Kyriakos Psarrakos

SPECT imaging evaluation in movement disorders: far beyond visual assessment

Single photon emission computed tomography (SPECT) imaging with 123I-FP-CIT is of great value in differentiating patients suffering from Parkinson’s disease (PD) from those suffering from essential tremor (ET). Moreover, SPECT with 123I-IBZM can differentiate PD from Parkinson’s “plus” syndromes. Diagnosis is still mainly based on experienced observers’ visual assessment of the resulting images while many quantitative methods have been developed in order to assist diagnosis since the early days of neuroimaging. The aim of this work is to attempt to categorize, briefly present and comment on a number of semi-quantification methods used in nuclear medicine neuroimaging. Various arithmetic indices have been introduced with region of interest (ROI) manual drawing methods giving their place to automated procedures, while advancing computer technology has allowed automated image registration, fusion and segmentation to bring quantification closer to the final diagnosis based on the whole of the patient’s examinations results, clinical condition and response to therapy. The search for absolute quantification has passed through neuroreceptor quantification models, which are invasive methods that involve tracer kinetic modelling and arterial blood sampling, a practice that is not commonly used in a clinical environment. On the other hand, semi-quantification methods relying on computers and dedicated software try to elicit numerical information out of SPECT images. The application of semi-quantification methods aims at separating the different patient categories solving the main problem of finding the uptake in the structures of interest. The semi-quantification methods which were studied fall roughly into three categories, which are described as classic methods, advanced automated methods and pixel-based statistical analysis methods. All these methods can be further divided into various subcategories. The plethora of the existing semi-quantitative methods reinforces the feeling that visual assessment is still the base of image interpretation and that the unambiguous numerical results that will allow the absolute differentiation between the known diseases have not been standardized yet. Switching to a commonly agreed—ideally PC-based—automated software that may take raw or mildly processed data (checked for consistency and maybe corrected for attenuation and/or scatter and septal penetration) as input, work with basic operator’s inference and produce validated numerical results that will support the diagnosis is in our view the aim towards which efforts should be directed. After all, semi-quantification can improve sensitivity, strengthen diagnosis, aid patient’s follow-up and assess the response to therapy. Objective diagnosis, altered diagnosis in marginal cases and a common approach to multicentre trials are other benefits and future applications of semi-quantification.

Evaluation of Dopaminergic Function in Frontotemporal Dementia Using 123I-FP-CIT Single Photon Emission Computed Tomography

Extrapyramidal symptoms are observed in frontotemporal dementia (FTD). 123I-FP-CIT (DaT scan) single photon emission computed tomography (SPECT) can detect loss of presynaptic dopamine transporters in the striatum. We aimed to evaluate the dopaminergic status of the striatum in patients with FTD using DaT scan. Seven patients (age range 65–76 years), who fulfilled the Neary criteria and in whom the diagnosis of FTD was confirmed by hexamethylpropyleneamine oxime SPECT, were included in the study. The severity of the extrapyramidal symptoms was evaluated by the motor part of the Unified Parkinson’s Disease Rating Scale (UPDRS). SPECT using 123I-FP-CIT was done. A (region – occipital)/occipital ratio was calculated for the striatum, putamen and caudate nucleus. The results were compared with those of the 7 age-matched normal controls. The uptake of the radiotracer in the right and left striatum was reduced to 62% (p = 0.000) and 68% (p = 0.000), respectively, compared to controls. The motor UPDRS score of the patients with FTD showed a negative correlation to the uptake of the radiotracer. The presynaptic dopamine transporter in FTD is impaired, related to the severity of the extrapyramidal symptoms. Since an effective treatment for FTD is still to be established, there is a need for evaluating the efficacy of dopaminergic drugs.

The dependence of patient dose on factors relating to the technique and complexity of Interventional Cardiology procedures

Dose-area product (DAP) measurements were conducted for 168 coronary angiography (CA) and 89 single vessel percutaneous transluminal coronary angioplasty (PTCA) to examine the factors influencing patient dose beyond the X-ray exposure parameters. It was found that for CA, the DAP increases with the number of catheters used and with the number of vessels with stenosis. DAP values for patients with a prior bypass surgery, were higher compared to those without such a medical record to surgery. In PTCA, the use of coronary stents did not enhance the patient radiation dose significantly. Noticeable differences were found in the percentage contribution of each projection to the total DAP between the three types of single vessel PTCA. Finally low variations in DAP were found among the cardiologists performing both procedures.

Tc-99m depreotide imaging of I-131-negative recurrent metastatic papillary thyroid carcinoma

The detection of radioiodine (I‐131)‐negative metastases of differentiated thyroid carcinoma (DTC) has been hitherto successfully tried by the well‐known synthetic somatostatin analogue indium‐111‐labeled DTPA‐octreotide (In‐111 pentetreotide). The objective of this study was to evaluate the usefulness of scintiscan with the newer synthetic somatostatin analogue Tc‐99m depreotide, in the restaging of papillary thyroid carcinoma (PTC) with detectable serum thyroglobulin (Tg) levels and negative I‐131 whole‐body scan (WBS). Whole‐body planar and cervico‐thoracic tomographic scintigraphy (single‐photon emission tomography—SPET) with Tc‐99m depreotide was performed in a 68‐year‐old male patient suffering from PTC stage III, with a mild increase in serum Tg levels coupled with a recent negative I‐131 WBS. The findings were compared with those of neck ultrasonography (US) and computerized tomography (CT). Nodal neck dissection and histopathology provided the definitive diagnosis. Tc‐99m depreotide scanning revealed foci of cervical lymph node metastases, which did not accumulate I‐131. The findings were in accordance with neck US and CT. Histopathology established the diagnosis of metastatic cervical lymph node PTC. Lymph node immunoreactivity was positive for the somatostatin receptor subtypes 2, 5 and 3. Scintigraphy with Tc‐99m depreotide could prove a useful adjunct to the armamentarium for the follow‐up of PTC, especially in the setting of detectable serum Tg and negative I‐131 WBS.

EFFECTS OF FOSINOPRIL ON RENAL FUNCTION IN PATIENTS WITH MILD TO MODERATE ESSENTIAL HYPERTENSION

SummaryIn a 10-week double-blind randomised placebo-controlled trial, the efficacy, safety and effect on renal function of a single dose of fosinopril 20mg once daily were studied in 23 patients with mild to moderate essential hypertension. After discontinuation of previous antihypertensive treatment and a 4-week washout period, all patients received placebo for the next 2 weeks. Patients were then randomly assigned, in a double-blind fashion, to 1 of 2 groups: the first group (group F) was made up of 12 patients who received fosinopril 20mg once daily; the second group (group PL) was made up of 11 patients who received one matching placebo tablet once daily. The duration of treatment was 4 weeks. At the end of the placebo period and after 4 weeks’ treatment, systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate were measured, routine blood and urine investigations performed, and plasma renin activity (PRA), plasma aldosterone and renal haemodynamics determined. A statistically significant reduction in both SBP (p < 0.001) and DBP (p < 0.001) was observed only in group F, 4 weeks after initiation of treatment. Heart rate remained unchanged and there were no adverse events in either group. In group F, PRA increased significantly (p < 0.05) and glomerular filtration rate remained unchanged; renal blood flow was significantly reduced (p < 0.01), although it remained within the normal limits. In conclusion, fosinopril demonstrated an adequate antihypertensive effect and was well tolerated, without any significant changes in renal haemodynamics.

MR urography: Anatomical and quantitative information on congenital malformations in children

Background and Aim: Magnetic resonance urography (MRU) is considered to be the next step in uroradiology. This technique combines superb anatomical images and functional information in a single test. In this article, we aim to present the topic of MRU in children and how it has been implemented in Northern Greece so far. The purpose of this study is to demonstrate the potential of MRU in clinical practice. We focus both on the anatomical and the quantitative information this technique can offer. Materials and Methods: MRU was applied in 25 children (ages from 3 to 11 years) diagnosed with different types of congenital malformations. T1 and T2 images were obtained for all patients. Dynamic, contrast-enhanced data were processed and signal intensity versus time curves were created for all patients from regions of interest (ROIs) selected around the kidneys in order to yield quantitative information regarding the kidneys function. Results: From the slopes of these curves we were able to evaluate which kidneys were functional and from the corticomedullary cross-over point to determine whether the renal system was obstructed or not. Conclusion: In all 25 cases MRU was sufficient, if not superior to other imaging modalities, to establish a complete diagnosis.

The variation of intrinsic spatial resolution across the UFOV of scintillation cameras.

The aim of the present study was to investigate in detail the variation of the intrinsic spatial resolution across the useful field of view (UFOV) of gamma-cameras and to explore whether this variation could lead to observable effects in clinical images. Two gamma-cameras were used, without their collimators, to acquire 560 (99m)Tc point source images at different points across their UFOVs, in order to measure the intrinsic spatial resolution at each point. Possible clinical effects of the resolution variation were examined on images of a thyroid phantom using a LEHR collimator, acquired at different locations on the UFOV and at various distances from the collimator. The gamma-camera intrinsic resolution varied significantly across the UFOV, being generally lower at the central region and deteriorating at the edges. Pronounced local maxima and minima were found at points corresponding to the centers of the photomultiplier tubes (PMTs) and halfway in between. Maximum differences of more than 50% were observed between the points presenting the best and worst intrinsic resolution. Differences between neighboring points reached 17%. The effects of resolution variation were clearly observable on the thyroid phantom images. It was concluded that an appropriate correction algorithm might be necessary in order to correct for the variation of the intrinsic spatial resolution across the UFOV of gamma-cameras.