Search

Background There is a growing interest in the use of F-18 FDG PET-CT to monitor tuberculosis (TB) treatment response. Tuberculosis lung lesions are often complex and diffuse, with dynamic changes during treatment and persisting metabolic activity after apparent clinical cure. This poses a challenge in quantifying scan-based markers of burden of disease and disease activity. We used semi-automated, whole lung quantification of lung lesions to analyse serial FDG PET-CT scans from the Catalysis TB Treatment Response Cohort to identify characteristics that best correlated with clinical and microbiological outcomes. Results Quantified scan metrics were already associated with clinical outcomes at diagnosis and 1 month after treatment, with further improved accuracy to differentiate clinical outcomes after standard treatment duration (month 6). A high cavity volume showed the strongest association with a risk of treatment failure (AUC 0.81 to predict failure at diagnosis), while a suboptimal reduction of the total glycolytic activity in lung lesions during treatment had the strongest association with recurrent disease (AUC 0.8 to predict pooled unfavourable outcomes). During the first year after TB treatment lesion burden reduced; but for many patients, there were continued dynamic changes of individual lesions. Conclusions Quantification of FDG PET-CT images better characterised TB treatment outcomes than qualitative scan patterns and robustly measured the burden of disease. In future, validated metrics may be used to stratify patients and help evaluate the effectiveness of TB treatment modalities.

Purpose Ventilation–perfusion single-photon emission computed tomography (VP SPECT) plays an important role in pulmonary embolism diagnosis. Rapid results may be obtained using same-day ventilation followed by perfusion imaging, but generally requires careful attention to achieving an optimal count rate ratio (P/V ratio) of ≥ 3:1. This study investigated whether the ratio of counts simultaneously acquired in adjacent primary and Compton scatter energy windows (Eratio) on V SPECT was predictive of final normalised perfusion count rate (PCRnorm) on P SPECT using [99mTc]Tc-macroaggregated albumin (MAA), thus allowing for optimisation of P/V ratios. Methods Same-day VP SPECT studies acquired using standard protocols in adult patients during a 2-year period (training dataset) were assessed. Studies were included provided they were acquired with correct imaging parameters, and injection site imaging and laboratory records were available for quality control and normalised count rate corrections. Extraction of DICOM information, and linear regression were performed using custom Python and R scripts. A predictive tool was developed in Microsoft Excel. This tool was then validated using a second (validation) dataset of same-day studies acquired over a subsequent 7-month period. Accuracy of the prediction tool was assessed by calculating the mean absolute percentage error (MAPE). Results Of 643 studies performed, the scans of 342 participants (median age 30.4 years, 318 female) were included in the training dataset, the analysis of which yielded a significant regression equation (F(1,340) = 1057.3, p R2 of 0.756 and MSE of 0.001089. A prediction tool designed for routine clinical use was developed for predicting final P/V ratio. Of an additional 285 studies, 198 were included in the second (validation) dataset (median age 29.7 years, 188 female). The Excel-based tool was shown to be 91% accurate (MAPE: 9%) in predicting P/V ratio. Conclusion The relationship between the ratio of simultaneously acquired counts in adjacent energy windows on V SPECT and perfusion count rate after administration of a known activity of [99mTc]Tc-MAA can be linearly approximated. A predictive tool based on this work may assist in optimising the dose and timing of [99mTc]Tc-MAA administration in same-day studies to the benefit of patients and workflows.

IntroductionPositron emission tomography-computed tomography (PET-CT) imaging is commonly used to identify nodal involvement in locally advanced cervical carcinoma, but its appropriateness for that purpose among HIV-positive patients has rarely been studied. We analyzed PET-CT findings and subsequent treatment prescribed in patients with locally advanced cervical carcinoma in Cape Town, South Africa.MethodsWe identified a cohort of consecutive cervical carcinoma patients International Federation of Gynecology and Obstetrics (FIGO) stage IIB to IIIB at our cancer center who underwent a planning 18-fluorodeoxyglucose (18FDG) PET-CT scan from January 2015 through December 2018. Demographics, PET-CT findings, and subsequent treatment prescribed were recorded. Patients were selected for PET-CT only if they had no signs of distant disease on staging chest X-ray or abdominal ultrasound; were deemed suitable for radical chemoradiation by the multi-disciplinary team; and had normal renal function. HIV-positive patients ideally had to have been established on continuous antiviral therapy for more than 3 months and to have a CD4 cell count above 150 cells/μL. Small cell and neuroendocrine carcinoma cases were excluded from the study. Differences in demographic and clinical measures between HIV-positive and HIV-negative patients were evaluated by means of t-tests for continuous variables and χ2 tests for categorical variables.ResultsOver a 4 year period, 278 patients—192 HIV-negative (69.1%) and 86 HIV-positive (30.9%)—met the inclusion criteria. HIV-positive patients had a median CD4 count of 475 cells/µL (IQR 307–612 cells/µL). More than 80% of patients had pelvic nodal involvement, and more than 40% had uptake in common iliac and/or para-aortic nodes. Nodal involvement was not associated with HIV status. Fifty-four patients (19.4%) had at least one site of distant metastatic disease. Overall, 235 patients (84.5%) were upstaged following PET-CT staging scan. Upstaging was not associated with HIV status (HIV-negative 83.9% vs HIV-positive 87.2%; p=0.47). Ten patients who did not return for radiotherapy were excluded from the analysis. Following their PET-CT scan, treatment intent changed for 124 patients (46.3%): 53.6% of HIV-positive patients and 42.9% of HIV-negative patients (p=0.11).ConclusionWe found no differences between HIV-positive or HIV-negative patients in nodal involvement or occult metastases, and PET-CT imaging did not lead to, or justify, treatment differences between the two groups. Future studies will evaluate survival and correlation of upstaging with outcome.

Introduction Parathyroidectomy is the choice of treatment for patients with primary and tertiary hyperparathyroidism. Scintigraphic, preoperative localization of hyperfunctioning parathyroid tissue depends on either a delayed washout technique, a subtraction technique, or a combination of the two. The rationale for adopting a combination approach is its presumed superior sensitivity, but there is limited evidence to support this strategy at the cost of patient inconvenience and impact on departmental workflows. Objective To determine whether a combined technique detects any additional lesions during scan interpretation compared to using subtraction-only technique in patients undergoing parathyroid scintigraphy before surgery. Methods A retrospective analysis was performed of parathyroid scans at Tygerberg Hospital between January 2012 and April 2018. Scans were reinterpreted by consensus by three readers, blinded to the original interpretation. A McNemar discordant pairs analysis was then performed. Results A total of 97 participant scans were reviewed (female: 71; mean age: 50.8 years). The number of patients with primary, secondary, and tertiary hyperparathyroidism were 63, 21, and 13, respectively. A total of 192 lesions were identified in this study. While both combined and subtraction-only approaches identified hyperfunctioning parathyroid lesions, only four lesions were identified using the combined technique that were missed by the subtraction technique. This result was not statistically significant (P = 0.125). Conclusion Based on our findings, the combined parathyroid scintigraphic technique does not improve lesion detection and may be dispensed with. Doing so will enhance patient convenience and comfort and improve departmental workflows without compromising lesion detection.

Objectives PET-CT imaging is commonly used as a staging tool to identify nodal involvement in locally advanced cervical carcinoma (LACC). The value of PET-CT for staging HIV-infected patients with locally advanced CC has not been previously described. We analyzed PET-CT findings in a cohort of patients with LACC in Cape Town, SA. Methods Patients with LACC FIGO Stage IIb or IIIB, and were referred, on the basis of stage and the availability of bookings, for PET-CT/radiotherapy planning CT from January 2015 to December 2018. A team of expert nuclear medicine physicians and radiologists reported the PET-CT examinations. Descriptive statistics and chi-squared tests were used to compare patients with and without HIV. Results A total of 286 patients underwent PET-CT. Eighty-nine patients (31.2%) were HIV-positive. Pelvic nodal involvement was notably found in 205 patients (72.4%), including 77.3% of those who had HIV and 70.3% of those who did not (p=0.22); para-aortic nodal disease in 114 patients (42.7% of HIV+ vs 38.8% HIV-, p=0.53); and distant disease in 55 patients (23.6% of HIV+ vs 17.3% HIV-; p=0.22). In total, 223 patients (79.3%), including 81.8% of patients without and 75.0% of patients with HIV (p=0.31), were prescribed standard fractionation EBRT. Twenty-two patients (7.8%) were prescribed hypofractionated EBRT, and 36 patients (12.8%) palliative therapy. Five patients (1.7%) did not return. Conclusions PET-CT imaging found no differences between LACC patients, with and without HIV, in nodal involvement or occult metastases and did not lead to, or justify, treatment differences.

A case of a 50-year-old woman who was referred for the evaluation of possible ACTH-dependent Cushing’s syndrome (CS) is described. The localisation of ACTH-dependent CS remains difficult despite many advances in diagnostic approaches. No single test can accurately determine the location of ACTH excess and therefore a combination of non-invasive imaging, stimulation and suppression tests are advised. The recent advances, current utility and pitfalls of each of these tests are reviewed. If non-invasive tests fail to confidently localise the source of ACTH excess, inferior petrosal sinus sampling (IPSS) should follow. Recent advances improving the diagnostic accuracy of IPSS, such as DDAVP stimulation and simultaneous sampling for prolactin is discussed. Where ectopic ACTH production is suspected, newer nuclear medicine techniques, such as somatostatin receptor imaging that recently became available in South Africa, can be utilised. The role of nuclear medicine imaging in identifying ectopic ACTH production is discussed briefly.Keywords: ACTH, cushing’s disease, pituitary

The estimation of predicted postoperative (PPO) lung function is important in lung resection candidates. We utilized simple anatomical calculations and single-photon emission computed tomography combined with computed tomography (SPECT-CT) to calculate PPO in 24 consecutive patients with impaired pulmonary function who underwent lung resection. PPO values calculated by anatomical calculations and three-dimensional lobar SPECT-CT quantification both correlated well with the postoperative forced expiratory volume in 1 s, with r = 0.825, p < 0.001 and r = 0.796, p < 0.001, respectively. Both techniques fared well at predicting postoperative lung function, but our observations unexpectedly suggested that simple anatomical calculations might be equivalent to three-dimensional SPECT-CT lobar quantification.

These recommendations are intended to serve an important and relevant role in advising referring physicians on the appropriate use of 18F-fluorodeoxyglucose (18F-FDG) and non-18F-FDG positron emission tomography/computed tomography (PET/CT), which can be a powerful tool in patient management in oncology, cardiology, neurology and infection/inflammation. PET is a non-invasive molecular imaging tool that provides tomographic images and quantitative parameters of perfusion, cell viability, proliferation and/or metabolic activity of tissues. These images result from the use of different substances of biological interest (sugars, amino acids, metabolic precursors, hormones) labelled with positron-emitting radionuclides (PET radiopharmaceuticals). Fusion of the aforementioned important functional information with the morphological detail provided by CT as PET/CT provides clinicians with a sensitive and accurate one-step whole-body diagnostic and prognostic tool, which directs and changes patient management. Hence PET/CT is currently the most widely used molecular imaging technology for a patient-tailored treatment approach. In these recommendations we outline which oncological and non-oncological indications are appropriate for PET/CT. Once each combination of pathology and clinical indication is defined, a recommendation is given as: 1. Recommended; 2. Recommended in select cases; 3. May be considered; or 4. Not recommended.

Right ventricular (RV) outflow obstruction (in the form of valvar or supravalvular pulmonary stenosis) is a well-known complication of the Takeuchi procedure. We describe a 13-year-old male with exertional chest pain, pulmonary stenosis, RV hypertrophy, and consequent RV ischemia, which was confirmed using stress echocardiography and single-photon emission tomography.

Preoperative localization of parathyroid lesions is potentially beneficial in renal patients with hyperparathyroidism. The aim of this study was to determine the localizing value of hybrid single-photon emission computed tomography combined with low-dose x-ray computed tomography (SPECT/LDCT) compared with SPECT alone and whether the LDCT improved reader confidence.A retrospective study examined parathyroid scintigraphy results of patients previously referred with a diagnosis of renal hyperparathyroidism. All patients underwent planar scintigraphy using technetium-99m (Tc)-pertechnetate, which was immediately followed with Tc-sestamibi and SPECT/LDCT ∼60 min after sestamibi injection and a delayed static image to assess differential washout. Planar subtraction images were generated. Two nuclear physicians, assisted by a radiologist, reported on planar+SPECT images followed by planar+SPECT/LDCT images.Thirty-seven patients (males: 21; females: 16) were included (mean age 39 years, range: 23.9-55.5). Mean creatinine level was 878 μmol/l (109-1839), mean corrected calcium level was 2.42 mmol/l (1.77-3.64), and median parathyroid hormone level was 156.2 pmol/l (2.4 to201). Twenty-three patients had positive planar and SPECT results (46 lesions), six had positive planar results only, and eight had negative scintigraphy results. In the patients with positive planar and SPECT results, 35 lesions were classified as eutopic and 11 as ectopic. After the addition of LDCT, localization of five eutopic lesions (on SPECT) was amended to ectopic locations (on SPECT/LDCT), principally by identifying posteriorly situated glands. The addition of LDCT led to increased confidence in localization in all cases.Compared with SPECT alone, SPECT/LDCT is beneficial in preoperative localization of lesions in renal hyperparathyroidism.

Introduction Reconstruction influences the quantitative results in PET imaging. The aim of this study was the evaluation of different image reconstruction parameters and their impact on quantification for 18 F-FDG PET of the brain. The reconstruction parameters studied were the number of iterations, smoothing levels (relaxation parameter lambda), and the use of time of flight (TOF) information. In addition, we investigated the effect of signal-to-noise ratio on each of these reconstructed brain images, as well as the effect of scan duration on image quality. Materials and Methods A Philips® Gemini-TF Big bore PET/CT was used for acquiring data of a 3D Hoffman Brain phantom. Data was acquired for 25 minutes in list mode format after injection of 40 MBq FDG, and reconstructed with a voxel size of 2 × 2 × 2 mm 3 using two different iterative reconstruction algorithms: LOR-RAMLA and BLOB-OS. The number of iterations and subsets was varied successive from 3/33 (vendor default) to 30/33, acquisition scan duration from 1 to 25 minutes, lambda was selected as smooth (0.7) and normal (1.0), and TOF was switched on and off for BLOB-OS. The impact on image quality was analyzed in 15 cortical and subcortical brain regions (volumes of interest, VOIs) and for grey and white matter. Results Contrast increased for all regions of the brain and for grey matter/white matter (GM/WM) ratio if the number of iterations increased. Image convergence was reached after fifteen iterations for all different algorithms. When varying the smoothing filter it was found that lambda 1.0 resulted in a faster convergence than 0.7. The coefficient of variation (COV) for all VOIs showed BLOB-OS with TOF to be superior to the other algorithms. The COV results for different scan durations showed only a minimal improvement after 5 minutes in high-activity regions (GM), and after 10 minutes in low-activity regions (WM). Conclusion Based on phantom data 18 F-FDG brain imaging for 10 minutes and reconstructed with the BLOB-OS algorithm including TOF information with 15 iterations is optimal on the Philips Gemini TF Big bore PET/CT. Further analyses is planned using patient data to verify if these findings remain valid in a clinical setting.

Individualised patient treatment approaches demand precise determination of initial disease extent combined with early, accurate assessment of response to treatment, which is made possible by positron emission tomography/computed tomography (PET/CT). PET is a non-invasive tool that provides tomographic images and quantitative parameters of perfusion, cell viability, and proliferation and/or metabolic activity of tissues. Fusion of the functional information with the morphological detail provided by CT as PET/CT can provide clinicians with a sensitive and accurate one-step whole-body diagnostic and prognostic tool, which directs and changes patient management. Three large-scale national studies published by the National Oncologic PET Registry in the USA have shown that imaging with PET changes the intended patient management strategy in 36.5% to 49% of cases, with consistent results across all cancer types. The proven clinical effectiveness and growing importance of PET/CT have prompted the College of Nuclear Physicians of South Africa, in collaboration with university hospitals, to develop a list of recommendations on the appropriate use of fluorine-18-fluorodeoxyglucose (18F-FDG) and non-18F-FDG PET/CT in oncology, cardiology, neurology and infection/inflammation. It is expected that other clinical situations will be added to these recommendations, provided that they are based upon solid clinical evidence. These recommendations are intended to offer advice regarding contemporary applications of PET/CT, as well as indicating novel developments and potential future indications. The CNP believes that these recommendations will serve an important and relevant role in advising referring physicians on the appropriate use of 18F-FDG and non-18F-FDG PET/CT. More promising clinical applications will be possible in the future, as newer PET tracers become more readily available.