Oedema in obesity; role of structural lymphatic abnormalities.

Oedema is a common finding in obesity and its cause is not always clear. Possible causes include impairment of cardiac, respiratory and/or renal function, chronic venous insufficiency and lymphatic problems. Lymphoscintigraphy is the best method to detect structural lymphatic abnormalities that can cause lymphoedema. We reviewed 49 female subjects with pitting oedema who had undergone lymphoscintigraphy, divided in three groups. The first group was comprised of severely obese patients in whom cardiorespiratory causes for oedema had been excluded. The second group consisted of non-obese patients with recognized causes for oedema and the third group was non-obese patients with 'idiopathic' oedema. A standard classification was used to interpret lymphoscintigraphy results. The frequency and severity of lymphoscintigraphic abnormalities was greatest in patients with clinical diagnoses of oedema related to 'recognized causes' (any abnormality in 50% of legs with obstruction in 22%). Obese patients and those with 'idiopathic'oedema had fewer (P=0.02 for both) and milder lymphoscintographic abnormalities (any abnormality 32 and 25%, respectively, obstruction 5 and 3%, respectively), and although the clinical oedema was invariably bilateral, the lymphoscintigraphy abnormalities were usually unilateral. In conclusion, structural lymphoscintigraphic abnormalities are uncommon in obesity and do not closely correlate with the clinical pattern of oedema.

Circulation time in man from lung to periphery as an indirect index of cardiac output.

Circulation time (Ct) between lung and periphery may be a surrogate for cardiac output, estimated here, for the most part, as the time between taking a breath of nitrogen and peripheral detection of a desaturation pulse. Use of pulse oximetry involves an internal, instrument delay; however, using the ear, we found shortening with exercise (12.1 +/- 0.37 sec, at rest; 9.1 +/- 0.25 sec at 100 watts), lengthening after beta-blockade, and lengthening in patients with echocardiographic and clinical left heart failure (8 patients 16.2 +/- 1.1 sec; 6 controls 12.0 +/- 0.5 sec). Pulse oximetry failed, however, to discriminate heart failure from normal in several patients. In patients referred to a department of nuclear medicine for assessment of chest pain, pulse oximetry (finger and ear) showed unacceptable variability. Nuclide delays between lung and carotid artery correlated significantly with the reciprocal of gated SPECT estimated cardiac output (Q(gs)); not so, however, for lung to finger. In normal subjects, an old Waters fast response oximeter gave short, reproducible Ct estimates and a significant correlation with the reciprocal of (indirect Fick) cardiac output (Q(if)). The relationship for normal subjects was: Ct = 0.28 x 60/Q(if) + 2.8 sec (Q(if) in L min.; P slope < .001).

A simple method for correcting left ventricular equilibrium radionuclide angiography for the effects of arrhythmias.

A simple method of correcting equilibrium radionuclide angiographic data for the effects of arrhythmias is proposed. This involves no further acquisition time or inconvenience to the patient. This correction is necessary in patients with marked arrhythmias as the left ventricular time-activity curve (LVTAC) becomes distorted with greater sampling time in the first few frames of the LVTAC than in later frames. This will show on the LVTAC as greater counts in the first few frames and will lead to an overestimation of left ventricular ejection fraction (LVEF) and wall motion. The method proposed normalises each frame to make the contribution from a non-cardiac region constant over the cardiac cycle. Results of the correction are presented and discussed.

The role of indium-labelled leukocyte imaging in pyrexia of unknown origin.

Indium-111-labeled white blood cell scanning is often used in the investigation of pyrexia of unknown origin (PUO) to locate an otherwise occult source of sepsis. From a series of 166 white blood cell studies performed for sepsis, 28 cases of true PUO were identified and reviewed. The sensitivity was 60% and specificity 70%, with a positive predictive value of 38% and negative predictive value of 90%. Only 11% of studies revealed a pyogenic cause for PUO. These results are discussed and the potential role of gallium scanning in PUO is raised.

Regional evaluation of the left ventricular wall motion by radionuclide ventriculography.

ECG gated radionuclide ventriculography was performed in 85 patients with heart disease. From the analysis of time activity curves of each pixel, sets of parametric scans were displayed. Of 496 parametric scans, 192 were normal and 304 showed wall motion abnormalities. There was good correlation between the individual parametric scans (r greater than or equal to 0.815) and between parametric scans and contrast ventriculograms (r greater than or equal to 0.631) in the occurrence and extent of regional wall motion abnormalities. The highest sensitivity was revealed by the peak filling rate (relaxation velocity) scan. The best specificity was shown by scans using the amplitude and phase of the first Fourier element. Good results were obtained by a combination of four parametric images. The ability of the phase scan to detect local dyskinesis may be better than that of the contrast ventriculogram. Changes in parametric scans were related to, but preceded, impairment of left ventricular function (r greater than or equal to 0.513), It is concluded that parametric scans provide a reliable, objective and non-invasive method for regional evaluation of left ventricular function, of great use in the diagnosis of local wall motion abnormalities and their effect on the heart performance.

Isotope bone imaging in suspected scaphoid trauma.

The unreliability of radiological examination in excluding or confirming a suspected scaphoid fracture after carpal trauma is a well-recognised diagnostic problem. This paper explores the role of isotope bone imaging (IBI) in the early identification of carpal bone injury. Abnormal generalized uptake of activity may be seen within the carpus, possibly as a consequence of diffuse soft tissue injury, particularly if imaging is performed within 48 hours of trauma. A focal area of increased uptake related to one carpal bone is suggestive of fracture though the part which ligamentous injury, localized periosteal reaction or incomplete cortical infarction may play in the production of such radionuclide appearances is uncertain. Ninety-nine patients with suspected recent scaphoid fracture but no demonstrable abnormality on radiological examination were subjected to IBI, using 555 MBq (15 mCi) of 99Tcm methylene diphosphonate. Abnormal focal increased uptake (AFIU) was found in 47 patients, this being localized to the scaphoid bone in 26. Of these 47 cases, 19 (42%) showed subsequent radiological evidence of fracture. The results of IBI, in our experience, can only be reliably interpreted if imaging is performed at least 48 hours after injury, though in cases of fracture AFIU may persist for several years. Using this technique, the possibility of fracture can be confidently excluded in that group of patients who show no AFIU. In selected cases of carpal trauma, IBI provides a satisfactory alternative means of identifying the presence and site of localized injury within the carpus and may be used to confidently exclude those patients with non-osseous symptomatology.

Technetium-99m hexamethylpropyleneamineoxime labelled leucocyte scanning in the initial diagnosis of Crohn's disease.

The technetium hexamethylpropyleneamineoxime labelled white cell scan (WCS) is not widely used as a screening test for Crohn's disease primarily because, though sensitive, it is perceived as being insufficiently specific. A series of 42 patients screened for Crohn's disease by this method was analysed retrospectively. The sensitivity was 100% and specificity 91%. This performance was maintained in a subgroup of these patients with very low prevalence of disease. If appropriate criteria for interpretation are used the WCS is a specific as well as a sensitive screening test for Crohn's disease.

The effect of various background protocols on the measurement of left ventricular ejection fraction in equilibrium radionuclide angiography.

Four methods of calculating left ventricular ejection fraction from equilibrium radionuclide angiography have been assessed for inter-observer variability and compared to single-plane contrast cineangiography. The superiority of data-processing methods which use a left ventricular region of interest which follows the changing size of the left ventricle into systole is demonstrated. A simple method of correcting for background is suggested as an alternative for those centres not possessing the necessary software for methods involving a changing region of interest.

Assessment of progression of secondary bone lesions following cancer of the breast or prostate using serial radionuclide imaging.

A serial study on 32 patients with bone metastases following cancer of the breast or prostate was performed over three years. Up to ten sets of images (average of four) per patient were obtained during this period using 99Tcm methylene diphosphonate as the radiopharmaceutical. Ninety-three paired serial images of individual lesions were qualitatively assessed for change by three physicians in nuclear medicine and the results were compared with the quantitative results from computer analysis. The reproducibility of the quantitative approach was determined by the analysis of 20 paired lesions by three physicists. It was found that quantitative changes in uptake of less than 20% between images were generally not detected by the medical observers; a change of 41% had only a 95% probability of being identified as change by the physicians. Although much more reproducible in determining changes in individual lesions, the quantitative approach was found to be inferior to the qualitative assessment of overall change in the majority of cases which involve multiple lesions. The basic assumption that uptake varies proportionally with progression of the bone lesion is discussed an is considered in some instances to be untenable. The conclusion is drawn that the determination of progression from changes of uptake in longstanding lesions is uncertain and is subsidiary in importance to the detection of new lesions.

left ventricular segmental wall motion-a comparison between equilibrium radionuclide angiography and contrast angiography.

The qualitative assessement of left ventricular wall motion using a four-point scale has been compared between left ventricular contrast angiography and equilibrium radionuclide angiography in the 30 degrees right anterior oblique projection. Analysis was carried out for five segments of the left ventricle. Four modes of analysis of equilibrium radionuclide angiography were compared and the reproducibility assessed. Overall accuracy of equilibrium radionuclide angiography compared to contrast angiography was greater than 82% to within one degree of motion. One method using a cine display, averaged 97%. We suggest that equilibrium radionuclide angiography using the cine display is the non-invasive investigation of choice in the screening of patients with suspected regional wall motion abnormalities.

Radionuclide ventriculography: a noninvasive method for the detection and quantification of left-to-right shunts in atrial septal defect.

The present investigation was undertaken to assess a new scintigraphic method for the diagnosis of left-to-right shunts due to atrial septal defect based on the differing stroke volumes of left and right ventricles and to compare it with oxymetric data. Radionuclide ventriculography was carried out after injection of 20 mCi 99mtechnetium-labeled red blood cells. Time-activity curves were obtained from the left and right ventricular regions, and the ratio (A) of end-diastolic-end-systolic count rate differences for the left and right ventricles was calculated. The left-to-right shunt (in percent of the pulmonary flow rate) is then given as 100 X (1 - A/1.43; 1.43 being the previously determined mean value of A in 66 normal patients. In 16 patients with an atrial septal defect and/or partial anomalous pulmonary venous connection a correlation of r = 0.81 was found between those shunts determined by the scintigraphic method and those calculated by oxymetric data. The specificity of the method and the sensitivity in detecting left-to-right shunts exceeding 30% are high. The method is practical and already widely used for determination of ejection fraction end-diastolic volume and other factors. The combination of this technique with other methods for shunt diagnosis such as gamma-fit analysis may prove of special value.

Scintimammography in conjunction with ultrasonography for local breast cancer recurrence in post-mastectomy breast.

The aim of this study was to compare the usefulness of (99)Tc(m)-methoxy-isobutyl-isonitrile (MIBI) scintimammography and ultrasonography, alone and in combination, for the detection of chest wall recurrence in the post-mastectomy breast. A total of 41 consecutive post-mastectomy patients (mean age 46.6 years; median age 45 years) with clinical suspicion of breast cancer recurrence were evaluated. For scintimammography all patients received a 740-900 MBq iv injection of (99)Tc(m)-MIBI; planar images were taken 5-10 min post-injection followed by supine single photon emission CT. Breast ultrasonography was performed in each patient using a 7.5 MHz transducer. Both MIBI uptake and ultrasound findings were documented using standard protocols. All patients had fine needle aspiration cytology biopsy (FNAC), core biopsy or excision biopsy for final tissue diagnosis. Of the 41 patients, 24 had true positive signs of local breast cancer recurrence upon ultrasonography, 10 were diagnosed as true negatives, a sensitivity of 86%, specificity 77%, positive predictive value (PPV) 89%, negative predictive value (NPV) 71% and accuracy 83% (p = 0.001). By comparison, scintimammography findings were found to be true positive in 25 patients and true negative in 12 patients - sensitivity 89%, specificity 92%, PPV 96%, NPV 80% and accuracy 90% (p = 0.001). Using a combination of these two modalities, the combined sensitivity was 100%, specificity 77%, PPV 90%, NPV 100% and accuracy 93%. The high NPV of the two studies in combination implies a potential use of this approach to exclude recurrent disease in patients with a low initial index of suspicion and/or when histology is indeterminate.