核医学与放射治疗

Breast cancer is the most frequently diagnosed cancer type among women worldwide. The treatment of breast cancer is multimodal and the current standard approach is surgery followed by adjuvant radiotherapy (RT) based on prognostic scores. Neoadjuvant chemotherapy and RT delivered in advance of surgery are used in some early stage and locally advanced cases, may offer an advantage over adjuvant therapy related to the potential benefits in the pathologic response and survival outcomes based the hypothesis of Abscopal effect.

Neurofibromatosis type 1 is an autosomal dominant disease. The worldwide estimated prevalence is 1 in 3000. Germline mutation in the NF1 tumor suppressor gene on long arm of chromosome 17 appears to be the causative factor. Patients with plexiformneurofibromasshows higher risk of transformation into malignant pathology also referred to as malignant peripheral nerve sheath tumors (MPNST). The relative lifetime risk is expected to be around 8-13%. Histology remains gold standard for diagnosing MPNST, but requires complete excision which is technically difficult. As a combined metabolic-anatomic method, PET/CT using the radiotracer 18F-FDG allows different parameters oftumours to be analysed simultaneously. It also helps to avoid unnecessary surgeries in benign cases. Hybrid PET/MRI will play a crucial role in future for evaluating nerve sheath tumours in NF1 patients by combining the pros of both the modalities.

Background: The main toxicity of trastuzumab, is the alteration of cardiac function. The objective of this study is to examine the acute cardiotoxicity of the combination of Radiotherapy (RT) and trastuzumab in the adjuvant treatment of breast cancer.

Materials and Methods: This is a retrospective study of 41 patients followed for localized breast cancer, treated by multimodal strategy combining chemotherapy, Radiotherapy and trastuzumab as adjuvant treatment in the medical oncology department at the Ibn Sina Military hospital of Marrakesh.

Results: All patients underwent adjuvant RT on the wall, including 17 on the left side. The median value of the Left Ventricular Ejection Fraction (LVEF) before starting treatment was 64%. The median value of the absolute decrease of LVEF, after the end of RT, was of the order of 4%. All patients received treatment with trastuzumab, during irradiation at usual doses for twelve months. Trastuzumab was stopped temporarily in seven patients, because of the fall in LVEF of more than 10%. After a median followup of 13 months, one patient developed congestive heart failure, imposing the definitive cessation of trastuzumab.

Conclusion: The association RT and trastuzumab, does not appear to increase the risk of acute cardiac toxicity, whatever the irradiated side.

Aim: This study investigates the dosimetric impact of a-Si 1200 over a-Si 1000 portal imager for 6 MV photon beam of a Varian Amorphous Silicon Electronic Portal Imaging Device (a-Si EPID) installed on Edge and Novalis TxLinac.
Materials and Methods: The performance of an a-Si EPID 1200 was assessed and compared to its performance with a-Si EPID 1000 and dose measurements using an ionization chamber. This study was conducted for 6MV photon energy and the EPID performance was assessed as function of the delivered dose, dose rate, field size, SDD effect, Ghosting effect, Backscatter arm shielding impact and intensity-modulated radiation therapy fields.
Results: The dose response for a-Si 1200 was within 0.5% for low MU (2-10) as compared to 1.4% for a-Si 1000 portal imager and less than 1% for both the imager above 10 MU. The output factor variation for 25 × 25 cm2 was 1.3% for a-Si 1200 and 3.8% for a-Si 1000 when compared with ionisation chamber. The ghosting was measured to be 0.2% for a-Si 1200 as compared to 0.8% for a-Si 1000 portal imager. There is a significant improvement in a-Si 1200 portal image due to backscatter shielding material attached to the back of the panel of a-Si 1200 portal imager.
Conclusion: The new aS1200 detector showed a significant dosimetric improvement when compared with previous aS1000 hence providing more accurate measurements for pre-treatment patient specific Quality Assurance (QA).

Background: Scientifically published studies have demonstrated that all isotopes, including Sestamibi redistribute. Measurement of this redistribution using FMTVDM©â„— provides an accurate method for determining wash-in and washout.
Methods: Using FMTVDM©â„— 1040 human coronary arteries were studied to determine their wash-in and washout redistribution measured on a pixel-by-pixel basis. From FMTVDM©â„— the percent diameter stenosis (%DS) for each artery was determined. This %DS was then used to calculate coronary flow reserve (Calculated SFR) using a proprietary quadratic equation (QCFR©, FCFR©) previously derived from quantitative coronary arteriography (QCA) measurements. These calculated CFR values were then compared with the actual measured CFR obtained directly from QCA.
Results: The results of the calculated CFR from FMTVDM©â„— with that obtained by direct QCA measurement showed a regression analysis of y= (0.8758•x)+0.4291, where y=the QCFR© and x=the QCA measured CFR. The R2 value (coefficient of determination) for this demonstrated a strong relationship at 0.87582.
Conclusions: The use of the FMTVDM©â„— for measurement of isotope redistribution, including Sestamibi, provides an accurate quantitative method for determining both redistribution wash-in and redistribution washout, from which %DS can be calculated on a pixel-by-pixel basis. This %DS can then be used with the proprietary equation (QCFR©, FCFR©) to calculate the CFR directly from the MPI result using FMTVDM©â„—. The implementation of this power tool, will provide for additional determination of the physiological effect of CAD without requiring additional QCA equipment and expertise costs, making QCFR© possible in most if not all hospitals with nuclear medicine departments.