C. A. Azlan

The accuracy of pharmacokinetic parameter measurement in DCE-MRI of the breast at 3 T.

The purpose of this work is to quantify the accuracy of pharmacokinetic parameter measurement in DCE-MRI of breast cancer at 3 T in relation to three sources of error. Individually, T1 measurement error, temporal resolution and transmitted RF field inhomogeneity are considered. Dynamic contrast enhancement curves were simulated using standard acquisition parameters of a DCE-MRI protocol. Errors on pre-contrast T1 due to incorrect RF spoiling were considered. Flip angle errors were measured and introduced into the fitting routine, and temporal resolution was also varied. The error in fitted pharmacokinetic parameters, K(trans) and v(e), was calculated. Flip angles were found to be reduced by up to 55% of the expected value. The resultant errors in our range of K(trans) and v(e) were found to be up to 66% and 74%, respectively. Incorrect T1 estimation results in K(trans) and v(e) errors up to 531% and 233%, respectively. When the temporal resolution is reduced from 10 to 70 s K(trans) drops by up to 48%, while v(e) shows negligible variation. In combination, uncertainties in tissue T1 map and applied flip angle were shown to contribute to errors of up to 88% in K(trans) and 73% in v(e). These results demonstrate the importance of high temporal resolution, accurate T1 measurement and good B1 homogeneity.

B1 transmission-field inhomogeneity and enhancement ratio errors in dynamic contrast-enhanced MRI (DCE-MRI) of the breast at 3T.

To quantify B1 transmission‐field inhomogeneity in breast imaging of normal volunteers at 3T using 3D T1‐weighted spoiled gradient echo and to assess the resulting errors in enhancement ratio (ER) measured in dynamic contrast‐enhanced MRI (DCE‐MRI) studies of the breast.

Quantification techniques to minimize the effects of native T1 variation and B1 inhomogeneity in dynamic contrast-enhanced MRI of the breast at 3 T.

The variation of the native T1 (T10) of different tissues and B1 transmission‐field inhomogeneity at 3 T are major contributors of errors in the quantification of breast dynamic contrast‐enhanced MRI. To address these issues, we have introduced new enhancement indices derived from saturation‐recovery snapshot‐FLASH (SRSF) images. The stability of the new indices, i.e., the SRSF enhancement factor (EFSRSF) and its simplified version (EF′SRSF) with respect to differences in T10 and B1 inhomogeneity was compared against a typical index used in breast dynamic contrast‐enhanced MRI, i.e., the enhancement ratio (ER), by using computer simulations. Imaging experiments with Gd‐DTPA‐doped gel phantoms and a female volunteer were also performed. A lower error was observed in the new indices compared to enhancement ratio in the presence of typical T10 variation and B1 inhomogeneity. At changes of relaxation rate (ΔR1) of 8 s−1, the differences between a T10 of 1266 and 566 ms are <1, 12, and 58%, respectively, for EFSRSF, EF′SRSF, and ER, whereas differences of 20, 8, and 51%, respectively, result from a 50% B1 field reduction at the same ΔR1. These quantification techniques may be a solution to minimize the effect of T10 variation and B1 inhomogeneity on dynamic contrast‐enhanced MRI of the breast at 3 T. Magn Reson Med, 2012.

A survey of radiation dose to patients and operators during radiofrequency ablation using computed tomography

Computed tomography (CT) fluoroscopy is able to give real time images to a physician undertaking minimally invasive procedures such as biopsies, percutaneous drainage, and radio frequency ablation (RFA). Both operators executing the procedure and patients too, are thus at risk of radiation exposure during a CT fluoroscopy. This study focuses on the radiation exposure present during a series of radio frequency ablation (RFA) procedures, and used Gafchromic film (Type XR-QA; International Specialty Products, USA) and thermoluminescent dosimeters (TLD-100H; Bicron, USA) to measure the radiation received by patients undergoing treatment, and also operators subject to scatter radiation. The voltage was held constant at 120 kVp and the current 70mA, with 5mm thickness. The duration of irradiation was between 150-638 seconds. Ultimately, from a sample of 30 liver that have undergone RFA, the study revealed that the operator received the highest dose at the hands, which was followed by the eyes and thyroid, while secondary staff dosage was moderately uniform across all parts of the body that were measured.

A low cost solution for post-biopsy complications using available RFA generator and coaxial core biopsy needle

Percutaneous image-guided needle biopsy is typically performed in highly vascular organs or in tumours with rich macroscopic and microscopic blood supply. The main risks related to this procedure are haemorrhage and implantation of tumour cells in the needle tract after the biopsy needle is withdrawn. From numerous conducted studies, it was found that heating the needle tract using alternating current in radiofrequency (RF) range has a potential to minimize these effects. However, this solution requires the use of specially designed needles, which would make the procedure relatively expensive and complicated. Thus, we propose a simple solution by using readily available coaxial core biopsy needles connected to a radiofrequency ablation (RFA) generator. In order to do so, we have designed and developed an adapter to interface between these two devices. For evaluation purpose, we used a bovine liver as a sample tissue. The experimental procedure was done to study the effect of different parameter settings on the size of coagulation necrosis caused by the RF current heating on the subject. The delivery of the RF energy was varied by changing the values for delivered power, power delivery duration, and insertion depth. The results showed that the size of the coagulation necrosis is affected by all of the parameters tested. In general, the size of the region is enlarged with higher delivery of RF power, longer duration of power delivery, and shallower needle insertion and become relatively constant after a certain value. We also found that the solution proposed provides a low cost and practical way to minimizes unwanted post-biopsy effects.

Multifunctional carbon-coated magnetic sensing graphene oxide-cyclodextrin nanohybrid for potential cancer theranosis

AbstractWe functionalized graphene oxide (GO) with cyclodextrin (CD) to increase the drug loading and cellular uptake of GO, and bound the GO-CD to carbon-coated iron nanoparticles (Fe@C) with superparamagnetic properties for potential magnetic-directed drug delivery and as a diagnostic agent. The GO-CD/Fe@C was loaded with an anticancer drug, doxorubicin (DOX), to form a multifunctional GO-CD/Fe@C/DOX nanohybrid. A cumulative increase in DOX loading was observed probably due to DOX adsorption to the graphitic domains in Fe@C and also to the GO-CD. In acidic pH that resembles the pH of the tumor environment, a higher amount of DOX was released from the GO-CD/Fe@C/DOX nanohybrid when compared to the amount released at physiological pH. The signal intensity and the contrast enhancement in magnetic resonance imaging of Fe@C decreased with its concentration. Besides, the cellular uptake of GO-CD/Fe@C/DOX nanohybrid was significantly higher by 2.5-fold than that of Fe@C/DOX in MDA-MB-231 human breast cancer model. The nanohybrids were internalized into the tumor cells via an energy-dependent process and localized mainly in the nuclei, where it exerts its cytotoxic effect, and some in the lysosomes and mitochondria. This has resulted in significant cytotoxicity in tumor cells treated with GO-CD/Fe@C/DOX. These findings highlight the potential use of multifunctional GO-CD/Fe@C nanohybrid for magnetic sensing anticancer drug delivery to tumor cells. Magnetic sensing graphene oxide-cyclodextrin nanohybrid for cancer theranosisGraphical abstract

Use of a capillary input function with cardiac output for the estimation of lesion pharmacokinetic parameters: preliminary results on a breast cancer patient

The objective of this work was to propose and demonstrate a novel technique for the assessment of tumour pharmacokinetic parameters together with a regionally estimated vascular input function. A breast cancer patient T2*-weighted dynamic contrast enhanced MRI (DCE-MRI) dataset acquired at high temporal resolution during the first-pass bolus perfusion was used for testing the technique. Extraction of the lesion volume transfer constant K(trans) together with the intravascular plasma volume fraction v(p) was achieved by optimizing a capillary input function with a measure of cardiac output using the principle of intravascular indicator dilution theory. For a region of interest drawn within the breast lesion a v(p) of 0.16 and a K(trans) of 0.70 min(-1) were estimated. Despite the value of v(p) being higher than expected, estimated K(trans) was in accordance with the literature values. In conclusion, the technique proposed here, has the main advantage of allowing the estimation of breast tumour pharmacokinetic parameters from first-pass perfusion T2*-weighted DCE-MRI data without the need of measuring an arterial input function. The technique may also have applicability to T1-weighted DCE-MRI data.

A Survey of Computed Tomography Dose to Operators and Patients During Radiofrequency Ablation

The ability of computed tomography (CT) Fluoroscopy in giving real time images leads to the adoption of this application in assisting interventional procedures such as biopsy, percutaneous drainage, and radiofrequency ablation (RFA). The radiation exposure from CT Fluoroscopy may be significant for patients and operators who are undergoing and performing this procedure. This study aims to survey the radiation dose received by operators and patients during radiofrequency ablation (RFA) treatments. Gafchromic film (Type XR-QA; International Specialty Products, USA) and thermoluminescent dosimeters (TLD-100H; Bicron, USA) were used to measure the radiation dose received by patients and the scattered dose exposed to operators respectively. A sample of 30 liver RFA’s were monitored to determine the average dose. In all the RFA procedures, the parameters setting were set at 120 kVp, 70 mA, 5 mm slice thickness while the fluoroscopy time was in the range of 150 – 638 sec. From our survey, it was found that the radiologist received a comparatively higher dose rate at the hand followed by eyes and thyroid. The radiation dose rate for the supporting staff appears relatively uniform at all parts of the body measured.

Temperature Modeling of Therapeutic Ultrasound: A Preliminary Finding

The temperature model of therapeutic ultrasound for human tissue is important in order to design an accurate instrumental assessment and calibration of therapeutic ultrasound device. The focus of this study is to verify temperature effects of ultrasound on tissues and explore the possibility of proposing a preliminary temperature model. A series of experiment had been conducted to clarify the relationship between output intensity and site of target tissue with temperature change in a phantom-tissue model for 10 minutes exposure of 3 MHz therapeutic ultrasound. It was found that 3 MHz ultrasound provided effectual heating at the superficial tissue, which is 1 cm from surface. It was also found that the experimental data had provided the necessary evidence for the development of preliminary temperature model. The temperature model had been produced by selecting suitable trend line for the graph of experimental data particularly for the temperature change at site of 1 cm from tissue surface. In conclusion, the preliminary finding of this study is the temperature effect of therapeutic ultrasound in homogeneous phantomtissue model has a suitable pattern to be modeled into a simple mathematical equation. This study also proposed further study to develop more reliable and holistic evidence-based temperature model.

Development of Web-based medical history compiler.

The medical industry is moving towards ‘personalized medicine’ in all aspects of healthcare services, due to the realisation that each human body is different and ideally requires particular combination of drugs and treatment. In line with this objective, a novel web-based application, written in ASP and utilising widely available Microsoft Access database, has been developed to help users in compiling their medical history. The current system has achieved its main objectives of adding and editing patient demographical and medical history data. The system is also capable of determining the health status level based on the recorded medical history. The system will be further developed using open source technologies.