The diagnostic imagings of liver metastases

The liver is an organ susceptible metastases. Malignant neoplasms of many organs frequently metastasize to the liver, particularly colon malignancies. Most metastases enter the liver via the blood circulation, but metastases through lymphatic vessels and the peritoneum are also common. The morphologies of liver metastases and findings on diagnostic images vary considerably. Numerous modalities are available for diagnostic imaging of liver metastases: ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), angiography, nuclear medicine, and others. Ultrasonography is the simplest, most non-invasive, and cheapest, but relies on the skill of the operator. CT and MRI are also non-invasive, and the sensitivities of these techniques have recently been improved with the development of multidetector CT, contrast agents for MRI that specifically accumulate in the liver, and other advances. Moreover, positron emission CT using fluorine-18-deoxyglucose (FDG-PET) displays a high sensitivity. Angiography is an invasive modality, but is adopted with CT during arterial portography (CTAP) and CT during hepatic arteriography (CTHA), or for the purpose of interventional radiology. Rational selection of appropriate modalities for a given purpose requires familiarity with the characteristics of each modality. In the present paper, we describe the morphologic characters of liver metastases and investigate the associated characteristics and usefulness of each modality.     

Combining anatomic and molecularly targeted imaging in the diagnosis and surveillance of embryonal tumors of the nervous and endocrine systems in children

Combining anatomical and functional imaging can improve sensitivity and accuracy of tumor diagnosis and surveillance of pediatric malignancies. MRI is the state-of-the-art modality for demonstrating the anatomical location of brain tumors with contrast enhancement adding additional information regarding whether the tumor is neuronal or glial. Addition of SPECT imaging using a peptide that targets the somatostatin receptor (Octreoscan) can now differentiate medulloblastoma from a cerebellar pilocytic astrocytoma. Combined MRI and Octreoscan is now the most sensitive and accurate imaging modality for differentiating recurrent medulloblastoma from scar tissue. CT is the most common imaging modality for demonstrating the anatomical location of tumors in the chest and abdomen. Addition of SPECT imaging with either MIBG or Octreoscan has been shown to add important diagnostic information on the nature of tumors in chest and abdomen and is often more sensitive than CT for identification of metastatic lesions in bone or liver. Combined anatomical and functional imaging is particularly helpful in neuroblastoma and in neuroendocrine tumors such as gastrinoma and carcinoid. Functional imaging with MIBG and Octreoscan is predictive of response to molecularly targeted therapy with 131I-MIBG and 90Y-DOTA-tyr3-Octreotide. Dosimetry using combined anatomical and functional imaging is being developed for patient-specific dosing of targeted radiotherapy and as an extremely sensitive monitor of response to therapy. Both MIBG and Octreotide are now being adapted to PET imaging which will greatly improve the utility of PET in medulloblastoma as well as increase the sensitivity for detection of metastatic lesions in neuroblastoma and neuroendocrine tumors.     

Imaging neuroendocrine tumors: Characterizing the spectrum of radiographic findings

Neuroendocrine tumors (NET) are a group of neoplasms with neuroendocrine differentiation affecting a wide range of organs. Functional NETs present with symptoms due to the particular hormone produced. Functional NETs are usually small at diagnosis and therefore can be challenging to diagnose. In contrast, non-functioning NETs are generally larger and present with mass effect. Imaging plays an indispensable role in diagnosis, staging and management of patients with NETs. The optimal modality and technique for imaging of NETs depend on the location of primary and metastatic lesions. Regardless of the imaging modality, dynamic contrast-enhanced imaging is essential for evaluation of NETs. In general, CT scan is typically the primary imaging modality for evaluating NETs. MRI is used as a complementary modality, being superior to other modalities to assess liver metastasis. Nuclear medicine imaging is also widely used in NET assessment.     

Imaging of tumor physiology: impacts on clinical radiation oncology

As the metabolic microenvironment markedly influences the therapeutic response of malignant tumors, imaging of the microenvironment is one of the goals researcher have been aiming at for years. Several methods such as positron emission tomography, functional magnetic resonance imaging (MRI) or contrast enhanced MRI/CT are now available. For radiation oncology, tumor oxygenation and perfusion are the most important (patho-) physiological parameters that might be included in radiotherapy regimens and treatment planning. In order to overcome resistance of tumor cells resulting from hypoxia, positron emission tomography (PET) using nitroimidazole tracers is the most advanced technique at this time. Since reproducibility of the PET signal/tracer distribution, thresholding and exact quantification are not thoroughly understood and further investigation is needed before including it into radiotherapy regimens. To image tumor perfusion, dynamic contrast enhanced computed tomography (DCE-CT) or dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) are the most suitable techniques. Co-investigation of tumor oxygenation and perfusion should be performed in order to investigate their interaction and consequences for radiooncology.     

Role of preoperative local and distant staging in rectal cancer

Preoperative imaging in rectal cancer is very important, as accurate staging determines optimal treatment strategy. In this review, imaging modalities for locoregional and distant staging in rectal cancer are discussed. For local staging, superficial tumors are best staged using endorectal US (EUS), as EUS is the most accurate modality for assessment of tumor ingrowth into the rectal wall layers. The more advanced tumors are best imaged using MRI, because MRI accurately predicts the distance from tumor to mesorectal fascia, and thus the circumferential resection margin (CRM), as well as possible invasion into surrounding organs. For the prediction of the nodal status none of the three imaging modalities - EUS, MRI and CT - can be reliably used for clinical decision-making. Only MRI using lymph node specific contrast (such as ultrasmall paramagnetic iron oxide-enhanced MRI) seems promising for the detection of nodal disease. For the detection of distant metastases transabdominal ultrasound and chest X-ray are used as a primary screening tool. However, for the high prevalence group (stage III) both methods are insufficiently sensitive, and CT of the chest plus abdomen is preferred.     

鼻咽癌的影像学诊断——MRI、CT、PET—CT

随着现代医学科学的发展,医学影像学在鼻咽癌诊断中发挥了十分重要的作用。MRI具有良好的软组织对比度和多参数成像．可清晰地从形态学和功能改变方面为肿瘤的定位定性提供丰富的诊断信息;应用对比剂增强和压脂序列扫描是目前评估鼻咽癌病灶范围、分级分期的最佳影像学手段。CT扫描在诊断颅底骨质侵犯方面具备优势。PET—CT则在发现原发灶和远处转移方面具有较高的敏感性。全文就目前各种不同影像学检查对鼻咽癌的诊断进行评价．并着重介绍了MRI的应用。     

Imaging in head and neck cancer

Opinion statement The goals of imaging in head and neck cancer are to establish tumor extent and size, to assess nodal disease, to evaluate for perineural tumor spread, and to distinguish recurrent tumor from post-treatment changes. MRI is the preferred modality for assessment of nasopharyngeal, sinonasal, and parotid tumors, because of better contrast resolution, high frequency of perineural spread, and less prominent motion artifacts. MRI is the best modality to delineate the extent of intraorbital and intracranial extension of malignant tumors. Tumors of the oropharynx, larynx, and hypopharynx are frequently primarily imaged with CT, which is less affected by breathing and swallowing artifacts. MRI is also the initial study of choice for tumors confined to the oral tongue, and possibly also for other oral cavity locations because MRI is superior in detection of tumor spread into the bone marrow. There is no clear advantage of CT or MRI for evaluation of nodal disease. Positron emission tomography (PET) is very sensitive for metastatic lymph nodes that are at least 8 mm in size and is the technique of choice in dubious cases. Imaging-guided biopsies are performed whenever needed. For imaging of treated head and neck cancer, PET scans have been found to generally offer higher sensitivity than MRI or CT. Combined PET/CT may be the modality of choice because it almost completely eliminates the false-positive and false-negative PET findings. Patients with head and neck cancer who are referred to tertiary care centers commonly arrive with cross-sectional images obtained at other institutions. Reinterpretation of these studies by dedicated radiologists frequently leads to changes in findings, which alter treatment and affect prognosis.     

Imaging of the kidney

Imaging of the kidney relies on three main imaging modalities: ultrasound, CT scan and MRI, on one hand, and scintigraphy, on the other hand. First intent ultrasound provides anatomic/vascular and functional information. Tissue perfusion assessment using ultrasound can be improved using contrast agents. Renal ultrasound is particularly useful but remains operator and tumor/patient-dependent (obese, ectopic kidney, type and site of tumor). It is cheap and does not irradiate. Ultrasound contrast agents can improve the sensitivity of ultrasound in many clinical situations. Intravenous urography has been replaced by CT scan. Multi-slice CT scan is indeed the main renal imaging modality: it allows for angiographic and urographic explorations. MRI provides anatomic and functional information. Renal failure must be looked for before performing CT scan or MRI so as to avoid iatrogenic complications. Severe renal failure is a contraindication to both. Each imaging modality has pros and cons and specific indications. CT scan is the mainstay of renal imaging provided that standardized injection protocols are used, that the dose is limited (low-dose protocol) and renal function is assessed. Dynamic renal scintigraphy can be used in situations where information on the function of each kidney is necessary.     

Literature review: Imaging in prostate cancer

Imaging plays an increasingly important role in the detection and characterization of prostate cancer (PC). This review summarizes the key conventional and advanced imaging modalities including multiparametric magnetic resonance imaging (MRI) and positron emission tomography (PET) imaging and tries to instruct clinicians in finding the best image modality depending on the patient`s PC-stage. We aim to give an overview of the different image modalities and their benefits and weaknesses in imaging PC.Emphasis is put on primary prostate cancer detection and staging as well as on recurrent and castration resistant prostate cancer. Results from studies using various imaging techniques are discussed and compared. For the different stages of PC, advantages and disadvantages of the different imaging modalities are discussed. Moreover, this review aims to give an outlook about upcoming, new imaging modalities and how they might be implemented in the future into clinical routine.Imaging patients suffering from PC should aim for exact diagnosis, accurate detection of PC lesions and should mirror the true tumor burden. Imaging should lead to the best patient treatment available in the current PC-stage and should avoid unnecessary therapeutic interventions. New image modalities such as long axial field of view PET/CT with photon-counting CT and radiopharmaceuticals like androgen receptor targeting radiopharmaceuticals open up new possibilities. In conclusion, PC imaging is growing and each image modality is aiming for improvement.     

脂肪肝内转移瘤的影像学表现

目的评价脂肪肝内转移瘤的影像学表现及各种检查方法（重点为ＣＴ）的价值。方法脂肪肝内转移瘤９例,随诊３～１３个月临床证实。原发肿瘤为乳腺癌６例,卵巢癌、恶性黑色素瘤、结肠癌各１例。ＣＴ扫描９例１９次,Ｂ超扫描９例２０次。ＭＲＩ４例４次,血管造影２例６次。结果Ｂ超扫描２例次在中重度脂肪肝漏诊转移瘤。ＣＴ平扫根据肝密度低于脾,并低于、等于、高于肝内血管影,分为重度、中度、轻度脂肪肝。瘤灶分别呈高密度（重度）,高、等、低密度（中度）和低密度（轻度脂肪肝）。增强后,中、重度脂肪肝背景瘤灶均呈高密度。４例瘤灶密度不均。平扫４例瘤灶周围有２～６ｍｍ高密度晕环。ＭＲＩ的ＳＥ序列Ｔ１Ｗ为低信号,Ｔ２Ｗ为高信号,反相位（ｏｐｐｏｓｅｄ－ｐｈａｓｅ）为较高信号。结论脂肪肝内转移瘤的影像学表现较为复杂,与脂肪浸润程度密切相关。ＣＴ平扫时,中度脂肪肝因等密度易漏诊转移瘤。见有全周或半周较高密度环或密度不均者,应警惕肝转移瘤的可能,必须加作增强扫描以免漏诊。细致的ＭＲＩ检查有助于检出转移瘤。     

Target Volume Definition in Rectal Cancer: What Is the Best Imaging Modality?

All patients with rectal cancer should undergo an accurate preoperative staging, including local staging for tumour extension and reliable staging for synchronous distant metastases. Imaging is of utmost importance as a basis for selecting the optimal treatment strategies and as an aid for precise target delineation. Anatomical imaging such as computed tomography (CT) and magnetic resonance imaging (MRI) have been the most commonly used pretreatment staging modalities, whereas endorectal ultrasonography may be useful for staging of smaller tumours (T2 or lower). MRI is the most accurate imaging technique for staging of T3 and T4 tumours. The role of fluorodeoxyglucose positron emission tomography (PET)/CT is under investigation, and diffusion-weighted MRI seems promising for prediction of pathological complete response. For target delineation, planning CT, preferably contrast-enhanced, is the most used imaging technique. For locally advanced tumours, coregistration with MRI or PET/CT may prove to be useful. In this article, the literature published on target delineation in rectal cancer radiotherapy is evaluated, with focus on the best imaging modality for volume definition and radiotherapy planning.     

Staging of pancreatic ductal adenocarcinoma with spiral CT and MRI

Detection of pancreatic adenocarcinoma is crucial for accurate staging both with spiral CT and dynamic MRI; consequently an accurate technique is required and so-called pancreatic phase is recognized as the best one for tumor conspicuity. For vascular involvement optimal results have been achieved in assessing unresectability; vein involvement seems more difficult to be defined as it is sustained by a different spread compared to arterial involvement. Grading of vessel circumference contact represents the best tool in "venous" staging, but shape deformation and collateral veins dilation are also important signs. Lymph node staging is less accurate, lacking in specificity, but spiral CT demonstrated better results if compared with dynamic MRI. Assessment of liver metastases has been improved by the advent of spiral CT and dynamic contrast enhanced MRI, while peritoneal staging seems to be unaffected. In conclusion, both spiral CT and dynamic contrast enhanced MRI are accurate in pancreatic adenocarcinoma staging, mainly for vessels and liver involvement; no definite differences have been established, because only a few studies have compared them both with state-of-art techniques. Therefore standardized multicentric trials are desirable. Up to now, the choice of which technique to employ should be based on local expertise; moreover, the aggressive approach of surgical equipes should be kept in mind.     

Updates in hepatic oncology imaging

The utilization of advanced imaging modalities play an important role in the detection and differentiation of benign and malignant hepatic lesions. Imaging characteristics of hepatic tumors can sometimes be atypical, often leading to diagnostic challenges. Recent technical improvements in contrast enhanced ultrasound (CEUS), computed tomography (CT), and magnetic resonance imaging (MRI) have helped to better characterize hepatic lesions. For example, contrast agents used in US can now better delineate liver lesions, while the ability to reliably produce multiplanar and 3-D reconstructions through the use of MDCT provides an additional advantage in the context of therapeutic decision making for patients with hepatic lesions. In addition, modern MR that includes the use of biliary excreted contrast material, various post-processing techniques like multiplanar reformation (MPR), as well as volume rendering (VR) allow detailed evaluation of the biliary tract, hepatic vasculature, and better characterization of hepatic tumors. As the imaging technologies available continue to evolve and advance, understanding how to effectively utilize these modalities is key to clinical practice. We herein provide a review of the various hepatic oncologic imaging modalities with a focus on how advancements and novel techniques within the different fields may be utilized in the diagnosis, treatment and management of different benign and malignant hepatic lesions.     

Preoperative imaging for hepatic resection of colorectal cancer metastasis

Despite recent advances in chemotherapeutic agents, the prognosis for metastatic colon cancer remains poor. Over the past two decades, hepatic metastasectomy has emerged as a promising technique for improving survival in patients with metastatic colon cancer and in some cases providing long-term cure. To maximize safety and efficacy of metastasectomy, appropriate pre-operative imaging is needed. Advancements in computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) have led to improved detection of occult lesions and better definition of surgical anatomy. While CT, PET and MRI have a comparable sensitivity for detection of large liver metastases, MRI excels at detection of subcentimeter liver metastases compared to CT and FDG-PET, especially with the combination of diffusion weighted imaging (DWI) and hepatocyte-specific contrast agents. CT may be useful as a screening modality or in preoperative planning such as volumetric estimation of the remnant liver size or in defining preoperative arterial anatomy for hepatic artery infusion pump placement. While technologic advancements have led to unprecedented image quality and clarity, this does not replace the need for a dedicated, competent radiologist with experience in hepatic imaging.Key Words: Colorectal metastases, preoperative imaging, hepatic artery infusion pump, volumetrics, hepatic resection     

La délimitation des volumes cibles en radiothérapie : application des techniques d’imagerie

The development of three-dimensional conformal radiotherapy (3DCRT) and intensity modulated therapy (IMRT) has enabled high dose radiation to be directed to tumors, this however subject to a perfect demarcation of the tumoral volume and the anatomical structures to be saved. At the same time, imaging modalities have improved their ability to demonstrate the location and the extension of tumors. The precise location of the target volume and the prediction of the dose absorbed by the tumor thus become an essential stage of the planning of the treatment. This planning is mostly determined on CT pictures. The technique usually used is a non enhanced CT allowing a location of the tumor by its mass effect mass or by its spontaneous difference of density from the adjacent structures. However, the clear visualization of the tumoral volume remains sometimes difficult for small-sized tumors or those with limited contrast with regard to surrounding tissues. This lack of contrast represents a source of variability for the demarcation of the target volume which has been highlighted in numerous papers. Tumors must be then localized by correlation with pictures made at the diagnosis time by other imaging modalities, essentially the MRI and the PET. This approach answers the concept of multimodality diagnosis which resumes the principle of complementarity of the various techniques. Every technique indeed brings, according to its physical principle, one or several specific information. It is advisable from then to clarify the contribution of every used imaging modality, this according to the pathologies and their localizations.     

Diagnosis of hepatocellular carcinoma: newer radiological tools

With the recent dramatic advances in diagnostic modalities, the diagnosis of hepatocellular carcinoma (HCC) is primarily based on imaging. Ultrasound (US) plays a crucial role in HCC surveillance. Dynamic multiphasic multidetector-row CT (MDCT) and magnetic resonance imaging (MRI) are the standard diagnostic methods for the noninvasive diagnosis of HCC, which can be made based on hemodynamic features (arterial enhancement and delayed washout). The technical development of MDCT and MRI has made possible the fast scanning with better image quality and resolution, which enables an accurate CT hemodynamic evaluation of hepatocellular tumor, as well as the application of perfusion CT and MRI in clinical practice. Perfusion CT and MRI can measure perfusion parameters of tumor quantitatively and can be used for treatment response assessment to anti-vascular agents. Besides assessing the hemodynamic or perfusion features of HCC, new advances in MRI can provide a cellular information of HCC. Liver-specific hepatobiliary contrast agents, such as gadoxetic acid, give information regarding hepatocellular function or defect of the lesion, which improves lesion detection and characterization. Diffusion-weighted imaging (DWI) of the liver provides cellular information of HCC and also has broadened its role in lesion detection, lesion characterization, and treatment response assessment to chemotherapeutic agents. In this article, we provide an overview of the state-of-the art imaging techniques of the liver and their clinical role in management of HCC.     

Radiothérapie des tumeurs cérébrales : quelles marges ?

Radiotherapy is a major modality in the treatment of brain tumours. The target volumes definition has to be precise for the radiation planification. The gross target volume (GTV) is most of the time delineated within the fusion of the planning CT scan with the appropriated MRI sequences. The clinical target volume (CTV) definition is more complex: it varies in time following the evolution of scientific knowledge and also depending of the school of thought. This article offers a review of the literature about the margins applied in brain tumours radiotherapy for gliomas (high grade, anaplastic, low grade and brain stem gliomas), embryologic tumours (medulloblastomas and primitive neuroectodermal tumours [PNET]), ependymomas, atypical teratoid rahbdoid tumours (ATRT), craniopharyngiomas, pineal gland tumours, primary central nervous cell lymphomas, meningiomas and schwannomas. New imaging modalities such as diffusion-weighted imaging, dynamic contrast enhanced, spectroscopic MRI and PET scan will allow us to delineate more precisely the target volumes and to realise dose-painting by adapting the dose to the tumour metabolism.     

Simultaneous positron emission tomography and magnetic resonance imaging for the detection and characterisation of liver lesions in patients with colorectal cancer: A pictorial review

Patients with colorectal cancer undergo frequent diagnostic imaging to stage the extent of metastatic disease and assess response to treatment. Imaging is typically via diagnostic contrast‐enhanced CT or combined FDG‐PET/CT. However, recent research has demonstrated promising benefits of combined FDG‐PET/MRI in oncologic imaging due to the superior soft‐tissue contrast of MRI. The extent of both intrahepatic and extrahepatic disease is important in establishing treatment options for colorectal cancer patients, and FDG‐PET/CT and dedicated liver imaging are often both required. FDG‐PET/MRI offers the advantage of a single examination which can be completed within a similar duration as dedicated liver MRI imaging. This improves patient convenience and anatomical co‐registration between PET and MRI imaging and provides a potential cost benefit. The diagnostic benefits of FDG‐PET/MRI include the simultaneous characterisation of focal liver lesions, exclusion of extrahepatic disease, the detection of additional hepatic metastases and extrahepatic disease, and the multi‐parametric assessment of treatment response. This pictorial review highlights examples of these benefits.     

Clinical effectiveness of intra-arterial chemotherapy combined with degradable starch microspheres (DSM) for liver metastases and prediction of effectiveness by diagnostic imaging]

The aim of this study was to evaluate the clinical effectiveness of intra-arterial chemotherapy combined with degradable starch microspheres (DSM) for liver metastases and the possibility of predicting the effectiveness of the chemotherapy by pretreatment diagnostic imaging. The subjects were 67 patients with metastatic liver cancer, treated with Seldinger method via the left brachial artery, and tumor selective hepatic injection using a micro-catheter. The early response rate was 38.7% for colorectal cancer, 42.8% for gastric cancer, 16.7% for bile tract cancer and 80% for uterine cancer. The relationship between effectiveness and the tumor occupation rate in the liver estimated from pretreatment CT images was not significant, but the degree of tumor stain in the early phase of contrast enhancement CT correlated well with early responsiveness of the liver metastases for this treatment. This suggests the possibility of pretreatment prediction of the effectiveness of intra-arterial chemotherapy combined with DSM for metastatic liver tumors.     

What’s New in Imaging for Gynecologic Cancer?

Magnetic resonance imaging (MRI) is the optimal modality for local staging of gynecological tumors. Advances in functional MRI with diffusion-weighted and dynamic contrast-enhanced sequences provide more detailed information regarding tumor cellularity, vascularity, and viability. Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) now has an established role in imaging for gynecological cancers, particularly staging of locally advanced cervical cancers and pre-salvage exenterative therapy in relapsed gynecologic tumors. Novel PET tracers, targeting other aspects of tumor biology, are being evaluated although none are currently in routine clinical use. New PET/MR scanners have the potential to combine the strengths of both modalities in one sitting. This review covers advances in gynecologic imaging concentrating on cervical, endometrial, and ovarian cancers.