Present status of Medical Physics practice in Mexico: An occupational analysis.

PURPOSE: To present an overview of the status of Medical Physics practice in Mexico, promote the legal recognition of Medical Physics high-end training, and provide information that will potentially improve the Mexican healthcare system. METHODS: For the purpose of this research, the concept of "Medical Physics Professional/s" (MPP) is introduced to refer to any person/s executing the role of a clinical medical physicist (cMP) in whole or in part independent of academic profile, training or experience. A database of MPP in Mexico was built from official sources and personal communication with peers. Database records included the following fields: employer/s, specialty, academic profile, and annual income (when available). RESULTS: 133 centers in Mexico employ MPP, 49% of which are public institutions. 360 positions involving cMP roles were identified at the National Healthcare System (occupied by 283 MPP), 77% of which corresponded to radiation therapy. Public healthcare services hold 65% of the reported positions. Only 40% of MPP hold a graduate degree in Medical Physics, 46% of whom were located in the most densely populated region of Mexico. Of all MPP, 32% were women. CONCLUSIONS: This work allowed to clearly identify the current challenges of Medical Physics practice in Mexico, such as: insufficiency and uneven geographical distribution of qualified manpower, gender imparity, multishifting and wage gap. The products derived from this work could be used to guide the efforts to improve the Mexican healthcare system.

Radiosurgical third ventriculostomy: Technical note.

BACKGROUND: We describe a minimally invasive technique to perform a radiosurgical third ventriculostomy in a patient with mild obstructive hydrocephalus secondary to malignant pathology. METHODS: A 42 years old woman with diagnosis of clear cells renal carcinoma and with right nefrectomy performed last year. Cranial Magnetic Resonance Imaging showed two brain metastasis: one right temporal, and other in the pons with Sylvian aqueduct partial obliteration and mild ventricular enlargement. The patient received radiosurgical treatment for brain metastasis; after this procedure a new target was defined on the floor of the third ventricle, in the midpoint between the mamillary bodies and the infundibular recess where we delivered 100 Gy delivered by an isocentric multiple noncoplanar arcs technique, with a 6 MV Novalis(®) dedicated LINAC. A series of 21 arcs was arranged with a radiation field generated by a 4 mm circular collimator. RESULTS: One week pos-irradiation in the head CT we did not find significant changes in the metastatic lesions; however the VSI diminished 4%, despite of persistent aqueduct obliteration. At three months we perform 3.0 T MRI where we confirmed the presence of the third ventriculostomy (2.63 mm diameter). CONCLUSION: This report demonstrates, for the first time, the ability of a dedicated LINAC to perform a precise third ventriculostomy without associate morbility in short term.

Intracranial arteriovenous malformations treated with LINAC-based conformal radiosurgery: validation of the radiosurgery-based arteriovenous malformation score as a predictor of outcome.

OBJECTIVE: To validate the radiosurgery-based arteriovenous malformation score (RBAS) as a predictor of outcome in patients with arteriovenous malformations (AVMs) treated with LINAC-based conformal radiosurgery. METHODS: We analysed 40 patients with a mean follow-up of 22 months. One patient (2.5%) pertained to Spetzler-Martin Grade I, 11 (27.5%) to Grade II, 19 (47.5%) to Grade III, eight (20%) to Grade IV and one (2.5%) to grade V. The mean RBAS was 2.0 (range: 0.76-5.56). The mean obliteration prediction index (OPI) and the Karlsson index (KI) were 0.74 (range: 0.2-2.86) and 109.48 (range: 3.0-350.7) respectively. Outcomes were analysed according to the OPI, KI and RBAS. RESULTS: We analysed different cutoff points in the RBAS and found a significant difference to predict the outcome in four scores: 1.2, 1.6, 1.7 and 1.8. In the group with RBAS < or = 1.8, 13 (68%) had an excellent outcome and six (33%) did not, while with RBAS>1.8, seven (32%) had an excellent outcome and 14 (67%) did not (p = 0.02). We did not find any correlation between Spetzler-Martin grading scale or OPI and outcome (p = 0.7 and p = 0.3 respectively). The KI predicted the excellent outcome in 8/9 patients (89%) with KI < or = 27 and in 12/31 patients (39%) with KI>27 (p = 0.08). CONCLUSION: The RBAS seems to be a good predictor of outcome in patients with AVMs treated with LINAC-based conformal radiosurgery as in patients treated with Gamma Knife. It remains only to find the best cutoff point based on a larger series and longer follow-up.

Intracranial arteriovenous malformations treated with linear accelerator-based conformal radiosurgery: clinical outcome and prediction of obliteration.

BACKGROUND: Little is written about the clinical outcome and predictor factors of obliteration and treatment success in patients with intracranial AVMs treated with LINAC-based conformal radiosurgery in Mexican institutions. METHODS: We analyzed 40 patients with intracranial AVMs with a mean follow-up of 29 (range, 23-34) months. Seven AVMs (17.5%) had a volume <1 cm(3); 10 (25%), 1 to 4 cm(3); 13 (32.5%), 4.1 to 10 cm(3); and 10 (25%), >10 cm(3). The mean prescription dose was 15.4 Gy. Twenty-six patients (68%) presented hemorrhage before treatment; 4 (10%), chronic headache; 14 (35%), seizures; and 3(8%), neurologic deficit. RESULTS: Seven patients (17.5%) underwent objective clinical improvement. Thirty patients (75%) remained without clinical changes. Three patients (7.5%) developed edema and 1 (2.5%) had a rebleeding after treatment. Twenty-five patients (63%) presented complete obliteration of the AVM. A successful treatment (obliteration without a new deficit) was obtained in 23 (58%) of the cases. The percentage of obliteration was in <1 cm(3) (86%), 1 to 4 cm(3) (80%), 4.1 to 10 cm(3) (54%), and >10 cm(3) (40%), without a significant difference between groups (P = .1). Patients with RBAS of 1.9, 48%; the successful treatment in the former resulted in 79% and, in the latter, 38% (P = .08 and P = .02, respectively). CONCLUSIONS: The clinical outcome was similar to other series. The RBAS seems to be a good predictor of obliteration and successful treatment in patients with AVMs treated with LINAC-based conformal radiosurgery.