A Thermal Sublimation Generator of ^131mXe

Round 1

Reviewer 1 Report

Please consider the following comments/questions:

 

Page 1, line 13: at least one reference is needed to justify the statement.

Page 1, lines 14-15: at least one reference is needed to justify the statement that “xenon has several important qualities”.

Page 2, line 34: please indicate the half-life of I131, to ease the reading

Page 2, line 35: at least one reference is needed to justify the “high-demand” statement

Page 2 line 69: please specify the manufacturer of the I131 as Na131I here, instead of lines 95-96.

Page 2 line 72: please introduce “BR”here instead of latter, at line 77

Page 7 line 185: please change “example spectra are” to “A typical spectrum is”

Page 7 line 185-186: please remove this sentence as it is unnecessary to explain what is a gamma-spectrometry spectrum

Page 7 line 185-190: why do you refer several times “spectra” as there is only one “spectrum presented”. Please correct

Page 7 line 192-193: what is the shape of the absolute efficiency of the HPGe used, and most of all its accuracy. Has you used a P-type detector, does the efficiency curve presents a significant knee in the 100-200 keV range and therefore one should avoid measurements below around 200 keV. Please comment on how good the efficiency calibration was as Ba133 and Eu152 sources are not enough in that energy range for that type of detector.

Page 7 line 195: please refer figure 6 here

Page 7 line 198, figure 5: the amount of “background radiation” lines seems far to numerous. Please you please comment and/or quantities these?

Page 8 line 219: please specify the value of alpha to be 62%. Was the activity of 131mXe determined before and after collection? If so, with the very same detector in both cases?

Page 9, figure 7: for sample nº1, is there any data measurement missing for temperature above 300ºC?

Page 10: lines 288-290: please refer to which - and quantify their amount- excipient present in the section” 3. Results”

Page 11, line 298-299: please refer the minimal activity of 131mXe that would be acceptable for your goal.

Page 11, line 303: please change “jumbo”

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is professionally and very well written, and I recommend the publication in its present form.
The context of the research (the use of gamma-emitting isotopes of Xenon for dual SPECT-MRI imaging) is very hot and is linked to the gamma-mri project funded by the European Community.
I read the manuscript carefully, finding no defects or corrections to suggest. A simple radiation protection advice could be to perform the work within a shielded cell, available in every hospital department of nuclear medicine, in order to also reduce gamma exposure to operators; a perspex bench shield is effective for beta rays only.
From the point of view of the application in hospital practice, the idea of using normal Na-I131 capsules is certainly excellent, in consideration of the easy availability. Thermal saturation extraction, once the procedure is engineered, could be performed with a module that is sufficiently small to ensure its positioning in a shielded cell. The fact of ordering
the product two weeks before extraction does not appear a problem.
The aspects of chemical purification and hyperpolarization of xenon to be carried out before administration seem to me more complicated to implement in a health facility. But these problems lie beyond the topic of the article.
I wish the authors and colleagues involved in the project full success.
 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript presents the study carried out to produce 131mXe by thermal sublimation from the decay of commercially obtained 131I in solid-state (Na131I salt).

In particular, the efficiency of the 131mXe has been quantified and temperature conditions optimized, thanks to gamma spectroscopy measurements at the different steps.

The production of long-lived Xe isotopes is interesting for medical imaging.

Motivation of the work is presented and the whole experimental process developed is very clearly described. Although limitations to be overcome are also pointed out in the text, very promising results have been obtained.

Therefore, I support the publication in Instruments. I recommend a very minor revision, listing below a few comments and suggestions.

 

 

178-180: I guess efficiency for the energies of interest (in Table 1) is obtained by interpolating efficiencies for gamma lines from the calibrated 152Eu and 133Ba sources; how self-absorption in powder or vial is taken into account? You could comment on this.

Figures 5 and 6: although stated in the text, I recommend to put in Y-axis label "counts per channel".

Section 3.1: to analyze the measured spectra to derive activity from the peak areas, do you use any commercial software? Detectors backgrounds are substracted? You could comment on these analysis methods.

255: put definition of MDA in this first appearance (it is given later in lines 260-261).

258-259: it would be interesting to remind the "danger" of having this 131I in the final 131mXe, taking into account the foreseen uses.

273-274: it would be interesting to comment which residual level of 131I is considered tolerable.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

This is well-written paper describing a method to extract Xe-131m from commercially available I-131. I recommend its publication in the journal with some minor edits described below.

Figure 1: What do the error bars represent? As I understand, this is an analytic calculation without associated errors.

Line 219: How was alpha determined? Could you elaborate?

Section 3.2: The clarity of the text in this section can be improved. Perhaps decribe the procedure (lines 235-245)  before explaining what Figure 7 is (lines 232-234).

Figure 7 and lines 232-234: If I understand it right, the percentages are the Xe-131m extracted at the specified temperature. This is counter-intuitive. It may be clearer if these were, instead, cumulative percentages -- percentages of Xe-131m extracted up until the temperature. This way, a trend that approaches 100% as T increases can be easily seen.

Line 285: I suggest this edit: "high signal of the Na^{131}I background"- > "high background from the Na^{131}I".

Line 297: By "recalled", do you mean to be "kept in mind"? 

Author Response

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Author Response File: Author Response.pdf