H. M. Abdel-Dayem

Mechanism of 201Tl uptake in tumours

We have studied the mechanism of tumour uptake of 201Tl by in vivo and in vitro studies. In a series of patients with breast cancer (n=26), lung cancer (n=56) and lymphoma (n=15), the time course of tumour uptake of 201Tl paralleled that in the myocardium with almost identical times of peak uptake being obtained in tumours and myocardium. In a patient with hepatic metastases from colonic cancer undergoing laparotomy, 99mTc labelled microspheres and 201Tl were injected into the hepatic artery and biopsies of metastatic and normal liver tissue obtained. The tumour to normal liver activity ratios for 201Tl were one tenth of those for 99mTc microspheres. In the final part of the study, cells from a lung cancer tissue culture line were incubated for 30 min with 201Tl with and without the addition of cardiac glycoside, which acts a sodium potassium pump blocker. The cells exposed to the cardiac glycoside showed markedly decreased uptake of 201Tl compared to the cells not so exposed (0.6%±0.1% vs 11.8±0.7.2% of the administered dose). The mechanism of 201Tl uptake of tumours is similar to that in the myocardium. Sodium potassium pump activity appears to be more important than tumour blood flow. 201Tl uptake may provide a useful means of studying tumour viability.

201Tl scintigraphy in the staging of lung cancer, breast cancer and lymphoma.

SummaryTo evaluate 201Tl in the detection of the primary tumour, lymph node involvement and mediastinal spread we have studied a total of 188 patients with histologically proven lung cancer, breast cancer or malignant lymphorna. Ten patients with benign lung disease were also examined. Static images were performed 20 min after intravenous injection of 75 MBq of thallous (201Tl) chloride. The results were compared with those of standard staging procedures including CT scanning and mediastinal exploration. Thallium-201 imaging was highly sensitive in detecting the primary tumour (lung cancer 86%, breast carcinoma 100%, lymphorna 85%), but showed low sensitivity in detecting mediastinal spread or lymph node involvement. Thallium-201 uptake was also observed in active sarcoidosis (one case) and active TB (two cases). We conclude that 201Tl imaging is unlikely to have a clinically useful role in the diagnosis or staging of lung cancer, breast cancer or lymphorna.

Is 99Tcm hexamethyl-propyleneamine oxime uptake in the tissues related to glutathione cellular content?

The relationship between the concentration of tissue glutathione (GSH) content and uptake of 99Tcm HMPAO in Sprague Dawley rats was investigated. The GSH content of rat tissue was depleted with diethyl-maleate (DEM) and the ratio of GSH in control to GSH depleted rat was approximately twice that in the brain, liver, kidney, spleen and lung. The GSH content in all the organs studied except the liver had no statistically significant relationship with the uptake of 99Tcm HMPAO. The apparent increase of radioactivity in the liver was due to longer retention of 99Tcm HMPAO. This longer retention was due to stasis of bile flow as confirmed by subsequent experiments in which cholecystokinin (CCK).was administered to GSH depleted rats and compared to the uptake of GSH depleted rats without injection of CCK.

Left ventricular ejection fraction and volumes calculated from dual gated SPECT myocardial imaging with 99Tcm-MIBI.

Dual gated (DG) cardiac single photon emission computed tomographic (SPECT) studies at end-diastole (ED) and end-systole (ES) were acquired in 27 ischaemic heart disease (IHD) patients after intravenous injection of 555-740 MBq 99Tcm-MIBI. Acquisition parameters were: 180 degrees from LPO to RAO, 32 projections, 64 x 64 matrix, 75 cardiac beats per projection, 80 ms at ED and 80 ms at ES for each cardiac cycle. A computer program was developed to calculate the ED and ES left ventricular (LV) volumes and LV ejection fraction (EF). The computational approach is interactive, semi-automatic and iterative with built-in visual quality control. Short axis slices are used with corresponding ED and ES slices processed as pairs from apex to base. Left ventricular cavity pixels are identified and summed on a slice-by-slice basis. Myocardial pixels are similarly identified. The computed LVEF and ED and ES volumes have been correlated with those from contrast ventriculography (CV). The mean calculated EF for 27 patients was 53.6 +/- 10.7% from DG SPECT versus 55.3 +/- 12.1% from CV (NS). The EF linear correlation coefficient was r = 0.97.

Reproducibility and action levels for gamma camera uniformity.

Deciding on the action level for gamma camera non-uniformity is difficult because the reproducibilities of quality control measurements and service adjustments are usually unknown. This work evaluated the reproducibilities of integral uniformity (IU), differential uniformity (DU) and the corrected relative standard deviation (CRSD). The latter was calculated by removing from the relative standard deviation of the pixel counts the component due to statistical fluctuations. The reproducibility of each parameter was evaluated by analysing 10 intrinsic flood acquisitions with total counts of 2, 5, 10 and 30 million. All three parameters were less reproducible at the lower count densities, but as expected IU and DU also showed higher mean values. CRSD was consistent and highly reproducible, at all count densities. At 10 million counts CRSD had a coefficient of variation (COV) of 1.3% which was a five-fold improvement over the 6.6% and 6.1% found for IU and DU, respectively. The relative sensitivity of IU, DU and CRSD was compared in monthly measurements on 10 gamma cameras over one year. No significant difference in relative sensitivity was demonstrated: a change in camera performance produced about the same percentage change in each parameter. The precision with which service engineers adjust gamma cameras was also assessed by measuring the uniformity of 10 gamma cameras immediately after service adjustment at monthly intervals over one year. Finally, general action levels were defined for IU, DU and CRSD at 7%, 5% and 2.5% respectively.

Evaluation of renal functional changes after extracorporeal piezoelectric lithotripsy (EPL) by radionuclide studies.

Extracorporeal piezoelectric lithotripsy (EPL) has been recently introduced as a non-invasive method for treatment of renal and gall bladder stones. Thirty seven patients treated with EPL for renal calculi were the subjects of radionuclide renal studies. The aim was to evaluate the effects of EPL as a new technology by radionuclide renography. 99 Tcm-DTPA and 99 Tcm-DMSA studies were performed pre-EPL and one day and one week post-EPL. Various parameters of the sequential radionuclide studies were evaluated. One day post-EPL, changes in parenchymal transit time index, relative uptake function, glomerular filtration rate, time-activity curves and kidney dimensions were observed. At one week post-EPL, different parameters returned to baseline status in the majority of cases. The study indicates that EPL has a variety of effects on the kidney that could be demonstrated and followed by sequential radionuclide renal studies. Furthermore the study suggests spacing of EPL sessions by approximately one week.

Segmental analysis of SPECT 99mTc-methoxy isobutyl isonitrile and 201Tl myocardial imaging in ischaemic heart disease.

To study the potential usefulness of99mTc-methoxy isobutyl isonitrile (99mTc-MIBI) as a substitute for201Tl in assessing patients with ischaemic heart disease, 24 patients underwent 1 day rest and exercise99mTc-MIBI single photon emission computerised topography (SPECT) 1 week after SPECT exercise201Tl. All patients were catheterized within 1 month after myocardial imaging. In 17 patients, resting first pass radionuclide angiography (FPRNA) was performed with99mTc-MIBI. The heart to lung ratio for99mTc-MIBI and201Tl was calculated both at rest and exercise. The segmental analysis for myocardial perfusion reveals that 87/96 segments (91 %) were correctly classified by SPECT201Tl and 84/96 segments (88%) were correctly classified by99mTc-MIBI. A significant correlation was present between LVEF measured by99mTc-MIBI FPRNA and contrast ventriculography (r = 0.85,P < 0.0001). The heart to lung ratio both at rest and exercise for99mTc-MIBI is significantly higher than201Tl (P < 0.01 and <0.001 respectively). We conclude that99mTc-MIBI is a promising agent for simultaneous evaluation of myocardial perfusion and cardiac function.

Quantitative analysis of cardiac function: comparison of electro-cardiogram dual gated single photon emission tomography, planar radionuclide ventriculogram and contrast ventriculography in the determination of LV volume and ejection fraction.

A dual gated tomography (DGT) program for end systolic and end diastolic acquisition and subsequent processing for calculation of LVEF, end diastolic and end systolic volumes (EDV, ESV) has been evaluated in 20 healthy volunteers (25 years–40 years) and 45 patients (25 years–60 years): 20 with ischaemic heart disease and 25 with valvular heart disease (VHD). All had biplane multigated blood pool (MUGA) studies in the 40° LAO projection using in vivo 99mTc- RBCs, immediately followed by DGT. The results in the patients group were correlated with contrast ventriculography (CV). In the volunteer group, the normal values for LVEF, EDV and ESV measured with DGT were found to be 63%±10%, 91 ml±6 ml and 30 ml±6 ml and r value for the LVEF=0.91 compared with MUGA. In the IHD group, r values compared with CV were 0.915 and 0.97 for the EDV and ESV and 0.934 for the LVEF. Compared with the MUGA, the r value for LVEF was 0.883. In the VHD group, r values were 0.98 for both the EDV and ESV and 0.948 for the LVEF (P<0.002) compared with CV and 0.789 for the LVEF compared with the MUGA. We feel that DGT is an accurate and reproducible technique for LV function measurements.

A preliminary report on the impact of 18F-FDG PET/CT in the management of paediatric head and neck cancer

IntroductionPaediatric head and neck malignancy accounts for 5% of all paediatric cancers. The choice of treatment and prediction of prognosis depend on the histological type of tumour, initial staging, evaluating treatment response and detection of early recurrence. Conventional imaging modalities have many limitations. Positron emission tomography/computed tomography (PET/CT) is more accurate; however, so far, the literature lacks reports of large groups of paediatric patients. AimTo report the role of PET/CT in factors affecting the choice of treatment at the newly established Children Cancer Hospital in Cairo, Egypt, which is one of the busiest dedicated paediatric oncology centres in the world. All findings were proven by histopathology, radiology and by clinical follow-up. Patient populationThirty-six paediatric patients (30 boys and six girls) with various histologically proven head and neck cancers were included in this study. Their age ranged from 2 to 17 years. High-resolution diagnostic CT and/or MRI of the head and neck, and in relevant cases also of the chest and the abdomen, were performed in all patients at a mean interval of 1.6 weeks (range, 1–3 months) before the PET/CT study. Results of PET/CT were compared with the findings of these conventional imaging modalities. ResultsThe sensitivity, specificity, accuracy, positive and negative predictive values of PET/CT against the conventional imaging were as follows: sensitivity 100 and, 53%, specificity 89.5 and 47%, accuracy 94.5 and 50%, positive predictive value 89.5 and 47% and negative predictive value 100 and 53% respectively. PET/CT changed patient management in 50% of the cases. ConclusionPET/CT in paediatric head and neck carcinoma is more accurate than conventional imaging. Therefore, it also has a significant impact on further patient management. We recommend that it should be the first imaging modality for all purposes in initial staging, evaluating treatment response and follow-up in paediatric head and neck carcinoma.

Indium-111 monoclonal anti-myosin antibody in assessing skeletal muscle damage in trauma.

Accurate assessment of the severity of soft tissue damage particularly skeletal muscle associated with fractures in trauma patients is important in determining the plan of management and prognosis. We used Indium-111 labelled anti-myosin to determine the extent of skeletal muscle injury in five patients involved in traumatic accidents. We found abnormal uptake in all 20 sites of muscle injury in four patients, 13 at the sites of fractures and seven away from fracture sites. There was good correlation between the degree of uptake and the extent of muscle injury. No uptake was seen in a case with no fracture and no muscle injury. At surgery this case proved to be haemarthrosis of the left knee. Indium-111 anti-myosin scanning is a potentially sensitive and useful technique in assessing extent of acute muscle injury in trauma patients.