Radionecrosis of the temporal lobe: dynamic susceptibility contrast MRI

We examined nine patients with histologically proven nasopharyngeal carcinoma (NPC), treated with radiotherapy, using dynamic susceptibility contrast MRI (DSC-MRI). In eight there was clinical evidence of radionecrosis of the temporal lobe, and one was examined for local recurrence in the nasopharynx. All patients had either high-signal finger-like or cystic lesions in the temporal lobes on T2-weighted images. Heterogeneous contrast enhancement occurred in all patients. Relative regional cerebral blood volume (rrCBV) mapping revealed marked hypoperfusion in all patients. One underwent bilateral temporal lobectomy and radionecrosis was confirmed histologically.

Synthesis and evaluation of a series of 2'-deoxy analogues of the antiviral agent 5,6-dichloro-2-isopropylamino-1-(beta-L-ribofuranosyl)-1H-benzimidazole (1263W94)

A series of 2'-deoxy analogues of the antiviral agent 5,6-dichloro-2-isopropylamino-1-(beta-L-ribofuranosyl)-1H-benzimidazole (1263W94) were synthesized and evaluated for activity against human cytomegalovirus (HCMV) and for cytotoxicity. The 2-substituents in the benzimidazole moiety correspond to those that were used in the 1263W94 series. In general, as was found in the 1263W94 series, cyclic and branched alkylamino groups were needed for potent activity against HCMV. Three analogues 3a, 3b and 3d were as potent as 1263W94. Further evaluation of two analogues, 3a and 3b, suggested that these 2'-deoxy analogues may act via a novel mechanism of action similar to that of 1263W94. These 2'-deoxy analogues generally lacked cytotoxicity in vitro. Pharmacokinetic parameters in mice and protein binding properties of 3a were quite similar to 1263W94. However, the oral bioavailability of 3a was only half of that observed for 1263W94.

Microfabricated polymer devices for automated sample delivery of peptides for analysis by electrospray ionization tandem mass spectrometry

Delivery of proteins and peptides to electrospray ionization mass spectrometers (ESI-MS) has been demonstrated using glass and quartz microfabricated devices. This paper reports the construction and use of poly(dimethylsiloxane) (PDMS) microfabricated soft polymer devices with mass spectrometry for protein analysis. The PDMS devices were fabricated using replica molding against a patterned photoresist generated by photolithographic techniques. The PDMS devices were connected to the mass spectrometer via a derivatized transfer capillary and samples were transferred by electroosmotic pumping. The formulation of PDMS was optimized for compatibility with ESI, and the devices were tested for performance. The practical application of PDMS devices was demonstrated by the identification of rat serum albumin separated by 2-D gel electrophoresis. Extended contact of the sample with the surface of the PDMS device did not significantly affect the sample analysis, and the limit of detection for samples run on a PDMS device was comparable to the limit of detection achieved on glass devices. This study suggests that PDMS devices fabricated using replica molding are compatible with ESI-MS. This will potentially lead to the construction of inexpensive microfabricated devices with complex designs and advanced functionalities.

MR imaging of breast paraffinomas

OBJECTIVE

Our objective is to present the MR appearance of breast paraffinoma, a late complication of breast augmentation by liquid paraffin wax, and to correlate this appearance with the histopathologic findings that were available for three of the 11 breasts we studied.

CONCLUSION

Breast paraffinomas have a characteristic MR appearance that correlates well with histopathologic findings. With MR imaging, we were able to visualize the location and extent of the paraffinoma, best seen on the fat-suppression sequence, and to evaluate the surrounding fibroglandular breast tissue.

Breath-hold 3D gadolinium-enhanced subtraction MRA in the detection of transplant renal artery stenosis

AIMS

The purpose of this study was to assess the value of breath-hold 3D gadolinium-enhanced subtraction magnetic resonance angiography (GD-MRA) in the detection of transplant renal artery stenosis (TRAS).

PATIENTS AND METHODS

Seven patients with suspected post-transplant renal artery stenosis were studied. GD-MRA was performed at 1.5T with a 3D fast spoiled gradient recalled echo (FSPGR) pulse sequence. Before injection of contrast medium, the 3D pulse sequence was performed to obtain a set of non-contrast images for subtraction purposes. Dynamic 3D imaging was performed simultaneously with the bolus injection of 40 ml of gadopentetate dimeglumine. Angiographic images were reconstructed using the Advantage Window workstation (version 2.0 GE Medical Systems) and subtraction was made with the pre-contrast image data. Any signal intensity cut-off or narrowing of more than 50% was regarded as significant stenosis. Ultrasound Doppler (USD) study was performed with both colour and spectral studies. Peak systolic velocity (PSV) of greater than 2.0 m/s and acceleration time (AT) greater than 120ms was regarded as positive for TRAS. These were then compared with the digital subtraction angiography (DSA) as the gold standard.

RESULTS

A total of nine examinations performed in seven patients were included in the analysis. MRA correlated with the DSA findings in eight examinations, with one false negative. USG correlated with DSA in six examinations, with two false negative and one false positive case.

CONCLUSION

In our opinion, GD-MRA is a promising and non-invasive technique in the detection of TRAS.

Determining the lumbar vertebral segments on magnetic resonance imaging

STUDY DESIGN

A study to test the ability of an additional cervicothoracic localizer scan to decrease interobserver discrepancy in the identification of vertebral segments in magnetic resonance imaging of the lumbar spine.

OBJECTIVES

To investigate whether lumbar vertebral segments can be identified correctly from lumbosacral magnetic resonance localizer scans, the degree of interobserver discrepancy, and the value of an additional cervicothoracic localizer scan.

SUMMARY OF BACKGROUND DATA

In magnetic resonance imaging of the lumbar spine, it may be difficult to identify transitional lumbosacral vertebral segments.

METHODS

The sagittal and coronal lumbosacral localizer scans of 141 consecutive patients referred for magnetic resonance imaging of the lumbosacral spine were reviewed independently by two radiologists with the aim of locating the L5 vertebra. An additional sagittal cervicothoracic localizer scan also was performed in each case. The final study group consisted of 129 patients. The L5 vertebra was identified by counting caudally from C2 using the sagittal cervicothoracic and lumbosacral localizer scans. In the 54 most recently studied patients, cod liver oil capsule surface markers were placed near the thoracolumbar junction to quantify any marker shift between the two sagittal localizer scans.

RESULTS

The lumbar segments could be identified consistently by counting caudally using cervicothoracic and lumbosacral localizer scans. Using sagittal lumbosacral localizer scans alone, the lumbar vertebral segments could be identified correctly in only 80.2% of patients. Coronal lumbosacral localizer scans produced similar results (82.2%). The accuracy fell to 77.9% when using a combination of both sagittal and coronal lumbosacral localizer scans. There was a 11.6% interobserver discordance in assessment of these levels. Lumbosacral transitional vertebrae were identified in 17 patients (13.2%), including 8 sacralized L5 and 9 lumbarized S1 vertebrae. Apparent surface-marker shift between cervicothoracic and lumbosacral localizer scans was insignificant, averaging only 1.9 mm (range, 0.0-5.6 mm).

CONCLUSIONS

The addition of a cervicothoracic localizer scan in magnetic resonance imaging of the lumbosacral spine is highly recommended.

Hypertrophic olivary degeneration following surgical excision of brainstem cavernous hemangioma: a case report

Hypertrophic olivary degeneration (HOD) is a rare type of neuronal degeneration involving the dento-rubo-olivary pathway. It is distinguished from other types of neuronal degeneration in that hypertrophy, rather than atrophy, takes place in the neurons in the inferior olivary nucleus. Prior to the invention of Magnetic Resonance Imaging (MRI), HOD was difficult to be detected, and a firm diagnosis could only be made at autopsy. We present a case of bilateral HOD following surgical excision of a cavernous hemangioma in the brainstem. The literature and imaging findings of this uncommon condition are reviewed.

Detection of hepatic tumor perfusion following transcatheter arterial chemoembolization with dynamic susceptibility contrast-enhanced echoplanar imaging

The aim of the study was to evaluate the usefulness of the magnetic resonance (MR) perfusion maps in the detection of liver tumor perfusion following transcatheter arterial chemoembolization (TACE). MR dynamic susceptibility contrast-enhanced imaging was performed in 12 patients with 10 confirmed hepatocellular carcinoma and 2 confirmed hepatic metastasis using single-shot echoplanar pulse sequence. Time-intensity curves for all hepatic tumors showed a transient signal drop and the hepatic blood volume (HBV) maps were reconstructed. On the HBV maps, most tumors (80%) demonstrated hyperperfusion before TACE and hypoperfusion following TACE. The site and the degree of residual hyperperfusion within the tumor on the HBV maps correlated well with the areas of hypervascularity on the angiograms. In conclusion, the MR perfusion maps can be a promising technique for detecting the perfusion of the residual tumor tissue following TACE.

The effect of using shorter echo times in MR imaging of knee menisci: a study using a porcine model

OBJECTIVE

Increasingly shorter TEs are being used for T1-weighted and proton density-weighted sequences in MR imaging of the knee. This study aims to evaluate the effect of a short TE on meniscal signal intensity.

MATERIALS AND METHODS

Thirty porcine knees were imaged with a 1.5-T MR scanner using spin-echo T1-weighted and proton density-weighted sequences. TR was kept constant at 700 msec for T1-weighted and 2200 msec for proton density-weighted sequences. For each set of sequences, sagittal images were obtained using these TE values: 9, 12, 16, 20, and 25 msec. Imaging parameters, such as slice thickness and interslice gap, number of excitations, matrix size, and field of view, were identical for each set of sequences. Using a fixed window level and width, we assessed the anterior and posterior horns of the medial meniscus for signal hyperintensity at each TE value. Signal intensity was also measured in eight knees. The menisci were then dissected and examined grossly and histopathologically.

RESULTS

Intrameniscal signal intensity increased progressively with shorter TEs. At a TE of 9 msec, signal hyperintensity was present in 100% of T1-weighted and 96.7% of proton density-weighted images. At a TE of 12 msec, signal hyperintensity was seen in 86.7% of T1-weighted and 80% of proton density-weighted images. At a TE of 16 msec, increased signal intensity was seen in only 3.3% of T1-weighted and 6.6% of proton density-weighted images. At TEs of 20 and 25 msec, increased signal intensity was seen in none of the T1-weighted and proton density-weighted images. Meniscal signal intensity increased exponentially at very short TE values. All menisci were found to be normal on gross and histopathological examination.

CONCLUSION

Spurious signal hyperintensity appears in normal menisci at short TE values. Images acquired with short TEs should be interpreted with caution, and a TE of 16 msec or more is recommended.

Lumbar spine magnetic resonance imaging: comparison between fast spin echo proton density and spin echo T1 axial scans

Spin echo (SE) T1 axial scans are routinely obtained in magnetic resonance imaging of the lumbar spine in many centres. This study directly compared matched SE T1 and fast SE (FSE) proton density (PD) axial scans. Both SE T1 and FSE PD axial scans of the lumbar spine were obtained in 116 consecutive patients. The imaging parameters (field-of-view, slice thickness, interslice gap, number of excitations and matrix size) and scan levels were identical for each pair of sequences. At two selected levels, L4/5 and L5/S1, various structures were independently graded by two observers. In 232 lumbar levels analysed, the bone marrow, epidural fat, disc, extradural nerve root and facet joint were equally well seen on both sequences by both observers (combined mean grades of 2.93-2.99). The thecal sac was marginally better depicted on FSE PD than on SE T1 images, with mean grades of 2.96 and 2.88, respectively. The psoas muscle was adequately visualized for diagnostic purposes on both sequences (mean grades of 2.30-2.32). The cauda equina were better seen on FSE PD (mean grade 1.92) than on SE T1 (mean grade 1.00) images. In conclusion, FSE PD scans are comparable to and may potentially replace SE T1 axial MR scans of the lumbar spine.

The magic angle phenomenon in tendons: effect of varying the MR echo time

Increased signal intensity on magnetic resonance (MR) imaging of tendons arising from the magic angle phenomenon is well recognized. This study aimed to evaluate the effect of varying the echo time (TE) upon tendon signal intensity, and to determine if a modified TE value produces acceptable T1 and proton density (PD) weighted images. Fresh bovine tendons were imaged in a 1.5 T MR scanner using spin echo (SE) T1 and PD weighted sequences and utilizing a number of different coils. For each set of sequences, the tendon was orientated at 55 degrees to the main magnetic field (B0) and imaged using constant TR and incremental TE values. Signal intensity was measured on images at each TR/TE value and compared with the signal intensities of tendons orientated at 0 degree to B0, obtained using minimum TE values. This experiment was repeated with a 1.0 T MR scanner and utilizing a spine coil. The Achilles tendon of a human volunteer was similarly imaged using a general purpose flex coil. For bovine and human tendons orientated at 55 degrees to B0, the signal intensities decreased exponentially with increasing TE. A critical TE value exceeding 37 ms, for each sequence, reduced the signal intensities to the levels obtained with the tendons orientated at 0 degree to B0, such that the magic angle phenomenon could be avoided. Although there was variability of the signal intensities with different coils, the critical TE value remained constant and the anatomical clarity was not degraded. The critical TE value was unaltered using two MR scanners of different field strengths.

Selective inhibitors of Candida albicans dihydrofolate reductase: activity and selectivity of 5-(arylthio)-2,4-diaminoquinazolines

The recent increase in fungal infections, especially among AIDS patients, has resulted in the need for more effective antifungal agents. In our search for such agents, we focused on developing compounds which inhibit fungal dihydrofolate reductase (DHFR). A series of 25 5-(arylthio)-2,4-diaminoquinazolines were synthesized as potentially selective inhibitors of Candida albicans DHFR. The majority of the compounds were potent inhibitors of C. albicans DHFR and much less active against human DHFR. High selectivity, as defined by the ratio of the I50 values for human and C. albicans DHFR, was achieved by compounds with bulky and rigid 4-substituents in the phenylthio moiety. For example, 5-[(4-morpholinophenyl)thio]-2,4-diaminoquinazoline displayed a selectivity ratio of 540 and was the most selective inhibitor synthesized to date. Substitution in the 2- or 3-position of the 5-phenylthio group provided only marginal selectivity. 6-Substituted-5-[(4-tert-butylphenyl)thio]-2,4-diaminoquinazolines showed potent activity against the C. albicans enzyme but were equally active against human DHFR. Most of the selective compounds were also good inhibitors of C. albicans cell growth, with minimum inhibitory concentration values as low as 0.05 microgram/ mL.

2,4-Diamino-5-benzylpyrimidines as antibacterial agents. 14. 2,3-Dihydro-1-(2,4-diamino-5-pyrimidyl)-1H-indenes as conformationally restricted analogues of trimethoprim

A conformationally restricted analogue of trimethoprim (1a) has been prepared by connecting the ortho position of the benzene ring to the methylene linkage with two methylene groups, thus forming a dihydroindene derivative (2b). The chemistry involved the condensation of barbituric acid with an indanone derivative, followed by a three-step conversion to a 2,4-diaminopyrimidine. The S isomer of 2b was found to have a minimum-energy conformation very similar to that of 1a when bound to Escherichia coli dihydrofolate reductase, in contrast to that of 1a in vertebrate DHFR. Theoretically such a derivative might have increased specificity and activity against the bacterial enzyme. Molecular modeling experiments suggested that the actual decreased activity was due to crowding in the enzyme, caused by the extra atoms needed to restrict the conformation.

2,4-Diamino-5-benzylpyrimidines and analogues as antibacterial agents. 11. Quinolylmethyl analogues with basic substituents conveying specificity

A series of nine 2,4-diamino-5-[6-( or 7-)quinolylmethyl]pyrimidines has been prepared by condensations of quinolinecarboxaldehydes with beta-anilinopropionitriles, followed by treatment with guanidine. All compounds has basic or methoxy substituents at the 2- or 4-positions of the quinoline ring. All of the 6-quinolylmethyl derivatives were highly inhibitory against Escherichia coli dihydrofolate reductase (DHFR), provided that an 8-substituent was present in the quinoline ring. Those compounds that had basic substituents in the 2-position of the quinoline ring were also highly specific for bacterial dihydrofolate DHFR, relative to a vertebrate counterpart. Protonation on the quinoline ring nitrogen is a possible cause of specificity.

The activity of alkyl phosphorylcholines and related derivatives against Leishmania donovani

Several alkyl phosphorylcholines and related derivatives were tested against Leishmania donovani amastigotes in mouse peritoneal macrophages in vitro and ED50 values were determined in the range of 1-12 microM. The three alkyl phosphorylcholines tested against L. donovani in BALB/c mice were active, an ED50 of 12.8 mg/kg/day X 5 was ascertained for one compound, but an alkyl phosphorylethanolamine was inactive.

SNR in optical velocimeters: effect of detection angle

Measurements of scattering power and SNR as a function of detection angle were carried out employing a differential heterodyne laser Doppler velocimeter (DLDV) and a white light fringe image velocimeter (WFIV). Particle diameters of 0.481 microm and 5.7 microm were employed for the DLDV and WFIV, respectively. In general, the measurements are in excellent agreement with calculations based on Mie theory.

SNR in optical velocimeters: effect of particle number density

Measurements of SNR as a function of number density (n) were carried out employing a Differential Heterodyne Laser Doppler Velocimeter (DLDV) and a White Light Fringe Image Velocimeter (WFIV). These two techniques made it possible to investigate separately the coherent and incoherent scattering modes, respectively. It was observed that with the WFIV the SNR is proportional to n for n values corresponding to less than one particle in the probe volume. The SNR remains constant for large n values. In the case of the DLDV the SNR was always found to be proportional to n when the coherence condition was satisfied. Consequently, it is concluded that the DLDV signal results entirely from coherent scattering, even when the number of particles in the probe volume is as low as 0.02 (the lower limit of the measurements).