Cumulative Radiation Dose in Patients with Aneurysmal Subarachnoid Hemorrhage

We applaud the efforts of Moskowitz et al to increase awareness of the risks of cumulative radiation dose in their article, “Cumulative Radiation Dose during Hospitalization for Aneurysmal Subarachnoid Hemorrhage.”[1][1] We certainly agree that it is essential to minimize radiation dose from all

vided in the article. The Table is based on the doses indicated in their "Equipment and Radiation Dose" section of the article. We used their projected dose from C-arm intraoperative angiography alone because the authors indicate that routine digital subtraction angiography (DSA) was not part of their treatment algorithm. This rough approximation indicates that the result published in the article for this group (average, 4.6 Gy) is significantly higher than the estimated cumulative dose (1.2 Gy).
We have additional concerns with this work. The article does not indicate the neurointerventional procedure dose from the biplane Axiom Artis dBA scanner (Siemens, Erlangen, Germany) but does state the dose by using a Siemens portable C-arm (Siremobil Iso-C). This dose of 310 mGy seems much higher than expected. The dose will depend on many factors, such as collimation, kilovolt, and milliampere settings and the magnification setting, which are not indicated in the article. If we assume a 1 R/min fluoroscopy rate and 100 mR/frame for the acquisition mode, then the dose for this procedure would be more like 90 mGy compared with 310 mGy.
Because the authors indicate that 87% of the cumulative dose could be accounted for by the neurointerventions, one would expect that their experience could be benchmarked against other studies of radiation exposure during similar interventions. A study from 2007 by D'Ercole et al 5 not only used the air kerma values but validated them against readings from a Gafchromic film (ISP, Wayne, New Jersey) placed on that patient. In their study of 21 procedures, the maximum absorbed dose was 3.20 Gy with mean of 1.1 Gy. Even assuming that all the patients in the article by Moskowitz et al had even more complex procedures, as the authors suggested, it is difficult to understand how their patients experienced doses that were 10-fold higher.
Because no comparative reference dosimetry method was used for the study of Moskowitz et al, it seems most likely that the numbers reported are misinterpreted or misrepresented by the equipment as the authors of the Moskowitz paper themselves suggest. Adding support to this premise, the unit used to indicate cumulative dose that was correlated with length of hospitalization in Fig 5 is milligray, while Figs 3 and 4 use gray for the same patients. The absence of any reports of acute radiation injury in their patient population does not support the authors conclusions since at the doses cited, most of their patients should have demonstrated substantial skin injuries and cataract formation, depending on the proximity and/or inclusion of the orbits in the radiation field.
We think that is it important that the authors review their calculations and validate their equipment against another standard. If their patients are indeed receiving such doses, the authors should re-evaluate their interventional techniques. While the cumulative doses of CT, CT perfusion, and CT angiography (CTA) in addition to DSA and neurointervention can approach 3 Gy in some patients, we do not think that the high doses reported in this article are representative of the average radiation dose in this patient group. If this proves to be an overestimation, it illustrates the difficulties that may be encountered when using estimated doses and highlights the speculative nature of some articles that use dose estimates instead of the measured radiation dose.