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Biomedical subjects

I Gordon

Publications and source records attributed to I Gordon.

At least 73 records · Page 4Linked to original sources
PubMed1998

An update of radiopharmaceutical schedules in children.

Proposed radiopharmaceutical schedules based on readily measured parameters (age, height, weight, surface area) have been considered with respect to their applicability in nuclear medicine. Although schedules based on age are considered to be inappropriate, there are valid cases for schedules based on height, weight and surface area. For many radiopharmaceutical studies, the most appropriate schedules are based on weight or surface area. Examination of simple theoretical physical models, including the influence of attenuation, suggests that the optimum administered amounts of radiopharmaceuticals fall mainly within the region bounded by these two schedules. The results of recent clinical studies designed to test the validity of different schedules are summarized. In general, they support the predictions of theoretical models, but also show how simple models can be influenced significantly by the age dependency of radiopharmaceutical biodistribution. The schedule based on surface area (or height) is less likely than that based on weight to require the identification of minimum administered amounts of radiopharmaceutical to preserve image quality in small children. However, recent studies have shown that the most appropriate schedule for regional cerebral blood flow with 99Tcm-HMPAO is that based on weight, without the need for a minimum activity. Paediatric radiation dosimetry is briefly summarized to indicate some recent innovations in methodology. Effective doses per unit of administered radiopharmaceutical (mSv MBq-1) have been calculated using five paediatric phantoms for a number of radiopharmaceuticals commonly used in children. Values of total effective dose resulting from the application of the weight and surface area schedules are presented, based on the adult reference amounts of administered radiopharmaceutical proposed by the Paediatric Task Group of the European Association of Nuclear Medicine. Although some values of effective dose exceed 10 mSv for the surface area schedule, the majority of values are less than 5 mSv.

Body Height↗
PubMed1998

Comparison of radiation dose from intravenous urography and 99Tcm DMSA scintigraphy in children.

Intravenous urography (i.v.u.) and 99Tcm DMSA scintigraphy are possible alternative diagnostic techniques in paediatric renal investigation. Radiation dose comparisons between them have been complicated in the past by the lack of paediatric data. In this study, evaluations relevant to children are used to compare estimates of effective dose from the two techniques. For the radiographic procedures, standard operating parameters and representative age-dependent values of entrance surface dose were established from recent literature. Conversion factors relating effective dose to entrance surface dose and dose-area product are presented and used to obtain values of effective dose for single radiographs of abdomen, kidneys and pelvis. Suggested i.v.u. procedures consisting of four ("minimum") or eight ("average") radiographs were adopted to derive the effective dose for full i.v.u. examinations. 99Tcm DMSA dose estimates, taken from our published work using an administered activity schedule based on body surface area, are almost constant at about 1 mSv for all children. In comparison, mean i.v.u. doses based on the "average" number of radiographs are similar to DMSA doses for infants (< 1 year) but may be twice as high for older children. Although the differences between procedures at this level of dose do not in themselves provide grounds for preference, when coupled with the lower diagnostic sensitivity of i.v.u. they suggest limitations of this procedure for detection of a renal scar.

Abdomen↗
PubMed1998

Issues surrounding preparation, information and handling the child and parent in nuclear medicine.

A successful pediatric nuclear medicine examination can be defined as a high-quality study coupled with the child and parent feeling that their emotional needs have been considered. To achieve this goal requires a team approach by all members of the nuclear medicine department as well as a comprehensive explanation of the procedure to the child and parent. Success often depends not so much on a department with the latest gamma camera but a department with an understanding of the needs of children and value of small items such as toys, posters, appropriate books and so on. The recognition that a child requires twice as long as an adult for the same examination dictates an appropriate appointment system to ensure that the staff have sufficient time to devote to the child and parent.

Adult↗
PubMed1998

Cerebral imaging in paediatrics.

Radioisotope brain imaging has focused mainly on regional cerebral blood flow (rCBF). However the use of ligands which go to specific receptor sites is being introduced in paediatrics, mainly psychiatry. rCBF is potentially available in many institutions, especially with the availability of multi-headed gamma cameras. The use of this technique in paediatrics requires special attention to detail in the manner of data acquisition and handling the child. The interpretation of the rCBF study in a child requires knowledge of normal brain maturation. The major clinical use in paediatrics is epilepsy because of the advances in surgery and the frequency of complex partial seizures. Other indications in paediatric neurology include brain death, acute neurological loss including stroke, language disorders, cerebral palsy, hypertension due to renovascular disease, traumatic brain injury and migraine. There are paediatric psychological conditions in which rCBF has been undertaken, these include anorexia nervosa, autism, Gilles de la Tourette syndrome (GTS) and attention deficit disorder-hyperactivity (ADHD). Research using different ligands to specific receptor sites will also be reviewed in paediatrics.

Anorexia Nervosa↗
PubMed1998

A case study comparing a meta-analysis and a pooled analysis of studies of sinonasal cancer among wood workers.

A pooled analysis of raw data from 12 case-control studies of sinonasal cancer has recently been conducted by the International Agency for Research on Cancer; the summary odds ratio for all wood-related occupations was 2.0 (95% confidence interval = 1.6-2.5). We have conducted a meta-analysis of the published results of 14 studies on the same topic, including 11 studies from the pooled analysis, and compared the results for several categories of wood workers. Usable results were available for 12 studies: male wood workers had a summary odds ratio of sinonasal cancer of 2.6 (95% confidence interval = 2.1-3.3). The corresponding value based only on the studies that were also included in the pooled analysis was 2.4 (95% confidence interval = 1.9-3.0). When our meta-analysis was based on a relatively large number of studies, results tended to be higher than those of the pooled analysis. As compared with the meta-analysis, the pooled analysis controlled the effect of publication bias by using data from studies for which no specific result was reported, and it reduced misclassification of exposure; the resources used in the pooled analysis, however, were one order of magnitude greater than those needed for the meta-analysis. Whether a pooled analysis of raw data or a meta-analysis should be carried out depends on the research question; we propose some criteria for this decision.

Case-Control Studies↗
PubMed1998

15-year follow-up of reflux nephropathy by imaging.

Reflux nephropathy i. e. renal scarring associated with vesico-ureteric reflux and urinary tract infection is primarily a diagnosis based on renal imaging. It is well known to be associated with hypertension and renal failure. This has led to regular long-term follow-up of patients, clinically and radiologically. We report the findings of renal imaging in a cohort of 37 patients with reflux nephropathy 15 or more years after successful surgical correction of vesico-ureteric reflux. The degree of renal scarring had been assessed and recorded at the beginning of the study utilizing a score on the original X-ray films. The scar scores of the current intravenous urography (IVU) imaging underestimate the degree of scarring in 35% of cases when compared with the previously recorded scar scores of the original IVU images suggesting a reduction in the renal scar score in some cases over the years. In the current review, concomitant renal images obtained by IVU and 99mTc dimercapto succinic acid (DMSA) scanning were in agreement for scar scoring in only 50% of cases. The original scar score by IVU or the current scar score by either technique does not correlate with blood pressure, urine albumin excretion or glomerular filtration rate (GFR). We conclude that serial long-term two-dimensional renal imaging in children with damaged kidneys who no longer have vesico-ureteric reflux, does not provide additional information that will alter clinical management. However, the changes in renal volume and echogenicity were not assessed in this study.

Adult↗
PubMed1997

Childhood-onset anorexia nervosa: towards identifying a biological substrate.

OBJECTIVE: The etiology of anorexia nervosa is not fully understood, but is probably multifactorial, including a biological substrate. The purpose of this paper is to investigate the possible underlying biological substrate. METHOD: Fifteen children and adolescents aged 8-16 years underwent regional cerebral blood blow radioisotope scans. All fulfilled DSM-IV criteria for anorexia nervosa. Three of the girls had a follow-up scan when they had regained their lost weight. RESULTS: Thirteen of the 15 patients had unilateral temporal lobe hypoperfusion, 8 on the left side and 5 on the right. The abnormality persisted in the 3 girls who had a follow-up scan after weight restoration. DISCUSSION: This is the first report of reduced regional cerebral blood flow in childhood-onset anorexia nervosa, and suggests an underlying primary functional abnormality.

Adolescent↗
PubMed1997

Autoradiographic imaging of cerebral ischaemia using a combination of blood flow and hypoxic markers in an animal model.

Current routine clinical techniques, including angiography and perfusional single-photon emission tomography, can be used to indicate problems in cerebral vascular supply and areas of cerebral hypoperfusion following a stroke, but cannot distinguish between ischaemic core and penumbra. In order to image specifically the penumbra, a method or indicator should be able to define areas with reduced blood flow, and a degree of metabolic compromise. In this context, the tissue could be regarded as hypoxic rather than ischaemic, and we have therefore chosen to investigate the potential of radio-labelled hypoxic markers in the study of ischaemia. In order to combine a hypoxic marker with a blood flow marker we used technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) and iodine-125 iodoazomycin arabinoside (125I-IAZA), during cerebral ischaemia in the rat middle cerebral artery occlusion model. 99mTc-HMPAO and 125I-IAZA were injected simultaneously 2 h following occlusion of the middle cerebral artery, and 5 h before decapitation. Paired autoradiograms were produced and compared. Three distinct patterns emerged from the autoradiograms: slightly decreased perfusion with no uptake of the hypoxic marker indicating an area of misery perfusion; moderately decreased perfusion with concomitant uptake of iodoazomycin arabinoside, a region of hypoxia; and severely decreased perfusion with no retention of the hypoxic tracer. In conclusion, we present a new use for an imaging agent in the investigation of cerebral hypoxia. This agent, IAZA together with HMPAO, provides a means of separating the penumbra into regions of misery perfusion and hypoxia. The potential impact of this may be important in the clinical investigation of stroke.

Animals↗
PubMed1997

Development of a radiopharmaceutical activity schedule for technetium-99m dimercaptosuccinic acid in children based on image quality criteria.

The aim of this study was to determine an activity schedule (amount of administered activity in relation to body weight) for technetium-99m dimercaptosuccinic acid examinations in children, from information present in renal scintigraphic images. Scans from 48 children (5 weeks to 14.8 years old) were graded for image quality according to the clarity of both kidney outline and internal structure. Numerical image data (kidney and background counts, signal-to-noise ratio) were associated with these subjective gradings to formulate three criteria, specifying the required values of the above-measured parameters to yield optimum grades of image quality. When applied to derived functions, a kidney uptake of 20% was required to satisfy the criterion based on the signal-to-noise ratio. Using this value with the other two criteria predicts the form of the weight-dependent activity schedule as a function of imaging time. Examples of schedules for imaging times of 300 and 600 s are compared with a schedule based on surface area.

Adolescent↗
PubMed1997

The characteristics of primary vesico-ureteric reflux in male and female infants with pre-natal hydronephrosis.

OBJECTIVE: To examine the characteristics of primary vesico-ureteric reflux (VUR) in young infants following prenatal hydronephrosis. PATIENTS AND METHODS: The study comprised 155 consecutive infants with VUR detected at a mean age of 8.7 weeks (SD 6.3). Reflux units (n = 236) were analysed for relationships between gender, severity of reflux, exposure to urinary tract infection (UTI) and the presence of focal and generalized types of kidney damage on imaging. Bladder wall thickness (from ultrasonography) was examined in comparison with a further group of 29 males without VUR. RESULTS: Male infants predominated (117 of 155, 75%); bilateral VUR affected the same proportion (52%) of males and females. Most kidneys exposed to VUR (158 of 236. 67%) were normal and of the 78 abnormal kidneys (57 without UTI), 53 showed generalized damage (only eight exposed to UTI) and 71 (91%) were associated with severe (grades IV and V) reflux that predominantly affected males (P < 0.001). Grade V reflux was almost exclusively a male disorder. Most female units (45 of 58, 78%) compared with 46% (82/178) of male units had mild (grades I to III) reflux that was independently associated with normal kidneys. The mean bladder wall thickness was significantly greater for males with VUR than for females with VUR and for males without VUR. CONCLUSIONS: Two distinct but not exclusive patterns of VUR were identified: (i) mild reflux associated with normal kidneys that affected most females and a proportion of males; (ii) severe reflux combined with kidney damage, most likely fetal in origin, that is almost exclusively a male disorder.

Female↗
PubMed1997

Assessment of drainage in PUJ dilatation: pelvic excretion efficiency as an index of renal function.

Renal function is important when assessing the response of a dilated renal pelvis to a diuretic stimulus. Yet there is little in the literature to suggest how this should be undertaken. Our aim was to develop a model which we have called pelvic excretion efficiency (PEE). The PEE, which may be used to assess drainage, is a mathematical model of the ratio of the total kidney excretion to the total amount of isotope extracted from the blood by the kidney. Thirty-three children with a prenatal diagnosis of unilateral renal pelvic dilatation (PUJ) were treated conservatively after birth. As a group, they underwent a total of 164 diuretic DTPA renograms up to the age of 72 months. Drainage was assessed as the response to frusemide (defined as the time for the corrected renal curve to fall to 75% of the maximum value in the frusemide part of the study; T75), response to bladder emptying, a change of posture after frusemide (PM), and PEE. The contralateral normal kidney showed a combination of both 'good' T75 and PM drainage in 51% of renograms while the PEE showed drainage in all. The affected kidney with renal pelvic dilatation showed a combination of both 'poor' T75 and PM drainage in 42% of renograms. The PEE was low in 99% of these 'poor drainage' renograms. The PEE, the ratio of the mathematical model of renal uptake to excretion, is readily calculated and may be a more accurate and specific technique to assess drainage on diuretic renography.

Child↗
PubMed1997

The investigation of renovascular hypertension in children: the accuracy of radio-isotopes in detecting renovascular disease.

Renovascular disease is an important cause of hypertension in children because it is potentially treatable by surgical or angioplasty techniques. The aim of this study was to assess the accuracy of radio-isotopes (DMSA, DTPA and MAG3) combined with the angiotensin converting enzyme inhibitor, captopril, in detecting children with renovascular hypertension. We retrospectively reviewed the ultrasound and pre- and post-captopril radionuclide studies (either DMSA and/or DPTA and/or MAG3) of children with sustained hypertension investigated at our institution. Renal angiography was used as the 'reference technique'. Thirty-nine children, over a period of 10 years, were evaluated: 17 (44%) children had renovascular disease that involved the proximal three divisions of the renal arteries, some of which were amenable to treatment. The overall sensitivity, specificity, positive predictive value and negative predictive value for detecting such renovascular disease, as assessed by changes between pre- and post-captopril radio-isotope studies, were disappointing at 59%, 68%, 59% and 68%, respectively. When considering only abnormalities in post-captopril studies, these indices were 82%, 41%, 52% and 75%, respectively. Three children with potentially treatable renovascular disease were not identified on the captopril studies. We conclude that renal angiography should remain the 'reference technique' in identifying children suspected of renovascular hypertension.

Adolescent↗
PubMed1997

Interictal 99Tc(m) HMPAO SPECT and 1H MRS in children with temporal lobe epilepsy.

PURPOSE: To understand the pathological basis of focal hypoperfusion seen on interictal 99Tc(m) hexamethylpropyleneamine oxime (HMPAO) single-photon-emission computed tomography (SPECT) in intractable temporal lobe epilepsy, and to determine why the technique may be misleading in the localization and lateralization of the seizure focus in some cases. METHODS: Interictal 99Tc(m) HMPAO SPECT and proton magnetic resonance spectroscopy (1H MRS) of the mesial temporal regions were performed in 14 children with intractable temporal lobe epilepsy not caused by a foreign tissue lesion. RESULTS: Hypoperfusion of one temporal lobe ipsilateral to the seizure focus was demonstrated in 10 (71%) of the children; 1H MRS correctly lateralised in eight of these 10. No asymmetry of perfusion of the anterior temporal regions was seen in the remaining four children; on 1H MRS, three of these were bilaterally abnormal but nonlateralising. Repeated SPECT and 1H MRS in three children demonstrated changes over time, the findings from the two techniques being consistent with each other on both the initial and the repeated scans. CONCLUSIONS: Abnormalities demonstrated by 1H MRS correlate well with those seen on interictal SPECT and can help to understand the pathologic basis of these SPECT abnormalities. Furthermore, the presence of bilateral damage can result in an absence of perfusion asymmetry on interictal SPECT.

Adolescent↗
PubMed1997

Ictal cerebral perfusion related to EEG in drug resistant focal epilepsy of childhood.

OBJECTIVES: To evaluate the EEG changes during seizures in children with drug resistant focal epilepsy who demonstrate hypoperfusion at the "seizure focus" interictally, but no perfusion change during the seizure. METHODS: Ictal EEG findings of six children with focal epilepsy who demonstrated hypoperfusion on rCBF SPECT after an interictal injection of (99)Tc(m) HMPAO concordant with the seizure focus, but who did not demonstrate rCBF change after an ictal injection (group 1) were reviewed. These were contrasted with the EEG data of six children matched as closely as possible for age, type of epilepsy, and pathology who did show hyperperfusion at the seizure focus on ictal scan when compared with the interictal study (group 2). RESULTS: The children in group 1 showed slowing of the EEG at the time of the (99)Tc(m) HMPAO injection relative to that seen at the onset of the seizure. Those in group 2 showed rhythmic activity, or sharp waves, or both on EEG at the time of injection. This last change was also seen consistently when the EEG data of a further 13 children who also showed ictal hyperperfusion at the seizure focus were reviewed. CONCLUSION: Ictal rCBF does not invariably increase at the seizure focus in patients with drug resistant focal epilepsy.

Adolescent↗
PubMed1997

The natural history of the multicystic dysplastic kidney in children.

The objective of this study was to examine the natural history of the multicystic dysplastic kidney and the use of sonography for follow-up studies. A retrospective study was performed on 66 children with a radiological diagnosis of multicystic kidney. The change in size demonstrated on sonograms was examined. Adequate follow-up was available on 55 children over a period of 32 months (range 2-69 months). 40/55 of the kidneys underwent a reduction in size, including 22 which were no longer detectable by ultrasound. 10/55 kidneys showed an increase in size and 5/55 showed no change. Reduction in size occurred at a mean age of 84 weeks (range 20-120 weeks). In conclusion, most multicystic kidneys undergo partial or complete involution over the first 2 years of life. The mean size of the multicystic kidney at diagnosis is a poor predictor of eventual outcome.

Follow-Up Studies↗
PubMed1997

Estimation of differential renal function in children with a prenatal diagnosis of unilateral pelvic dilatation.

PURPOSE: We compared the estimation of differential renal function by 99mtechnetium (Tc)-dimercapto-succinic acid (DMSA) and 99mTc-pentetic acid scintigraphic methods for followup of prenatally diagnosed unilateral renal pelvic dilatation. MATERIALS AND METHODS: We retrospectively analyzed differential renal function estimations calculated by static and dynamic methods in time matched test pairs that were included in the charts of 51 children monitored for prenatally diagnosed unilateral renal pelvic dilatation at our institution in a 5-year period. RESULTS: There were 96 test pairs with available archived raw data. Using the analytic method of assessment of agreement between the 2 tests, a 95% limit of agreement of +/-9% was calculated. Of the 96 pairs of tests the results of 94 revealed no significant difference. Subgroup analysis by patient age and operative intervention (13 postoperative pairs) also showed no difference in the results of the 2 tests. CONCLUSIONS: We established the 95% limits of agreement between 99mTc-DMSA and 99mTc-pentetic acid tests of differential renal function to be +/-9% discrepancy in 96 test pairs. During followup of prenatally diagnosed unilateral renal pelvic dilatation the assessment of differential renal function can be made by 99mTc-DMSA static or dynamic diuretic renography techniques. This interchangeability is consistent at all patient ages regardless of operative intervention. Since dynamic diuretic renography provides differential function and drainage data, using 99mTc-DMSA in this context is unnecessary and subjects patients to an unnecessary radiation burden.

Dilatation, Pathologic↗