Hemodynamic assessment in a child with renovascular hypertension using time-resolved three-dimensional cine phase-contrast MRI.

Renovascular hypertension (RVH) is an important cause of hypertension in children. It is essential to assess the hemodynamics of RVH lesions in detail. We herein report the case of a 9-year-old female with RVH caused by left renal artery stenosis in which the hemodynamics of the lesions were assessed with time-resolved three-dimensional cine phase-contrast MRI (3D cine PC MRI) with a vastly undersampled 3D radial projection imaging trajectory before and after percutaneous transluminal renal angioplasty (PTRA). The utility of 3D cine PC MRA for diagnosing RVH and evaluating the renal blood flow pre- and post-PTRA is presented.

Assessment of epidermal growth factor receptor status in glioblastomas.

OBJECTIVES: Our previous study showed that a newly designed tracer radioiodinated 6-(3-morpholinopropoxy)-7-ethoxy-4-(3'-iodophenoxy)quinazoline ([(125)I]PYK) is promising for the evaluation of the epidermal growth factor receptor (EGFR) status and prediction of gefitinib treatment of non-small cell lung cancer. EGFR is over-expressed and mutated also in glioblastoma. In the present study, the expressions and mutation of EGFR were tested with [(125)I] PYK in glioblastoma in vitro and in vivo to determine whether this could be used to predict the sensitivity of glioblastoma to gefitinib treatment. METHODS: Glioblastoma cell lines with different expression of EGFR were tested. Growth inhibition of cell lines by gefitinib was assessed by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) colorimetric assay. Uptake levels of [(125)I]PYK were evaluated in cell lines in vitro. Tumor targeting of [(125)I]PYK was examined by a biodistribution study and imaging by single photon emission computed tomography (SPECT). RESULTS: High concentrations of gefitinib were needed to suppress EGFR-mediated proliferation. The uptake of [(125)I] PYK in cell lines in vitro was low, and showed no correlation with EGFR expression or mutation status. Biodistribution study and SPECT imaging with [(125)I]PYK for xenografts showed no [(125)I]PYK uptake. CONCLUSION: The results showed prediction of gefitinib effectiveness was difficult in glioblastoma by [(125)I]PYK, which might be due to the complicated expression of EGFR status in glioblastoma. Thus, new tracers for sites downstream of the mutant EGFR should be investigated in further studies.

Dosimetric assessment of the field abutment region in head and neck treatments using a multileaf collimator.

BACKGROUND AND PURPOSE: The use of conventional asymmetric collimators for junctioning of abutted fields can lead to significant dose inhomogeneity, due to jaw misalignment. However, recent technologic advances enable us to fabricate much finer leafpositioning accuracy. Consequently, it is anticipated that the use of multileaf collimator (MLC) will potentially improve dose homogeneity at the junction of abutted fields. In this work, we evaluated the dose inhomogeneities at the match-plane in monoisocentric three-field head and neck setups, using MLC for field abutment. MATERIAL AND METHODS: To define either the anterior or the lateral fields, the MLC was used with either the longitudinal (0 degree angle) or the transverse (90 degree angle) settings. For 0 degree setting, each leaf moves in a direction perpendicular to the gantry rotation axis, hence the "tongue and groove" (T&G) design can effect matching-area dose at the side of the leaf (Figure 1a). For 90 degree setting, the rounded shape of the leaf produces its effect at the leaf end (Figure 1b). Four combinations of abutted anterior field and abutted lateral field defined by MLC, i.e., abutted using MLC side-by-side, side-by-end, end-by-side and end-by-end, were compared (Table 1). Dose inhomogeneity was measured at the junction of the two abutted fields with films in a solid water phantom (Figure 2). The effect of jaw settings as a backup diaphragm on the dose distribution was also studied. Reproducibility of the results was confirmed by repeated measurements over a 1-year period. RESULTS: Abutted fields using MLC side-by-side caused underdose of approximately 15% (Figure 3a). Abutted fields using MLC side-by-end produced > 10% overdose that could be improved to +/- 1% for 0.5 mm overlap of the leaf end from the lateral portals (Figure 4). When using end-by-side, an overdose of approximately 15% was observed. However, the dose improved to a homogeneous dose for 0.8 mm overlap of leaf end from the anterior portal (Figure 5). End-by-end showed an overdose of > 20% (Figure 3b). This overdose could be smoothed out by overlaps of both leaf ends by 0.8 mm from both lateral and anterior portals (Figure 6). The ideal jaw position was found to be at 1 mm away from the beam central axis in any combination (Table 2). CONCLUSION: The use of MLCs for photon field junction matching is appropriate and represents an alternative approach to the problem of field matching using the asymmetric jaws in head and neck treatments.

Assessment of a potential tumor-seeking manganese metalloporphyrin contrast agent in a mouse model.

The performance of a newly developed potential tumor-seeking magnetic resonance (MR) contrast agent alpha-Aqua-13,17-bis(1-carboxypropionyl) carbamoylethyl-3,8-bis(1-phenethyloxyethyl)-beta-hydroxy-2,7,12,18-tetramethyl-porphyrinato manganese (III) (HOP-8P) was tested using a mouse model. Tumor-bearing (SCC-VII) mice were imaged using a 1.5T MR imager before and after intravenous administration of 0.1 mmol/kg of HOP-8P. A biodistribution analysis was performed using an optical emission spectrometer. Significant enhancement of the transplanted tumor was observed in MR images 24 h after intravenous injection of HOP-8P. The biodistribution assessment of manganese also correlated with the results of the imaging study. During the 24-h period following contrast administration, HOP-8P was consistently cleared from the circulation, liver, kidneys, and muscle; however, it was progressively accumulated within the tumor. HOP-8P is a promising tumor-seeking metalloporphyrin MR contrast agent with a wide imaging window.