Motor activation in multiple system atrophy and Parkinson disease: a PET study.

BACKGROUND: Multiple system atrophy (MSA) is an atypical parkinsonian syndrome including cerebellar impairment and poor response to levodopa. We assessed right hand motor activation in patients with MSA before and after an acute levodopa challenge in comparison with patients with PD and healthy volunteers (HVs). METHODS: Eighteen patients with MSA, 8 patients with PD, and 10 age-matched HVs were included. Regional cerebral blood flow measurements with H(2)(15)O PET were performed at rest and during a right hand movement. Statistical parametric mapping was used to analyze motor vs rest in OFF and ON conditions and the effect of levodopa on motor activation. RESULTS: Before levodopa, patients with MSA activated most known cerebral motor areas. Compared with HVs, patients with MSA exhibited less bilateral cerebellar activation and greater left superior parietal activation. They also had less bilateral cerebellar and greater supplementary motor and left superior parietal activation than patients with PD. Conversely, patients with PD had greater activation than HVs in the right cerebellum and less in the supplementary motor cortex. After levodopa, patients with MSA exhibited reduced activation in anterior cingulate, whereas patients with PD had greater activation in the right cerebellum. CONCLUSION: Patients with MSA and patients with PD recruited different motor networks. Patients with PD preferentially activated cerebellar pathways, possibly to compensate for basal ganglia dysfunction. This was not observed in patients with MSA, probably because of cerebellar dysfunction; other frontoparietal cortical areas were recruited.

Synthesis and biodistribution of new oxo and nitrido 99mTc complexes with asymmetrical potentially dianionic or trianionic tetradentate SNNO ligands derived from methyl-2-aminocyclopentene-1-dithiocarboxylic acid.

In this work, 10 new asymmetrical tetradentate SNNO ligands were prepared by reaction of the amine function of methyl 2-[(beta-aminoethyl)amino]cyclopentene-1-dithiocarboxylate with various bifunctional substituents bearing hydroxyl/ketone and hydroxyl/aldehyde functional groups and with diethyl oxalate. 99mTc labeling efficiency was optimized by adjusting temperature and pH conditions. Seven nitrido and two oxo 99mTc complexes were isolated. Six of them proved to be stable near physiological conditions. Biodistribution studies in the rat showed a significant heart uptake for four of them and strong kidney and liver uptake for the other two.

[Characterization of the response of hexagonal parallel-hole collimators of scintillation cameras]. / Caractérisation de la réponse des collimateurs à trous parallèles hexagonaux des caméras à scintillation.

This paper presents a formulation of the frequency response of hexagonal parallel-hole collimator scintillation cameras. To describe this response, we propose an equation determined semi-empirically from a great number of simulations. The utility of the equation is that it enables the simple calculation of the response from collimator characteristics by taking into account the collimator's hexagonal structure. Because the equation does not assume translation invariance, the results can be directly compared with experimental measurements obtained with a point source. It is particularly interesting for collimators with large holes, like the medium-resolution ones used for high-energy radiation. Quality control and physical performance measurements are thus facilitated for this kind of collimator. Also, we present a new parameter that gives a quantitative assessment of the importance of partition penetration. This parameter is measured directly from the collimator frequency response. It has been studied by simulation, taking into account gamma photon attenuation in collimator partitions. The experimental measurements that have been made are in accord with the proposed equations.

Technetium labeling of bi, tri and tetradentate ligands derived from 2-aminocyclopentene-1-dithiocarboxylic acid: characterization and biodistribution of their oxo and nitrido 99mtechnetium complexes.

We have synthesized and characterized seven ligands derived from 2-aminocyclopentene-1-dithiocarboxylic acid with different donor sets (SN2-, SNO2-, SNN2-, SNNO3- and SNNN3-) and different substituents on the sulfur moieties-SR (with R = H, CH3 or C2H5O(CH3)CH). With five of these ligands technetium nitrido complexes have been obtained with high yields (over 95%) using rather harsh conditions (pH = 1, temperature > or = 80 degrees C), whereas for technetium oxo complexes similar high yields were only obtained with two ligands but with mild conditions (pH = 7-8, temperature approximately equal to 50 degrees C). Changing an OH group for an NH2 has a drastic effect upon labeling yields. The possibility of complexing ligands as either oxo (TcO)3+ or nitrido (TcN)2+ derivatives increases the number of available labeled agents with different overall change and consequently with different biological behavior.

Imaging of hyperparathyroidism: US, CT, MRI and MIBI scintigraphy.

Hyperparathyroidism is a rare condition although recently the incidence has increased, particularly the asymptomatic form, as a result of routine serum calcium measurements. A definitive diagnosis can be made using modern bio-assays giving direct measurements of parathormone (PTH). Various methods are currently available for pre-operative localisation of pathological parathyroid glands. Ultrasound is sufficient prior to the initial surgery. However, if primary surgical exploration fails to localise the parathyroid glands then the surgeon faces a more complex problem and requires precise localisation prior to repeat surgery to reduce operating time and risk. No radiological method is available to localise pathological glands in 100% of cases. The surgeon is usually satisfied when two different methods are positive and in concordance. The non-invasive methods such as ultrasound, CT, MRI and scintigraphy are initially performed and if the result remains equivocal then more invasive methods such as arterial or venous sampling are undertaken. Our preliminary results in secondary hyperparathyroidism, before repeat surgery, indicate that associated and complementary tests, morphological and functional, MRI (fat-sat, T1, gadolinium) and MIBI scintigraphy, have greater efficacy.

Feasibility of first-pass radionuclide angiocardiography with a 10-mCi technetium bolus using a single-crystal digital gamma camera: implications for technetium-sestamibi single-day protocols.

To test the feasibility of rest first-pass radionuclide angiocardiography (FPRNA) using a 370-MBq (10-mCi) bolus and a single-crystal gamma camera, 40 patients underwent both FPRNA and equilibrium radionuclide angiocardiography (ERNA). Ejection fraction (EF) and regional wall motion (RWM) were assessed by three observers. The interobserver reproducibility was good: the intraclass correlation coefficient was 0.97 for both techniques. The correlation coefficient between FPRNA and ERNA EFs ranged between 0.90 and 0.92. FPRN EFs were significantly higher (P < 0.003) by less than 5 percentage points, this difference having no clinical implications for patient classification. The study provides arguments as to why this difference may be explained self-attenuation rather than counts statistics problems. Both techniques were concordant for RWM analysis. We conclude that FPRNA with 10 mCi is a reliable tool to assess rest left ventricular function, which makes it possible to perform simultaneously myocardial perfusion and function assessment in a single-day protocol using a single-crystal gamma camera.

Normalization of stress and delayed thallium-201 myocardial SPECT: where is the normal reference area?

We describe an unusual uptake pattern in a thallium SPECT study performed after dipyridamole infusion in a patient with a documented history of prior inferior infarction and recent typical chest pain. The stress study exhibited maximum uptake in the inferior wall. The delayed study showed an inferior defect more consistent with the notion of inferior necrosis, with a maximum uptake in the anterior wall. The authors propose a pathophysiologic interpretation consistent with coronary angiography findings, based on the assumption of coronary steal suggested by the occurrence of chest pain at the end of the dipyridamole infusion. The problem of selecting myocardial normal reference area(s) necessary to normalization prior to quantitative comparison stress and delayed studies is discussed.

[A simulation method for studying scintillation camera collimators]. / Une méthode d'étude par simulation des collimateurs des caméras à scintillation.

This paper presents a computer simulation of photon interaction with collimator septa, which allows the point spread function of scintillation camera collimators to be calculated. The method simulates photon attenuation along their propagation direction in a determinist way. Using this simulation, the spatial resolution, geometric efficiency and penetration index of collimators may be easily assessed. Results obtained with this method are presented and compared with those obtained from standard formulae. We show the usefulness of the simulation which precisely accounts for effects of septum penetration. Measurements performed on two collimators with 131I and 99Tcm point sources provide results consistent with those obtained from the simulation method. In conclusion we show that this method is an accurate tool to assist conception of collimators for nuclear medicine.

Correlations between M-mode markers of left ventricular hypertrophy and radionuclide angiographic indices of left ventricular diastolic function in mild to moderate hypertension.

This study was undertaken to determine the correlations between left ventricular hypertrophy and left ventricular diastolic function in mild to moderate essential hypertension. M-mode echocardiography and rest equilibrium radionuclide angiography were performed in 53 hypertensive subjects. The following M-mode echocardiographic parameters were measured: interventricular septal thickness, posterior wall thickness, left ventricular mass index, left atrial diameter and relative wall thickness. The following radionuclide angiography parameters were measured: ejection fraction, peak filling rate, time to peak filling rate, first third filling fraction and atrial contribution to total filling. Weak correlations were shown between left ventricular diastolic function and the M-mode echocardiographic parameters. The peak filling rate was negatively correlated with the interventricular septal thickness (r = -0.345; P less than 0.05), with the sum of the interventricular septal thickness and the posterior wall thickness (r = -0.395; P less than 0.01), with the left atrial diameter (r = -0.345; P less than 0.05), and with the relative wall thickness (r = -0.297; P less than 0.05). The time to peak filling rate was positively correlated with the left ventricular mass index (r = + 0.310; P less than 0.05) and with the left atrial diameter (r = + 0.323; P less than 0.05). These findings suggest that diastolic abnormalities in hypertensive heart disease are only in part related to the degree of left ventricular hypertrophy.

Atrial natriuretic peptide, plasma renin activity, plasma volume, systemic vascular resistance and cardiac output in patients with cirrhosis.

The present study aimed to assess relationships between plasma levels of atrial natriuretic peptide (ANP) and plasma volume, systemic vascular resistances, cardiac output and plasma renin activity in patients with cirrhosis. Thirty patients were included: eight with no history of liver disease were used as controls; 22 patients had biopsy-proven alcoholic cirrhosis without ascites (n = 11) and with ascites (n = 11). Mean ANP plasma level was significantly higher in both groups of cirrhotic patients than in controls (P less than 0.05). In the control group, ANP and plasma renin activity were inversely correlated (P less than 0.05) but no correlation was found in cirrhotic patients. In the group of patients with ascites, ANP plasma levels were inversely correlated to plasma volume (P less than 0.05) and to cardiac output (P less than 0.01) and directly correlated to systemic vascular resistances (P less than 0.01). Using multiple regression analysis, ANP remained correlated only with systemic vascular resistances (P less than 0.05). These results suggest that cirrhotic patients have high plasma levels of ANP whether or not they have ascites. In the light of current knowledge of ANP actions, the relationships between ANP plasma levels and plasma volume, cardiac output, and systemic vascular resistances are paradoxical in cirrhotic patients with ascites. ANP does not seem to play a critical role in the pathogenesis of sodium and water retention observed in these patients.

Prone decubitus: a solution to inferior wall attenuation in thallium-201 myocardial tomography.

We propose an efficient method to suppress inferior wall attenuation in 201TI 180 degrees myocardial tomography. We systematically performed redistribution studies in both supine and prone decubitus, assuming that the latter should result in shifting with respect to each other's cardiac structures and diaphragm as well as subphrenic organs possibly responsible for attenuation. The comparison of both studies in 25 normal subjects by visual interpretation and circumferential profiles analysis showed a complete suppression of significant attenuation in the inferior wall in prone studies. In addition and consequently, the standard deviation of activity in this area was markedly reduced and became close to its value in anterior and lateral walls. This simple technique now routinely performed in over 400 patients drastically improves specificity in the evaluation of inferior wall abnormalities by suppressing attenuation artifacts and, incidently, the effect of high individual variability in left phrenic and subphrenic anatomic configuration.

Human brain and spinal cord scan after intracerebroventricular administration of iodine-123 morphine.

[123I]iodomorphine (IMPH) was administered intracerebroventriculary (i.c.v.) in eight patients treated by i.c.v. morphinotherapy (i.c.v.m.). Scans obtained by gamma-scintigraphy over 1 h post-injection showed only a slight diffusion of IMPH beyond the ventricular system, particular attention being paid to the spinal cord. These data agree well with induced i.c.v.m. analgesia (mean latency 20 min) and biological results such as HPLC assay of morphine in the lumbar cerebrospinal fluid, supporting the action of morphine only on the central opiate receptors.

[Acupuncture meridians demythified. Contribution of radiotracer methodology]. / Les méridiens d'acupuncture démythifiés. Apport de la méthodologie des radiotraceurs.

Radioactive trajectories can be visualized by injecting a radioactive tracer, technetium 99 m, at the site of acupuncture points. To determine the exact nature of these trajectories we performed several experiments on healthy volunteers, and our results may be summarized as follows. The target organs of technetium 99 m, and notably the thyroid gland, were always visualized. The circulating radioactivity, visible on scintiscans and confirmed by venous blood counts, was not negligible. The radioactive trajectories we observed were often divided at their starting point and did not extend along the whole length of the acupuncture meridians they might have made visible. The radioactive trajectories disappeared after venous blockade to reappear when the blockade was lifted. Finally, the radioactive trajectories obtained were very similar after injection at the acupuncture point and at a control point. These findings indicate a lymphatic and venous drainage of the radioactive tracer at the site of injection followed by transportation through the veins, rather than visualization of acupuncture meridians as suggested by some authors.

Utility of caudal view in pelvic bone imaging.

Bone imaging of the lower pelvis often is impaired by the radioactivity of the bladder. The caudal view produces an image that clearly distinguishes the bladder from the bones. Thus, it is helpful in patients with bony lesions of the lower and anterior pelvis. The caudal view examination is completed by a backward tilting of the camera head that clarifies this distinction.

Usefulness of cephalad views in thallium-201 myocardial imaging.

In addition to imaging in the conventional positions, TI-201 myocardial imaging was also performed in a 25 degree cephalad projection. This resulted in improved imaging, especially of the inferior wall. Myocardial images are presented in five patients in whom areas of absent activity were most sharply delineated in the 25 degree cephalad projection.