Phase-contrast imaging with synchrotron X-rays for detecting cancer lesions

RATIONALE AND OBJECTIVES

We obtained image contrast in pathologic specimens without the use of contrast material by using phase-contrast imaging with synchrotron X-rays.

METHODS

An experiment was performed at the three-pole superconducting vertical wiggler beam line BL-14B at the Photon Factory in Tsukuba, Japan. The X-ray phase-contrast imaging system consisted of a double crystal monochromator, an asymmetrically cut crystal monochromator, a triple Laue-case X-ray interferometer, and film. The pathologic specimen was a sample from human liver that had metastatic carcinoma.

RESULTS

The X-ray phase-contrast images of the pathologic specimen clearly depicted the cancerous lesion without the use of contrast enhancement, and the image showed good correlation with the photograph of the specimen. The X-ray absorption image did not differentiate between the normal liver tissue and the tumor.

CONCLUSION

The results of this preliminary experiment reveal that for materials such as biologic specimens with a low atomic number, X-ray phase-contrast imaging better differentiates tissues than does the absorption contrast imaging commonly used in radiology.

Two-dimensional intravenous coronary arteriography using above-K-edge monochromatic synchrotron X-ray

RATIONALE AND OBJECTIVES

For intravenous (i.v.) coronary arteriography, a real-time two-dimensional (2D) imaging system is being developed using above-K-edge monochromatic X-rays alone. The potential diagnostic value of this system was examined in the current study.

METHODS

The angiographic system consisted of an asymmetric silicon (311) monocrystal, an image intensifier, and a charged-coupled device camera. It was constructed at the beam line of the Tristan Accumulation Ring. Monochromatic X-rays of 33.32 keV were used, and each image was recorded over 2 msec.

RESULTS

Ventricular wall motion and the anatomy of the coronary arteries could be seen in dogs by sequential images obtained without subtraction. The left anterior descending coronary artery, left circumflex coronary artery, and right coronary artery and the branches of these vessels were observed. The parts of the coronary arteries overlapping the aorta and left ventricle were revealed somewhat during washout of the contrast material.

CONCLUSION

For a 2D imaging system, monochromatic i.v. coronary angiography using an energy above the iodine K-edge might be able to image the coronary arteries without subtraction. However, the image quality needs to be improved by increasing the X-ray flux, decreasing background radiation scatter from the object, and decreasing contamination with 99-keV X-rays.

Usefulness of hyperventilation thallium-201 single photon emission computed tomography for the diagnosis of vasospastic angina

To establish a safe and sensitive diagnostic procedure for detecting coronary vasospasm, we utilized 201-thallium myocardial SPECT combined with hyperventilation (HV-SPECT) in 29 patients with vasospastic angina (VAP) and 11 controls. Twenty-five of 29 patients with VAP and 5 of 11 controls developed transient perfusion defects on HV-SPECT, resulting in a sensitivity and specificity calculated at 86% and 55%, respectively. Overall accuracy in identifying corresponding vessels with coronary vasospasm, respectively. Coronary vasospasm tended to be identified more accurately in the left anterior descending branch and the right coronary artery than in the circumflex branch (75%, 71% and 50%, respectively). The hyperventilation test induced ischemic ECG changes in 11 of 29 patients with VAP, yielding a sensitivity of 38%. Analyzing the washout rate of HV-SPECT in patients with VAP, both the extent and severity scores of patients with ischemic ECG changes were larger than those of patients without. No serious complications occurred during HV-SPECT. In conclusion, HV-SPECT was a safe and sensitive procedure as a primary diagnostic approach for VAP. From the results of washout analysis, HV-SPECT could detect more mild myocardial ischemia than could the ECG, and seemed quite useful especially for detecting coronary vasospasm accompanied by minimal ischemic ECG changes.

[The efficacy of early 123I-MIBG scintigraphy for pheochromocytoma diagnosis]

Early scintigraphy, that obtained 6 hours after intravenous administration of a low dose of 123I-metaiodobenzylguanidine (111 MBq) was evaluated for diagnostic efficacy. The accumulation of 123I-MIBG in the tumor masses of nine patients with pheochromocytoma and one patient with cortical adenoma were noted. The smallest pheochromocytoma visualized was 3 cm in diameter. The hepatic uptake of this radiolabeled compound was helpful to understand the anatomical position of the abnormal uptake. Three of five postoperative cases of pheochromocytoma showed uptake in the metastasis in the skeleton or recurrences in the neck or contralateral adrenal gland. No ectopic pheochromocytoma was found in the pelvic cavity. Faint accumulation in the normal medulla was noted in 45% of the cases. The present results demonstrate that superior images can be obtained in scintigrams takes 6 hours after administration of a lower dose of 123I-MIBG.

Congenital ossification of the stapedius tendon: diagnosis with CT

PURPOSE

To describe the features of congenital ossification of the stapedius tendon at thin-section computed tomography (CT).

MATERIALS AND METHODS

Thin-section CT scans, clinical records, and surgical findings were retrospectively evaluated in nine ears of five patients with surgically proved congenital ossification of the stapedius tendon. Thin-section CT scans of 50 control ears were also reviewed.

RESULTS

On thin-section CT scans, a linear area of soft-tissue attenuation was demonstrated between the monopod stapes and the pyramidal eminence (nine ears), as well as thickening of the stapes footplate (two ears). In the 50 control ears, the normal stapes tendon was not clearly seen on thin-section CT scans.

CONCLUSION

At CT, a linear area of soft-tissue attenuation that extends from the pyramidal eminence to the monopod stapes is suggestive of congenital ossification of the stapedius tendon or a bony bar adjacent to it.

31P NMR study of acute toxic effects of cadmium chloride on rat liver

In this study, acute effects of cadmium ions (Cd2+) on energy metabolism in rat livers were analyzed in vivo after intravenous administration using 31P NMR. Both inorganic phosphate (Pi) and nucleotide triphosphate (NTP) peaks of in vivo Cd-treated livers gradually decreased over a 6-h period. In the extract, NTP peaks in Cd-treated livers were lower, as in the in vivo experiments, but the Pi peak was significantly higher than the control. The apparent decrease in Pi in in vivo liver treated with Cd could be caused by the reduced visibility of Pi because of its uptake into mitochondria from cytoplasm, accompanied by the uncoupling of oxidative phosphorylation by Cd2+. These results indicated that total Pi in the hepatocytes increases after Cd administration. However, only 10% of Pi was visible in Cd-treated livers in vivo, whereas 34% of Pi was visible in controls. Significant increases in phosphocholine and glycerophosphocholine were also observed in extracts of Cd-treated livers.

[MR imaging features of chronically torn anterior cruciate ligament]

Magnetic resonance (MR) images of 40 knee joints with arthroscopically proved chronic anterior cruciate ligament (ACL) tears were retrospectively evaluated. MRI demonstrated various features of chronic ACL tears: 19 knees revealed with no identifiable ligamentous structure, and 21 had residual ligamentous structures. These pseudoligaments, 14 discontinuous bands and seven continuous bands with elongation, were residual torn ligamentous fibers and/or synovial tissues. All the discontinuous bands were disrupted from the femoral attachment and were likely to traverse the lower intercondylar space. Six disrupted ligaments were attached to the lateral aspect of the posterior cruciate ligament (PCL). Coronal T2-weighted gradient echo images showed better delineation of the disrupted femoral attachment and adhesion to the PCL. A chronic ACL tear with minimal elongation or with PCL attachment at a higher position may occasionally be difficult to distinguish from an intact ligament.

Resting asynchronous left ventricular contraction abnormality analyzed by a phase method in spastic angina pectoris

Quantitative phase analysis of equilibrium ventriculography was performed to study the character of left ventricular (LV) wall motion abnormalities in patients with spastic angina pectoris, who may have clinically and electrocardiographically silent ischemia combined with myocardial stunning, during rest and hyperventilation stress testing.

METHODS

Phase analysis of the left ventricle at rest was performed by equilibrium radionuclide ventriculography in 13 control subjects and 36 patients with spastic angina pectoris. First-pass methodology along with hyperventilation stress testing was performed to assess spasm occurrences. Phase analysis of equilibrium multigated blood-pool scintigrams was performed to evaluate LV asynchrony at rest.

RESULTS

The mean s.d. of LV phase distribution in the patients with variant and vasospastic angina was greater than that in the healthy control subjects (11.28 +/- 1.79 and 10.02 +/- 1.57 degrees versus 6.16 +/- 1.07 degrees). In addition, the mean s.d. of LV phase distribution in the variant angina group was greater than that in the vasospastic angina group. Furthermore, a linear correlation was found between the s.d. of LV phase distribution at rest and the percent decrease in ejection fraction during hyperventilation stress.

CONCLUSION

Asynchronous LV contraction without significant hypokinesis was detected at rest in spastic angina pectoris. The severity of this asynchronous contraction corresponded well with decreases in ejection fraction during hyperventilation stress testing. Thus, analysis of the s.d. of LV phase distribution at rest is expected to provide useful information regarding LV asynchrony in spastic angina pectoris.

Focal fatty masses of the pancreas

Five patients with solitary fatty mass of the pancreas examined with CT and ultrasound (US) were evaluated. The areas of fat replacement were located in the pancreatic neck, body or tail. The size ranged from 4 to 30 mm in the longest diameter. The shape varied from roundish, to ovoid to semicircular, and the contour was universally well defined. The internal structure was homogeneous in 3 patients, but in one case there were thin septa and, in another, a slightly hyperdense part in the peripheral portion. All the masses except the smallest one were in part contact with pancreatic fat. CT showed fat with the same density as the peripancreatic fat and low HU units. The mass was hypoechoic in 2 cases and hyperechoic in one. The masses in the tail of the pancreas were not detected by US.

Fat tissue: relationship between chemical shift and magnetization transfer

The middle calves of the legs of 25 volunteers (12 men and 13 women, aged 18-25 years), as well as phantoms, were examined with 1.5-T magnetic resonance imaging. Gradient-recalled technique was combined with magnetization transfer contrast (MTC) and chemical shift imaging. Periodic oscillation of the MTC effect in fat tissue with variation of echo time was identified at the frequency corresponding to the water-fat chemical shift difference.

Percutaneous ethanol injection therapy for hepatocellular carcinoma: validity of MR imaging in the evaluation of treatment effect

To evaluate the validity of magnetic resonance imaging for the follow-up of percutaneous ethanol injection therapy, 14 patients with a single hepatocellular carcinoma lesion smaller than 2.5 cm in diameter underwent MR imaging at 0.5 Tesla before and after treatment. Posttreatment follow-up examination included ultrasonography, contrast-enhanced computed tomography, and fine-needle biopsy in all cases. Only one patient showed recurrence within the 12-month follow-up period. After treatment, HCC lesions showed hypointensity on T1-, and T2-weighted images that lasted 12 months after treatment. In three cases, wedge-shaped hyperintense regions peripheral to the HCC nodule were observed after treatment on T2-weighted images. Obstructive vasculitis of the portal vein was considered to occur as a result of the drainage of ethanol injected in the tumor. These MR imaging findings may be helpful in clinical practice.

[Secondary signs of anterior cruciate ligament tear at MR imaging]

The value of secondary signs of anterior cruciate ligament (ACL) tear was evaluated MR images of 47 knees, 15 with normal, 6 with acutely torn and 26 with chronically torn ACLs confirmed at arthroscopy, were reviewed. Lateral and medial anterior tibial translocations (ATT), posterior cruciate ligament (PCL) bowing ratio and depth of lateral femoral notch (LFN) were measured. The degrees of lateral and medial ATTs and the PCL bowing ratio of the chronically torn ACLs were significantly higher than those of normal ACLs. With cutoff values of 5-mm lateral ATT, 2.5-mm medial ATT and 0.35-PCL bowing ratio, torn ligaments were distinguished from intact ligaments with accuracies of over 80%. Depth of LFN was less sensitive and less accurate. All knees with lateral ATT of 6.4 mm, medial ATT of 3.5 mm, PCL bowing ratio of 0.43 and LFN depth of 1.5 mm or more had torn ACLs. Higher correlations were revealed between lateral ATT and medial ATT, and also between lateral ATT and PCL bowing ratio. Combined criteria of lateral ATT and PCL bowing ratio indicated the highest diagnostic value as a reliable secondary sign of torn ACLs.

Study on the primary visual cortex of visually impaired subjects by means of 123I-IMP SPECT and MRI

We conducted a study of rCBF in the primary visual cortex of visually impaired subjects who have not been subjected to external stimulation for a long period, by means of 123I-IMP SPECT and MRI. The four subjects had lost their sight due to brain tumors (n = 2), glaucoma (n = 1) and trauma (n = 1). 123I-IMP SPECT showed no differences between the visually impaired group and a visually sound control group on visual analysis as well as semiquantitative analysis. MRI of the visually impaired subjects showed no organic changes, such as atrophy, in the occipital cortex. In conclusion, visually impaired subjects have no decrease in rCBF and no anatomical changes in the primary visual cortex.

Hepatic tumors: magnetization transfer MR imaging with gadolinium enhancement

Thirty patients with 15 hepatocellular carcinomas, 10 metastases, four hemangiomas, and one cholangiocarcinoma underwent magnetic resonance imaging at 1.5 T with T1-weighted, T2-weighted spin-echo (SE) images, gradient-echo (GRE) magnetization transfer (MT) images, and gadolinium-enhanced T1-weighted SE and MT-GRE images. The MT effect and lesion-liver contrast-to-noise ratio (C/N) were calculated and visual assessment (qualitative analysis) performed for unenhanced and enhanced MT-GRE images and enhanced T1-weighted SE images. The C/N values for hepatic adenocarcinomas (seven metastases and one cholangiocarcinoma) and hemangiomas were larger for enhanced MT-GRE images (adenocarcinoma, 8.4 +/- 2.3 [P < .01]; hemangioma 24 +/- 2.1 [P < .05]) than for enhanced GRE images (5.0 +/- 1.9 and 18 +/- 2.7, respectively). These enhancing tumors had the highest scores in the qualitative analysis. Enhanced MT-GRE images showed no advantage for depiction of hepatocellular carcinomas relative to the other images.

Magnetization transfer contrast on gradient echo MR imaging of the temporomandibular joint

Thirty-nine temporomandibular joints (TMJ) from 20 patients with suspected internal derangements were imaged by a 1.5 T MR imager. The on-resonance binomial magnetization transfer contrast (MTC) pulse was applied to gradient echo images with a dual receiver coil (9 s/section). With the use of an opening device, a series of sequential images were obtained at increments of mouth opening and closing. The tissue signal intensities with (Ms) and without (Mo) MTC were measured and subjective image analysis was performed. Compared with the standard images, MTC technique provided selective signal suppression of disks. The average of Ms/Mo ratio of the disks (0.56) was lower than that of the retrodiskal pad (0.79) and of the effusion (0.89). With MTC technique, fluid conspicuity was superior to standard image. However, no significant superiority was found in disk definition subjectivity.

Hepatobiliary cysts in patients with autosomal dominant polycystic kidney disease: prevalence and CT findings

OBJECTIVE

Hepatobiliary (intrahepatic and peribiliary) cysts have been described for patients with autosomal dominant polycystic disease. The purpose of this study was to determine the prevalence of these cysts and to describe the wide variation in their appearance on CT scans.

MATERIALS AND METHODS

We studied CT scans for 64 patients (31 men and 33 women) who either had known autosomal dominant polycystic kidney disease or had renal cysts and a family member with polycystic kidney disease. Contrast enhancement was used for 31 patients. CT scans were retrospectively evaluated by consensus by two experienced radiologists. The presence, number, and size of hepatobiliary cysts and the presence and appearance of the two variations, peribiliary and intrahepatic cysts, were analyzed. Peribiliary cysts were determined to be present when many small (< or = 10-mm) cysts were seen adjacent to the larger (up to the third order) portal triad. Cysts present in the hepatic parenchyma but not in contact with the larger portal triad were regarded as intrahepatic cysts.

RESULTS

CT showed hepatobiliary cysts in 56 of the 64 patients (24 men and 32 women; 88%). Intrahepatic cysts were noted in all 56 patients; peribiliary cysts were definitely seen on CT scans for 22 patients and were probably seen (fewer than five cysts and/or cysts located only on one side of the portal vein) on CT scans for 19 patients (73% of all patients with hepatobiliary cysts). Peribiliary cysts appeared as discrete cysts in 31 patients, as a string of cysts in six patients, and as a tubular structure in four patients. Intrahepatic cysts generally were round but occasionally were polygonal. They were variable in number, size, and location.

CONCLUSION

Hepatobiliary cysts were noted in 56 of 64 patients (intrahepatic cysts in all cases and peribiliary cysts in 73% of positive cases). Intrahepatic cysts varied widely in number, size, and location, whereas peribiliary cysts were small and appeared as discrete cysts, a string of cysts, or a tubular structure adjacent to the larger portal triad. It is important to be aware of the wide variety of findings for hepatobiliary cysts so that they are not confused with other abnormalities.

[Spatial and temporal alteration of the dual supply of the hepatic circulation with transient occlusion of the hepatic veins: spiral volumetric CT during arterial portography and arteriography]

To elucidate the contribution of hepatic veins to the blood flow of liver, CT arterial portography and/or arteriography was performed in eight patients having hepatocellular carcinoma with transient occlusion of the hepatic vein and eight without occlusion. In each patient with occlusion of the hepatic vein, CT showed a well-demarcated fan-shaped area of low density during arterial portography and increased density during arteriography in the corresponding area. Hepatic vein occlusion could result in the pooling of arterial blood in the liver parenchyma. Transient segmental hepatic venous occlusion might improve the results of transcatheter arterial infusion and transcatheter arterial embolization for liver tumors.

Muscle metabolism during exercise using phosphorus-31 nuclear magnetic resonance spectroscopy in adolescents

Very little has been reported on muscle energetics during exercise in adolescents. This is attributable to the difficulty of subjecting children to muscle biopsy. The purpose of this study was to investigate the characteristics of muscle metabolism during exercise in vivo in adolescents by comparing firstly, with adults and secondly, the differences resulting from physical activity using phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy. The subjects were boys aged 12 to 15 years, comprising 21 trained boys and 23 control boys, and 6 adults controls. The ratio of phosphocreatine (PCr):(PCr + P(i)), where P(i) is inorganic phosphate intracellular pH at exhaustion and the time constant of PCr during recovery were measured in all the subjects using 31P NMR. Both groups of children showed higher values of PCr:(PCr + P(i)) and intracellular pH at exhaustion than did the adult control group (P < 0.01 or P < 0.05). However, no significant differences were found between the trained boys and the control boys with respect to PCr:(PCr + P(i)) and intracellular pH at exhaustion. On the other hand, we found the same values for PCr time constant in all groups. This result suggested no differences of the muscle oxidative capacity between children and adults. We concluded that the adolescents, aged 12 to 15 years in both the trained and control groups, had less glycolytic ability during exercise than the adults.

Acute effects of exercise on muscle MRI in peripheral arterial occlusive disease

The midcalf muscles of eight patients who had peripheral arterial occlusive disease were evaluated by exercise MRI before and after bypass surgery or percutaneous transluminal angioplasty. MRI showed a high intensity of these muscles, especially the posterior muscles, after exercise in all patients before intervention. The mean T2 relaxation time was maximal immediately after exercise (tibialis anterior, T2 = 30.8 ms; soleus, T2 = 36.2 ms; gastrocnemius, T2 = 32.8 ms) and then gradually decreased to the preexercise level. The difference in the T2 relaxation time of the soleus between immediately after exercise and at rest was smaller along with improvement of ankle pressure indices (API) after successful intervention (mean T2 difference: 4.91 and 0.72 ms (p < .001); mean API: 0.54 and 0.86 (p < .001) before and after intervention, respectively). The mean resting midcalf T2 relaxation time was significantly higher after intervention (tibialis anterior, T2 = 28.4 and 29.5 ms (p < .05); soleus, T2 = 31.4 and 32.9 ms (p < .05); gastrocnemius, T2 = 29.5 and 31.1 ms (p < .01) before and after intervention, respectively). T2 relaxation time may be a useful quantitative parameter in peripheral arterial occlusive disease as well as in other muscle studies.

Control of the rate of phosphocreatine resynthesis after exercise in trained and untrained human quadriceps muscles

We examined the effect of differences in exercise intensity on the time constant (tc) of phosphocreatine (PCr) resynthesis after exercise and the relationships between tc and maximal oxygen uptake (VO2max) in endurance-trained runners (n = 5) and untrained controls (n = 7) (average VO2max = 66.2 and 52.0 ml.min-1.kg-1, respectively). To measure the metabolism of the quadriceps muscle using phosphorus nuclear magnetic resonance spectroscopy, we developed a device which allowed knee extension exercise inside a magnet. All the subjects performed four types of exercise: light, moderate, severe and exhausting. The end-exercise PCr: [PCr+inorganic phosphate (P(i))] ratio decreased significantly with the increase in the exercise intensity (P < 0.01). Although there was little difference in the end-exercise pH, adenosine diphosphate concentration ([ADP]) and the lowest intracellular pH during recovery between light and moderate exercise, significant changes were found at the two higher intensities (P < 0.01). These changes for runners were smaller than those for the controls (P < 0.05). The tc remained constant after light and moderate exercise and then lengthened in proportion to the increase in intensity (P < 0.05). The runners had a lower tc at the same PCr and pH than the controls, particularly at the higher intensity (P < 0.05). There was a significant correlation between tc and [ADP] in light exercise and between tc and both end-exercise PCr and pH in severe and exhausting exercise (P < 0.05). The threshold of changes in pH and tc was a PCr: (PCr+P(i)) ratio of 0.5. There was a significant negative correlation between the VO2max and tc after all levels of exercise (P < 0.05). However, in the controls a significant correlation was found in only light and moderate exercise (P < 0.05). These findings suggest the validity of the use of tc at an end-exercise PCr: (PCr+P(i)) ratio of more than 0.5 as a stable index of muscle oxidative capacity and the correlation between local and general aerobic capacity. Moreover, endurance-trained runners are characterized by the faster PCr resynthesis at the same PCr and intracellular pH.