3T non-injected phase-contrast MRI sequences for the mapping of the external carotid branches: In vivo radio-anatomical pilot study for feasibility analysis

Investigating the effect of flow compensation and quantitative susceptibility mapping method on the accuracy of venous susceptibility measurement

Quantitative susceptibility mapping (QSM) is a promising non-invasive method for obtaining information relating to oxygen metabolism. However, the optimal acquisition sequence and QSM reconstruction method for reliable venous susceptibility measurements are unknown. Full flow compensation is generally recommended to correct for the influence of venous blood flow, although the effect of flow compensation on the accuracy of venous susceptibility values has not been systematically evaluated. In this study, we investigated the effect of different acquisition sequences, including different flow compensation schemes, and different QSM reconstruction methods on venous susceptibilities. Ten healthy subjects were scanned with five or six distinct QSM sequence designs using monopolar readout gradients and different flow compensation schemes. All data sets were processed using six different QSM pipelines and venous blood susceptibility was evaluated in whole-brain segmentations of the venous vasculature and single veins. The quality of vein segmentations and the accuracy of venous susceptibility values were analyzed and compared between all combinations of sequences and reconstruction methods. The influence of the QSM reconstruction method on average venous susceptibility values was found to be 2.7-11.6 times greater than the influence of the acquisition sequence, including flow compensation. The majority of the investigated QSM reconstruction methods tended to underestimate venous susceptibility values in the vein segmentations that were obtained. In summary, we found that multi-echo gradient-echo acquisition sequences without full flow compensation yielded venous susceptibility values comparable to sequences with full flow compensation. However, the QSM reconstruction method had a great influence on susceptibility values and thus needs to be selected carefully for accurate venous QSM.

Extending the Indication of the Superior Thyroid Artery as a Recipient Vessel for Complex Upper Body Defects

BACKGROUND

Reconstruction of complex chest and upper back defects can pose a challenge to microsurgeons, especially when prior surgery, scarring, tumor resection, or radiotherapy, have caused a shortage of recipient vessels. Although already being a standard approach for head and neck reconstructions, we investigated whether the indication of the superior thyroid artery (STA) as a safe and universal recipient vessel could be extended for reconstruction in aforementioned regions.

METHODS

Seventeen patients received free myocutaneous vastus lateralis (MVL) muscle flaps for reconstruction of upper body defects (chest n = 11; upper back n = 6). In all cases, the STA was used for microvascular anastomosis because of a lack of standard recipient vessels. A retrospective chart review was performed and the data was screened for patients' demographics, intraoperative and perioperative details, flap survival, surgical complications, and overall long-term outcomes. Patients had a minimum follow-up of 6 months.

RESULTS

Defects resulted from infections after cardiac surgery (n = 10), infections after spinal neurosurgery (n = 2) or tumor resection (n = 5). Average defect size measured 144.6 (range, 40-286 cm2; ±67.9 cm2), with a mean size of the MVL free flaps of 266.8 (range, 160-384 cm2; ±69.5 cm2). The flap success rate was 100%, with minor complications in 4 patients. No major complications were observed in any of the patients.

CONCLUSIONS

The STA is a viable and safe alternative as a recipient vessel for reconstruction of upper body defects, especially when other vessels in proximity to the defect are deprived.

Contribution of flow MRI in the therapeutic management of middle face high flow arteriovenous malformation: A case report

BACKROUND

The radiosurgical management of high flow arteriovenous malformations (HFAVM) in the "destructive" stage requires a precise hemodynamic and anatomical assessment.

PATIENT AND METHODS/CASE REPORT

We report the case of a 32 years-old patient with a large ulcerated face HFAVM, on which Doppler ultrasound was impossible to perform. We show that, by combining 3D PCA and 2D CINE PC-MRI sequences, magnetic resonance imaging is capable to provide a complete morphometric and velocimetric mapping of the nidus and feeding arteries of the HFAVM.

CONCLUSION

Although Doppler ultrasound is the reference examination in the HFAVM, Flow MRI without contrast agent provides an advantageous alternative to assess vascular pathologies and choose the therapeutic strategy.

Case series: effect of dermis-fat implants in different late onset socket problems encountered in retinoblastoma patients

BACKGROUND

Cosmetic dissatisfaction, pain, and chronic discharge may present months till years after enucleation in patients operated because of retinoblastoma. If noninvasive treatment modalities are insufficient, socket reconstruction can be considered. In this study, we discuss the results of dermis-fat exchange to treat these problems.

METHOD

Four patients with late onset post enucleation socket problems with a request for treatment were included in this prospective study. Socket inspection was documented and pictures at baseline and at a follow-up of at least 6 months were taken. To quantify the problem 'pain', a VAS score at baseline and at follow up was used. For the problem 'cosmetic dissatisfaction' standardized questionnaires were used.

RESULTS

Two patients were included because of cosmetic dissatisfaction; one was included with chronic pain and one with chronic discharge. Reconstruction of the socket using autologous dermis-fat insertion was done in all four. In one of them, severe shrinking of the fat developed. This patient was treated with additional injectable fillers. Both of them, ultimately, had satisfactory results. Autologous fat transplantation also solved the problem of chronic discharge and pain in the two other patients.

CONCLUSION

Socket reconstruction by autologous dermis-fat exchange may solve different post enucleation socket problems. However, shrinking of the transplanted fat may occur and require additional procedures.

Quantitative assessment of the flow distribution in the branches of the external carotid by non-injected flow MRI

Owing to the lack of databases of blood flow distributions in the external carotid branches, surgeons currently rely on per-operative imaging and on their experience to choose the recipient vessels for microsurgical facial reconstructions. But, thanks to three-dimensional phase contrast angiography (PCA) and kinematic CINE phase contrast (PC) sequences, MRI technologies have the potential to provide quantitative anatomical and hemodynamic information without injection of contrast agent. Having developed and optimized PC-MRI sequences for the small facial vessels, our objective was to investigate the haemodynamic and blood flow distribution in the external carotid branches. We included 31 healthy volunteers in an MRI prospective study. Two-dimensional CINE PC-MRI sequences (average duration time of 2 min 40 s ± 24 s) were performed in the external carotid collaterals (n = 290). A statistical analysis of the flow measurements showed that, despite large interpersonal variabilities, a general flow distribution pattern was obtained by dividing the vessel flow rates by the external carotid artery one (providing local percentages of the incoming flow). The vessels could then be classified in three haemodynamic groups (p < 0.05 Student's test): "low flow" group (lingual artery-12.5 ± 5% of incoming flow), "intermediate flow" group (superior thyroid artery-16.5 ± 10%, internal maxillary artery-20.5 ± 11%, superficial temporal artery-18.4 ± 6%), "high flow" group (facial artery -26.6 ± 10%). Thanks to this general flow distribution mapping, it is now possible to estimate the flow rates in the distal branches of any individual from a single blood flow measurement in the external carotid artery.