Carcinoma of the breast wire localisation post nuclear medicine sentinel lymph node imaging. Are radiologists receiving a significant dose?

OBJECTIVE: To assess the radiation dose received by the radiologist when performing wire localisation for axillary radio-isotope sentinel node imaging-guided biopsy in patients with impalpable breast cancers treated with breast-preserving excision. When wire placement follows radio-isotope sentinel node imaging (RSNI) the radiologist is exposed to a radiation risk that has never been previously assessed. METHODS: Radiation doses to radiologists performing ultrasound-guided localisation following nuclear medicine sentinel node imaging were measured for procedures on the day of surgery (20 MBq) and also on the day before surgery (40 MBq). These measurements were compared with theoretically calculated doses. RESULTS: Twelve patients showed comparable results between measurements and estimated doses. The mean measured dose was 1.8 muSv (estimated 1.8 muSv) for same-day and 4.8 muSv (estimated 3.4 muSv) for next-day surgery cases. At worst, radiologists who perform 36 wire localisations per year immediately following RSNI receive a radiation dose of 0.17 mSv. CONCLUSIONS: This study highlights the need to inform radiologists of the relative risk when performing pre-surgical localisation after RSNI. This risk should be justified locally in accordance with the total dose received by the localising radiologist. Particular consideration should be given to pregnant staff and the possibility of performing wire localisations before radio-isotope injection.

SPECT neuroimaging in schizophrenia with religious delusions.

Functional neuroimaging techniques such as single-positron emission computed tomography (SPECT) and positron emission tomography (PET) offer considerable scope for investigating disturbances of brain activity in psychiatric disorders. However, the heterogeneous nature of disorders such as schizophrenia limits the value of studies that group patients under this global label. Some have addressed this problem by considering schizophrenia at a syndromal level, but so far, few have focussed at the level of individual symptoms. We describe the first neuroimaging study of the specific symptom of religious delusions in schizophrenia. 99mTc HMPAO high-resolution SPECT neuroimaging showed an association of religious delusions with left temporal overactivation and reduced occipital uptake, particularly on the left.

Delayed gastric emptying in human immunodeficiency virus infection: correlation with symptoms, autonomic function, and intestinal motility.

Gastric emptying may be delayed in HIV infection. We aimed to characterize the pattern of gastric emptying in HIV seropositive subjects and correlate the findings with symptoms, as well as to identify possible etiological factors. Solid gastric emptying was measured using scintigraphy in 54 HIV seropositive subjects and 12 HIV seronegative controls. Gastrointestinal symptoms were evaluated using a standardized numerical score, and autonomic function was assessed using spectral analysis of heart rate variability. Fasting and postprandial duodenojejunal activity was recorded using strain gauge manometry catheters. Gastric emptying rate, but not lag phase, was significantly delayed in HIV-infected subjects, particularly those with enteric infections and more advanced disease. Delayed gastric emptying did not correlate with symptoms, autonomic dysfunction, or small intestinal motility. In conclusion, abnormalities found in autonomic function and gastric emptying in HIV infection are multifactorial in nature. The contribution of upper gastrointestinal motor dysfunction to gastric symptoms in such individuals is unclear.

Natural history of the spontaneous reperfusion of human cerebral infarcts as assessed by 99mTc HMPAO SPECT.

OBJECTIVE: Little is known about the effect of spontaneous reperfusion of human cerebral infarcts. Single photon emission computerised tomography (SPECT) data were analysed from a study using 99Tc(m) HMPAO (99Tc(m) hexamethylpropyleneamine oxime) in human cerebral infarction for the frequency of reperfusion and to see if it affected infarct size, oedema, haemorrhagic transformation, or functional outcome. METHODS: Fifty sequential cases of ischaemic stroke were studied with 124 99Tc(m) HMPAO SPECT at around one day, one week, and three months after stroke along with detailed clinical and functional assessments. RESULTS: Visually apparent reperfusion occurred in 14 of 50 patients (28%) with a mean delay of 5.8 days and reperfusion was seen in seven others in whom it was identified on the basis of changes in perfusion deficit volume. It occurred in 13 of 23 embolic events but only in three of 23 other events. In only two cases did spontaneous reperfusion occur early enough to preserve tissue or function. Reperfusion did not otherwise reduce infarct size, or improve clinical or functional outcome, and was not associated with oedema but an association with haemorrhagic transformation was suggested. Reperfusion significantly decreased the apparent perfusion defect as measured by SPECT one week from the ictus, but was mostly non-nutritional and transient. The mean volume of tissue preserved by nutritional reperfusion was 10 cm3, but this was unequally distributed between cases. Late washout of 99Tc(m) HMPAO from areas of hyperaemic reperfusion may be a good prognostic marker but is a rare phenomenon and too insensitive to be of general applicability. CONCLUSIONS: Spontaneous reperfusion after cerebral infarction occurs in 42% of cases within the first week but is associated with clinical improvement in only 2%. It has few adverse consequences although it may be associated with haemorrhagic transformation.

Abnormal saccadic distractibility in patients with schizophrenia: a 99mTc-HMPAO SPET study.

Recent research has shown that some patients with schizophrenia have a severe impairment in the suppression of reflexive saccadic eye movements in the ANTI-saccade task. This saccadic distractibility has previously been found in patients with lesions of dorsolateral prefrontal cortex, implicating an abnormality of prefrontal cortex. The objective of the present study was to determine the contribution of these and other areas to the ANTI-saccadic abnormality in schizophrenia by functional neuroimaging. Using 99mtechnetium-HMPAO high resolution multidetector single-photon emission tomography, regional cerebral blood flow (rCBF) during performance of the ANTI-saccade eye-movement task was compared, by statistical parametric mapping, in ten male schizophrenic patients on stable antipsychotic medication who had a high distractibility error rate on the task, and eight similar patients who had normal distractibility error rates. Compared with the normal error group, the patients with high error rates showed significantly decreased rCBF bilaterally, in the anterior cingulate, insula, and in left striatum. These same patients also had increased perseverative errors on the Wisconsin Card Sort Test.

Magnitude and time course of acute hypoxic pulmonary vasoconstriction in man.

Acute hypoxic pulmonary vasoconstriction has an established role in the preservation of ventilation-perfusion balance. To further characterize this homeostatic response in man we have attempted to measure both the time course and magnitude of blood flow diversion from single hypoxic lobes. Lobar hypoxia (mean PO2 38 +/- 1.5(SEM)mmHg, mean PCO2 39.9 +/- 0.9 mmHg) was induced by inflating catheter-tip balloons in left upper lobe bronchi during fibreoptic bronchoscopy under local anaesthesia in 8 normal subjects. An index of lobar blood flow was obtained by acquiring dynamic scintigraphic lung images during a continuous intravenous infusion of the short-lived radioisotope krypton-81m dissolved in 5% glucose solution. In 3 subjects blood flow to the occluded lobes was monitored while the lobes were maintained under hyperoxic conditions (mean PO2 127.8 +/- 31.5 mmHg, mean PCO2 40.2 +/- 1.3 mmHg). Under hypoxic conditions the blood flow to the occluded lobes fell to 53% of baseline after 5 min with a mean time constant of 151 +/- 24.8 sec. Under hyperoxic conditions there was no significant change from baseline blood flow. We conclude that this technique has allowed us to monitor both the dynamic and steady state responses of the pulmonary circulation to lobar hypoxia in man.

Regional matching of ventilation and perfusion during lobar bronchial occlusion in man.

1. Ventilation-perfusion balance in the presence of airway obstruction will depend on the efficiency of hypoxic pulmonary vasoconstriction beyond obstructed airways and the matching of redistributed blood flow and ventilation to the rest of the lung. This study investigated the relative importance of these mechanisms in man during experimental bronchial occlusion. 2. The bronchus to the left lower lobe was temporarily occluded with a balloon-tipped catheter during fibreoptic bronchoscopy in eight supine normal volunteers. Respiratory gas tensions were measured within the occluded lobe with a respiratory mass spectrometer. The distribution of ventilation and perfusion was assessed under control conditions and after 5 min of bronchial occlusion by computer analysis of the regional distribution of radioactivity during inhalation of 81mKr gas and following injection of 99mTc-labelled macroaggregated albumin respectively. 3. Respiratory gas partial pressures within the occluded lobes rapidly stabilized at mixed venous gas tensions: PO2 43.4 +/- 2.2 (SEM) mmHg, PCO2 40.2 +/- 1.8 mmHg. During occlusions the arterial oxygen saturation fell from a baseline of 96.3 +/- 0.46% to a nadir of 92.1 +/- 0.43%. Bronchial occlusion produced underventilation in the left lung relative to perfusion, both in the region of the occluded lower lobe and at the lung apex. Relative overventilation occurred in the right lung. 4. It is concluded that arterial hypoxaemia during lobal bronchial occlusion is caused primarily by shunting of mixed venous blood, though the shunt fraction is reduced by approximately 50% by hypoxic pulmonary vasoconstriction. In lung adjacent to obstructed regions reduced compliance may impair ventilation more than perfusion to contribute to hypoxaemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Predictive value of captopril transit renography in essential hypertension and diabetic nephropathy.

Captopril renography was utilized to assess the presence of angiotensin II dependent renovascular dysfunction in (1) 28 patients with mild to moderate essential hypertension (EH) with unimpaired renal function, and (2) 25 hypertensive patients with diabetic nephropathy (HDN). These studies were classified according to the diagnostic criteria outlined by the Working Party on Diagnostic Criteria of Renovascular Hypertension with Captopril Renography and the mean parenchymal transit time (MPTT) was used as an index for detecting the presence of angiotensin II dependent renal haemodynamic change. Patients with EH showed non-significant or non-specific alterations in the MPTT. Four patients in the HDN group showed a significant prolongation of MPTT in the presence of renin-angiotensin-aldosterone activation due to renal artery stenosis, and the other patients in this group showed a significant decrease in MPTT after captopril, consistent with increased blood flow and improved tubular transport function in the presence of microangiopathy only. We conclude that addition of MPTT to the standard diagnostic criteria of captopril renography may be helpful in predicting the beneficial or detrimental impact of angiotensin II inhibition treatment in HDN and in limiting the test protocol in EH to one post-captopril study.

Changes in regional pulmonary blood flow during lobar bronchial occlusion in man.

1. Acute hypoxic pulmonary vasoconstriction is important in the restoration of ventilation-perfusion balance in the presence of regional alveolar hypoventilation. However, the magnitude and time course of this response in man has not been adequately characterized in regions smaller than an entire lung. We have studied the effectiveness of hypoxic vasoconstriction in diverting blood from hypoxic lobes in normal supine subjects, and have documented the redistribution of pulmonary blood flow under these conditions. 2. Lobar hypoxia was induced for 80-300 s by placing occluding balloon-tipped catheters in lobar bronchi during fibreoptic bronchoscopy in 10 normal subjects. Respiratory gas partial pressures within occluded lobes were measured with a mass spectrometer. The percentage reduction in blood flow to the hypoxic lobes was assessed after injection of 99mTc-labelled albumin by gamma-scintigraphy, and compared with a control scan performed 1 week later. A computer program was used to analyse changes in regional pulmonary perfusion. 3. During lobar bronchial occlusion respiratory gas partial pressures rapidly approached reported values for mixed venous partial pressures. After a mean time of occlusion of 3.5 min lobar blood flow was reduced by 47 +/- 5%. During occlusions pulmonary blood flow was not evenly redistributed, but was preferentially redistributed to more cranial lung regions. 4. We conclude that acute hypoxic pulmonary vasoconstriction in occluded lobes is more effective at rapidly diverting pulmonary blood flow away from hypoxic lung regions than has previously been reported in man during unilateral hypoxia of an entire lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Captopril renal scintigraphy in patients with hypertension and chronic renal failure.

UNLABELLED: The aim of this prospective study was to determine the ability of the captopril renogram to reveal the presence of angiotensin II-dependent renovascular disorder in hypertensive patients with chronic renal failure and to assess the possibility of predicting beneficial effect of angiotensin-converting enzyme (ACE) inhibitors on renal function. METHODS: Forty-one patients were evaluated. Baseline renal scintigraphy was performed with 80 MBq of 99mTc-mercaptoacetyltriglycine (MAG3) injected intravenously. Scintigraphy was repeated within a week with 25 mg of oral captopril given 60 min prior to the test. Using the measurements outlined by the Working Party on Diagnostic Criteria of Renovascular Hypertension with Captopril Renography, the patients were categorized into high (7 patients), indeterminate (19 patients) and low (15 patients) probability for renal artery stenosis (RAS). RESULTS: In five of the seven patients with high probability, the presence of RAS was confirmed angiographically and corrective surgical procedure performed in two. In patients with GFR of 10 ml/min/1.73 m2 and/or split renal function of 10% or less, all qualitative and semiquantitative scintigraphic parameters were nonspecific. Mean parenchymal transit time of tracer was a useful parameter to predict the beneficial effect of ACE inhibition therapy in 23 patients (14 low and 9 indeterminate probability of RAS). CONCLUSION: In hypertensive patients with renal failure, captopril renal scintigraphy can be utilized to identify the presence of angiotensin II-dependent renal dysfunction and possibly help to predict the beneficial effect of ACE inhibitor therapy.

The limitations of posterior view ventilation scanning in the diagnosis of pulmonary embolism.

In the diagnosis of pulmonary embolism some centres using 133Xe for comparison with multiple view 99Tcm perfusion images perform only single-breath posterior view ventilation scans. The purpose of this study was to test the reliability of the posterior view ventilation scan in the detection of lobar and segmental defects in ventilation. Occluding balloon catheters were placed in lobar and segmental bronchi during fibreoptic bronchoscopy to produce defects of known anatomical location and size in normal volunteers. Subjects breathed 81Krm/air during the occlusions and images were acquired in the posterior, posterior/oblique and lateral projections. The posterior view images were classified by three experienced nuclear medicine physicians as normal or abnormal. If abnormal, the observers were asked to state which lobe or segment was involved. Segmental defects were missed in 28% of scan readings. Segmental defects were detected but incorrectly sited in 50% of readings and correctly sited in only 22% of readings. The posterior view scan with a defect involving the entire lingula was judged to be normal by all observers. Defects involving the right and left lower lobes were underestimated. We conclude that ventilation scanning techniques that assess the distribution of ventilation in the posterior view alone are unreliable in the detection of segmental and lobar defects, and are likely to increase the false positive rate in the diagnosis of pulmonary embolism.

The underestimation of segmental defect size in radionuclide lung scanning.

Criteria used to place ventilation-perfusion lung scans into categories with different probabilities for pulmonary embolism depend largely on the size and anatomical distribution of defects recognized. These criteria assume that actual segmental defects appear segmental on the lung scan. This study examined the accuracy with which four experienced observers were able to estimate the size of defects of known anatomical location and size, using images of segmental defects in ventilation produced with a bronchoscopic technique and 81mKr. Of the 24 segmental defects produced in this study, 17% were interpreted as being < 25% of a segment; 23% were interpreted as being 25%-50% of a segment; 17% were interpreted as 50%-75% of a segment; 40% were interpreted as being 75%-100% of a segment and 4% were interpreted as being > 100% of a segment. Intra- and interobserver agreement as assessed by the Kappa statistic varied with the number of size categories used but was generally poor. Underestimation of defect size observed in this study may explain why many patients with pulmonary embolism do not have high probability scans. We conclude that the subjective impression of the size of a defect on a lung scan is an unreliable indication of a defect's true segmental or subsegmental nature and that scoring systems based on these criteria should be viewed with caution.

The anatomy of radioisotope lung scanning.

An appreciation of the appearances of segmental and lobar defects on a lung scan is important for the diagnosis of pulmonary embolism. The appearances of segmental and lobar ventilation defects of known anatomical location have been examined on 81mKr ventilation scans in normal human subjects, utilizing fibreoptic bronchoscopy to place temporary occlusions under direct vision at the orifices of lobar and segmental bronchi. Scans were obtained in the posterior, posterior-oblique and lateral projections. Anterior views were included if the defects could not be adequately visualized on the other views. The completeness of the occlusion and the site and size of each defect could be confirmed by ventilating the segment itself with 81mKr via the balloon catheter while the occlusion was maintained. Segmental defects located anterior to the hilum of the lung tended to be optimally visualized on the lateral view and defects located posterior to the hilum tended to be optimally visualized on the posterior-oblique view. The size of segmental defects could be underestimated on the lung scan, especially those involving the anterior and lateral basal segments of both lower lobes. Defects involving the medial basal segment of the right lower lobe were undetectable on any view. By implication, the same conclusions apply to 99mTc perfusion scans.

Factor analysis of dynamic function studies using a priori physiological information.

The computation of physiological factors and factor images by factor analysis in dynamic structures using the constraints of positive factors and spatial distribution of these factors (FADS), currently used by a number of research workers, is investigated. While the positivity constraints used may be quite acceptable physically, they cannot be strictly said to have direct correlations with the underlying physiological mechanisms in a dynamic study. In principle, FADS estimates the underlying model in the absence of a priori physiological information, and therefore, it is possible that in some situations an incorrect model is extracted. A procedure called IBFADS (information-based factor analysis in dynamic structures) is described which incorporates the IM (intersection method) technique previously developed into FADS, in order to reduce the error in the estimation of the correct model. IM uses a constraint based on physiology of one of the dynamic structures in the model. A computer simulated dynamic phantom study is used to demonstrate IBFADS.

A completely automatic method of processing 131I-labelled Rose Bengal dynamic liver studies.

A completely automatic method of measuring Rose Bengal uptake by the liver, expressed in terms of the half-time T1/2, is described. There is no requirement to construct time-activity curves with blood background activity correction as in the conventional regions-of-interest method. All the dixels in the image of a study are used in the actual data analysis. The method is therefore independent of operator influence. The intersection method is offered as an alternative to the manual method. The intersection method uses principal components analysis as a first step in the computation of the intersection of a theory space and a study space. A simple exponential function is used to generate the liver theory space. Sixty 131I Rose Bengal liver function studies were processed by the intersection method. The first forty minutes of patient data were used in the analysis. To validate the new method, computed T1/2 values were compared with those obtained by the manual method. A standard statistical test showed no significant difference between the two methods. Regression analysis gave a value for the coefficient of correlation of 0.89. The intersection method is currently in routine use for the automatic analysis of Rose Bengal liver studies and is faster than the manual method.

Towards automatic analysis of dynamic radionuclide studies using principal-components factor analysis.

A method is proposed for automatic analysis of dynamic radionuclide studies using the mathematical technique of principal-components factor analysis. This method is considered as a possible alternative to the conventional manual regions-of-interest method widely used. The method emphasises the importance of introducing a priori information into the analysis about the physiology of at least one of the functional structures in a study. Information is added by using suitable mathematical models to describe the underlying physiological processes. A single physiological factor is extracted representing the particular dynamic structure of interest. Two spaces "study space, S' and "theory space, T' are defined in the formation of the concept of intersection of spaces. A one-dimensional intersection space is computed. An example from a dynamic 99Tcm DTPA kidney study is used to demonstrate the principle inherent in the method proposed. The method requires no correction for the blood background activity, necessary when processing by the manual method. The careful isolation of the kidney by means of region of interest is not required. The method is therefore less prone to operator influence and can be automated.