The effect of LRRK2 mutations on the cholinergic system in manifest and premanifest stages of Parkinson's disease: a cross-sectional PET study.

BACKGROUND: Markers of neuroinflammation are increased in some patients with LRRK2 Parkinson's disease compared with individuals with idiopathic Parkinson's disease, suggesting possible differences in disease pathogenesis. Previous PET studies have suggested amplified dopamine turnover and preserved serotonergic innervation in LRRK2 mutation carriers. We postulated that patients with LRRK2 mutations might show abnormalities of central cholinergic activity, even before the diagnosis of Parkinson's disease. METHODS: Between June, 2009, and December, 2015, we recruited participants from four movement disorder clinics in Canada, Norway, and the USA. Patients with Parkinson's disease were diagnosed by movement disorder neurologists on the basis of the UK Parkinson's Disease Society Brain Bank criteria. LRRK2 carrier status was confirmed by bidirectional Sanger sequencing. We used the PET tracer N-11C-methyl-piperidin-4-yl propionate to scan for acetylcholinesterase activity. The primary outcome measure was rate of acetylcholinesterase hydrolysis, calculated using the striatal input method. We compared acetylcholinesterase hydrolysis rates between groups using ANCOVA, with adjustment for age based on the results of linear regression analysis. FINDINGS: We recruited 14 patients with LRRK2 Parkinson's disease, 16 LRRK2 mutation carriers without Parkinson's disease, eight patients with idiopathic Parkinson's disease, and 11 healthy controls. We noted significant between-group differences in rates of acetylcholinesterase hydrolysis in cortical regions (average cortex p=0·009, default mode network-related regions p=0·006, limbic network-related regions p=0·020) and the thalamus (p=0·008). LRRK2 mutation carriers without Parkinson's disease had increased acetylcholinesterase hydrolysis rates compared with healthy controls in the cortex (average cortex, p=0·046). Patients with LRRK2 Parkinson's disease had significantly higher acetylcholinesterase activity in some cortical regions (average cortex p=0·043, default mode network-related regions p=0·021) and the thalamus (thalamus p=0·004) compared with individuals with idiopathic disease. Acetylcholinesterase hydrolysis rates in healthy controls were correlated inversely with age. INTERPRETATION: LRRK2 mutations are associated with significantly increased cholinergic activity in the brain in mutation carriers without Parkinson's disease compared with healthy controls and in LRRK2 mutation carriers with Parkinson's disease compared with individuals with idiopathic disease. Changes in cholinergic activity might represent early and sustained attempts to compensate for LRRK2-related dysfunction, or alteration of acetylcholinesterase in non-neuronal cells. FUNDING: Michael J Fox Foundation, National Institutes of Health, and Pacific Alzheimer Research Foundation.

Development of a preclinical 211Rn/211At generator system for targeted alpha therapy research with 211At.

INTRODUCTION: The availability of 211At for targeted alpha therapy research can be increased by the 211Rn/211At generator system, whereby 211At is produced by 211Rn electron capture decay. This study demonstrated the feasibility of using generator-produced 211At to label monoclonal antibody (BC8, anti-human CD45) for preclinical use, following isolation from the 207Po contamination also produced by these generators (by 211Rn α-decay). METHODS: 211Rn was produced by 211Fr electron capture decay following mass separated ion beam implantation and chemically isolated in liquid alkane hydrocarbon (dodecane). 211At produced by the resulting 211Rn source was extracted in strong base (2N NaOH) and purified by granular Te columns. BC8-B10 (antibody conjugated with closo-decaborate(2-)) was labeled with generator-produced 211At and purified by PD-10 columns. RESULTS: Aqueous solutions extracted from the generator were found to contain 211At and 207Po, isolated from 211Rn. High radionuclidic purity was obtained for 211At eluted from Te columns, from which BC8-B10 monoclonal antibody was successfully labeled. If not removed, 207Po was found to significantly contaminate the final 211At-BC8-B10 product. High yield efficiencies (decay-corrected, n=3) were achieved for 211At extraction from the generator (86%±7%), Te column purification (70%±10%), and antibody labeling (76%±2%). CONCLUSIONS: The experimental 211Rn/211At generator was shown to be well-suited for preclinical 211At-based research. ADVANCES IN KNOWLEDGE: We believe that these experiments have furthered the knowledge-base for expanding accessibility to 211At using the 211Rn/211At generator system. IMPLICATIONS FOR PATIENT CARE: As established by this work, the 211Rn/211At generator has the capability of facilitating preclinical evaluations of 211At-based therapies.

211Rn/211At and 209At production with intense mass separated Fr ion beams for preclinical 211At-based α-therapy research.

Mass-separated francium beams (211Fr or 213Fr) were implanted into solid targets for producing 211Rn (14.6h half-life) or 209At (5.41h), in situ. 211Rn was transferred to dodecane and isolated from contaminants, providing sources for 211At (7.21h) production by 211Rn decay (73%). 209At was recovered with high radionuclidic purity in aqueous solutions, directly. These experiments demonstrated Fr beam implantations as a novel method for producing preclinical quantities of 211Rn/211At (for therapy) and 209At (for imaging).

Overexpression of HER-2 in MDA-MB-435/LCC6 Tumours is Associated with Higher Metabolic Activity and Lower Energy Stress.

Overexpresssion of HER-2 in the MDA-MB-435/LCC6 (LCC6(HER-2)) tumour model is associated with significantly increased hypoxia and reduced necrosis compared to isogenic control tumours (LCC6(Vector)); this difference was not related to tumour size or changes in vascular architecture. To further evaluate factors responsible for HER-2-associated changes in the tumour microenvironment, small animal magnetic resonance imaging (MRI) and positron emission tomography (PET) were used to measure tumour tissue perfusion and metabolism, respectively. The imaging data was further corroborated by analysis of molecular markers pertaining to energy homeostasis, and measurements of hypoxia and glucose consumption. The results showed a strong trend towards higher perfusion rates (~58% greater, p = 0.14), and significantly higher glucose uptake in LCC6(HER-2) (~2-fold greater; p = 0.025), relative to control tumours. The expression of proteins related to energy stress (P-AMPK, P-ACC) and glucose transporters (GLUT1) were lower in LCC6(HER-2) tumours (~2- and ~4-fold, respectively). The in vitro analysis showed that LCC6(HER-2) cells become more hypoxic in 1% oxygen and utilise significantly more glucose in normoxia compared to LCC6(Vector)cells (p < 0.005). Amalgamation of all the data points suggests a novel metabolic adaptation driven by HER-2 overexpression where higher oxygen and glucose metabolic rates produce rich energy supply but also a more hypoxic tumour mass.

Production of Y-86 and other radiometals for research purposes using a solution target system.

INTRODUCTION: Diagnostic radiometals are typically obtained from cyclotrons by irradiating solid targets or from radioisotope generators. These methods have the advantage of high production yields, but require additional solid target handling infrastructure that is not readily available to many cyclotron facilities. Herein, we provide an overview of our results regarding the production of various positron-emitting radiometals using a liquid target system installed on a 13 MeV cyclotron at TRIUMF. Details about the production, purification and quality control of (89)Zr, (68)Ga and for the first time (86)Y are discussed. METHODS: Aqueous solutions containing 1.35-1.65 g/mL of natural-abundance zinc nitrate, yttrium nitrate, and strontium nitrate were irradiated on a 13 MeV cyclotron using a standard liquid target. Different target body and foil materials were investigated for corrosion. Production yields were calculated using theoretical cross-sections from the EMPIRE code and compared with experimental results. The radioisotopes were extracted from irradiated target material using solid phase extraction methods adapted from previously reported methods, and used for radiolabelling experiments. RESULTS: We demonstrated production quantities that are sufficient for chemical and biological studies for three separate radiometals, (89)Zr (Asat = 360 MBq/µA and yield = 3.17 MBq/µA), (86)Y (Asat = 31 MBq/µA and yield = 1.44 MBq/µA), and (68)Ga (Asat = 141 MBq/µA and yield = 64 MBq/µA) from one hour long irradiations on a typical medical cyclotron. (68)Ga yields were sufficient for potential clinical applications. In order to avoid corrosion of the target body and target foil, nitrate solutions were chosen as well as niobium as target-body material. An automatic loading system enabled up to three production runs per day. The separation efficiency ranged from 82 to 99%. Subsequently, (68)Ga and (86)Y were successfully used to radiolabel DOTA-based chelators while deferoxamine was used to coordinate (89)Zr.

The medical isotope crisis: how we got here and where we are going.

(99m)Tc is the most widely used radionuclide in nuclear medicine. The reactor stoppages that occurred in recent years illustrated the vulnerability of the availability of radiotracers for imaging. With many of the reactors due for shutdown over the next 5-10 y, alternative routes to producing the (99)Mo/(99m)Tc pair are being explored. This brief review examines how we have reached this situation and what the near and distant future holds for securing the availability of these radioisotopes.

Cross-linked polyethylene glycol beads to separate 99mTc-pertechnetate from low-specific-activity molybdenum.

UNLABELLED: We report a kit-based approach for the purification of sodium pertechnetate ((99m)TcO4 (-)) from solutions with high MoO4 (2-) content. METHODS: Cross-linked polyethylene glycol resins (ChemMatrix) were used to separate (99m)Tc and molybdenum in 4N NaOH. The resins were loaded at various flow rates and eluted with water to release (99m)Tc. The (99m)Tc solution was passed through a cation exchange resin and an alumina cartridge, followed by saline elution. This process was tested with cyclotron-produced (99m)Tc using an automated system and disposable kits. RESULTS: Optimal results were obtained by loading 500 mg of resin at flow rates of up to 3.1 mL/min, with quantitative extraction of (99m)Tc from the molybdate solution and complete release of (99m)Tc after elution with water. The automated system was highly efficient at isolating Na(99m)TcO4 within minutes, with a recovery rate of 92.7% ± 1.1% (mean ± SD) using cyclotron-produced (99m)Tc. CONCLUSION: ChemMatrix resins were highly effective at separating (99m)TcO4 (-) from molybdate solutions.

Implementation of Multi-Curie Production of (99m)Tc by Conventional Medical Cyclotrons.

UNLABELLED: (99m)Tc is currently produced by an aging fleet of nuclear reactors, which require enriched uranium and generate nuclear waste. We report the development of a comprehensive solution to produce (99m)Tc in sufficient quantities to supply a large urban area using a single medical cyclotron. METHODS: A new target system was designed for (99m)Tc production. Target plates made of tantalum were coated with a layer of (100)Mo by electrophoretic deposition followed by high-temperature sintering. The targets were irradiated with 18-MeV protons for up to 6 h, using a medical cyclotron. The targets were automatically retrieved and dissolved in 30% H2O2. (99m)Tc was purified by solid-phase extraction or biphasic exchange chromatography. RESULTS: Between 1.04 and 1.5 g of (100)Mo were deposited on the tantalum plates. After high-temperature sintering, the (100)Mo formed a hard, adherent layer that bonded well with the backing surface. The targets were irradiated for 1-6.9 h at 20-240 µA of proton beam current, producing up to 348 GBq (9.4 Ci) of (99m)Tc. The resulting pertechnetate passed all standard quality control procedures and could be used to reconstitute typical anionic, cationic, and neutral technetium radiopharmaceutical kits. CONCLUSION: The direct production of (99m)Tc via proton bombardment of (100)Mo can be practically achieved in high yields using conventional medical cyclotrons. With some modifications of existing cyclotron infrastructure, this approach can be used to implement a decentralized medical isotope production model. This method eliminates the need for enriched uranium and the radioactive waste associated with the processing of uranium targets.

An alternate approach to the production of radioisotopes for nuclear medicine applications.

There is a growing need for the production of radioisotopes for both diagnostic and therapeutic medical applications. Radioisotopes that are produced using the (n,γ) or (γ,n) reactions, however, typically result in samples with low specific activity (radioactivity∕gram) due to the high abundance of target material of the same element. One method to effectively remove the isotopic impurity is electro-magnetic mass separation. An Ion Source Test Facility has been constructed at TRIUMF to develop high-intensity, high-efficiency, reliable ion sources for purification of radioactive isotopes, particularly those used in nuclear medicine. In progress studies are presented.

Manganese-52 positron emission tomography tracer characterization and initial results in phantoms and in vivo.

PURPOSE: Manganese(II) is employed as a contrast agent with magnetic resonance imaging (MRI) for study of neuronal activation in rats and mice. However, at the concentrations required for MRI, Mn may induce pharmacological or toxic effects. Positron emission tomography (PET) imaging of (52)MnCl2 at tracer doses has the potential to allow similar Mn studies as manganese-enhanced MRI while providing quantitative results and avoiding toxic effects. In this work, (52)MnCl2 is produced and characterized as a PET tracer in phantoms and in rats. METHODS: (52)MnCl2 was produced by proton irradiation of natural Cr foil and separated by column chromatography. Images were acquired on a Siemens Focus 120 small animal PET scanner. Phantom images were acquired to assess uniformity, resolution, cascade background correction, and count rate linearity. Images of rats were also acquired after systemic and intracerebroventricular (ICV) administration of (52)MnCl2 to investigate Mn(II) distribution in vivo. RESULTS: Irradiation yield was 74.6 ± 8.5 kBq/µA min (52)Mn at end of bombardment with initial specific activity of at least 3.5 MBq/nmol. (52)Mn PET images show similar uniformity and resolution to (18)F. (18)F based detector efficiency normalization is adequate for (52)Mn imaging. Subtraction of a rescaled random events distribution from sinogram data is effective for cascade correction of (52)Mn PET data. After systemic injection, (52)Mn appears in structures throughout the body of rats, including bones, liver, intestines, and the pituitary gland, but does not appear detectably throughout the brain. After ICV injection, (52)Mn remains in the brain and spinal cord. CONCLUSIONS: (52)Mn is a promising tracer for small animal PET imaging, yielding image quality comparable to (18)F. Potential applications include studies similar to Mn-enhanced neuronal MRI, and in other organ systems including bones, spinal cord, and the digestive tract.

Sulfonyl fluoride-based prosthetic compounds as potential 18F labelling agents.

Nucleophilic incorporation of [(18)F]F(-) under aqueous conditions holds several advantages in radiopharmaceutical development, especially with the advent of complex biological pharmacophores. Sulfonyl fluorides can be prepared in water at room temperature, yet they have not been assayed as a potential means to (18)F-labelled biomarkers for PET chemistry. We developed a general route to prepare bifunctional 4-formyl-, 3-formyl-, 4-maleimido- and 4-oxylalkynl-arylsulfonyl [(18)F]fluorides from their sulfonyl chloride analogues in 1:1 mixtures of acetonitrile, THF, or tBuOH and Cs[(18)F]F/Cs(2)CO(3(aq.)) in a reaction time of 15 min at room temperature. With the exception of 4-N-maleimide-benzenesulfonyl fluoride (3), pyridine could be used to simplify radiotracer purification by selectively degrading the precursor without significantly affecting observed yields. The addition of pyridine at the start of [(18)F]fluorination (1:1:0.8 tBuOH/Cs(2)CO(3(aq.))/pyridine) did not negatively affect yields of 3-formyl-2,4,6-trimethylbenzenesulfonyl [(18)F]fluoride (2) and dramatically improved the yields of 4-(prop-2-ynyloxy)benzenesulfonyl [(18)F]fluoride (4). The N-arylsulfonyl-4-dimethylaminopyridinium derivative of 4 (14) can be prepared and incorporates (18)F efficiently in solutions of 100 % aqueous Cs(2)CO(3) (10 mg mL(-1)). As proof-of-principle, [(18)F]2 was synthesised in a preparative fashion [88(±8) % decay corrected (n=6) from start-of-synthesis] and used to radioactively label an oxyamino-modified bombesin(6-14) analogue [35(±6) % decay corrected (n=4) from start-of-synthesis]. Total preparation time was 105-109 min from start-of-synthesis. Although the (18)F-peptide exhibited evidence of proteolytic defluorination and modification, our study is the first step in developing an aqueous, room temperature (18)F labelling strategy.

An automated module for the separation and purification of cyclotron-produced 99mTcO4-.

INTRODUCTION: The shortage of reactor-produced molybdenum-99 ((99)Mo, t(½)=66 h) has renewed interest in alternative production methods of its daughter isotope, technetium-99m ((99m)Tc, t(½)=6.02 h). While adsorption chromatography serves as a mechanism for selective elution of sodium pertechnetate from technetium generators, this method of purification is not sufficient for many alternative production methods. Several ion-separation/solid phase extraction chromatography methods are known, yet none have been demonstrated on cyclotron-produced [(99m)Tc]TcO(4)(-). Herein we describe the design, manufacture and optimization of a remotely operated module for the purification of sodium pertechnetate from a bulk solution of molybdate. METHODS: The automated purification module was designed to separate [(99m)Tc]TcO(4)(-) using either Dowex 1x8 or an Aqueous Biphasic Extraction Chromatography (ABEC) resin. (100)Mo composite targets were irradiated with 18.5 MeV protons for 10 µA·h using an ASCI TR19 cyclotron. Once purified, the radiopharmaceutical quality of (99m)TcO(4)(-) isolated from each process (Dowex and/or ABEC) was established by assaying for molybdate breakthrough, alumina levels and, in the case of the Dowex approach, residual organics. RESULTS: The separation processes are efficient (75% for Dowex, 90% for ABEC) and complete in less than 30 min. Overall, up to 2.1 GBq of (99m)Tc was produced using the (100)Mo(p,2n)(99m)Tc transformation, processed using the separation module and subjected to a detailed chemical and radionuclidic analysis. Due to its expense and limited availability, (100)MoO(4)(2-) was recovered in >90% yield using a precipitation/filtration/lyophilization approach. CONCLUSIONS: Na[(99m)Tc]TcO(4) was produced using a medical cyclotron, recovered using an automated purification module and found to exceed all established quality control parameters.

THE EFFECTS OF IRON AND COPPER AVAILABILITY ON THE COPPER STOICHIOMETRY OF MARINE PHYTOPLANKTON(1).

We studied the interactive effects of iron (Fe) and copper (Cu) availability on the growth rates, Cu quotas, and steady-state Cu-uptake rates (ρss Cu) of 12 phytoplankton (from four classes and two marine environments). A mixed-effect statistical model indicated that low Fe significantly decreased phytoplankton growth rates. In contrast, lowering Cu levels only decreased the growth rates of the oceanic phytoplankton. Under Fe/Cu sufficiency, the Cu quotas ranged from 0.36 to 3.8 µmol Cu · mol(-1) C. Copper levels in the growth medium had a significant positive effect on the Cu quotas, and this effect was dependent on the algal class. Under Fe/Cu sufficiency, the highest average Cu quotas were observed for the Bacillariophyceae, followed by the Cyanophyceae, Prymnesiophyceae, and lastly the Dinophyceae. Similar taxonomic trends were observed for the ρss Cu. Although the Cu:C ratios were not significantly higher in oceanic strains, there are five independent lines of evidence supporting a more important role of Cu in the physiology of the oceanic phytoplankton. The mixed-effect model indicated a significant Cu effect on the growth rates and ρss Cu of the oceanic strains, but not the coastal strains. In addition, lowering the Cu concentration in the media decreased the Cu quotas and ρss Cu of the oceanic strains to a greater extent (5.5- and 5.4-fold, respectively) than those of the coastals (3.8- and 4.7-fold, respectively). Iron limitation only had a significant effect on the Cu quotas of the oceanic strains, and this effect was dependent on Cu level and taxonomic class. Our results highlight a complex physiological interaction between Fe and Cu in marine phytoplankton.

Longitudinal evolution of compensatory changes in striatal dopamine processing in Parkinson's disease.

Parkinson's disease is a relentlessly progressive neurodegenerative disease. Breakdown of compensatory mechanisms influencing putaminal dopamine processing could contribute to the progressive motor symptoms. We studied a cohort of 78 subjects (at baseline) with sporadic Parkinson's disease and 35 healthy controls with multi-tracer positron emission tomography scans to investigate the evolution of adaptive mechanisms influencing striatal dopamine processing in Parkinson's disease progression. Presynaptic dopaminergic integrity was assessed with three radioligands: (i) [(11)C](±)dihydrotetrabenazine, to estimate the density of vesicular monoamine transporter type 2; (ii) [(11)C]d-threo-methylphenidate, to label the dopamine transporter; and (iii) 6-[(18)F]fluoro-L-DOPA, to assess the activity of aromatic amino acid decarboxylase and storage of 6-[(18)F]-fluorodopamine in synaptic vesicles. The subjects with Parkinson's disease and the healthy controls underwent positron emission tomography scans at the initial visit and after 4 and 8 years of follow-up. Non-linear multivariate regression analyses with random effects were utilized to model the longitudinal changes in tracer values in the putamen standardized relative to normal controls. We found evidence for possible upregulation of dopamine synthesis and downregulation of dopamine transporter in the more severely affected putamen in the early stage of Parkinson's disease. The standardized 6-[(18)F]fluoro-L-DOPA and [(11)C]d-threo-methylphenidate values tended to approach [(11)C](±)dihydrotetrabenazine values in the putamen in later stages of disease (i.e. for [(11)C](±)dihydrotetrabenazine values <25% of normal), when the rates of decline in the positron emission tomography measurements were similar for all the markers. Our data suggest that compensatory mechanisms decline as Parkinson's disease progresses. This breakdown of compensatory strategies in the putamen could contribute to the progression of motor symptoms in advanced disease.

Cyclotron production of (99m)Tc: experimental measurement of the (100)Mo(p,x)(99)Mo, (99m)Tc and (99g)Tc excitation functions from 8 to 18 MeV.

INTRODUCTION: The cyclotron-based (100)Mo(p,2n)(99m)Tc transformation has been proposed as a viable alternative to the reactor based (235)U(n,f)(99)Mo→(99m)Tc strategy for production of (99m)Tc. Despite efforts to theoretically model the amount of ground-state (99g)Tc present at end of bombardment for the (p,2n) reaction, experimental validation has yet to be performed. The co-production of (99g)Tc may have important implications in both the subsequent radiopharmaceutical chemistry and patient dosimetry upon injection. METHODS: To determine the extent of (99g)Tc co-production, we have experimentally measured the (100)Mo(p,x)(99)Mo, (99m)Tc, and (99g)Tc excitation functions in the 8-18 MeV range using a combination of natural abundance and 97.42% enriched (100)Mo foils along with γ-ray spectrometry and ICP-MS. Although the excitation functions for production of (99)Mo and (99m)Tc have been presented previously in the literature, to the best of our knowledge, this work presents the first experimental evaluation of the (100)Mo(p,2n)(99g)Tc excitation function. RESULTS: From the experimental cross-section measurements, the (99m)Tc production yields and (99m)Tc/(99m+g)Tc nuclei ratio were calculated for various thick target irradiation conditions. Results suggest that TBq quantities of (99m)Tc can be achieved with a (99m)Tc/(99m+g)Tc nuclei ratio that is on par with the current (99)Mo/(99m)Tc generator standard eluted at a 24-h frequency. CONCLUSION: These findings suggest that the cyclotron production of (99m)Tc may be a feasible alternative to the current reactor-based production strategy.

Age-specific progression of nigrostriatal dysfunction in Parkinson's disease.

OBJECTIVE: To investigate in vivo the impact of age on nigrostriatal dopamine dysfunction in Parkinson's disease (PD). METHODS: PD patients (n = 78) and healthy control subjects (n = 35) underwent longitudinal positron emission tomography assessments using 3 presynaptic dopamine markers: (1) [¹¹C](±)dihydrotetrabenazine (DTBZ), to estimate the density of the vesicular monoamine transporter type 2; (2) [¹¹C]d-threo-methylphenidate, to estimate the density of the plasma membrane dopamine transporter; and (3) 6-[¹8F]-fluoro-L-dopa, to estimate the activity of the enzyme dopa-decarboxylase. RESULTS: The study comprised 438 PD scans and 241 control scans (679 scans in total). At symptom onset, the loss of putamen DTBZ binding was substantially greater in younger compared to older PD patients (p = 0.015). Remarkably, however, the rate of progression of DTBZ binding loss was significantly slower in younger patients (p < 0.05). The estimated presymptomatic phase of the disease spanned more than 2 decades in younger patients, compared to 1 decade in older patients. INTERPRETATION: Our results suggest that, compared to older patients, younger PD patients progress more slowly and are able to endure more damage to the dopaminergic system before the first motor symptoms appear. These observations suggest that younger PD patients have more efficient compensatory mechanisms.

A new and simple calibration-independent method for measuring the beam energy of a cyclotron.

This work recommends a new and simple-to-perform method for measuring the beam energy of an accelerator. The proposed method requires the irradiation of two monitor foils interspaced by an energy degrader. The primary advantage of the proposed method, which makes this method unique from previous energy evaluation strategies that employ the use of monitor foils, is that this method is independent of the detector efficiency calibration. This method was evaluated by performing proton activation of (nat)Cu foils using both a cyclotron and a tandem Van de Graaff accelerator. The monitor foil activities were read using a dose calibrator set to an arbitrary calibration setting. Excellent agreement was noted between the nominal and measured proton energies.