Current Medical Imaging Reviews (v.5, #2)

Editorial by E. Kim (71-71).
In this May issue of CMIR there are again excellent papers dealing with clinical applications of advanced neuroimaging techniques which evaluate either directly or indirectly image the structure as well as function or pharmacology. In addition, there is a paper proposing algorithms of the comprehensive pre- and posttherapeutic imaging for the locoregional treatment of metastatic colorectal cancer in the liver. The bicaudate index (BCI) is the ratio of the width of both lateral ventricles at the level of the heads of the caudate nuclei to the distance between the outer tables of the skull at the same level. Hungting's disease has shown to have more than double of contrl BCI. Bonifacic reports that BCI progressively increases after the age of 50 and rises to levels that nearly double those found in the age group of 30 or younger. The concept of lacunar stroke is still controversial because of different definitions of lacunes have been used. Originally, lacunes were defined pathologically as small subcortical infarcts in the territory of the deep penetrating arteries, but they now are diagnosed on clinical and imaging methods. Gunda et al. summarize recent knowledge about the capacity of various imaging modalities to identify lacunar infarcts and judge their clinical relevacne as well as for the differential diagnosis and mechanisms to produce small subcortical infarcts. Mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS) is one of the family of mitochondrial cytopathies caused by defects in the mitochondrial genome. It affects many of the body's systems, particularly the brain, nervous system and muscles. Most affected individuals experience stroke-like episodes beginning before age 40 and have a buildup of lactic acid in their bodies including bloods. Munoz et al. describe neuroimaging patterns of the most common MELAS affecting children on conventional MRI as well as diffusion-weighted imaging and proton MR spectroscopy in two parts. MR spectroscopy has provided objective neurochemical information, therby altering treatment, when MRI is indeterminate in evaluating brain tumors. Methods of quantifying tumor metabolites under in vivo MR spectral profiles have been progressively developed to improve diagnostic accuracy. Most of them are not always directly applicable to cancer lesions because of their inherent heterogeneity, and thus peak area ratios may be better indicators of disease progression and therapeutic response in some cases. Canese et al. overview the principal methods currently applied for the quantification of metabolites detected by proton MR spectroscopy in tumors. Locally ablative treatment of hepatic colorectal metastases is still lacking of large controlled trials to definitely prove its benefits on the patient survival in contrast to surgical or cytostatic therapy. Many different modalities have been developed for minimally invasive locoregional treatments such as radiofrequency ablation, laser induced thermotherapy or transarterial radioembolization. All of these modalities have been performed under imaging guidance, but there are not yet comprehensive guidelines on the use of locally ablative therapies. Algorithms are needed for pretherapeutic decision making regarding the appropriate treatment strategy as well as for posttherapeutic followup of treatment response. Schnapauff et al. review current opinions to the use of diagnostic imaging for differrent image-guided treatments and also proposed comprehensive pre- and posttherapeutic imaging algorithms.

Normal Bicaudate Index by Aging by Melita Kukuljan, Zlatko Kolic, David Bonifacic, Duje Vukas, Damir Miletic (72-74).
Background: The aim of our study was to determine the normal ventricular size of the intracranial cavity based on the bicaudate index (BCI) calculation which was obtained through the computed tomography. Methods: We reviewed consecutive CT examinations in 1406 patients with symmetrical intracranial ventricular system and normal density of the white and gray matter, and without neurological deficits or psychiatric disorders. Results: Our series included 711 female and 695 male examinees; aged from 3 months to 89 years, mean age 46,3 and#xB1; 23,9 years. The positive correlation between age and bicaudate indexes was significant (p andlt; 0.01). In our series, upper limit of the BCI (99th percentile) was 0.13 for the first three decades. In the fourth and fifth decade it increases to 0.15 and 0.19, respectively. Conclusions: After the age of 50, BCI progressively increases and rises to levels that are nearly double those found in the age group of 30 or younger. This is important in CT assessments of potential developments of hydrocephalus in older patients.

Challenges in Diagnosing Cerebral Lacunar Infarcts by Bence Gunda, Gyorgy Varallyay, Gabor Rudas, Daniel Bereczki (75-84).
The classical and#x201C;lacunar hypothesis and#x201D; based on pathological and CT studies states that particular clinical syndromes - and#x201C;lacunar syndromes and#x201D; - are caused by small ( andlt; 15 mm) subcortical infarcts due to the occlusion of a small perforating artery. In many cases however the clinical syndromes are not associated with any detectable changes on classsical CT imaging. Recent advances in neuroimaging help us to better visualize lesions with relevance to actual clinical syndromes and with respect to functional systems thus leading to earlier and more accurate etiologic diagnosis and refinement of clinico-anatomical correlations. Therefore we re-evaluate the lacunar hypothesis and the clinico-pathological entity of lacunar stroke. We summarize recent knowledge about the capacity of various imaging modalities 1. to identify and localize lacunar infarcts, 2. to judge their clinical relevance by establishing their age and following their time course, 3. to differentiate between lacunar and non-lacunar mechanisms producing small subcortical infarcts and 4. to differentiate lacunar infarcts from other small cerebral lesions like Unidentified Bright Objects and dilated Virchow-Robin spaces. On the other hand lesions may frequently be identified in patients with apparently no corresponding clinical syndromes. Therefore we discuss the clinical relevance of silent brain infarcts and other imaging abnormalities.

Mitochondrial Encephalomyopathies in Children. Part I: Conventional MR Imaging Findings by Alberto Munoz, Fernando Mateos, Rogelio Simon, Elena Martin-Hernandez, Ana Camacho, Paloma Ferrando, Joaquin Arenas, Miguel Martin (85-99).
Background and Purpose: Mitochondrial encephalomyopathies (ME) may promote many brain abnormalities that can be detected with advanced neuroradiologic tools. The aim of this first of two reports is to evaluate if there are representative neuroradiological patterns of the most common ME disorders affecting children. Methods: Non-selected longitudinal study in 55 patients over 15 years. All of them underwent one or more MR imaging studies. Five different patterns of imaging involvement were proposed: 1-Myelinization delay and atrophy, 2-Gray nuclei involvement, 3-Leukodystrophyc pattern, 4-Menke's pattern, and 5-Others. Results: Leigh's disease (LD): 19 (34.5and#x25;), Alper's disease (AD):12 (22.18and#x25;), Kearns-Sayre syndrome (KSS): 3 (5.4and#x25;); Menkes and Menkes-like diseases and variants: 4 (9and#x25;), others: 17 (30.9and#x25;). On imaging grounds, there were statistical association between the main syndromes and the patterns proposed. Conclusion: MRI imaging shows non-specific features in about one third of the patients, whereas the other two third are associated with some few characteristic neuroradiologic-phenotypes proposed. Although these findings are not pathognomonic they provide a guide in imaging approach for children suspected of ME.

Mitochondrial Encephalomyopathies in Children. Part II: Advanced MR Tools and the Importance for its Early Recognition in the Acute Clinical Setting by Alberto Munoz, Fernando Mateos, Rogelio Simon, Elena Martin-Hernandez, Ana Camacho, Paloma Ferrando, Joaquin Arenas, Miguel Martin (100-109).
Background and Purpose: There is a need for new non-invasive quick test that provides physicians accurate information for the early diagnosis of mitochondrial encephalomyopathies (ME). Advances in MR technology have provided new insight in the diagnosis of metabolic and other complex metabolic diseases in children, therefore, we sought to see if new technological MR tools, namely Diffusion-Weighted imaging (DWI) and proton MR spectroscopy (1H-MRS) helped in the early diagnosis of ME. Methods: From a population of 55 patients diagnosed with ME, 10 patients also underwent DW imaging and/or 1HMRS, at 1.5 T, by means of PRESS monovoxel short TE acquisition (TE: 35 ms) or 2D multivoxel long TE acquisition (TE:144 ms). Results: On DW imaging, patients with acute clinical status showed statistically more lesions than on their conventional counterparts. On 1HMRS, all patients with acute clinical status showed brain lactate, which was superior to its detection on serum/CSF. Conclusion: Neuroradiologic information provided for current MR advanced tools is becoming the first para-clinical test in the early tentative diagnosis of ME, in children with acute onset of encephalopatic status.

Metabolite Quantification in Tumours by Magnetic Resonance Spectroscopy: Objectives, Results and Perspectives by Rossella Canese, Egidio Iorio, Alessandro Ricci, Maria Pisanu, Massimo Giannini, Franca Podo (110-127).
Magnetic resonance spectroscopy (MRS) allows non invasive detection of tissue metabolism. Absolute or relative quantification of metabolites and chemical compounds detected by 1H and 31P MRS can today be performed in a number of pathological tissues including different types of cancer lesions, consequently improving accuracy in disease diagnosis and prognosis. Methods allowing quantification of tumour metabolites under in vivo MR spectral profiles have been progressively developed in the past and are now entering the clinical routine. Several methods of quantification have been proposed and validated in healthy tissues in a number of single- and multi-centre studies. Most of these approaches are not always directly applicable to cancer lesions because of their inherent heterogeneity or variability in water content, thus peak area ratios can, in some cases, represent better indicators of disease progression and response to therapy. An additional important limitation may derive from the excessive duration of some MRS measurement protocols, which would be added to a routine clinical MRI examination in the same session. We propose a critical overview of the principal methods currently applied for the quantification of metabolites and chemical compounds, mostly detected by 1H MRS in tumours.

In contrast to surgical therapy and cytostatic therapy, locally ablative treatment of colorectal liver metastases is still lacking of large controlled trials to definitely prove its benefit on patient survival. Despite this, many different modalities have been developed for minimal invasive locoregional treatment, such as thermotherapy (radiofrequency ablation, laser induced thermotherapy) or brachytherapy (interstitial brachytherapy, transarterial radioembolization). As all of these modalities are performed under imaging guidance, success and risk strongly depends on the imaging strategy chosen for patient evaluation, treatment monitoring, and follow-up. There are not yet comprehensive guidelines on the use of locally ablative therapies, and, even more so, the use of diagnostic imaging largely depends on individual experiences and policies. Beyond oncological routines, the planning and monitoring of locally ablative treatment pose specific demands on the available imaging procedures. Many innovative applications of ultrasound, CT, MRI, PET and SPECT help to fulfill these requirements. Algorithms are needed for pretherapeutic decision making regarding the appropriate treatment strategy, as well as for posttherapeutic follow-up to confirm local control and to rule out new disease. This review summarizes current opinions to the use of diagnostic imaging in the scope of different image guided therapy modalities. Important, partly unpublished data for comprehensive pre- and posttherapeutic imaging algorithms is worked up. It also outlines challenges and possible solutions for improved guidance and monitoring of minimal invasive locoregional cancer treatment.