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[Brain SPECT with 123I-labelled iodobenzamide (IBZM): aspects of semiquantitative evaluation]
Abstract
The striatal dopamine-D2-receptor uptake of 123I-IBZM in 32 patients (18 without and 14 under therapy with typical neuroleptics) was measured semiquantitatively using different ROI techniques. The aim of the study was to evaluate the influence of these techniques on the different ratios (striatum/cortex) found by various examiners. Using the same SPECT system no major differences were found between rectangular and manually drawn ROIs of the same size. All ROI techniques could differentiate between patients with and without therapy on a highly significant level. Therefore, the resulting ratio is mainly dependent on the spatial resolution of the camera system and only to a relatively minor extent on the ROI technique. Ratios obtained by different observers are not comparable quantitatively.
Objective:
To perform a descriptive analysis of the clinical and diagnostic implications of (123)I-IBZM SPECT in the patients studied in our center for movement disorders suggestive of Parkinson-Plus Disease (PP).
Subjects and methods:
(123)I-IBZM SPECT was performed in 46 patients referred from the movement disorders consultation due to suspicion of PP. According to their symptoms, they were distributed into 3 groups: 35 patients had atypical symptoms (AS) for Parkinson's Disease, 2 showed no response to standard therapy (NR) and 9 presented both factors (AS, NR). The results of SPECT were only assessed qualitatively.
Results:
The (123)I-IBZM supported the diagnosis of PP in 15(42.9%) out of the 35 patients with AS. The (123)I-IBZM was pathological in one of the two NR patients. Regarding the third group of patients (AS+NR), the (123)I-IBZM was pathological in 6 cases (66.7%). In 95.7% of our sample (44 patients), AS with or without NR was the main factor leading to suspicion of PP and the (123)I-IBZM was altered in only 47.7% (22 patients). Of these 22 cases, the final diagnosis was PP (with high positive predictive value) in 20(91%).
Conclusion:
The study with (123)I-IBZM is useful in the clinical practice because it provides objective diagnostic information with implications for the treatment and prognosis of patients with suspicion of PP.
Objectives
To assess utility of SPECT with 123I-Iolopride (123I-IBZM) in the differential diagnosis of patients with Parkinsonian symptoms and try to establish an adequate quantification method.
Material and method
We analyzed a total of 34 patients who underwent a study with 123I-IBZM SPECT. Studies were analyzed qualitatively (visually) and quantitatively, using different quantification methods. We used different sums of slices (2, 3, 4, and 7 slices) with different cortical regions as a reference (frontal and occipital regions). Results were analyzed statistically. The final diagnosis of patients was established by two neurologists, specialized in movement disorders.
Results
Studies were visually assessed as normal in 24 cases and as pathologic in the other 10 cases. Scintigraphic studies had an adequate diagnostic correlation in 33 of the 34 patients. Four of the 8 methods used in the quantification were statistically significant in the differentation between normal and pathological. The use of different cortical brain regions as reference did not improve differentation between normal and pathologic studies. Global quantitative assessment of the studies showed that normal studies had higher values than pathological ones, with important overlapping between both categories.
Conclusions
123I-IBZM SPECT is an effective diagnostic tool in the establishment of the differential diagnosis in patients with Parkinson's disease and Parkinson-Plus. Quantification of these studies had limited utility since the overlapping of index values between normal and pathological restricts their use in individual cases.
To perform a descriptive analysis of the clinical and diagnostic implications of (123)I-IBZM SPECT in the patients studied in our center for movement disorders suggestive of Parkinson-Plus Disease (PP).
(123)I-IBZM SPECT was performed in 46 patients referred from the movement disorders consultation due to suspicion of PP. According to their symptoms, they were distributed into 3 groups: 35 patients had atypical symptoms (AS) for Parkinson's Disease, 2 showed no response to standard therapy (NR) and 9 presented both factors (AS, NR). The results of SPECT were only assessed qualitatively.
The (123)I-IBZM supported the diagnosis of PP in 15(42.9%) out of the 35 patients with AS. The (123)I-IBZM was pathological in one of the two NR patients. Regarding the third group of patients (AS+NR), the (123)I-IBZM was pathological in 6 cases (66.7%). In 95.7% of our sample (44 patients), AS with or without NR was the main factor leading to suspicion of PP and the (123)I-IBZM was altered in only 47.7% (22 patients). Of these 22 cases, the final diagnosis was PP (with high positive predictive value) in 20(91%).
The study with (123)I-IBZM is useful in the clinical practice because it provides objective diagnostic information with implications for the treatment and prognosis of patients with suspicion of PP.
The purpose of this study was to compare the binding of various typical and atypical neuroleptics to striatal D2 dopamine receptors in schizophrenic patients.
Fifty-six inpatients with schizophrenia, including 14 with schizoaffective disorder and one with schizophreniform disorder, were evaluated. Fourteen patients were neuroleptic free. Single photon emission computed tomography (SPECT) was performed 90 minutes after intravenous injection of [123I]benzamide ([123I]IBZM). Subsequent semiquantitative analysis of D2 receptor binding was done with the use of the basal ganglia (striatum)/frontal cortex (BG/FC) ratio of activity. Clinical symptoms were rated with the Positive and Negative Syndrome Scale and the Hamilton Depression Rating Scale.
The BG/FC ratios in patients taking typical neuroleptics were significantly lower than those in the neuroleptic-free subjects but not lower than those in the patients taking atypical neuroleptics (clozapine, remoxipride). For atypical antipsychotics, a dose-dependent relationship with striatal D2 receptor binding could not be demonstrated. BG/FC ratios were not significantly correlated with clinical symptoms or with duration of illness.
The results indicate that [123I]IBZM SPECT is useful for semiquantitative imaging of striatal D2 dopamine receptors and for estimating their blockade by neuroleptics. Thus, it may improve drug monitoring in psychiatric patients. Furthermore, the findings suggest a complex relationship between the antipsychotic effect of atypical neuroleptics and D2 receptor blockade.
D2-dopamine receptors can be visualized in the human brain in vivo by Single Photon Emission Tomography (SPECT) and the radiolabeled benzamide [123I]IBZM. The present paper reviews the current status of this type of functional brain imaging with respect to basic methodological aspects, data analysis and quantification. The results from published clinical studies in different psychiatric patient populations and normal controls with [123I]IBZM are reviewed. [123I]IBZM-SPECT is a powerful tool for the investigation of D2-dopamine receptor status in psychiatric disorders, different types of drug treatment as well as therapeutic and side effects of pharmacologic agents. However, there still is a need for standardized imaging times and image-processing procedures. Advantages and disadvantages of SPECT with special regard to Positron Emission Tomography (PET) are also discussed.
Single photon emission tomographic investigations of the extrapyramidal system have become easier to perform since the development of the ligands [123I]-beta-CIT and [123I]-IBZM. Thirty-three patients were investigated with [123I]-IBZM. The images were evaluated visually and semi-quantitatively (ratio of the striatum to front cortex). Ten controls showed a mean (+/- S.D.) ratio of 1.513 +/- 0.06; nine patients with Parkinson's disease had a smaller ratio of 1.425 +/- 0.095; six patients with Huntington's disease had a significantly lower ratio (1.147 +/- 0.105). Eight patients were not classified, because of different nosologic entities. Twenty-three patients were investigated with [123I]-beta-CIT. They were evaluated using standard techniques and the ratio of the striatum to cerebellum. Six controls had a mean ratio of 5.128 +/- 0.787. In 11 Parkinson patients, the ratio was significantly less (3.359 +/- 0.769). Patients with focal dystonia showed normal values. One patient with Huntington's disease had a significantly lower ratio. Receptor studies of the extrapyramidal system may help with diagnoses and could be of relevance therapeutically.
A number of neurodegenerative diseases have been evaluated with 123I-iodobenzamide (123I-IBZM) dopamine receptor scintigraphy, including Parkinson's disease. Differential diagnosis is based on the semi-quantitative determination of striatal uptake in the basal ganglia. Seven procedures for calculating basal ganglia uptake were compared and checked statistically in (1) 28 previously untreated de novo parkinsonian patients before and (2) 14 patients after (mean of 9 months) commencement of anti-Parkinson medication. Of the 21 hemi-parkinsonian patients, 16 demonstrated increased uptake contralaterally (mean right-to-left difference = 8%, sensitivity = 76%) using the most robust uptake procedure. The difference in uptake between the affected and contralateral sides (mean = 6%) was significant (P = 0.02). The mean (+/- S.D.) basal ganglia/frontal cortex (BG/FC) ratio was 1.55 +/- 0.14 (attenuation-corrected). Attenuation correction did not affect the relative ratio of basal ganglia uptake (P = 0.01). The anti-Parkinson medication did not result in any significant changes in the BG/FC ratio at follow-up, but responders could be differentiated from non-responders based on initial uptake (mean BG/FC ratio of 1.58 and 1.39 respectively). We conclude that 123I-IBZM can be used routinely to identify which Parkinson patients will benefit from dopaminergic medication.
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