Role of FDG PET-CT in the treatment management of Hodgkin lymphoma

Fluorodeoxyglucose (FDG) positons emission tomography (PET)-computed tomography (CT) is used in many ways at baseline and during the treatment of patients with Hodgkin lymphoma. Many properties of the technique are used in the different steps of patient's management. Initial staging with PET-CT is more accurate than conventional imaging and PET-CT also became the gold standard imaging at the end of treatment with a negative PET-CT mandatory for reaching a complete remission. Early assessment of response by PET-CT is one of the most powerful prognostic factors for progression-free survival of patients with localized and advanced stages and allows guiding treatment. Conversely, previous studies showed that there is no role of FDG PET-CT for the patient's follow-up.

A systematic review of the predictive value of 18F-fluoro-2-deoxyglucose positron emission tomography on survival in locally advanced rectal cancer after neoadjuvant chemoradiation

AIM

Treatment of locally advanced rectal cancer (LARC) includes preoperative radiation therapy with or without chemotherapy followed by radical surgery, but the clinical outcome is uncertain. A systemic review was carried out to determine the predictive value of (18)F-fluoro-2-deoxyglucose positron emission tomography ((18)FDG-PET) for assessing disease-free (DFS) and overall survival (OS) in LARC.

METHOD

A literature search (PubMed/MEDLINE, EMBASE, Cochrane) up to January 2012 to identify full papers with sequential (18)FDG-PET and survival data, using indexing terms and free text words. The inclusion criteria were: a study of at least 10 patients, having sequential (18)FDG-PET imaging before and after adjuvant chemoradiation and a minimal follow-up of 24 months. Studies were selected by two of the authors. A meta-analysis was performed for DFS and OS using the hazard ratio (HR) as the primary outcome.

RESULTS

Five eligible studies were identified including 330 patients (mean age 63 years, 64% men), in which PET-CT or PET imaging was used. The American Joint Committee on Cancer stage distribution was as follows: Stage I, 2%; Stage II, 44%; Stage III, 52%; Stage IV, 1%. The pooled HRs for complete metabolic response versus partial or no response were 0.39 (95% CI 0.18-0.86; P = 0.02) for OS and 0.70 (95% CI 0.16-3.14; P = 0.64) for DFS. The lack of significance for DFS might be explained by different follow-up characteristics. There was also clinical heterogeneity among the different studies.

CONCLUSION

This systematic review indicates that complete metabolic response on sequential (18)FDG-PET data after preoperative chemoradiation of LARC is predictive of OS, but not of DFS.

Polyurethane does not protect better than polyvinyl cuffed tracheal tubes from microaspirations

BACKGROUND

Mechanically ventilated patients are prone to develop ventilator associated pneumonia due to microaspirations of subglottic secretions around the endotracheal tube cuff (usually constructed of polyvinyl material). A novel polyurethane cuff has been designed to minimize these leakages. The aim of the study was to compare the tracheal sealing capacities between the two tubes.

METHODS

Twenty-nine consecutive patients from whom tracheal intubation was necessary as part of their care were randomized to receive either a polyvinyl HI-LO Evac® or a polyurethane SEALGUARD Evac® endotracheal tube. Patients requiring emergency intubation, with unstable hemodynamics or history of tracheal/laryngeal disease were excluded. For the entire study, cuff pressure was set at 30 cmH2O, and ventilator parameters were adjusted for a plateau pressure ≤30 cmH2O; Patients were fasting, placed in a strict 45° position during 12 hours and sedated if needed. After injection of 74 MBq 99mTc-DTPA diluted in 5 mL 0.9% NaCl just above the cuff, tracheal radioactivity was assessed sequentially (hourly from T0 to T6, then T8 and T12 hours) using a scintillation camera.

RESULTS

Sixteen polyurethane and 13 polyvinyl tubes were compared. Leakages were observed in 11/29 patients (38%) (5/16 polyurethane and 6/13 polyvinyl tubes [P=NS]). Leakages occurred more often in female (7/8) than in male patients (4/21) (P<0.001). Microaspirations were decreased with larger tubes (size 9 vs. ≤8.5: 24% vs. 75%; P=0.01), whatever the cuff membrane.

CONCLUSION

These preliminary results suggest that both tubes are poorly effective in preventing microaspirations.

Radioimmunotherapy with radioactive nanoparticles: biological doses and treatment efficiency for vascularized tumors with or without a central hypoxic area

PURPOSE

Radioactive atoms attached to monoclonal antibodies are used in radioimmunotherapy to treat cancer while limiting radiation to healthy tissues. One limitation of this method is that only one radioactive atom is linked to each antibody and the deposited dose is often insufficient to eradicate solid and radioresistant tumors. In a previous study, simulations with the Monte Carlo N-Particle eXtended code showed that physical doses up to 50 Gy can be delivered inside tumors by replacing the single radionuclide by a radioactive nanoparticle of 5 nm diameter containing hundreds of radioactive atoms. However, tumoral and normal tissues are not equally sensitive to radiation, and previous works did not take account the biological effects such as cellular repair processes or the presence of less radiosensitive cells such as hypoxic cells.

METHODS

The idea is to adapt the linear-quadratic expression to the tumor model and to determine biological effective doses (BEDs) delivered through and around a tumor. This BED is then incorporated into a Poisson formula to determine the shell control probability (SCP) which predicts the cell cluster-killing efficiency at different distances "r" from the center of the tumor. BED and SCP models are used to analyze the advantages of injecting radioactive nanoparticles instead of a single radionuclide per vector in radioimmunotherapy.

RESULTS

Calculations of BED and SCP for different distances r from the center of a solid tumor, using the non-small-cell lung cancer as an example, were investigated for 90Y2O3 nanoparticles. With a total activity of about 3.5 and 20 MBq for tumor radii of 0.5 and 1.0 cm, respectively, results show that a very high BED is deposited in the well oxygenated part of the spherical carcinoma.

CONCLUSIONS

For either small or large solid tumors, BED and SCP calculations highlight the important benefit in replacing the single beta-emitter 90Y attached to each antibody by a 90Y2O3 nanoparticle.

Is a lung perfusion scan obtained by using single photon emission computed tomography able to improve the radionuclide diagnosis of pulmonary embolism?

Planar pulmonary scintigraphy is still regularly performed for the evaluation of pulmonary embolism (PE). However, only about 50-80% of cases can be resolved by this approach. This study evaluates the ability of tomographic acquisition (single photon emission computed tomography, SPECT) of the perfusion scan to improve the radionuclide diagnosis of PE. One hundred and fourteen consecutive patients with a suspicion of PE underwent planar and SPECT lung perfusion scans as well as planar ventilation scans. The final diagnosis was obtained by using an algorithm, including D-dimer measurement, leg ultrasonography, a V/Q scan and chest spiral computed tomography, as well as the patient outcome. A planar perfusion scan was considered positive for PE in the presence of one or more wedge shaped defect, while SPECT was considered positive with one or more wedge shaped defect with sharp borders, three-plane visualization, whatever the photopenia. A definite diagnosis was achieved in 70 patients. After exclusion of four 'non-diagnostic' SPECT images, the prevalence of PE was 23% (n =15). Intraobserver and interobserver reproducibilities were 91%/94% and 79%/88% for planar/SPECT images, respectively. The sensitivities for PE diagnosis were similar for planar and SPECT perfusion scans (80%), whereas SPECT had a higher specificity (96% vs 78%; P =0.01). SPECT correctly classified 8/9 intermediate and 31/32 low probability V/Q scans as negative. It is concluded that lung perfusion SPECT is readily performed and reproducible. A negative study eliminates the need for a combined V/Q study and most of the 'non-diagnostic' V/Q probabilities can be solved with a perfusion image obtained by using tomography.

Guidelines for brain radionuclide imaging. Perfusion single photon computed tomography (SPECT) using Tc-99m radiopharmaceuticals and brain metabolism positron emission tomography (PET) using F-18 fluorodeoxyglucose. The Belgian Society for Nuclear Medicine

The purpose of these guidelines is to assist nuclear medicine practitioners in recommending, performing, interpreting, and reporting the results of brain perfusion SPECT studies using Tc-99m radiopharmaceuticals and brain metabolism PET studies using F-18 fluorodeoxyglucose (FDG). These guidelines have been adapted and extended from those produced by the Society of Nuclear Medicine (Juni et al., 1998) and the European Association of Nuclear Medicine by a Belgian group of experts in the field trained in neurology and/or nuclear medicine. Some indications are not universally approved (e.g. brain death), but largely supported by the literature. They have been included in these guidelines in order to provide recommendations and a standardised protocol.

Gastric acidity and duodenogastric reflux during nasojejunal tube feeding in mechanically ventilated patients

OBJECTIVE

In order to prevent gastric microbial overgrowth, which may complicate nasogastric feeding, administration of nutrients more distally into the gut has been advocated in intensive care patients, as it offers the advantage of keeping the stomach empty and acid. In this study, we assessed the impact of jejunal feeding upon gastic pH in a group of mechanically ventilated, critically ill patients, with special focus on duodenogastric reflux as a possible cause of gastric alkalinization during jejunal nutrition.

DESIGN

Prospective experimental study.

SETTING

Multidisciplinary intensive care unit of a university hospital.

PATIENTS AND METHODS

Gastric pH was recorded by continuous pHmetry over a 4-h period of fasting followed by a 4-h period of nasojejunal feeding at 100 kcal/h in 21 mechanically ventilated, critically ill patients. To determine the contribution of duodenogastric reflux to modifications of gastric acidity, the diet was traced with [(111)In] DTPA (pentetic acid) in 11 of these 21 patients; gastric contents were aspirated every 30 min, then analysed for measurement of radioactivity, glucose, and bile acid concentration.

MEASUREMENTS AND RESULTS

Median intragastric pH increased slightly from 1.59 (1.20-2.73; interquartile range) (fasting) to 2.33 (1.65-4.64) (feeding) (p = 0.013), and the length of time that the pH was 4 or above increased from 1 (0-24) to 9 (0-142) min (p = 0.026). The variability of pH values and the number of acute alkalinization episodes did not change between the two phases. In 10 of 11 patients in which the diet was labeled with [(111)In] DTPA, reflux was documented at a given time of the feeding period. Bile acid concentrations in the stomach increased from 392 (61-1076) (fasting) to 1446 (320-2770) micromol/l (feeding) (p = 0.010) and mean glucose concentration increased from 59 (28-95) to 164 (104-449) mg/dl (p = 0.006).

CONCLUSION

Duodenogastric reflux is common in mechanically ventilated critically ill patients with nasojejunal feeding tubes. It occurs both during fasting and during nasojejunal feeding. During nasojejunal feeding, moderate alkalinization of the gastric contents occurs as a result of bile and nutrient reflux.

Cerebral metabolic differences in Parkinson's and Alzheimer's diseases matched for dementia severity

Despite controversial clinicopathological distinctions between Parkinson's disease with dementia (PDD) and Alzheimer's disease (AD), similar patterns of metabolic reduction in the posterior brain were reported previously using PET with [18F]fluorodeoxyglucose. The current study was designed to examine more specific regional differences in cerebral glucose metabolism between PDD and AD using accurate and objective brain mapping techniques.

METHODS

This study included nine normal subjects, nine PDD patients and nine AD patients. PDD and AD groups were matched carefully for age, sex and general dementia severity as measured by Mini-Mental State Examination and Clinical Dementia Rating scales. Each subject underwent [18F]fluorodeoxyglucose-PET and neuropsychological testing. After anatomic standardization of PET image sets and stereotactic data extraction, absolute and normalized cerebral metabolic rates were assessed by region of interest and pixel-by-pixel analyses.

RESULTS

PDD and AD showed global glucose metabolic reduction with similar regional accentuation involving the lateral parietal, lateral temporal and lateral frontal association cortices and posterior cingulate cortex in comparison to normal controls. When comparing between PDD and AD, however, PDD showed greater metabolic reduction in the visual cortex and relatively preserved metabolism in the medial temporal cortex.

CONCLUSION

Although a common feature of metabolic abnormalities in the posterior brain exists in PDD and AD, the presence of regional metabolic differences suggests different degrees and combinations of disease specific underlying pathological and neurochemical processes.

Effects of dopaminergic drug treatments on in vivo radioligand binding to brain vesicular monoamine transporters

The effects of various dopaminergic drug treatments on the in vivo regional brain distribution of high-affinity radioligands ([11C]dihydrotetrabenazine and [11C]methoxytetrabenazine) for the rat brain vesicular monoamine transporter (VMAT2) were determined. Acute treatments with reserpine (2 mg/kg i.p.), tetrabenazine (10 mg/kg i.v.) or related benzoisoquinolines significantly reduced radiotracer binding in vivo. In contrast, radiotracer distributions remained unchanged after treatments with other dopaminergic drugs, whether given by single injection (haloperidol, 1 mg/kg i.p., pargyline 80 mg/kg), repeatedly (pargyline, 80 mg/kg s.c., 14 days), or by continuous infusion (deprenyl, 10 mg/kg/day, 5 days; L-DOPA methyl ester 100 mg/kg/day, 5 days). Repeated injections of tetrabenazine (5 mg/kg i.p., twice daily, 3 days) did not alter in vivo radioligand binding measured after allowing drug washout from the brain. These studies support the proposal that in vivo PET imaging of VMAT2 radioligands in patients with extrapyramidal movement disorders will not be affected by concurrent use of L-DOPA or deprenyl.

Alzheimer disease: improved visual interpretation of PET images by using three-dimensional stereotaxic surface projections

PURPOSE

To compare the diagnostic usefulness of three-dimensional (3D) stereotaxic surface projection (SSP) with that of standard transaxial display in brain positron emission tomography (PET) in Alzheimer disease (AD).

MATERIALS AND METHODS

Standard transaxial section display and 3D-SSP PET image sets obtained after administration of 2-deoxy-2-[fluorine-18]fluoro-D-glucose in 39 patients with probable AD (aged 53-82 years; 15 men, 24 women) and 40 subjects without AD (aged 21-78 years; 14 men, 26 women) were randomly interpreted. Receiver operating characteristic (ROC) analysis was performed.

RESULTS

Diagnostic performance was superior with 3D SSP (Az[section]=0.94,Az[3D SSP]=0.99[Az=area under the ROC curve];P=.043). With 3D SSP, diagnosis of AD was equally good in beginners and experts. The sensitivity and specificity in questionable or mild dementia were 94% and 99% with 3D SSP and 79% and 88% with standard transaxial display.

CONCLUSION

Accuracy of detecting AD was improved in PET with 3D SSP.

In vitro and in vivo studies of benzisoquinoline ligands for the brain synaptic vesicle monoamine transporter

Tetrabenazine is a high-affinity inhibitor of the vesicular monoamine transporter in mammalian brain. As part of a program to develop in vivo imaging agents for these transporters in human brain, a series of 2-alkylated dihydrotetrabenazine ligands was synthesized and evaluated in vitro and in vivo for binding to the brain vesicular monoamine transporter. Additions of organometallic reagents to tetrabenazine produced 2-methyl, 2-ethyl, 2-n-propyl, 2-isopropyl, and 2-isobutyl derivatives of dihydrotetrabenazine. The stereochemistry and conformation of the addition products were thoroughly verified by two-dimensional NMR techniques. All of these alkyl derivatives displayed in vitro affinity for the vesicular monoamine transporter binding site in rat brain using competitive assays with the radioligand [3H]methoxytetrabenazine. Except for the isopropyl derivative, all compounds when tested at 10 mg/kg iv showed an ability to inhibit in vivo accumulation of the radioligand [11C]methoxytetrabenazine in the mouse brain striatum. Derivatives with small alkyl groups (methyl, ethyl) were more effective than those with large groups (propyl, isobutyl). These studies suggest that large groups in the 2-position of the benzisoquinoline structure will significantly diminish both in vitro and in vivo binding of these compounds to the vesicular monoamine transporter.

The vesicular monoamine transporter is not regulated by dopaminergic drug treatments

The number of neuronal synaptic vesicular monoamine transporters (vesicular monoamine transporter type 2; VMAT2) has been recently proposed as an index of monoamine presynaptic terminal density. The present study investigated the possible regulation of the vesicular monoamine transporter. Rats were treated for 2 weeks with drugs known to influence dopaminergic neurotransmission, including those commonly used in the treatment of Parkinson's disease. Autoradiographic assays were performed using [3H]methoxytetrabenazine, [3H]raclopride, and [3H]WIN 35,428 ([3H]2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane) to measure vesicular monoamine transporter, dopamine D2 receptor and synaptic plasma membrane dopamine re-uptake site bindings, respectively. None of the drug treatments significantly modified levels of vesicular monoamine transporter binding. In contrast, both dopamine D2 receptors and dopamine re-uptake sites were altered by some of the treatment regimens. These data extend preliminary results that suggest the vesicular monoamine transporter is not easily regulated and confirm the plasticity of dopamine D2 receptors and the dopamine re-uptake site. Measures of striatal vesicular monoamine transporter density may, thus, provide objective estimates of monoaminergic innervation in neurodegenerative diseases, unaffected by the use of symptomatic therapies.

Binding of alpha-dihydrotetrabenazine to the vesicular monoamine transporter is stereospecific

The two enantiomers of alpha-dihydrotetrabenazine were separated using chiral high performance liquid chromatography. The (+)-isomer showed high affinity in vitro (Ki = 0.97 +/- 0.48 nM) for the vesicular monoamine transporter (VMAT2) in rat brain striatum, whereas the (-)-isomer was inactive (Ki = 2.2 +/- 0.3 microM). Each isomer was then synthesized in carbon-11 labeled form, and regional brain biodistributions in mice determined after intravenous injection. Only (+)-alpha-dihydrotetrabenazine showed selective and specific accumulations in regions of dense monoaminergic innervation (e.g., striatum, hypothalamus), which could be blocked by coinjection of unlabeled tetrabenazine. Binding of alpha-dihydrotetrabenazine to the vesicular monoamine transporter is thus stereospecific.

Brain tumor imaging with PET and 2-[carbon-11]thymidine

METHODS

To assess the potential of thymidine for imaging brain tumors, 20 patients with untreated (n = 14) and recurrent (n = 6) supratentorial intracranial tumors were studied with PET by using 2-[11C]thymidine (Tdr), and the results were compared with [18F]fluorodeoxyglucose (FDG) PET data.

RESULTS

Blood analysis consistently revealed a rapid clearance of the intact Tdr together with the appearance of CO2/HCO3- that, with time, accounted for approximately 70% of the total blood activity. As soon as 10 min after tracer injection, brain images showed a low and homogeneous Tdr distribution over the normal brain structures (cortex-to-blood ratio approximately 1). Visual and quantitative analysis revealed increased Tdr uptake (tumor-to-cortex ratio > or = 1.2) in 11 of 14 untreated tumors and in 5 of 6 recurrent tumors. No correlation was found between Tdr uptake and tumor grade. In 12 of the 14 untreated tumors, FDG uptake was low (tumor-to-cortex ratio: 0.83 +/- 0.79), but a FDG hot spot was visualized in 8 of 10 high-grade and in none of the 4 low-grade tumors. FDG uptake was consistently low in recurrent tumors (tumor-to-cortex ratio: 0.49 +/- 0.19), and PET-FDG was negative in 3 of the 6 cases.

CONCLUSION

These data indicate the feasibility of brain tumor imaging with Tdr and suggest the potential clinical usefulness of the method in the detection of tumor recurrences. The specificity of the method remains, however, to be investigated.

Noninvasive measurement of liver regeneration with positron emission tomography and [2-11C]thymidine

The feasibility of liver regeneration determination with [2-11C]thymidine and positron emission tomography was investigated in partially hepatectomized rats. Serial tomographic scans were performed over a 120-minute period after injection of [2-11C]thymidine together with tritium-labeled thymidine. Within 10 minutes after injection, positron emission tomography scans showed a twofold higher hepatic uptake in regenerating than in nonregenerating livers. Time-activity curves over the liver area indicated that the maximal uptake was followed by a faster decrease of 11C radioactivity in controls than in regenerating animals, so that total 11C activity remaining in the liver at 120 minutes accounted for 68% of maximum in regenerating and only 38% in controls. Tissue distribution studies performed at 120 minutes showed that total 11C radioactivity, expressed in percent injected dose per gram, was six times higher in regenerating livers than in controls (0.62% +/- 0.07% in regenerating livers and 0.10% +/- 0.03% in nonregenerating livers; P less than 0.001) and correlated with 3H radioactivity measured in the nuclear fraction (r = 0.92; P less than 0.001). When the hepatic uptake was expressed in percent of dose per organ, the difference between both groups increased (2.31% +/- 0.23% in regenerating livers and 0.29% +/- 0.02% in nonregenerating livers; P less than 0.001) because of higher weight of regenerating livers than of nonregenerating livers (3.83 +/- 0.11 g in regenerating livers and 2.96 +/- 0.16 g in nonregenerating livers; P less than 0.001). In other organs examined, no difference in 11C radioactivity was found between the two groups of rats. These results indicated the potential usefulness of [2-11C]thymidine and positron emission tomography for noninvasive measurement of liver regeneration.

Production of [2-11C]thymidine for quantification of cellular proliferation with PET

A three-step synthesis of [2-11C]thymidine, using [11C]urea as precursor, is described. [2-11C]Thymine was obtained by cyclization of [11C]urea and diethyl beta-methylmalate in fuming sulfuric acid. After purification of the reaction mixture, [2-11C]thymine and 2'-deoxyribose-1-phosphate were incubated in the presence of thymidine phosphorylase to form [2-11C]thymidine. The whole synthesis procedure, including purification and pharmaceutical package, was achieved within 60 min with a decay corrected yield of 30-35%.