New trends in radiodiagnostic and radiotherapy.

T. Cammarota

The developments of Radiodiagnostics and Radiotherapy in Oncology are represented by the clinical application of different technological innovations and by the employment of new contrast media.
The chief technological development over these last few years, besides Computerized Tomography and Magnetic Resonance, is CT-PET which, after the earliest applications in the field of lymphomatous pathologies, is now applied in various sectors of Oncology, according to protocols that are still in the process of being designed.
Other developments are real-time Fusion Imaging (Ultrasound Scanning and CT) and the employment of second-generation ultrasound scanning contrast media in guiding ablative therapies and in following up on treated lesions, on the liver and in other areas too.
Extravascular interventionist radiology is chiefly applied in the treatment of pathologies affecting the biliary ducts, especially those of a neoplastic nature, with written drainage indications, whether of a temporary nature, in pre-surgery conditions, or of a final nature, for palliation purposes.

T. Cammarota
Department of radiology
“Ospedale Le Molinette”
Torino Italy

 

Imaging progresses in ablative
therapies guidelines

L. Solbiati

Local ablation using chemical agents (ethanol, acetic acid) or thermal energy (radiofrequency, laser, microwaves, cryo) has become the treatment of choice for most liver malignancies in recent years. Diagnostic imaging plays a key role in all steps of local tumor ablation: detection of lesions and selection of patients for treatment, targeting of lesions and guidance of the procedure, immediate assessment of treatment result and long-term follow-up.
Sonography (US) represents the most commonly used imaging modality for the guidance of percutaneous ablative treatments owing to its availability, rapidity and ease of use.
Throughout the world the majority of ablations of liver malignancies are performed in the US room, also for cost-effectiveness considerations. However, differentiation of induced necrosis from viable tumor is not possible with baseline and color Doppler sonography and therefore both immediate and long-term assessment of therapeutic result is usually accomplished by contrast-enhanced helical CT and MRI which are not real-time modalities and can be performed only at the end of treatment sessions (if these do not take place in CT (or MRI) room). Furthermore, the possibility of achieving local tumor control following percutaneous ablation is largely related to the target tumor size. Accordingly, there is an increased need to detect and treat small tumors. In some instances, these are clearly visualized by CT , and not adequately detected by ultrasound.
These major limitations of US for guiding ablation of liver malignancies (inability to assess necrosis and difficult visualization of small targets in critical anatomic locations) are currently almost entirely overcome by two crucial advancements of sonography : contrast-enhanced sonography (CEUS) and fusion imaging of US with CT (or MRI) in real time.
As lack of vascularity is the most easily detectable sign of treatment efficacy, in the last 4-5 years contrast-enhanced sonography (CEUS) with first (initially) and second generation contrast agents (microbubbles) was introduced and routinely performed before, during and immediately at the end of ablation procedures to monitor and assess the extent of necrosis achieved (that is the therapeutic result) prior to closing treatment session. Contrast specific-software in continuous mode with very low mechanical index has to be employed.
CEUS is helpful for guiding electrode insertions into targets hardly visible with unenhanced sonography : this is achieved, in real-time, in arterial phase for HCCs and in portal phase for metastases. However, the most important role of CEUS is the immediate post-ablation control of the result of RFA.
In a group of 169 patients with HCC in liver cirrhosis (292 lesions) and in 123 patients with liver metastases (178 lesions) undergoing a single session of percutaneous RFA, the sensitivity of CEUS for the detection of residual tumor was almost equivalent to that of contrast-enhanced helical CT : only in 23/470 (4.9%) tumors CT detected foci of residual tumor which had not been visualized by CEUS.
Since the introduction of intraoperative CEUS the rate of partially unablated tumors has dropped from 16.1% to 4.9%. Cost-effectiveness and reduction of patients’ discomfort related to the need of re-treatment are the two most outstanding advantages of CEUS in RFA of liver malignancies.

L. Solbiati, L. Cova, T. Ierace,
Department of Radiology General Hospital,
Busto Arsizio - Varese, Italy

PET/CT in oncology

R. Canini

In recent years molecular imaging is acquiring importance for the evaluation of cancer patients, being complementary to conventional imaging methods as CT, MRI and US for the correct and precise assessment of disease extension and relapse.
Positron Emission Tomography is a widely diffuse total body molecular imaging technique in clinical oncology and it is routinely used in patients affected by a large variety of malignant neoplastic diseases. Many papers in the literature demonstrate the utility of this innovative technique which is able to distinguish viable neoplastic tissue from non neoplastic tissue in patients already treated for cancer, being very helpful in case of unclear findings at conventional morphological imaging.
The main limitation of PET scans is the difficulty to correctly localize lesions especially within abdomen, pelvis and head&neck, as the metabolic map of the body does not always allow to recognize organs with complex anatomical detail. To avoid localization mistakes, hybrid scanners were implemented, combining a PET scanner and a CT scanner. This technique (called PET/CT) allows to superimpose PET images and correspondent low dose CT images in order to locate each PET finding on a morphological CT map of the body. The combination of functional data (given by PET) and anatomic details (provided by CT) allows to significantly increase diagnostic accuracy, essentially due to a better specificity.
Main indications for PET/CT use in clinical oncology are: characterization of uncertain lesions; staging; early evaluation of response to therapy; evaluation of residual disease at therapy completion and identification of relapse during follow-up. A typical example of lesion characterization is pulmonary solitary nodule. As regards tumor staging, PET/CT ensures an accurate evaluation of nodes involvement at disease onset, as the diagnosis of nodes malignancy is based not only on size but also on a metabolic index.
Evaluation of response to therapy is important in many neoplastic affection, such as malignant lymphoma: PET/CT is often the only methods enabling to document the presence of residual disease after therapy. Regarding reccurence, PET/CT is particularly important when conventional imaging is inconclusive. Apart from those well established indications, the use of PET/CT is gaining a relevant role in other situations, for example radiotherapy planning.
Many positron emitter tracers are available and each one is specific of a number of neoplastic diseases. The most employed tracer is 18F-FluoroDeoxyGlucose (FDG). FDG PET scan gives important information about tissues glucose consuption, usually very increased in the most frequent malignancies as lymphomas, colon carcinoma, lung cancer, breast cancer, gynecologic malignancies, gastric cancer, head&neck cencer, testis cancer, oesophageal cancer and melanoma, covering about 90% of all PET scans. Some malignancies, however, do not show increase in glucose consumption and are almost invisible with FDG and thus other tracers were developed to mark other metabolic pathways. 11C-Choline is a marker of cell membrane metabolism and is particularly useful for prostate cancer detection; 11C-Methionine shows proteic metabolism and is successfully employed for CNS neoplastic diseases; 18F-DOPA is an amynoacid specific for neuroendocrine tumors; 18F-Fluoride is useful for the detection of bone secondary lesions.
In the near future it is likely that more tracers will be available for clinical imaging, as many efforts are currently paid to develop new PET radiopharmaceuticals.
In conclusion PET/CT is becoming more and more important for oncology, as it is a unique method to accurately evaluate cancer patients in a one-step exam, safe and total body.

R. Canini, S. Fanti, C. Nanni, G. Battista
Clinical Department of Radiological and Istiocytophatological Sciences,
University of Bologna, Italy

The role of interventional radiology in treatment
of malignant biliary strictures

S. Barbero

Interventional Radiology plays a major role in non-surgical palliative treatment of inoperable malignant jaundice.
Stricture location is usually the main selection criterium to decide whether an endoscopic or percutaneous transhepatic approach should be used.
In particular, apart from those cases where an endoscopic approach fails, interventional radiology is indicated for lesions involving the medioproximal third of the common bile duct and the hepatic duct confluence.
Percutaneous treatment is based on biliary stenting; in our experience, most of the times stents should be metallic when the mediodistal CBD is involved, and plastic for confluence lesions or when two or more stents are necessary.

S.Barbero
Institute of Radiology,
University of Torino,Italy