Magnetic resonance angiography: the state of the art

Three-dimensional contrast magnetic resonance angiography has rapidly advanced over recent years. It is now a highly accurate and safe method of diagnosing vascular abnormalities of the thoracic, abdominal and peripheral vessels. We describe techniques for the examination of the thoracic and abdominal aorta, the renal arteries and the lower limb vessels together with strategies to improve their diagnostic accuracy. Received: 15 June 2000 Accepted: 18 July 2000     

Apoptosis-detecting radioligands: current state of the art and future perspectives

This review provides a critical and thorough overview of the radiopharmaceutical development and in vivo evaluation of all apoptosis-detecting radioligands that have emerged so far, along with their possible applications in nuclear medicine. The following SPECT and PET radioligands are discussed: all forms of halogenated Annexin V (i.e. (123)I-labelled, (124)I-labelled, (125)I-labelled, (18)F-labelled), (99m)Tc/(94m)Tc-labelled Annexin V derivatives using different chelators and co-ligands (i.e. BTAP, Hynic, iminothiolane, MAG(3), EDDA, EC, tricarbonyl, SDH) or direct (99m)Tc-labelling, (99m)Tc-labelled Annexin V mutants and (99m)Tc/(18)F-radiopeptide constructs (i.e. AFIM molecules), (111)In-DTPA-PEG-Annexin V, (11)C-Annexin V and (64)Cu-, (67)Ga- and (68)Ga-DOTA-Annexin V. In addition, the potential role and clinical relevance of anti-PS monoclonal antibodies and other alternative apoptosis markers are reviewed, including: anti-Annexin V monoclonal antibodies, radiolabelled caspase inhibitors and substrates and mitochondrial membrane permeability targeting radioligands. Nevertheless, major emphasis is placed on the group of Annexin V-based radioligands, in particular (99m)Tc-Hynic-Annexin V, since this molecule is by far the most extensively investigated and best-characterised apoptosis marker at present. Furthermore, the newly emerging imaging modalities for in vivo detection of programmed cell death, such as MRI, MRS, optical, bioluminescent and ultrasound imaging, are briefly described. Finally, some future perspectives are presented with the aim of promoting the development of potential new strategies in pursuit of the ideal cell death-detecting radioligand.     

Interventional MR imaging: state of the art and future perspectives

Summary The concept of MR guidance of invasive diagnostic and minimally invasive therapeutic procedures is based on the excellent morphologic and functional properties of MR imaging. Prerequisites are adequate patient monitoring and adherence to safety guidelines. Fast and ultrafast sequences, temperature quantification, visualization of intravascular devices, thermal stability of contrast media and thermosensitive contrast media are discussed. The spectrum of clinical applications includes biopsies, thermal ablation modalities, vascular applications, MR endoscopy and intraoperative MR imaging. The development of interventional MR imaging is still in its infancy. In the future, MR imaging may play an important role in interventional radiology and minimally invasive therapy.      

Magnetic resonance angiography of the neck vessels: technique and anatomy

The authors identified the standard projections for studying neck vessels with magnetic resonance angiography. Sixty volunteers underwent angio-MR of the arterial neck vessels with FISP 3D FT sequences obtained on the coronal and sagittal planes. The gradient-echo sequence (FISP 3D FT) was acquired with TR = 0.04-0.08 s and TE = 15 ms, with 25 degrees flip angle. Single excitated slices of thickness ranging from 1-2 mm were included in the acquisition volume. These sequences were subsequently processed by the maximum intensity projection method. Two radiologists examined our results to choose the optimal projections. We used a semiquantitative scale which allowed us to distinguish 3 different diagnostic levels for each projection: well-visualized vessels, poorly-visualized, and non-visualized ones. For each section axial rotations were performed ranging from 0 degree to 180 degrees, with 15 degrees intervals. On the coronal plane, rotations from -45 degrees to 45 degrees were the optimal ones to visualize the studied vessels. The 0 degree-15 degrees-30 degrees-45 degrees-135 degrees-165 degrees-180 degrees projections allowed the common carotids to be clearly demonstrated together with the vertebral arteries. The other projections appeared to be useless for diagnostic purposes. On the sagittal plane, rotations from 60 degrees to 120 degrees were the optimal ones. The 90 degrees projection allowed the demonstration of all the big arterial vessels of the neck, including carotid bifurcation and internal and external carotids. The assessment of the optimal diagnostic projections for angio-MR of the neck vessels is helpful to reduce post-processing time. As a matter of fact, the immediate visualization, during the examination, of the standard projections allows further acquisitions to be obtained--if needed--to try to solve specific diagnostic doubts.     

Magnetic resonance angiography of the head and neck vessels

Stroke, a major cause of death and disability in the developed world, is usually caused by atherosclerosis, most commonly an arterioocclusive lesion at the carotid bifurcation. Numerous multicentre trials have demonstrated that carotid endarterectomy can reduce the risk of stroke in these patients. However, because of the morbidity of catheter angiography coupled with the risks of surgery, the benefits outweigh the risks of surgery only for those with >70% carotid artery stenosis. The gold standard method for assessing the degree of stenosis is catheter-directed cerebral digital subtraction angiography; however, this is associated with a small but substantial stroke risk in addition to inherent risks associated with use of ionizing radiation and nephrotoxic contrast agents. The requirement for alternative imaging techniques that do not contribute to morbidity is ideally met by contrast-enhanced magnetic resonance angiography, which eliminates the need for direct catheterization and therefore eliminates stroke risk associated with a patient work-up. Advances in contrast-enhanced magnetic resonance angiography technology have led to a technique that achieves the goals of high spatial and temporal resolution required for stenosis assessment and streamlining of patients along surgical or medical lines. With the advent of a novel contrast agent, gadofosveset trisodium (Vasovist, Bayer Schering Pharma AG, Berlin, Germany), which has a high relaxivity and an extended imaging time, improved diagnosis of carotid artery stenoses with magnetic resonance angiography can be expected. Gadofosveset trisodium facilitates improved first-pass imaging and also delays steady-state imaging with one injection. Although developed for vascular imaging, gadofosveset trisodium may also allow assessment of brain vascularity, blood-brain barrier breakdown and neurodegenerative disease.     

Magnetic resonance imaging of head and neck tumors

Magnetic resonance imaging (MRI) provides several advantages over computed tomography (CT) in the evaluation of head and neck region tumors. The improved soft-tissue contrast among normal and abnormal tissues provided by MRI now permits the exact delineation of tumor margins in the nasopharynx, oropharynx, and skull base regions. In addition, the ability to depict cross-sectional anatomy and pathology in three planes without intravenous contrast, patient manipulation, or ionizing irradiation is a distinct advantage of MRI over CT scanning. Drawbacks of MRI include the detection of subtle osseous abnormalities, patient motion, and artifacts introduced by ferromagnetic dental appliances. These drawbacks appear minimal when compared to the benefits of improved soft-tissue contrast and the ability to image exact tumor volumes.     

MR-guided radiotherapy for prostate cancer: state of the art and future perspectives

Advances in radiotherapy technology have increased precision of treatment delivery and in some tumour types, improved cure rates and decreased side effects. A new generation of radiotherapy machines, hybrids of an MRI scanner and a linear accelerator, has the potential to further transform the practice of radiation therapy in some cancers. Facilitating superior image quality and the ability to change the dose distribution online on a daily basis (termed “daily adaptive replanning”), MRI-guided radiotherapy machines allow for new possibilities including increasing dose, for hard to treat cancers, and more selective sparing of healthy tissues, where toxicity reduction is the key priority.These machines have already been used to treat most types of cancer, although experience is still in its infancy. This review summarises the potential and current evidence for MRI-guided radiotherapy, with a predominant focus on prostate cancer. Current advantages and disadvantages are discussed including a realistic appraisal of the likely potential to improve patient outcomes. In addition, horizon scanning for near-term possibilities for research and development will hopefully delineate the potential role for this technology over the next decade.     

Magnetic resonance imaging of extracranial head and neck tumours.

The role of magnetic resonance imaging (MRI) in the investigation of head and neck tumours (excluding those primarily arising from the central nervous system or orbits) has been investigated. Follow-up data were obtained on 45 scans on 42 patients. MRI provided significant additional information compared with computed tomography (CT) in nine out of 17 (53%) scans performed for staging purposes. In the assessment of 19 patients with suspected tumour recurrence, MRI demonstrated a sensitivity of 100%, a specificity of 80% and an accuracy of 89%.     

Magnetic resonance imaging staging of nasopharyngeal carcinoma in the head and neck

Magnetic resonance imaging (MRI) is the modality of choice for staging nasopharyngeal carcinoma in the head and neck. This article will review the patterns of primary and nodal spread on MRI with reference to the latest 7th edition of the International Union Against Cancer/American Joint Committee on Cancer staging system.     

Current and future state of chemoradiotherapy for head and neck cancer

Radiation therapy was the conventional treatment for locally advanced, nonresectable head and neck cancer. However, therapeutic results were poor with this treatment modality, and chemoradiotherapy has been used in an effort to improve therapeutic results. Improved local-regional control and disease-free or overall survival have been shown in several randomized trials using a concurrent or alternative approach. Induction chemotherapy (neoadjuvant chemotherapy), however, has not been shown to improve local-regional control or survival. Induction chemotherapy followed by definitive radiotherapy may be useful in the selection of patients who are likely to benefit from non-surgical organ preservation treatment schemes. Further clinical trials are needed to clarify the most suitable combination of chemotherapy and radiation. Intraarterial chemotherapy combined with radiation therapy for head and neck cancer has been attempted for many years. However, the indications, clinical significance, and selection of suitable anti-cancer drugs remain unclarified. The modern superselective intraarterial approach should be re-evaluated. Many head and neck cancers have been found to overexpress the receptor to epidermal growth factor (EGFR). Antibodies such as IMC-C225 that specifically target EGF receptors with radiotherapy and/or chemotherapy may prove to be valuable contributors to the treatment of advanced head and neck cancer.     

Magnetic resonance imaging of the wrist: anatomy and pathology of interosseous ligaments and the triangular fibrocartilage complex

The complex anatomy of the radiocarpal joint and proximal carpus renders high-quality magnetic resonance imaging difficult and interpretation more problematic than in other areas of the skeleton. Added to this, the common occurrence of abnormal communications through the triangular fibrocartilage complex, scapholunate, and lunotriquetral ligaments often results in difficulty in assessing the importance of findings. This article reviews the anatomy, gives suggestions for protocols for scanning the wrist, and reviews the pathologic conditions that may be seen in these structures. In particular, it emphasizes the 3-dimensional nature of these structures and how best to evaluate them in axial, coronal, and sagittal planes.     

Magnetic resonance angiography of the vessels of the neck. Study technique and normal anatomy

Magnetic Resonance Angiography (MRA) is a new diagnostic technique which allows vascular structures to be studied atraumatically and without any contrast medium. Its basic principles are reported in the present paper, together with the results of a preliminary study of normal neck anatomy. Twenty healthy volunteers and 10 patients with no cerebral vascular diseases underwent this MRA study. Internal and common carotid arteries were always well visualized, while external carotid was demonstrated in 87% of cases. Among intracranial vessels, the middle cerebral artery was clearly depicted in 63% of cases, while the anterior cerebral artery was visible in 18% of the study population only.