The Role of 18F-FDG PET/CT in Suspected Intraocular Sarcoidosis and Tuberculosis.

Purpose: To determine the utility of fluorine-18 fluorodeoxyglucose Positron Emission Tomography Computed Tomography (FDG PET/CT) in patients with suspected ocular sarcoidosis (OS) or intraocular tuberculosis (IOTB) in a resource-constrained, TB endemic area.Methods: Independent review of the FDG PET/CTs, Computed Tomography (CT) scans and chest radiographs (CXRs) of patients with suspected OS or IOTB and inconclusive conventional workup.Results: Twenty-nine PET/CTs and CXRs were reviewed, with 38% of PET/CTs and CTs demonstrating evidence of TB or sarcoidosis, compared to 21% of CXRs. The sensitivity, specificity, positive and negative predictive values for PET/CT and CT were similar - 85.7%, 95.5%, 85.7% and 95.5% for OS, and 33.3%, 100%, 100% and 68% for IOTB respectively and for CXR, 57.1%, 100%, 100% and 88% for OS, and 16.7%, 100%, 100% and 63% for IOTB.Conclusion: PET/CT added no significant additional benefit over Chest CT in patients with suspected OS or IOTB.

South African guidelines for receptor radioligand therapy (RLT) with Lu-177-PSMA in prostate cancer.

BACKGROUND: Prostate cancer is an important cause of morbidity and mortality in South Africa, as it is in the rest of the world. In African men, however, prostate cancer tends to follow a more aggressive course when compared to their European counterparts. This is attributed to a plethora of diverse factors of which an underlying genetic component has been shown to be an important aspect. Such differences highlight the need for individualised therapy and for local guidelines. The aim of this guideline is to aid nuclear physicians and other clinicians who manage patients with prostate cancer in the correct identification and treatment of patients who are likely to benefit from receptor radioligand therapy. RECOMMENDATIONS: There are a multitude of treatment modalities available for the treatment of prostate cancer and these therapies may be required at various time points during the course of the disease in any individual patient. A multidisciplinary approach is crucial in deciding which therapy, or combination of therapies, would be most advantageous at particular time points. The multidisciplinary team should include a urologist, oncologist and nuclear medicine physician as a minimum, and should ideally also involve a palliative/pain specialist, a dietician and a psychologist. CONCLUSION: Treatment with 177Lu-PSMA has emerged as a promising systemic modality, which involves the delivery of targeted radiation therapy in the form of ß-particles to sites of tumour tissue. Therapy is provided on an outpatient basis, is well tolerated with relatively few side effects and has a positive effect on overall survival and quality of life. At present, it is used mostly in the setting of advanced, castrate-resistant cancer. Patients are selected (amongst other criteria) based on the prior PSMA-based SPECT/PET/CT imaging (99mTc-,68Ga- or 18F-PSMA), which should demonstrate sufficient receptor expression in order to consider PSMA-based targeted radionuclide therapy. Such imaging of an intended target prior to its therapeutic targeting is known as a theranostic approach.

The College of Nuclear Physicians of South Africa Practice Guidelines on Peptide Receptor Radionuclide Therapy in Neuroendocrine Tumours.

BACKGROUND: Peptide receptor radionuclide therapy (PRRT) for metastatic or inoperable neuroendocrine tumours (NETs) is a systemic therapy which targets somatostatin receptors overexpressed by differentiated NETs for endoradiotherapy. This guideline has been compiled by the College of Nuclear Physicians of the Colleges of Medicine of South Africa, with endorsement by the South African Society of Nuclear Medicine and the Association of Nuclear Physicians to guide Nuclear Medicine Physicians in its application during the management of these patients. RECOMMENDATIONS: Patients with well- to moderately-differentiated NETs should be comprehensively worked-up to determine their suitability for PRRT. Treatment should be administered by a Nuclear Medicine Physician in a licensed, appropriately equipped and fully staffed facility. Patient monitoring is mandatory during and after each therapy cycle to identify and treat therapy-related adverse events. Patients should also be followed-up after completion of therapy cycles for monitoring of long-term toxicities and response assessment. CONCLUSION: PRRT is a safe and effective therapy option in patients with differentiated NETs. Its use in appropriate patients is associated with a survival benefit.

Solitary pulmonary nodule evaluation with 99mTc-methoxy isobutyl isonitrile in a tuberculosis-endemic area.

High prevalence of tuberculosis increases the odds for nonmalignant solitary pulmonary nodules (SPNs). Positron emission tomography (PET) using (18)F-fluorodeoxyglucose is the method of choice for the identification of malignant SPNs requiring curative surgery. However, PET is not widely available. Technetium-99m methoxy isobutyl isonitrile (MIBI) is inexpensive, widely available and shows increased uptake in malignant SPNs. The aim of the present study was to prospectively evaluate the diagnostic value of MIBI single photon emission computed tomography to distinguish between benign and malignant SPNs in a tuberculosis-endemic area. In total, 49 patients with radiologically indeterminate SPNs (single lesion < or =6 cm in diameter) were prospectively evaluated with MIBI. The final diagnosis was established with bronchoscopy, fine-needle aspiration, surgical resection or clinical follow-up for > or =2 yrs. A total of 12 (92%) out of 13 malignant lesions showed increased uptake of MIBI, while no uptake was observed in 33 (92%) out of 36 benign lesions. MIBI uptake indicated malignancy with a sensitivity and specificity of 92% and a negative predictive value of 97%. In this tuberculosis-endemic area, technetium-99m methoxy isobutyl isonitrile single photon emission computed tomography evaluation of solitary pulmonary nodules had a high negative predictive value. Therefore, it has the potential to prevent unnecessary surgical resections of benign nodules and serve as a low-cost alternative when positron emission tomography is not available.

Radiative lifetime of a bound excited state of Te-.

We report on the first experimental study of the lifetime of a bound excited state of a negative ion. A new experimental technique was developed and used to measure the radiative lifetime of the 5p(5) (2)P(1/2) level of Te-. The experiment was performed in a magnetic storage ring, where a laser beam was applied along one of the straight sections. In the experiment the population of the excited J=1/2 level was probed each time the Te- ions passed through the laser field. A decay curve was built up by sampling the population of the excited level of the Te- ions as a function of time after injection into the ring. A multiconfiguration Dirac-Hartree-Fock calculation was performed in conjunction with the experiment. The calculation yielded a radiative lifetime of 0.45 s, in excellent agreement with the measured value of 0.42(5) s.

99mTc-MIBI stress-rest myocardial perfusion scintigraphy in patients with complete left bundle branch block.

BACKGROUND: Patients with complete left bundle branch block (LBBB) often show a false-positive ischaemic pattern in the interventricular septum on thallium-201 (201TI) stress-rest myocardial perfusion scintigraphy. Equivocal results have been reported with technetium-99m labelled hexakis-methoxyisobutyl isonitrile (99mTc-MIBI) in such patients. The aim of this retrospective study was to determine the effect of LBBB on the septal uptake of 99mTc-MIBI during stress-rest single photon emission computed tomography (SPECT) scintigraphy. METHODS: We studied 75 consecutive patients with LBBB, referred for 99mTc-MIBI stress-rest SPECT. Studies were evaluated by visual analysis using a semi-quantitative grading technique. In all patients with abnormal septal segments, the presence or absence of ischaemic heart disease was confirmed either clinically or by means of angiographical examination. RESULTS: Forty-three patients (57.3%) had completely normal studies. Only 15 (20%) had septal abnormalities (11 with reversible and 4 with fixed defects), while 17 patients (22.7% had abnormal segments in areas other than the interventricular septum. Except for 1 patient lost to follow-up, ischaemic heart disease was confirmed in all the patients with septal changes. CONCLUSION: We conclude that 99mTc-MIBI is more specific than 201TI for identifying ischaemic heart disease in the presence of LBBB.

Excretion of technetium 99m hexakismethoxyisobutylisonitrile in milk.

The amount of radioactivity excreted in breast milk following the administration of technetium 99m hexakismethoxyisobutylisonitrile (99mTc-MIBI) to a patient referred for cold spot myocardial scintigraphy was determined. During the first 24 h after administration, only 41.2 kBq 99mTc (0.0084% of the injected dose) was excreted in 448 ml milk with the highest concentration of 0.49 kBq/ml in the first sample. The images obtained show a high concentration of 99mTc-MIBI in the lactating breasts contrary to the very small percentage excreted in the milk. Comparison with various recommendations regarding nursing after administration of radiopharmaceuticals seems to indicate that the administration of 99mTc-MIBI does not necessitate an interruption of breast-feeding.

Optimisation of density and contrast yielded by multiformat photographic imagers used for scintigraphy.

The maximum optical density (MOD) and contrast (characterised by an effective gamma, gamma eff) yielded by multiformat photographic imagers used for scintigraphy, was determined by densitometry of a computer image, which consisted of a pattern of uniform squares containing known counts. A series of clinical scintigrams were photographed using various MOD and gamma eff values, and were graded by three experienced clinicians. It was found that a MOD of 1.6 and a gamma eff of 2.9 yielded optimal images for general use if bone scintigrams are also to be photographed. Lesion detectability in phantom images using extreme MOD and gamma eff values that were still clinically acceptable was determined. At very low false-positive rates (less than or equal to 1%) the higher gamma eff yielded a significantly greater lesion detectability (p = 0.02) at an information density of 2200 counts cm-2 in accordance with White-head's theory. It is concluded that quantification and optimisation of density and contrast factors are important and that the technique described enables quality control of multiformat imagers with respect to these factors.

Hepatobiliary scintigraphy in surgical patients.

Hepatobiliary scintigraphy as an investigative procedure has a definite role in the investigation of the surgical patient with various biliary problems. As it outlines the functional anatomy of the biliary tract, it has been employed for some time in the diagnosis of acute cholecystitis. In addition, it has a place in the investigation of patients with chronic cholecystitis, common bile duct obstruction and biliary leaks and in evaluating the integrity of biliary bypass procedures.