Diffusion Magnetic Resonance Imaging in the Head and Neck James Schafer, MD, Ashok Srinivasan, MD, Suresh Mukherji, MD  Magnetic Resonance Imaging Clinics  Volume 19, Issue 1, Pages 55-67 (February 2011) DOI: 10.1016/j.mric.2010.10.002 Copyright © 2011 Elsevier Inc. Terms and Conditions

Fig. 1 A freehand ROI drawn around the lesion (squamous cell carcinoma of the oral tongue) on the ADC map, used to generate the mean ADC of the lesion (which measured 0.8×10−3 mm2/s in this lesion). Magnetic Resonance Imaging Clinics 2011 19, 55-67DOI: (10.1016/j.mric.2010.10.002) Copyright © 2011 Elsevier Inc. Terms and Conditions

Fig. 2 A lesion in the left posterior tongue. Mean ADC may not be an accurate representation of the lesion because a homogeneous lesion demonstrating intermediate ADC values (gray) (A) can have the same mean as a heterogeneous lesion that contains areas of increased ADC values (white) and decreased ADC values (black) (B). Magnetic Resonance Imaging Clinics 2011 19, 55-67DOI: (10.1016/j.mric.2010.10.002) Copyright © 2011 Elsevier Inc. Terms and Conditions

Fig. 3 The parametric response map principle comparing pre- and posttherapy ADC maps. A user-defined color coding is used to visually represent the change in ADC that occurs on a voxel-to-voxel basis between the 2 scans. In this example, voxels showing an increase in ADC are red, those showing a decrease are blue, and those that show no change are gray. This visual technique is a quick way of comparing tumors that show different responses to therapy. Magnetic Resonance Imaging Clinics 2011 19, 55-67DOI: (10.1016/j.mric.2010.10.002) Copyright © 2011 Elsevier Inc. Terms and Conditions

Fig. 4 The parametric response map technique comparing pre- and posttherapy scans may not work well if the tumor has changed in its axis (A) or changed substantially in size (B) because the voxel-to-voxel correlation is then lost for a large number of voxels, rendering the technique less effective in demonstrating changes. Magnetic Resonance Imaging Clinics 2011 19, 55-67DOI: (10.1016/j.mric.2010.10.002) Copyright © 2011 Elsevier Inc. Terms and Conditions

Fig. 5 (Left) A freehand ROI drawn around a squamous cell carcinoma of the tongue on the ADC map. (Right) A histogram is then generated for this lesion, where the x-axis represents the ADC values and the y-axis represents the number of voxels within the lesion for a particular ADC value. Magnetic Resonance Imaging Clinics 2011 19, 55-67DOI: (10.1016/j.mric.2010.10.002) Copyright © 2011 Elsevier Inc. Terms and Conditions

Fig. 6 ADC histograms provide another way of comparing lesions that otherwise have the same mean ADC value. In this example, the histograms show a different spread of voxels within 2 lesions that have the same mean ADC value. Lesion B shows a normal distribution centered at a single value; lesion A, despite having the same mean ADC, shows a bimodal distribution with 2 peaks that represent 2 parts of the same mass with very different physiologies. Therefore, ADC histograms are a more accurate way of characterizing a lesion. Magnetic Resonance Imaging Clinics 2011 19, 55-67DOI: (10.1016/j.mric.2010.10.002) Copyright © 2011 Elsevier Inc. Terms and Conditions

Fig. 7 T2-weighted, postcontrast T1-weighted, b1000 DW images of a 47-year-old patient demonstrate a large T2 hyperintense lesion (A) in the right carotid sheath that shows moderate heterogeneous enhancement (B) and mild increased diffusion signal (C). The ADC in the lesion measured 1.6×10−3 mm2/s, and pathology confirmed the lesion to be a schwannoma. The high ADC in the lesion is consistent with a benign process that tends to show increased ADC values. Magnetic Resonance Imaging Clinics 2011 19, 55-67DOI: (10.1016/j.mric.2010.10.002) Copyright © 2011 Elsevier Inc. Terms and Conditions

Fig. 8 T2-weighted, postcontrast T1-weighted, b1000 DW images and an ADC map of a 65-year-old patient demonstrate a T2 hyperintense (A), intensely enhancing (B) lesion along the posterior tongue base. The lesion shows bright diffusion signal (C) and decreased ADC (D), with the ADC measuring 0.7×10−3 mm2/s. Pathology confirmed the presence of a squamous cell carcinoma. The low ADC in the lesion is likely because of the hypercellularity seen within malignant neoplasms. Magnetic Resonance Imaging Clinics 2011 19, 55-67DOI: (10.1016/j.mric.2010.10.002) Copyright © 2011 Elsevier Inc. Terms and Conditions

Fig. 9 T2-weighted, postcontrast T1-weighted images and an ADC map of a patient with known malignancy in the head and neck show a small, mildly T2 hyperintense lymph node at left level II, adjacent to the carotid artery (A). The lymph node shows only mild enhancement (B) and measured 1.0×0.8 cm, which is below the size for suspicion of metastasis. However, the lymph node was dark on the ADC map (C) and showed an ADC of 0.8×10−3 mm2/s, suggesting that there may be metastatic deposits. This lymph node was removed at surgery and confirmed to be metastatic. Hence, in patients with known head and neck malignancies, the presence of decreased ADC within normal-sized lymph nodes should be viewed with suspicion in the appropriate clinical setting. Magnetic Resonance Imaging Clinics 2011 19, 55-67DOI: (10.1016/j.mric.2010.10.002) Copyright © 2011 Elsevier Inc. Terms and Conditions

Fig. 10 T2-weighted, postcontrast T1-weighted, b1000 DW images and an ADC map of a patient treated with malignancy in the left masticator space demonstrate a T2 hyperintense, enhancing region along the medial left pterygoid (A, B). However, this region is not increased in diffusion signal (C) and shows an ADC values (D) that is brighter than the brain on the same image. The ADC measured 1.3×10−3 mm2/s, and there was no evidence of recurrent neoplasm on surgical pathology. Magnetic Resonance Imaging Clinics 2011 19, 55-67DOI: (10.1016/j.mric.2010.10.002) Copyright © 2011 Elsevier Inc. Terms and Conditions

Fig. 11 T2-weighted, postcontrast T1-weighted, b1000 DW images and an ADC map of the same patient as in Fig. 10 (performed 10 months later) demonstrate a T2 hypointense, enhancing region along the medial left pterygoid (A, B) This region now shows increased diffusion signal (C) and decreased ADC values (D). The ADC now measured 0.6×10−3 mm2/s, suggesting the possibility of neoplastic recurrence, which was confirmed on pathology. Magnetic Resonance Imaging Clinics 2011 19, 55-67DOI: (10.1016/j.mric.2010.10.002) Copyright © 2011 Elsevier Inc. Terms and Conditions