Tomi Kauppinen

Biodistribution and radiation dosimetry of [123I]ADAM in healthy human subjects: preliminary results

Abstract. [123I]ADAM [2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine (ADAM)] has recently been shown to be a very promising imaging ligand for the detection of serotonin transporters (SERT) in human brain, because of its high specificity for SERT. [123I]ADAM has previously been used only for animal studies. In this work, we investigated the radiation dosimetry and biodistribution of [123I]ADAM based on whole-body scans in healthy human volunteers. Following the administration of 196±20xa0MBq (range 157–220xa0MBq) [123I]ADAM, serial whole-body images were performed up to 24xa0h. Estimates of radiation absorbed dose were calculated using the MIRDOSE 3.0 program with a dynamic bladder model. Twelve source organs were considered in estimating absorbed radiation doses for organs of the body. The highest absorbed organ doses were found to the lower large intestine wall (8.3·10–2xa0mGy/MBq), kidneys (5.2·10–2xa0mGy/MBq), urinary bladder wall (4.9·10–2xa0mGy/MBq) and thyroid (4.3·10–2xa0mGy/MBq). The effective dose was estimated to be 2.2·10–2xa0mSv/MBq. The results suggest that [123I]ADAM is of potential value as a tracer for single-photon emission tomography imaging of serotonin receptors in humans, with acceptable dosimetry and high brain uptake.

Sentinel lymph node mapping using SPECT–CT fusion imaging in patients with oral cavity squamous cell carcinoma

Lymphoscintigraphic planar imaging is commonly performed to locate the sentinel lymph nodes (SLN) preoperatively. The images are, however, obscure lacking anatomical information and only rough topographical orientation of the SLNs is possible. Image fusion of Single Photon Emission Computed Tomography (SPECT) and Computed Tomography (CT) has been suggested to be an anatomically more precise method for preoperative SLN mapping. In the present study, preoperative lymphoscintigraphic SLN mapping was performed by using a hybrid gamma-camera with CT system (SPECT–CT) in addition to conventional planar lymphoscintigraphy in 15 consecutive patients with squamous cell carcinoma (SCC) of the oral cavity. The planar images were compared to fused SPECT and CT images. SPECT–CT fusion images showed only one SLN that was not detected in planar images. Two SLNs suspected in planar images could be excluded by SPECT–CT. The location of the SLNs could be determined more accurately by SPECT–CT. SPECT–CT fusion imaging was found feasible for preoperative SLN identification in patients with oral cavity SCC. It enables more accurate localisation of the SLNs, but it rarely reveals SLNs, that are not detected on planar images.

Improvement of Report Workflow and Productivity Using Speech Recognition—A Follow-up Study

Speech recognition (SR), available since the 1980s, has only recently become sufficiently reliable to allow utilization in medical environment. This study measured the effect of SR for the radiological dictation process and estimated differences in report turnaround times (RTTs). During the transition from cassette-based reporting to SR, the workflow of 14 radiologists was periodically followed up for 2xa0years in a university hospital. The sample size was more than 20,000 examinations, and the radiologists were the same throughout the study. A RTT was defined as the time from imaging at the modality to the time when the report was available for the clinician. SR cut down RTTs by 81% and the standard deviation by 83%. The proportion of reports available within 1xa0h escalated from 26% to 58%. The proportion of reports created by SR increased during a follow-up time of this study from 0% up to 88%. SR decreases turnaround times and may thus speed up the whole patient care process by facilitating online reporting. SR was easily adopted and well accepted by radiologists. Our findings encourage the utilization of SR, which improves the productivity and accelerates the workflow with excellent end-user satisfaction.

Improvement of brain perfusion SPET using iterative reconstruction with scatter and non-uniform attenuation correction

Abstract. Filtered back-projection (FBP) is generally used as the reconstruction method for single-photon emission tomography although it produces noisy images with apparent streak artefacts. It is possible to improve the image quality by using an algorithm with iterative correction steps. The iterative reconstruction technique also has an additional benefit in that computation of attenuation correction can be included in the process. A commonly used iterative method, maximum-likelihood expectation maximisation (ML-EM), can be accelerated using ordered subsets (OS-EM). We have applied to the OS-EM algorithm a Bayesian one-step late correction method utilising median root prior (MRP). Methodological comparison was performed by means of measurements obtained with a brain perfusion phantom and using patient data. The aim of this work was to quantitate the accuracy of iterative reconstruction with scatter and non-uniform attenuation corrections and post-filtering in SPET brain perfusion imaging. SPET imaging was performed using a triple-head gamma camera with fan-beam collimators. Transmission and emission scans were acquired simultaneously. The brain phantom used was a high-resolution three-dimensional anthropomorphic JB003 phantom. Patient studies were performed in ten chronic pain syndrome patients. The images were reconstructed using conventional FBP and iterative OS-EM and MRP techniques including scatter and non-uniform attenuation corrections. Iterative reconstructions were individually post-filtered. The quantitative results obtained with the brain perfusion phantom were compared with the known actual contrast ratios. The calculated difference from the true values was largest with the FBP method; iteratively reconstructed images proved closer to the reality. Similar findings were obtained in the patient studies. The plain OS-EM method improved the contrast whereas in the case of the MRP technique the improvement in contrast was not so evident with post-filtering.

Brain serotonin transporter binding of [123I]ADAM: within-subject variation between summer and winter data.

The neurotransmitter serotonin (5‐HT) controls several physiological functions, and a disturbance of the 5‐HT system is implicated in many psychiatric conditions. Seasonal variation has been suggested in the 5‐HT system. We investigated within‐subject seasonal variation in brain serotonin transporter (SERT) binding with the SERT‐ligand [123I]ADAM and single photon emission computed tomography (SPECT) in 12 healthy individuals. No systematic variation was found in the midbrain or thalamus areas between scans done in summer and winter. Our results suggest that factors other than season are more important in causing within‐subject variation of brain SERT binding between summer and winter. (Author correspondence: anu.koskela@helsinki.fi)

Serotonin transporter binding of [123I]ADAM in bulimic women, their healthy twin sisters, and healthy women: a SPET study

BackgroundBulimia Nervosa (BN) is believed to be caused by an interaction of genetic and environmental factors. Previous studies support the existence of a bulimia-related endophenotype as well as disturbances in serotonin (5-HT) transmission. We studied serotonin transporter (SERT) binding in BN, and to investigate the possibility of a SERT-related endophenotype for BN, did this in a sample of female twins. We hypothesized clearly reduced SERT binding in BN women as opposed to healthy women, and intermediate SERT binding in unaffected co-twins.MethodsWe studied 13 female twins with BN (9 with purging and 4 with non-purging BN) and 25 healthy women, including 6 healthy twin sisters of BN patients and 19 women from 10 healthy twin pairs. [123I]ADAM, a selective SERT radioligand for single photon emission tomography (SPET) imaging, was used to assess SERT availability in the midbrain and the thalamus.ResultsNo differences in SERT binding were evident when comparing the BN women, their unaffected co-twins and the healthy controls (p = 0.14). The healthy sisters of the BN patients and the healthy control women had similar SERT binding in both brain regions. In a post hoc subgroup analysis, the purging bulimics had higher SERT binding than the healthy women in the midbrain (p = 0.03), but not in the thalamus.ConclusionOur finding of increased SERT binding in the midbrain in the purging BN women raises the possibility that this subgroup of bulimics might differ in serotonergic function from the non-purging ones. The similarity of the unaffected co-twins and the healthy controls doesnt support our initial assumption of a SERT-related endophenotype for BN. Due to the small sample size, our results need to be interpreted with caution and verified in a larger sample.

ASP archiving solution of regional HUSpacs

The application service provider (ASP) model is not novel, but widely used in several non-health care-related business areas. In this article, ASP is described as a potential solution for long-term and back-up archiving of the picture archiving and communication system (PACS) of the Hospital District of Helsinki and Uusimaa (HUS). HUSpacs is a regional PACS for 21 HUS hospitals serving altogether 1.4 million citizens. The ultimate goal of this study was to define the specifications for the ASP archiving service and to compare different commercial options for archiving solutions (costs derived by unofficial requests for proposal): in-house PACS components, the regional ASP concept and the hospital-based ASP concept. In conclusion, the large scale of the HUS installation enables a cost-effective regional ASP archiving, resulting in a four to five times more economical solution than hospital-based ASP.

Learning Curve of Speech Recognition

Speech recognition (SR) speeds patient care processes by reducing report turnaround times. However, concerns have emerged about prolonged training and an added secretarial burden for radiologists. We assessed how much proofing radiologists who have years of experience with SR and radiologists new to SR must perform, and estimated how quickly the new users become as skilled as the experienced users. We studied SR log entries for 0.25 million reports from 154 radiologists and after careful exclusions, defined a group of 11 experienced radiologists and 71 radiologists new to SR (24,833 and 122,093 reports, respectively). Data were analyzed for sound file and report lengths, character-based error rates, and words unknown to the SR’s dictionary. Experienced radiologists corrected 6 characters for each report and for new users, 11. Some users presented a very unfavorable learning curve, with error rates not declining as expected. New users’ reports were longer, and data for the experienced users indicates that their reports, initially equally lengthy, shortened over a period of several years. For most radiologists, only minor corrections of dictated reports were necessary. While new users adopted SR quickly, with a subset outperforming experienced users from the start, identification of users struggling with SR will help facilitate troubleshooting and support.

Framework for systematic assessment of the regional HUSpacs after the reengineering of hospital and external processes

Installing one of the largest regional PAC systems de novo in the Hospital District of Helsinki and Uusimaa (HUS) with 1, 4 million inhabitants has several potential benefits as the financially inefficient intermediate steps to digital radiography are eliminated. However, the capital costs to achieve this filmless digital environment within the existing three university hospitals, four regional hospitals and 32 communal health centres of HUS are enormous. It has been suggested that by re-engineering the x-ray service processes the number of stages in the overall process may be cut down by at least 25 %. This also speeds up the transfer time between processes. Since the number of imaging procedures in HUS reaches annually figures of 1.000.000, this points to the possibility that genuine cost savings may be achieved. The aim of the assessment is to study the effectiveness of the HUSpacs regarding its capacity to improve the quality of health care, to increase the equity of access to health care and to reduce the cost of delivering health care. This may be achieved by designing a framework for the systematic assessment of HUSpacs. A brief description of the regional integration of PACS with the planned security solution will be presented.

PACS: a prerequisite for image fusion in nuclear medicine

Abstract Digital images of nuclear medicine (NM) are produced by a gamma camera. Compared with radiological images, the resolution of NM images is low. However, they reveal regional functional differences, whereas radiological images show high-resolution anatomical details. Combination of anatomical and functional image data from the same part of the body is important and can enhance the understanding of functional abnormalities. The purpose of this study was to introduce a picture archiving and communication system (PACS) for practical clinical use in the divisions of nuclear medicine. The effect of PACS on customizing image fusion in nuclear medicine was also evaluated. For routine use of image fusion, it is essential to have a fast image network for transferring images from different modalities and a PACS for storing them. It is also essential to have a common commitment to Digital Imaging and Communications in Medicine (Dicom) standard. Open-architecture PACS seems to remove the remaining difficulties in customising image fusion. The PACS introduced in the hospital district will be one of the largest in the world when completed in 2003.