The choline/creatine ratio in five benign neoplasms: comparison with squamous cell carcinoma by use of in vitro MR spectroscopy

BACKGROUND AND PURPOSE

The choline (Cho)/creatine (Cr) ratio has been shown to be a reliable proton MR spectroscopy metabolic marker for differentiating squamous cell carcinoma (SCCA) from normal muscle in the upper aerodigestive tract. However, it is unclear whether the Cho/Cr ratio can be used to differentiate a malignant tumor from a benign neoplasm in the extracranial head and neck. Our purpose was to determine whether the Cho/Cr ratio can be used to differentiate benign from malignant tumors in this region.

METHODS

In vitro one-dimensional proton MR spectroscopy (2,000/136,272 [TR/TE]) was performed at 11 T on tissue specimens obtained from glomus tumors (n = 3), inverting papilloma (n = 1), and schwannoma (n = 1). Cho/Cr area ratios were calculated and compared with similar, previously reported in vitro (11 T) findings and with samples of SCCA and normal muscle.

RESULTS

The Cho/Cr ratio was elevated in relation to muscle in all benign tumors at TE = 136 (glomus tumors = 4.52, inverting papilloma = 3.85, schwannoma = 2.2) and at TE = 272 (glomus tumors = 8.01, inverting papilloma = 2.1, schwannoma = 4.28). The average Cho/Cr ratio for benign lesions was 3.92 (TE = 136) and 6.11 (TE = 272). The Cho/Cr ratio was significantly higher in benign tumors than in both SCCA and muscle. The average Cho/Cr ratio for muscle at TEs of 136 and 272 was 1.16 and 1.31, respectively, whereas for SCCA the average Cho/Cr ratio at TEs of 136 and 272 was 1.67 and 2.45, respectively.

CONCLUSION

In our small group, the Cho/Cr ratio was significantly higher in benign tumors than in muscle and SCCA of the extracranial head and neck.

Contrast-enhanced 3D FISP MR angiography of the aortic arch ostia: preliminary results

PURPOSE

The goal of this work was to evaluate three-dimensional (3D) contrast-enhanced MR angiography (MRA) for the detection of ostial stenoses of the aortic arch.

METHOD

Sixteen patients with suspected carotid atherosclerotic disease prospectively underwent digital subtraction angiography of the aortic arch followed by contrast-enhanced MRA using a 3D fast imaging with steady-state precession (FISP) technique (TR = 5 ms, TE = 2 ms, flip angle = 30 degrees). Three neuroradiologists blindly measured stenoses on the catheter angiograms and MRA. Evaluation included the ostia of the innominate, left carotid, and left subclavian arteries. Any significant disagreement on catheter angiography was resolved by consensus. The MRA grades of each of the three observers were then compared with the consensus grades of the contrast angiogram.

RESULTS

Forty-eight vessels were scored, of which five had significant stenoses. MRA demonstrated 100% sensitivity, 89% specificity, 52% positive predictive value, and 100% negative predictive value. The Bowker test for symmetry indicated no significant difference between conventional angiography and MRA scores (p = 0.32-0.75), and there was good agreement between the three observers (weighted kappa = 0.75-0.86).

CONCLUSION

Contrast-enhanced 3D FISP MRA may be a useful imaging modality for the detection of significant stenoses at the ostia of the major aortic arch branches.

The ability of tumor volume to predict local control in surgically treated squamous cell carcinoma of the supraglottic larynx

PURPOSE

Pretreatment CT volumetric measurement of the primary tumor has been shown to be a predictor of local control in patients with laryngeal carcinoma treated with radiation therapy (RT) alone. A direct association has been demonstrated between tumor volume of supraglottic squamous cell carcinoma (SGSCCA) and local control. However, the association between tumor volume of SGSCCA and local control has not been investigated in patients treated surgically. The purpose of this study was to determine the relationship between SGSCCA tumor volume and local control in patients treated surgically.

MATERIALS AND METHODS

Primary site tumor volume was calculated from pretreatment CT studies in 37 laryngeal supraglottic carcinomas treated surgically. All patients had clinical follow-up for evidence of recurrent tumor along the surgical margins at the primary site for a minimum of 2 years after completion of treatment. Statistical analysis consisted of Mantel-Haenszel chi-square tests and Fisher's exact test.

RESULTS

Overall local control rate was 92% (33 of 37). Tumor volume was significantly associated with local control (p <. 05). Local control rate for tumors with volumes <16 cc was 94% (32 of 34) (p <.05).

CONCLUSIONS

Pretreatment CT volumetric analysis is useful for predicting local control in patients with SGSCCA carcinoma treated surgically.

CT evaluation of prosthetic ossicular reconstruction procedures: what the otologist needs to know

Postoperative otologic evaluation of patients who have undergone ossicular reconstruction is often difficult. However, thin-section computed tomography (CT) can help determine the type of prosthesis used for reconstruction and adequately assess for complications that may be causing postoperative conductive hearing loss. A variety of prostheses may be used in ossicular reconstruction (eg, stapes prosthesis, incus interposition graft, Applebaum prosthesis, Black oval-top prosthesis, Richards centered prosthesis, Goldenberg prosthesis) and can usually be identified at CT by their shapes and locations. Several causes of prosthetic failure are readily demonstrated at CT, including recurrent cholesteatoma and otitis media, formation of granulation tissue or adhesions, and various mechanical problems (eg, subluxation, dislocation, extrusion, fracture, bending). Perilymphatic fistula can be difficult to identify at CT but may be suggested by the presence of pneumolabyrinth, unexplained middle ear effusion, or fluid accumulation within the mastoid air cells. The presence of soft tissue within the oval window niche 4-6 weeks following surgery may indicate poststapedectomy granuloma or fibrosis. Familiarity with the normal and abnormal CT appearances of ossicular prostheses will enable the radiologist to assist the otologist in identifying patients in whom revision surgery is most appropriate.

National athletic trainers' association position statement: fluid replacement for athletes

OBJECTIVE

To present recommendations to optimize the fluid-replacement practices of athletes.

BACKGROUND

Dehydration can compromise athletic performance and increase the risk of exertional heat injury. Athletes do not voluntarily drink sufficient water to prevent dehydration during physical activity. Drinking behavior can be modified by education, increasing accessibility, and optimizing palatability. However, excessive overdrinking should be avoided because it can also compromise physical performance and health. We provide practical recommendations regarding fluid replacement for athletes.

RECOMMENDATIONS

Educate athletes regarding the risks of dehydration and overhydration on health and physical performance. Work with individual athletes to develop fluid-replacement practices that optimize hydration status before, during, and after competition.

Embryology and anatomy of the neck

As a prelude to understanding pathologic conditions of the pediatric neck, this article presents the embryologic development of the neck, fascial planes, and key anatomic structures. Detailed discussion includes the normal development of the neck and illustrates, using selected CT and MR images, the fascial spaces, larynx and trachea, thyroid, parathyroid, and vascular and lymphatic anatomy.

Imaging of congenital anomalies of the branchial apparatus

One of the most challenging topics for radiologists is congenital anomalies arising from abnormal embryogenesis of the branchial apparatus. Defects of the branchial apparatus result in a spectrum of anomalies that includes fistulas, sinuses, cysts, temporal bone anomalies, craniofacial malformations, and systemic disorders. A better understanding of the various radiologic abnormalities is aided by an understanding of their embryonic origins. This article reviews the spectrum of abnormalities that are secondary to anomalous embryogenesis of the branchial arches.

Proton-bound cluster ions in ion mobility spectrometry

Gaseous oxygen and nitrogen bases, both singly and as binary mixtures, have been introduced into ion mobility spectrometers to study the appearance of protonated molecules, and proton-bound dimers and trimers. At ambient temperature it was possible to simultaneously observe, following the introduction of molecule A, comparable intensities of peaks ascribable to the reactant ion (H2O)nH+, the protonated molecule AH+ and AH+ H2O, and the symmetrical proton bound dimer A2H+. Mass spectral identification confirmed the identifications and also showed that the majority of the protonated molecules were hydrated and that the proton-bound dimers were hydrated to a much lesser extent. No significant peaks ascribable to proton-bound trimers were obtained no matter how high the sample concentration. Binary mixtures containing molecules A and B, in some cases gave not only the peaks unique to the individual compounds but also peaks due to asymmetrical proton bound dimers AHB+. Such ions were always present in the spectra of mixtures of oxygen bases but were not observed for several mixtures of oxygen and nitrogen bases. The dimers, which were not observable, notable for their low hydrogen bond strengths, must have decomposed in their passage from the ion source to the detector, i.e. in a time less than approximately 5 ms. When the temperature was lowered to -20 degrees C, trimers, both homogeneous and mixed, were observed with mixtures of alcohols. The importance of hydrogen bond energy, and hence operating temperature, in determining the degree of solvation of the ions that will be observed in an ion mobility spectrometer is stressed. The possibility is discussed that a displacement reaction involving ambient water plays a role in the dissociation.

Absolute interferometry with a 670-nm external cavity diode laser

In the past few years there has been much interest in use of tunable diode lasers for absolute interferometry. Here we report on use of an external cavity diode laser operating in the visible (lambda approximately 670 nm) for absolute distance measurements. Under laboratory conditions we achieve better than 1-microm standard uncertainty in distance measurements over a range of 5 m, but significantly larger uncertainties will probably be more typical of shop-floor measurements where conditions are far from ideal. We analyze the primary sources of uncertainty limiting the performance of wavelength-sweeping methods for absolute interferometry, and we discuss how errors can be minimized. Many errors are greatly magnified when the wavelength sweeping technique is used; sources of error that are normally relevant only at the nanometer level when standard interferometric techniques are used may be significant here for measurements at the micrometer level.

Normal canals at the fundus of the internal auditory canal: CT evaluation

PURPOSE

Knowledge of the normal anatomy of the four bony canals located at the fundus of the internal auditory canal (IAC) is necessary during evaluation of temporal bone trauma, congenital anomalies affecting the individual nerves, and some neuro-otologic surgeries. The purpose of this work was therefore to characterize the normal appearance of the four bony canals and to measure their dimensions.

METHOD

A retrospective study was performed using CT studies of the temporal bones in 50 patients to identify and characterize the bony canals for the labyrinthine segment of the facial nerve (BCFN), superior vestibular nerve (BCSVN), cochlear nerve (BCNC), and the inferior vestibular nerve (singular canal; SC) located at the fundus of the IAC. All the patients underwent high resolution temporal bone CT for evaluation of uncomplicated inflammatory (n = 49) and neoplastic (n = 1) diseases involving the temporal bone. CT studies were done using 1-mm-thick contiguous sections in axial and coronal planes. Measurements of the canals were performed by one radiologist. No patient had a prior history of trauma, vertigo, and sensorineural hearing loss or facial nerve paralysis.

RESULTS

The BCFN, BCSVN, and BCNC were identified in all studies, whereas the SC was seen in 93% of studies. The BCFN, BCSVN, and BCNC arise from the fundus of the IAC, whereas the SC arises medial to the fundus. Mean +/- SD measurements (in mm) of the length and width were as follows: BCFN = 2.92+/-0.48 and 0.91+/-0.28; BCSVN = 2.36+/-0.53 and 0.89+/-0.28; BCNC = 0.93+/-0.21 and 2.13+/-0.44; and SC = 3.22+/-0.73 and 0.50+/-0.14.

CONCLUSION

These small canals are routinely visualized on thin section (1 mm) CT of the temporal bone and should not be confused with fractures. This study provides baseline measurements that may be used to evaluate congenital anomalies of these canals. These data may also be helpful in the presurgical evaluation of patients undergoing singular neurectomies for benign positional vertigo.

Simultaneous investigation of indinavir nonlinear pharmacokinetics and bioavailability in healthy volunteers using stable isotope labeling technique: study design and model-independent data analysis

Indinavir follows nonlinear pharmacokinetics upon oral administration at clinical doses. A study employing the stable isotope administration technique in a three-treatment design was conducted to identify the source of the nonlinearity and to determine the dose-dependency of systemic bioavailability. In treatment A, 400 mg of unlabeled indinavir (D0) was coadministered orally with 16 mg of a hexadeutero analogue of indinavir (D6) intravenously. In treatment B, 800 mg of D0 po was coadministered with 16 mg of D6 intravenously. In treatment C, 16 mg of iv D6 was infused concurrently with 16 mg iv of D0. Plasma concentrations of D0 and D6 were determined by an LC/MS/MS assay method. Concentrations of indinavir in plasma increased greater than dose-proportionally over the 400- to 800-mg dose range. No meaningful kinetic isotope effects were found in treatment C. Plasma concentrations of D6 were dependent on the coadministered D0-indinavir dose and were lowest in treatment C, higher in treatment A, and highest in treatment B. The bioavailability of indinavir was high (60-65%) and comparable between the 400- and 800-mg doses. There was a significant contribution of nonlinear kinetics in the systemic circulation to the observed disproportional increase in plasma concentrations following oral dosing. The high bioavailability at clinically relevant doses suggests a high degree of saturation of first-pass metabolism. These results further demonstrate that the concomitant administration technique in combination with the LC/MS/MS method can provide a realistic and reliable means of elucidating important pharmacokinetic properties of drug candidates during product development.

Evaluation of CSF leaks: high-resolution CT compared with contrast-enhanced CT and radionuclide cisternography

BACKGROUND AND PURPOSE

Radiologic evaluation of CSF leaks is a diagnostic challenge that often involves multiple imaging studies with the associated expense and patient discomfort. We evaluated the use of screening noncontrast high-resolution CT in identifying the presence and site of CSF rhinorrhea and otorrhea and compared it with contrast-enhanced CT cisternography and radionuclide cisternography.

METHODS

We retrospectively reviewed the imaging studies and medical records of all patients who were evaluated for CSF leak during a 7-year period. Forty-two patients with rhinorrhea and/or otorrhea underwent high-resolution CT of the face or temporal bone and then had CT cisternography and radionuclide cisternography via lumbar puncture. The results of the three studies were compared and correlated with the surgical findings in 21 patients.

RESULTS

High-resolution CT showed bone defects in 30 of 42 patients (71%) with CSF leak. High-resolution, radionuclide cisternography and CT cisternography did not show bone defects or CSF leak for 12 patients (29%) who had clinical evidence of CSF leak. Among the 30 patients with bone defects, 20 (66%) had positive results of their radionuclide cisternography and/or CT cisternography. For the 21 patients who underwent surgical exploration and repair, intraoperative findings correlated with the defects revealed by high-resolution CT in all cases. High-resolution CT identified significantly more patients with CSF leak than did radionuclide cisternography and CT cisternography, with a moderate degree of agreement.

CONCLUSION

Noncontrast high-resolution CT showed a defect in 70% of the patients with CSF leak. No radionuclide cisternography or CT cisternography study produced positive results without previous visualization of a defect on high-resolution CT. CT cisternography and radionuclide cisternography may be reserved for patients in whom initial high-resolution CT does not identify a bone defect or for patients with multiple fractures or postoperative defects.

Leukoencephalopathy complicating an Ommaya reservoir and chemotherapy

We describe the imaging findings in an unusual case of biopsy-proven, methotrexate-induced leukoencephalopathy complicating a malfunctioning Ommaya reservoir in a patient with lymphoma.

High-resolution MR imaging of the auditory pathway

MR imaging is a valuable tool in the evaluation of the auditory pathway. The current techniques in high-resolution MR imaging of the temporal bone are presented followed by a review of normal anatomy. Several diseases involving the middle ear, inner ear, internal auditory canal, and cerebellopontine angle are then presented. A radiologic-pathologic approach is used to illustrate the nature of these diseases and their appearance on MR imaging.

Single-dose pharmacokinetics of indinavir and the effect of food

Indinavir sulfate is a human immunodeficiency virus type 1 (HIV-1) protease inhibitor indicated for treatment of HIV infection and AIDS in adults. The purpose of this report is to summarize single-dose studies which characterized the pharmacokinetics of the drug and the effect of food in healthy volunteers. Indinavir concentrations in plasma and urine were obtained by high-pressure liquid chromatography and UV detection assay methods. The results indicate that indinavir was rapidly absorbed in the fasting state, with the time to the maximum concentration in plasma occurring at approximately 0.8 h for all doses studied. Over the 40- to 1,000-mg dose range studied, concentrations in plasma and urinary excretion of unchanged drug increased greater than dose proportionally. The nonlinear pharmacokinetics were attributed to the dose-dependent oxidative metabolism of first-pass metabolism as well as to metabolism in the systemic circulation. Renal clearance slightly exceeded the glomerular filtration rate, suggesting a net tubular secretion component. At high concentrations in plasma, tubular secretion appeared to be lowered because there was a trend for a decreased renal clearance. Administration of 400 mg of indinavir sulfate following a high-fat breakfast resulted in a blunted and decreased absorption (areas under the concentration-time curves [AUCs], 6.86 microM.h in the fasted state versus 1.54 microM.h in the fed state; n = 10). However, two types of low-fat meals were found to have no significant effect on the absorption of 800 mg of indinavir sulfate (AUCs, 23.15 microM.h in the fasted state versus 22.71 and 21.36 microM.h, respectively, in the fed state; n = 11). Immediately following dosing, the concentrations of indinavir in urine often exceeded its intrinsic solubility. To reduce the risk of nephrolithiasis, it is recommended that indinavir sulfate be administered with water.

Electrospray mass-spectrometric, spectrophotometric and electrochemical methods do not provide evidence for the binding of nitric oxide by pyocyanine at pH 7

In several recent publications on pyocyanine, its mechanism of action has been attributed to an ability to react with nitric oxide (NO), resulting in the formation of an adduct. We examined the chemical interaction of pyocyanine and NO using electrospray (ES) MS, spectrophotometry and voltammetry at neutral pH and with 10-100 microM pyocyanine. No binding of NO to pyocyanine was observed. Alternative mechanisms for the inhibition of NO-induced vasorelaxation by pyocyanine should be sought.

Comparison of hemodynamic and sympathoneural responses to adenosine and lower body negative pressure in man

Adenosine increases heart rate and sympathetic nerve activity reflexively in conscious humans through several mechanisms. The purpose of this study was to assess the relative contributions of arterial baroreceptor unloading, carotid chemoreceptor stimulation, and other adenosine-sensitive afferent nerves to these responses. In 12 healthy men, the effect on blood pressure, heart rate (HR), and muscle sympathetic nerve activity (MSNA; peroneal nerve) of lower body negative pressure (LBNP; -15 mmHg (1 mmHg = 133.3 Pa)) was compared with the effect of intravenous adenosine (35, 70, and l40 micrograms.kg-1.min-1). In eight subjects, the highest dose was reinfused during 100% oxygen to suppress arterial chemoreceptors. Blood pressure reductions during LBNP and adenosine (140 micrograms.kg-1.min-1) were similar. HR did not change significantly during LBNP (+2 +/- 2 beats/min; mean +/- SE) but increased at the highest adenosine dose (+25 +/- 3 beats/min; p < 0.05). MSNA increased significantly (p < 0.05) during both interventions (+255 +/- 82 and +247 +/- 58 units/100 beats for adenosine and LBNP, respectively), and there was no difference in the MSNA response to these two stimuli (p > 0.1). Oxygen inhibited adenosine-induced increases in HR and MSNA (from +305 +/- 99 to +198 +/- 75 units/100 beats and from +26 +/- 4 to +18 +/- 3 beats/min; p < 0.05 for both comparisons). The MSNA response to these combined stimuli was similar to that observed during LBNP. In contrast, the residual HR response (+18 +/- 3 beats/min) was significantly greter than the response to LBNP (+2 +/- 2 beats/min; p < 0.05). These data indicate that arterial baroreceptor unloading cannot account for the marked adenosine-induced increase in HR, but may be sufficient to explain its effect on MSNA. The effect of 100% oxygen confirms that stimulation of carotid chemoreceptors accounts for approximately one-third of the HR and MSNA response to adenosine. However, other mechanisms, such as stimulation of adenosine-sensitive afferent nerves in other vascular beds, are involved in the HR and possibly the MSNA response.

Alpha 1-antitrypsin deficiency: evaluation of bronchiectasis with CT

PURPOSE

To assess bronchiectasis depicted with computed tomography (CT) in patients with alpha 1-antitrypsin deficiency and to examine associated clinical correlates.

MATERIALS AND METHODS

CT scans in 14 patients with alpha 1-antitrypsin deficiency were evaluated by two thoracic radiologists for the presence and extent of bronchiectasis and emphysema. The findings were correlated with numeric infection scores on the basis of symptoms of sputum production and respiratory infection and with a history of conditions that may predispose to development of bronchiectasis.

RESULTS

Six (43%) of 14 patients had CT evidence of bronchiectasis. Patients with bronchiectasis had significantly higher infection scores than did patients without bronchiectasis (P < .005). Two patients had diffuse cystic bronchiectasis, and neither reported a history of illness that may have predisposed them to this condition.

CONCLUSION

Bronchiectasis may be more common in patients with alpha 1-antitrypsin deficiency than has been previously recognized. The diagnosis of alpha 1-antitrypsin deficiency should be considered in patients with emphysema and diffuse cystic bronchiectasis.

Frequency stabilization of a green He-Ne laser

A new process for stabilizing the frequency of commercially available 543-nm He-Ne lasers is described. The stabilization method is based on anomalous dispersion of the gain medium. A total of four green lasers have been stabilized-two at the National Institute of Standards and Technology and two at the Institute of Scientific Instruments of the Czech Academy of Sciences-making it possible to study frequency variations of the lasers relative to each other. We have also stabilized a 633-nm laser by the use of the same method used for 543 nm.

Quantitative analysis of fentanyl in pharmaceutical preparations by gas chromatography-mass spectrometry

Fentanyl (1-[2-phenethyl]-4-N-[N-propionylanilino]piperidine) is a potent synthetic opiate commonly used for surgical analgesia and sedation. Reports of abuse of this highly addictive drug among health care personnel have prompted the need to verify the concentration in the unused portion of single-dose ampules returned to the pharmacy. We describe a simple quantitative method for the analysis of fentanyl citrate (Sublimaze) in syringes returned to the pharmacy following surgery. Fentanyl citrate (0.1 mL) and 2H5-fentanyl (internal standard, 0.05 mL, 100 mg/L) were extracted with Toxi-A tubes (Toxi-Lab, Irvine, CA) and analyzed by gas chromatography-mass spectrometry. Calibration was linear from 1 to 60 mg/L (correlation coefficient of 0.997, n = 13) and had a limit of detection of 0.4 mg/L. Mean recovery at concentrations from 5 to 50 mg/L was 89% (range, 69-104%). No interferences were found with morphine, ketamine, midazolam, sufentanil, or alfentanil. These drugs were not selected for their potential chromatographic interference but for their availability in surgical syringes. This assay is useful in verifying that any unused fentanyl is discarded according to narcotic regulations, thereby avoiding the possibility of diversion for illicit consumption.