancement followed by progressive centripetal fill-in. Nine of 11 focal nodular hyperplasias (FNHs) showed profuse arterial enhancement (5 with a transient "spokewheel") and contrast uptake similar to normal liver thereafter. One FNH showed a subtle central scar.

CONCLUSION

Low MI real time US with SonoVue markedly improves the characterization of focal hepatic lesions in comparison with unenhanced sonography.

[Rotational malalignment of the components may cause chronic pain or early failure in total knee arthroplasty]

Rotational alignment of the tibial and femoral component plays an important role in modern total knee replacement surgery. After correct frontal alignment and proper soft tissue balancing, the rotational placement of the components represents the "third dimension" in knee endoprosthetic surgery. Improved surgical techniques with modified instruments and better rotational component positioning will lead to better functional outcomes. Patients with painful total knee arthroplasties (TKA) or early failure without evident classic implantation failures or signs of infection should be evaluated for malrotation of the components. In a prospective study in 26 patients with painful TKA and malrotation of the tibia and/or femur component, revision surgery with exchange of the components was performed. Twenty-five cases showed clinically relevant internal malrotation of the tibial component (ø 8.4 degrees ) and/or femoral component (ø 5.6 degrees ). Only one patient had 10 degrees of external malrotation of the femoral component. Combined malrotations of the tibia and femur were found in ten knees (38%). After revision surgery and correction of malrotations, 20 patients (78%) were scored with excellent and good results. Patients with painful TKA resistant to conservative therapy and evident malrotations of the component should be considered for revision surgery with change of the malrotated components.