Inhibitory effect of somatostatin analogue RC-160 on the growth of hepatic metastases of colon cancer in rats: a study with magnetic resonance imaging.

The effect of somatostatin analogue RC-160 on the growth of hepatic metastases of colon cancer was investigated in rats using magnetic resonance imaging. Experimental liver metastatic tumors were established in syngeneic BDIX rats after intrasplenic injection of DHD/K12 colon adenocarcinoma cells. Each rat with implanted liver tumors received s.c. injections of somatostatin analogue RC-160 (50 micrograms/kg) or the vehicle (control) twice a day for 4 weeks, starting 3 weeks after tumor inoculation. During the treatment with RC-160, the growth of liver tumors was studied quantitatively by measuring liver tumor volumes in vivo with magnetic resonance imaging at intervals of 7 days. Chronic administration of RC-160 inhibited the growth of hepatic metastases of colon cancer in rats. Significant inhibition of liver tumor growth in RC-160-treated rats was observed throughout the treatment. The final liver tumor volume in the treated rats was decreased by 56.1% as compared to the controls. The treatment with RC-160 reduced the percentage increase in liver tumor volume from 1575 +/- 674% (mean +/- SEM) for the control to 1034 +/- 727% in the treated group. The tumor volume doubling time in treated rats was 3.7 days longer than the controls. The liver tumor growth delay time was 15.1 days. At the end of the treatment, the incidence of ascites and the weights of tumorous livers were also decreased by RC-160 treatment. Administration of RC-160 prolonged the median survival time by 13 days in treated rats. In cell cultures, significant inhibitory effects of somatostatin-14 and RC-160 on the growth of DHD/K12 colon cancer cells were determined by MTT assay and [3H]-thymidine incorporation assay, indicating direct effects of these peptides on the growth of colon cancer cells in vitro. These data suggest that administration of RC-160 could inhibit the growth of colon cancer and their hepatic metastases in rats. Somatostatin analogue RC-160 might be considered as a potential new agent for the treatment of patients with hepatic metastases of colorectal cancers.

Absolute quantification of 31P muscle metabolites using NMRS with an internal standard and a high-Q, double-tuned coil.

31P-nuclear magnetic resonance spectroscopy (NMRS) is used to determine absolute concentrations of 31P metabolites in rat muscle. A technique exploiting tissue water 1H as internal concentration reference and a highly sensitive, double-tuned coil is described and evaluated experimentally. On KH2PO4 solutions of known concentration and varying coil loading it is shown to allow neutralization of systematic errors due to conductive losses, which normally range up to 20% or more. In vivo application in the determination of the absolute concentrations of ATP, PCr and Pi in eight rat thighs yields results that are in good agreement with literature values.

Prevalence of annular tears and disc herniations on MR images of the cervical spine in symptom free volunteers.

STUDY DESIGN: Prospective MR analysis of the cervical spine of 30 asymptomatic volunteers. OBJECTIVES: To evaluate the prevalence of annular tears, bulging discs, disc herniations and medullary compression on T2-weighted and gadolinium-enhanced T1-weighted magnetic resonance (MR) images of the cervical spine in symptom free volunteers. SUMMARY OF BACKGROUND DATA: Few studies have reported the prevalence of cervical disc herniations in asymptomatic people, none have reported the prevalence of cervical annular tears on MR images of symptom free volunteers. MATERIALS AND METHODS: Thirty symptom-free volunteers (no history or symptoms related to the cervical spine) were examined using sagittal T2-weighted fast spin-echo (SE), sagittal gadolinium-enhanced T1-weighted SE imaging and axial T2(*)-weighted gradient echo (GRE). The prevalence of bulging discs, focal protrusions, extrusions, nonenhancing or enhancing annular tears and medullary compression were assessed. RESULTS: The prevalence of bulging disk and focal disk protrusions was 73% (22 volunteers) and 50% (15 volunteers), respectively. There was one extrusion (3%). Eleven volunteers had annular tears at one or more levels (37%) and 94% of the annular tears enhanced after contrast injection. Asymptomatic medullary compression was found in four patients (13%). CONCLUSION: Annular tears and focal disk protrusions are frequently found on MR imaging of the cervical spine, with or without contrast enhancement, in asymptomatic population. The extruded disk herniation and medullary compression are unusual findings in a symptom-free population.

Fat fraction of lumbar bone marrow using in vivo proton nuclear magnetic resonance spectroscopy.

Localized proton spectra of the human lumbar vertebral body were recorded in vivo at 1.5 T, using the STEAM (stimulated echo acquisition mode) pulse sequence. Thirty-seven patients (18 men, 19 women) were examined, ranging in age from 21 to 68 years (mean = 40, SD = 13). The fat fraction of the bone marrow was calculated from the areas of the fat and water peaks in the spectrum. The results demonstrate that, in the course of aging, there is a systematic increase in measured fat percentage of about 7% per decade of age. No sex difference could be established on the basis of our results.

Mineral content of vertebral trabecular bone: accuracy of dual energy quantitative computed tomography evaluated against neutron activation analysis and flame atomic absorption spectrometry.

The goal of this study was to evaluate the accuracy of preprocessing dual energy quantitative computed tomography (QCT) for assessment of trabecular bone mineral content (BMC) in lumbar vertebrae. The BMC of 49 lumbar vertebrae taken from 16 cadavers was measured using dual energy QCT with advanced software and hardware capabilities, including an automated definition of the trabecular region of interest (ROI). The midvertebral part of each vertebral body was embedded in a polyester resin and, subsequently, an experimental ROI was cut out using a scanjet image transmission procedure and a computer-assisted milling machine in order to mimic the ROI defined on QCT. After low temperature ashing, the experimental ROIs reduced to a bone powder were submitted to either nondestructive neutron activation analysis (n = 49) or to flame atomic absorption spectrometry (n = 45). BMC obtained with neutron activation analysis was closely related (r = 0.896) to that derived from atomic absorption spectrometry, taken as the gold standard, with, however, a slight overestimation. BMC values measured by QCT were highly correlated with those assessed using the two reference methods, all correlation coefficients being > 0.841. The standard errors of the estimate ranged 47.4-58.9 mg calcium hydroxyapatite in the regressions of BMC obtained with reference methods against BMC assessed by single energy QCT, 47.1-51.9 in the regressions involving dual energy QCT. We conclude that the trabecular BMC of lumbar vertebrae can be accurately measured by QCT and that the superiority in accuracy of dual energy is moderate, which is possible a characteristic of the preprocessing method.

Dual-energy X-ray absorptiometry of lumbar vertebrae: relative contribution of body and posterior elements and accuracy in relation with neutron activation analysis.

The bone mineral content of 34 lumbar vertebrae obtained from ten cadavers (three men, seven women; age 61-88 years) was measured using a pulsed source dual-energy X-ray absorptiometry (DEXA) apparatus. Scanning was performed in the frontal projection and was repeated on the vertebral bodies obtained after removal of the posterior elements of the vertebrae. Subsequently a nondestructive neutron activation analysis (NAA) was performed. The mineral content of the vertebral bodies was found to represent (mean, SEM) 53.0% (1.9%) of the content of the whole vertebrae. The mineral content of the vertebral bodies assessed with NAA (BMC NAA) and with DEXA (BMC DEXA) showed a high correlation: BMC NAAA = (1.016 x BMC DEXA) + 0.990 r = 0.949 (p less than 0.001). We conclude that the mineral content of lumbar vertebral bodies can be accurately measured in vitro in a water environment by DEXA, and that the mean contribution of the posterior elements of the vertebra to the calcium hydroxyapatite content of whole vertebrae measured in the frontal projection is as high as 47.0%.

Cortical mineral content of the radius assessed by peripheral QCT predicts compressive strength on biomechanical testing.

Our aim was to evaluate the role of cortical bone in resistance to compression in the human radius. Thirty-three left cadaver forearms were scanned on an XCT 960 Stratec CT scanner. Cortical density and cortical thickness were measured at the junction of the middle and distal third of the radius. Subsequently, 2-cm-high cylindrical specimens, centrated on the level of the CT slice, were cut. After removal of the endosteal trabecular bone, the specimens were submitted to compressive testing, using an Instron machine, and load deformation curves were obtained. Maximal stress (load corrected for cross-sectional area) showed a significant relationship with the density (r = 0.78) as well as with the thickness (r = 0.74) of the cortex. The closest correlation involved the maximal load and the mineral content of the cortex specimens (r = 0.87). We conclude that the mineral content of these radius cortex specimens, measured using peripheral QCT, predicts their compressive strength on biomechanical testing.

Cortical and total bone mineral content of the radius: accuracy of peripheral computed tomography.

The aim of the study was to evaluate the accuracy of an XCT 960 Stratec peripheral quantitative computed tomography (pQCT) device in assessing bone mineral content of the radius. We scanned 27 left forearm specimens excised from cadavers and focused on cortical bone mineral content (BMCc) at the junction of the middle and distal third and on total bone mineral content (BMCtot) at the distal end of the radius. Cylindrical specimens matched with those two sites were cut using a diamond circular saw, embedded in a polyester resin and subsequently submitted to two reference methods, nondestructive neutron activation analysis and flame atomic absorption spectrometry. Mineral contents measured by pQCT were closely correlated with those assessed by using the two reference methods, with correlation coefficients ranging from 0.862 to 0.960. The standard error of the estimate amounted 7-10% for the BMCc (junction of the middle and distal third), and 17-18% for the BMCtot (distal end). We conclude that pQCT is able to measure either cortical or total mineral content of the radius with a high degree of accuracy.

Percutaneous needle biopsy of localized pulmonary, mediastinal, and pleural diseased tissue with an automatic disposable guillotine soft-tissue needle. Preliminary results.

Percutaneous needle biopsy (PNB) of localized thoracic disease has become a widespread procedure in many institutions. The development of special small caliber needles has increased the diagnostic yield of PNB partly by increasing the amount of tissue from biopsy, often enabling histologic examination. Nevertheless, in a significant number of patients only cytopathologic examination is possible on the retrieved biopsy fragments, necessitating the presence of a trained cytopathologist in the biopsy room. Furthermore multiple biopsy needle passages often are required, increasing the risk for complications such as pneumothorax. We have evaluated the use of a small-caliber tissue biopsy cutting needle, consistently yielding sufficient biopsy tissue for histologic examination. In 25 pleural and mediastinal lesions, which could be biopsied without passage through aerated lung, there was a 93% sensitivity (7% false-negative results) for neoplasm and a 100% accuracy for benign disease. There were no complications. In 32 patients with lesions of 1 cm in diameter or more surrounded with aerated lung tissue, adequate histologic examination was feasible on every biopsy specimen after only one needle passage. There was an 87% sensitivity of PNB in neoplastic disease (13% false-negatives). In the patients with benign disease, there was a 100% accuracy. There was a 15.6% risk for pneumothorax. In only one patient (3%), however, was chest drainage necessary. One patient (3%) had mild hemoptysis. We conclude that percutaneous biopsy of localized pulmonary, pleural, and mediastinal lesions with a new small-caliber automatic guillotine cutting needle is safe and efficient, enabling recovery of sufficient tissue for histologic examination with a single-pass procedure, thus minimizing the risk for pneumothorax, eliminating the need for a cytopathologist in the biopsy room, and shortening the duration of the procedure.

A technique for simultaneous microangiographic and cytochemical investigation of resin-embedded tissues.

A method for simultaneous acquisition of information on cytochemical and microangiographic characteristics of tissue after perfusion with contrast medium was developed. The technique is based on the use of hydrosoluble resin as embedding material and is illustrated by the demonstration of gamma-glutamyltranspeptidase activity and of the microcirculation in rat liver during chemically induced hepatocarcinogenesis and experimental metastasis. The method is applicable to investigations aimed at correlating microangiographic and cytochemical characteristics of normal or altered tissues.

Size of cortical bone and relationship to bone mineral density assessed by quantitative computed tomography image segmentation.

RATIONALE AND OBJECTIVES: The accuracy of the measurement of the size of cortical bone on computed tomography (CT) images of human vertebrae was evaluated using an automated contour detection and segmentation procedure. METHODS: Forty human lumbar vertebrae were scanned using 8-mm slices and an automated detection for definition of trabecular and cortical region of interest. The vertebrae were embedded in a polyester resin and 8-mm-thick midvertebral specimens were excised using a diamond circular saw. Contact radiographs of these specimens were performed and, after photograph magnification, the cortical area was measured using computerized planimetry. RESULTS: Cortical area measured on CT images was highly correlated with the area measured by planimetry on the specimens (r = .91; P < .001) with, however, a systematic over-estimation. A significant relationship was found between density and width of the cortex (r = .56; P < .001). CONCLUSIONS: Computed tomography is able to assess the size of cortical bone in human vertebrae, but a threshold detection algorithm, as used in the current study, is not adequate to obtain the precise anatomic dimensions.

31P-NMR spectroscopy and the metabolic properties of different muscle fibers.

To study the in vivo recruitment of different fiber types and their metabolic properties, 31P-nuclear magnetic resonance spectroscopy (31P-NMRS) of the human calf muscle was performed in seven normal sedentary subjects. In the exhaustive exercise protocol used, the work load was increased every minute during 5 min. This resulted in a prominent split of the Pi resonance in all subjects, indicating pH compartmentation in the muscles studied. From the chemical shift of the Pi peaks relative to phosphocreatine (PCr) at the end of the exercise, intracellular pH (pHi) averaged 6.92 +/- 0.05 (SD) in compartment 1 and 6.23 +/- 0.15 in compartment 2. The recovery of both Pi resonances after exercise could be followed easily in five of these subjects. The recovery rate of the Pi peak is a good estimate of the oxidative metabolism at the end of the exercise. A monoexponential regression analysis showed that the mean initial recovery rate S0 was 2.49 +/- 0.17%/s in compartment 1 and only 0.87 +/- 0.12%/s in compartment 2, indicating aerobic function three times higher in compartment 1 at the end of exercise. The mean relative ATP fraction dropped significantly (P less than 0.001), from 20.0 +/- 1.0% of the total 31P signal integral before exercise to 14.0 +/- 1.6% at the end of exercise. The simultaneous visualization of two compartments, in good order, one with high pHi and fast recovery and another with low pHi and slow recovery, is rationalized by the different metabolic behavior of type I and II fibers in human calf muscle in response to exhaustive exercise. This study demonstrates that 31P-NMRS is an excellent noninvasive procedure to quantify aerobic metabolism in both fiber types simultaneously.

A comparison between different imaging strategies for diffusion measurements with the centric phase-encoded turboFLASH sequence.

The study compared the results of three centrally reordered phase-encoded turboFLASH sequences for diffusion-weighted imaging (DWI). The sequences were conventional turboFLASH, turboFLASH with subtraction of T1-related effects, and turboFLASH with correction for T1-related effects during the imaging period only. The relative merits were studied with respect to image quality and accuracy by computer simulation and by experimental validation on phantoms and on in vivo rat brain. A T1-related underestimation of the diffusion coefficient ranging from -30% (T1 approximately 200 ms) to -5% (T1 approximately 1 s) was found to exist for the conventional sequence. Image artifacts, caused by longitudinal relaxation during the imaging period, are reflected in calculated diffusion maps. When the correction sequence is used, the artifacts and the systematic errors are reduced but longitudinal relaxation during the delay between preparation and imaging periods remains large enough to induce significant errors (-15% for T1 approximately 200 ms to -3% for T1 approximately 1 s). The subtraction sequence eliminates the influence of T1 effects on the calibrations, but leads to identical artifacts for all diffusion-weighted images.

Bone loss in young hypoestrogenic women due to primary ovarian failure: spinal quantitative computed tomography.

Vertebral bone mineral density was investigated in 22 young (29.3 +/- 1 years) women with primary ovarian failure, attending for infertility. The lumbar spine was studied, using a preprocessing dual-energy quantitative computed tomography technique and assessing vertebral bone mineral density from the reconstructed 125-kV image. Previously untreated women had significantly (P less than 0.001) lower values than a group of age-matched healthy controls, while the difference between those women having received estrogen therapy and the same controls was not significant. Sixteen patients were restudied after 6 to 21 months of estrogen therapy, part of a regimen intended to prepare the endometrium for oocyte donation, and vertebral bone mineral density increased in 12 of them. The authors conclude that primary ovarian failure is a cause for bone loss in these young women and that estrogen therapy is effective.

Optimization of sequence parameters in fast MR imaging of the brain with FLASH.

Owing to the intrinsically complex behavior of the signal intensity of fast gradient-refocusing MR sequences, agreement as to the clinically most useful sequence parameters has not yet been reached. This study evaluates the FLASH (fast low-angle shot) sequence for gray-white matter differentiation on normal volunteers at 1.5 T. The FLASH gradient-echo sequence is essentially T1-dependent. For very fast imaging and T1 weighting, the following parameters yield the best results: a flip angle of 30-50 degrees with TR = 20 and TE = 10. To replace T1-weighted SE by the faster FLASH sequence, the best results are achieved by a flip angle of 70-120 degrees with TR = 150-300 and TE = 10 (or shorter, if possible). The most valuable proton-density aspect is achieved by a flip angle of 30 degrees with TR = 300 and TE = 16.

Diffusion-weighted MR imaging of an acute venous stroke: case report.

A patient with a superior sagittal sinus thrombosis had progressively worsening symptoms and signs that resolved after IV heparin therapy. MR imaging revealed abnormalities in diffusion, similar to those seen with acute arterial stroke. Abnormalities shown on a T2-weighted fast spin-echo and fluid-attenuated inversion recovery images resolved completely. The findings in this report contradict those from previous reports that suggest diffusion-weighted imaging with quantitative apparent diffusion coefficients may be used in selecting patients for dural venous sinus thrombolysis.

Use of diffusion-weighted MR imaging in differential diagnosis between intracerebral necrotic tumors and cerebral abscesses.

The differential diagnosis between intracerebral necrotic tumors and cerebral abscesses is frequently impossible with conventional MR imaging. We report two cases of cerebral abscesses that showed high signal on diffusion-weighted echo planar imaging and a strongly reduced apparent diffusion coefficient. This appearance was not present in our cases of necrotic/cystic gliomas (eight cases) and necrotic metastases (two cases). We believe that diffusion-weighted MR imaging may be a diagnostic clue in cases of cerebral "ring-enhancing" masses.

Diffusion-weighted MR imaging of intracerebral masses: comparison with conventional MR imaging and histologic findings.

BACKGROUND AND PURPOSE: The purposes of this study were to find the role of diffusion-weighted MR imaging in characterizing intracerebral masses and to find a correlation, if any, between the different parameters of diffusion-weighted imaging and histologic analysis of tumors. The usefulness of diffusion-weighted imaging and apparent diffusion coefficient (ADC) maps in tumor delineation was evaluated. Contrast with white matter and ADC values for tumor components with available histology were also evaluated. METHODS: Twenty patients with clinical and routine MR imaging/CT evidence of intracerebral neoplasm were examined with routine MR imaging and echo-planar diffusion-weighted imaging. The routine MR imaging included at least the axial T2-weighted fast spin-echo and axial T1-weighted spin-echo sequences before and after contrast enhancement. The diffusion-weighted imaging included an echo-planar spin-echo sequence with three b values (0, 300, and 1200 s/mm(2)), sensitizing gradient in the z direction, and calculated ADC maps. The visual comparison of routine MR images with diffusion-weighted images for tumor delineation was performed as was the statistical analysis of quantitative diffusion-weighted imaging parameters with histologic evaluation. RESULTS: For tumors, the diffusion-weighted images and ADC maps of gliomas were less useful than the T2-weighted spin-echo and contrast-enhanced T1-weighted spin-echo images in definition of tumor boundaries. Additionally, in six cases of gliomas, neither T2-weighted spin-echo nor diffusion-weighted images were able to show a boundary between tumor and edema, which was present on contrast-enhanced T1-weighted and/or perfusion echo-planar images. The ADC values of solid gliomas, metastases, and meningioma were in the same range. In two cases of lymphomas, there was a good contrast with white matter, with strongly reduced ADC values. For infection, the highest contrast on diffusion-weighted images and lowest ADC values were observed in association with inflammatory granuloma and abscess. CONCLUSION: Contrary to the findings of previous studies, we found no clear advantage of diffusion-weighted echo-planar imaging in the evaluation of tumor extension. The contrast between gliomas, metastases, meningioma, and white matter was generally lower on diffusion-weighted images and ADC maps compared with conventional MR imaging. Unlike gliomas, the two cases of lymphomas showed hyperintense signal on diffusion-weighted images whereas the case of cerebral abscess showed the highest contrast on diffusion-weighted images with very low ADC values. Further study is required to find out whether this may be useful in the differentiation of gliomas and metastasis from lymphoma and abscess.

Excision of a trabecular ROI from resin-embedded vertebrae: report on a computer-assisted method.

A major problem when evaluating the accuracy of quantitative computed tomography (QCT) against chemical analysis of bone mineral is to ensure that the same region of interest (ROI) is measured with two techniques. The method described here attempts to reach this objective. Forty-nine lumbar vertebrae were scanned. The mid-vertebral portion was sawed and embedded in a polyester resin. The ROI defined with an automated contour detection was transmitted, using a Hewlett-Packard scanjet, to a computer-assisted milling machine which excised a trabecular ROI sample. The volume of each trabecular sample was determined using an Archimedian method. ROI volumes assessed on QCT were highly correlated with those obtained with the Archimedian method (r = 0.98). The standard error of the estimate was 170 mm3 (4.5%). These results suggest that trabecular samples obtained with this method optimally agree with the ROIs selected on QCT examination.

Excitation characteristics of adiabatic half-passage RF pulses used in surface coil MR spectroscopy. Application to 13C detection of glycogen in the rat liver.

Properties of sech/tanh and sin/cos half-passage RF pulses are discussed in view of their use in surface coil MR spectroscopy. We focus on the use of these pulses in a regime which is partially adiabatic, i.e. not strictly adiabatic off-resonance, while on-resonance the adiabaticity condition is fulfilled. It is shown that the frequencies of the singular points of the excitation profiles, as well as their number, depend on the B1 field. This leads to a signal intensity reduction from off-resonance spectral regions over much broader ranges than generally believed. We show in particular that with surface coil, sin/cos RF pulses may perform particularly well, providing optimal excitation on resonance and a desired attenuation over a broad spectral range off-resonance. This feature is applied for the in vivo detection of rat liver glycogen by means of 13C MR spectroscopy. Under suitable RF power conditions, a remarkable attenuation of the signals from the saturated carbons of the subcutaneous fat can be achieved.