Current Medical Imaging - Volume 6, Issue 3, 2010

This issue has a variety of clinical applications of high intensity focused ultrasound, multi-scale statistical shape model analysis, ambient lighting in the reading room, training children to reduce motion for MRI as well as imaging findings of gastric cancer, hepatic tumors and renal artery aneurysm. Qian believes that there are several problems in clinical applications of the high intensity focused ultrasound, and presents detailed analysis on these problems related to heat dosage, temperature monitoring, working mode and aiming of the focused region and possible solutions. Mofrad et al. propose a novel wavelet based multi-scale statistical shape model-analysis for more accurate and robust hepatic discrimination. They discuss the outcomes of the current approach, clarify their achievements and conclude the remaining works and future trends. Optimizing image observation and interpretation is a multifactorial process and requires consideration of complex parameters. Brennan et al. discuss the physiology of vision and its impact on image interpretation as well as issue of ambient lighting in the reading room. There are a number of difficulties in imaging children. Woods-Frohlich et al. outline interventions that can be used to prepare children for MRI and to limit their motion during medical imaging procedures. Gastric cancer is one of the leading causes of death worldwide. Ishigami et al. present a pictorial review of various unusual metastatic lesions from gastric cancer. Focal hepatic lesions are common and are broadly classified as benign and malignant. Mulla and Singh also present a pictorial review of some of the common focal hepatic lesions and their characteristic features on US, CT and MRI scans. Extrahepatic collaterals are frequently seen in patients receiving transcatheter arterial chemoembolization (TACE). Finding and properly embolizing these collaterals are very important for tumor control. Tsai et al. report a case demonstrating decreased extrahepatic collaterals in hepatoma by using sorafenib which may have a synergistic effect with TACE. The detection of renal artery aneurysm has increased, and endovascular therapy has emerged as a viable treatment option. Fitzpatrick et al. describe the CT and angiographic findings of a large ruptured renal artery aneurysm and its successful endovascular treatment with stent-grafts.

The author believes that there are several problems in clinical applications of the high intensity focused ultrasound (HIFU), for example, the heat dosage and the temperature monitoring, the working mode (CW, pulse or phasing) of the acoustic source, and aiming of the focused region at the target etc. They need to be resolved in order to enhance the safety and efficacy in clinical applications. Presented here are detailed analysis on these problems and possible solutions.

Several methods have been proposed to construct Statistical Shape Model (SSM) to aim image analysis using computer in field Computer Aided Diagnosis (CAD), Computer Assisted Surgery (CAS), and other medical applications by providing a prior knowledge. The major challenge for liver shape model is a high variation in geometry such as size, shape and volume between livers. In this paper, we have presented a new technique for the automatic Multi-Scale Statistical Shape Model (MS-SSM) of three-dimensional (3-D) liver from volumetric segmented images data. The procedure included both building of Spherical Harmonics shape description and the Wavelet transform. Principal Component Analysis (PCA) was applied to corresponding landmarks on the tanning shapes for performing leave-one-out test. Validation metrics, for comparing performances of the MS-SSM method against SSM, were the Hausdorff distance measure and statistical parameter of Dice Similarity Coefficient (DSC). We evaluated the performance of our proposed method against to traditional method. The results confirmed that the proposed MS-SSM technique was successful, and more accurate for liver domain. We also examined robustness of the method in liver classification. In this research classification was performed on feature vector obtained from PCA using Support Vector Machine (SVM) and k-Nearest Neighbors (k-NN) classifiers. Diagnostic accuracy was determined by leave-one-out cross-validation method and Receiver Operating Characteristic (ROC) analysis for each observer. The results showed that our proposed method to be more accurate and robust for liver discrimination.

Much research has focussed on optimisation of acquisition of diagnostic images, whilst relatively little work has been done on optimising the reading environment. We discuss the physiology of vision, particularly regarding light adaptation, and its impact on image interpretation. With this background in mind, we then discuss the issue of ambient light in the reading room. Research by our group and others suggests that optimal reading room lighting may be close to 50 lux.

In this review, we outline interventions that can be used with children to prepare them for magnetic resonance imaging (MRI) and to limit their motion during medical imaging procedures. Children, especially those diagnosed with a developmental disability or other mental health challenges, may have difficulty remaining still for long periods of time. Children also experience fear, anxiety and curiosity in the MRI environment due to the noise, size of the machines, and overall overwhelming experience. These difficulties can affect the ability of researchers and other professionals to perform clinical tests such MRI, which require the child to remain motionless for the duration of the scan. A few studies have described methods used to prepare children for the MRI environment and train them for successful completion of the MRI scans. These include standard operating procedures as used in clinical scanning, such as appropriate information dissemination, standard physical restraint procedures and sedation. Other motion reduction techniques range from low-cost nontechnical but people heavy approaches, such as mock scanner training sessions, systematic desensitization and guided imagery techniques to more technical engineering type approaches, such as behavior feedback methods and the use of postprocessing motion correction algorithms.

Purpose: The purpose of this pictorial review was to present imaging findings of various unusual metastatic lesions from gastric cancer. Conclusion: Because of its tendency to cause the development of peritoneal implants, diffuse retroperitoneal tumor infiltration, and lymphangitic spread, poorly differentiated gastric adenocarcinoma can involve various organs and superficial regions. In addition, metastasis from alpha-fetoprotein (AFP)-producing gastric cancer may show giant lymph node metastasis, portal venous tumor thrombus, and hypervascular liver metastasis.

Focal liver lesions are common incidental findings seen usually on ultrasound examination in healthy individuals. Although they are largely benign some can be malignant primaries or metastatic lesions to the liver, hence it is important to accurately characterise these lesions. There are several imaging modalities used in their characterisation. We present a pictorial review of the common focal liver lesions in an attempt to define their characteristic features on different imaging modalities namely ultrasound, CT and MR scans.

An old male with multiple hepatocellular carcinomas received six courses of transcatheter arterial chemoembolization. Some tumors supplied by extrahepatic collaterals were seen in treatment period and made it difficult to achieve transcatheter chemoembolization completely. After oral sorafenib treatment and during the 7th transcatheter chemoembolization course, we found that the features of tumor angiogenesis were markedly decreased. Due to disappearance of the extrahepatic collaterals, it took less time (62' 51” vs. 22' 51”) to perform transcatheter chemoembolization. Our case is the first one in the literature to report that antiangiogenic therapy can reduce collateral formation at the gross and angiographic levels, and shows that there may be a synergistic effect between transcatheter chemoembolization and sorafenib.

The detection of renal artery aneurysms has increased with the expanded utilization of cross sectional imaging. Although these lesions have traditionally been treated with surgery, endovascular therapy has emerged as a viable treatment option both in the emergent and the elective settings. We describe the CT and angiographic findings of a large ruptured renal artery aneurysm and its successful endovascular treatment with stent-grafts in the emergent setting. Our clinical and technical success under emergent conditions supports treatment of renal artery aneurysms with stent placement in the elective setting.