videokymography larynx vocal fold examination ENT PG review

https://pmc.ncbi.nlm.nih.gov/articles/PMC10234949

videokymography vocal fold vibration assessment

mkdir -p /home/daytona/workspace/videokymography-essay

~/videokymography-essay/generate_pdf.py

from reportlab.lib.pagesizes import A4
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.units import cm, mm
from reportlab.lib.colors import HexColor, black, white
from reportlab.platypus import (
    SimpleDocTemplate, Paragraph, Spacer, Table, TableStyle,
    HRFlowable, KeepTogether, PageBreak
)
from reportlab.lib.enums import TA_CENTER, TA_LEFT, TA_JUSTIFY
from reportlab.lib import colors

OUTPUT_PATH = "/home/daytona/workspace/videokymography-essay/Videokymography_ENT_PG_Essay.pdf"

# ── Colour palette ──────────────────────────────────────────────────────────
DARK_BLUE   = HexColor("#1A3560")
MED_BLUE    = HexColor("#2E6DA4")
LIGHT_BLUE  = HexColor("#D6E8F7")
ACCENT      = HexColor("#C0392B")
GOLD        = HexColor("#F39C12")
LIGHT_GREY  = HexColor("#F4F6F8")
BORDER_GREY = HexColor("#BDC3C7")

# ── Document setup ───────────────────────────────────────────────────────────
doc = SimpleDocTemplate(
    OUTPUT_PATH,
    pagesize=A4,
    leftMargin=2.2*cm, rightMargin=2.2*cm,
    topMargin=2.2*cm, bottomMargin=2.2*cm,
)

W = A4[0] - 4.4*cm   # usable width

# ── Styles ───────────────────────────────────────────────────────────────────
styles = getSampleStyleSheet()

cover_title = ParagraphStyle("cover_title",
    fontName="Helvetica-Bold", fontSize=28,
    textColor=white, alignment=TA_CENTER, spaceAfter=6)

cover_sub = ParagraphStyle("cover_sub",
    fontName="Helvetica-BoldOblique", fontSize=14,
    textColor=LIGHT_BLUE, alignment=TA_CENTER, spaceAfter=4)

cover_info = ParagraphStyle("cover_info",
    fontName="Helvetica", fontSize=11,
    textColor=white, alignment=TA_CENTER, spaceAfter=3)

h1 = ParagraphStyle("h1",
    fontName="Helvetica-Bold", fontSize=14,
    textColor=white, backColor=DARK_BLUE,
    spaceAfter=4, spaceBefore=14,
    leftIndent=-0.3*cm, rightIndent=-0.3*cm,
    borderPad=5, leading=18)

h2 = ParagraphStyle("h2",
    fontName="Helvetica-Bold", fontSize=12,
    textColor=DARK_BLUE,
    spaceAfter=3, spaceBefore=8,
    borderPad=3)

h3 = ParagraphStyle("h3",
    fontName="Helvetica-BoldOblique", fontSize=11,
    textColor=MED_BLUE,
    spaceAfter=2, spaceBefore=6)

body = ParagraphStyle("body",
    fontName="Helvetica", fontSize=10.5,
    leading=16, alignment=TA_JUSTIFY,
    spaceAfter=5, textColor=HexColor("#1C1C1C"))

bullet = ParagraphStyle("bullet",
    fontName="Helvetica", fontSize=10.5,
    leading=16, leftIndent=18, bulletIndent=5,
    spaceAfter=2, textColor=HexColor("#1C1C1C"))

bold_bullet = ParagraphStyle("bold_bullet",
    fontName="Helvetica-Bold", fontSize=10.5,
    leading=16, leftIndent=18, bulletIndent=5,
    spaceAfter=2, textColor=DARK_BLUE)

caption = ParagraphStyle("caption",
    fontName="Helvetica-Oblique", fontSize=9,
    textColor=HexColor("#555555"), alignment=TA_CENTER, spaceAfter=4)

highlight = ParagraphStyle("highlight",
    fontName="Helvetica", fontSize=10.5,
    leading=16, backColor=LIGHT_BLUE,
    leftIndent=10, rightIndent=10,
    spaceAfter=5, spaceBefore=4,
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key_point = ParagraphStyle("key_point",
    fontName="Helvetica-Bold", fontSize=10.5,
    leading=16, backColor=HexColor("#FFF9E6"),
    leftIndent=10, rightIndent=10,
    spaceAfter=4, spaceBefore=4,
    borderPad=6, textColor=HexColor("#6B3A00"))

ref_style = ParagraphStyle("ref_style",
    fontName="Helvetica", fontSize=9,
    leading=13, textColor=HexColor("#444444"),
    spaceAfter=2)

# ── Helper ────────────────────────────────────────────────────────────────────
def section_heading(text):
    return [
        Spacer(1, 4),
        Paragraph(f"  {text}", h1),
        Spacer(1, 4),
    ]

def sub_heading(text):
    return [Paragraph(text, h2)]

def sub_sub_heading(text):
    return [Paragraph(text, h3)]

def para(text):
    return [Paragraph(text, body)]

def blt(text, bold_label=""):
    if bold_label:
        return [Paragraph(f"<b>{bold_label}</b> {text}", bullet)]
    return [Paragraph(f"• {text}", bullet)]

def hr():
    return [HRFlowable(width="100%", thickness=0.5, color=BORDER_GREY, spaceAfter=4)]

def spacer(h=6):
    return [Spacer(1, h)]

# ── Build story ───────────────────────────────────────────────────────────────
story = []

# ═══════════════════════════════════════════════════════════════════════════════
# COVER PAGE  (table gives background colour)
# ═══════════════════════════════════════════════════════════════════════════════
cover_data = [[
    Paragraph("VIDEOKYMOGRAPHY", cover_title),
], [
    Paragraph("A Comprehensive Essay for ENT Postgraduate Examination", cover_sub),
], [
    Spacer(1, 0.4*cm),
], [
    Paragraph("Including Related Laryngeal Investigations", cover_info),
], [
    Spacer(1, 0.3*cm),
], [
    Paragraph("Based on Cummings Otolaryngology &amp; Scott-Brown's ORL HNS", cover_info),
], [
    Spacer(1, 0.2*cm),
], [
    Paragraph("Prepared July 2026", cover_info),
]]

cover_table = Table(cover_data, colWidths=[W])
cover_table.setStyle(TableStyle([
    ("BACKGROUND", (0,0), (-1,-1), DARK_BLUE),
    ("ROUNDEDCORNERS", [8]),
    ("VALIGN", (0,0), (-1,-1), "MIDDLE"),
    ("TOPPADDING", (0,0), (-1,0), 40),
    ("BOTTOMPADDING", (0,-1), (-1,-1), 40),
    ("LEFTPADDING", (0,0), (-1,-1), 20),
    ("RIGHTPADDING", (0,0), (-1,-1), 20),
]))
story.append(cover_table)
story.append(Spacer(1, 0.6*cm))

# Gold accent bar
accent_data = [[Paragraph("<b>ENT POSTGRADUATE EXAMINATION SERIES</b>",
    ParagraphStyle("ab", fontName="Helvetica-Bold", fontSize=11,
        textColor=white, alignment=TA_CENTER))]]
accent_table = Table(accent_data, colWidths=[W])
accent_table.setStyle(TableStyle([
    ("BACKGROUND", (0,0), (-1,-1), GOLD),
    ("TOPPADDING", (0,0), (-1,-1), 8),
    ("BOTTOMPADDING", (0,0), (-1,-1), 8),
    ("ROUNDEDCORNERS", [4]),
]))
story.append(accent_table)
story.append(PageBreak())

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 1 – INTRODUCTION
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("1. Introduction")
story += para(
    "The human vocal folds vibrate at frequencies ranging from approximately 70 Hz (bass voice) "
    "to 1000 Hz (soprano falsetto). Standard video endoscopy records at only 25-30 frames per "
    "second (fps), far too slow to capture individual vibratory cycles. Videokymography (VKG) "
    "is a high-speed, single scan-line imaging technique that overcomes this limitation by "
    "generating composite kymographic images from successive video frames at rates up to "
    "<b>8,000 images per second</b> — more than adequate to capture the full glottal width cycle. "
    "It provides direct, real-time visualisation of vocal fold vibratory behaviour regardless "
    "of whether phonation is periodic or aperiodic, making it a powerful adjunct to "
    "videostroboscopy in the clinical voice laboratory."
)
story += para(
    "The term 'kymography' derives from the Greek kyma (wave) and graphein (to write). "
    "Applied to the larynx, a kymogram plots displacement of a selected horizontal scan line "
    "across the vocal folds over time, yielding a two-dimensional space-time image. "
    "Videokymography was introduced by Jan G. Svec and Harm K. Schutte in the mid-1990s "
    "and has since gained recognition as a clinically valuable, real-time tool for "
    "assessment of voice disorders."
)

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 2 – PRINCIPLE
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("2. Principle of Videokymography")
story += sub_heading("2.1 The Kymographic Concept")
story += para(
    "In conventional endoscopy, each video frame captures the entire glottal image at one "
    "instant in time. Kymography instead selects <b>a single horizontal line (scan line) "
    "across the midpoint of the vocal folds</b> and assembles these scan lines from "
    "successive frames into a 2-D image. The horizontal axis of the resulting kymogram "
    "represents <b>glottal width</b> (lateral displacement of the vocal folds) and the vertical "
    "axis represents <b>time</b>. This produces an intuitive 'wave' pattern that directly "
    "reflects the opening and closing of the glottis with each phonatory cycle."
)
story += para(
    "Kymography can be conceptualised as a <b>one-dimensional version of laryngeal high-speed "
    "videoendoscopy (LHSV)</b>: it shows movement of a single horizontal line, whereas LHSV "
    "allows observation of the full length of both vocal folds simultaneously "
    "(Cummings Otolaryngology, Chapter 54)."
)

story += sub_heading("2.2 Technical Implementation — Two Methods")

# Table for two methods
methods_data = [
    ["Method", "Frame Rate", "Mechanism", "Notes"],
    ["Standard video-based VKG\n(Svec & Schutte, 1996)",
     "7,200 fps\n(equivalent)",
     "CCD camera modified to read only one line per field rather than the full frame, giving 7,200 lines/sec",
     "Real-time display; original system; uses modified rigid laryngoscope camera"],
    ["Digital VKG from LHSV\n(post-processing)",
     "2,000–10,000+ fps",
     "A horizontal scan line is extracted from each frame of a full high-speed video sequence",
     "Allows retrospective line selection; not real-time; requires LHSV system"],
    ["2-D scanning VKG\n(newer)",
     "Variable",
     "Multiple scan lines acquired simultaneously, covering the entire vocal fold length",
     "Provides whole mucosal wave pattern; overcomes single-line limitation"],
]
methods_table = Table(methods_data, colWidths=[W*0.22, W*0.15, W*0.36, W*0.27])
methods_table.setStyle(TableStyle([
    ("BACKGROUND", (0,0), (-1,0), DARK_BLUE),
    ("TEXTCOLOR", (0,0), (-1,0), white),
    ("FONTNAME", (0,0), (-1,0), "Helvetica-Bold"),
    ("FONTSIZE", (0,0), (-1,-1), 9),
    ("ALIGN", (0,0), (-1,-1), "LEFT"),
    ("VALIGN", (0,0), (-1,-1), "TOP"),
    ("ROWBACKGROUNDS", (0,1), (-1,-1), [LIGHT_GREY, white]),
    ("GRID", (0,0), (-1,-1), 0.5, BORDER_GREY),
    ("TOPPADDING", (0,0), (-1,-1), 5),
    ("BOTTOMPADDING", (0,0), (-1,-1), 5),
    ("LEFTPADDING", (0,0), (-1,-1), 6),
    ("RIGHTPADDING", (0,0), (-1,-1), 6),
    ("FONTNAME", (0,1), (0,-1), "Helvetica-BoldOblique"),
]))
story.append(methods_table)
story += spacer(6)

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 3 – EQUIPMENT
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("3. Equipment and Setup")
story += para(
    "The original VKG system (Svec-Schutte) uses a <b>rigid 70° or 90° laryngoscope</b> "
    "attached to a modified video camera with a special CCD sensor that records only a "
    "single horizontal line per video field. Modern systems include:"
)
for item in [
    ("Rigid laryngoscope (70° or 90°)", "Provides superior image quality and stable focal plane for reliable scan-line positioning."),
    ("Flexible nasopharyngolaryngoscope", "Used in patients who cannot tolerate rigid scopes; high-definition chip-tip scopes are preferred."),
    ("High-speed camera / modified CCD", "Captures 7,200 or more scan lines per second. Frame rate must exceed twice the maximum phonation frequency (Nyquist criterion)."),
    ("Real-time monitor", "Displays kymogram simultaneously alongside the conventional endoscopic image."),
    ("Computer workstation", "Records, stores, and processes the kymographic data. Software (e.g., Wolf HRES Endocam, Laryngograph Ltd.) allows post-processing analysis."),
    ("Acoustic microphone", "Simultaneous voice recording synchronised with the kymogram allows correlation of acoustic events with vibratory patterns."),
]:
    story += [Paragraph(f"• <b>{item[0]}:</b> {item[1]}", bullet)]
story += spacer(4)

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 4 – TECHNIQUE
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("4. Examination Technique")
story += para(
    "The patient is seated upright. Topical anaesthesia of the oropharynx (lignocaine spray) "
    "may be used with rigid laryngoscopy. The laryngoscope is introduced transorally and the "
    "vocal folds are brought into view."
)
story += sub_heading("4.1 Scan Line Placement")
story += para(
    "The scan line is positioned perpendicular to the axis of the vocal folds, typically "
    "at the <b>midpoint (middle third)</b> of the membranous portion. This is the point of "
    "maximum mucosal wave amplitude and maximum vibratory displacement. For focal lesions, "
    "the line may be repositioned across the lesion to characterise its vibratory behaviour. "
    "Multiple lines can be analysed retrospectively from LHSV-derived kymograms."
)
story += sub_heading("4.2 Phonation Tasks")
for task_item in [
    "Sustained vowel /i/ (ee) at comfortable pitch and loudness — primary task",
    "Sustained /a/ — for comparison",
    "Pitch glide (lowest to highest) — assesses mucosal wave change with tension",
    "Soft versus loud phonation — assesses amplitude changes",
    "Onset and offset of phonation — captures short aperiodic events missed by stroboscopy",
    "Conversational speech (if flexible scope used)",
]:
    story += [Paragraph(f"• {task_item}", bullet)]
story += spacer(4)
story += [Paragraph(
    "<b>Key advantage:</b> Unlike stroboscopy, VKG does not rely on vocal periodicity. "
    "It captures voice onset, offset, pitch breaks, register transitions, and aperiodic dysphonic phonation.",
    key_point)]

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 5 – KYMOGRAPHIC PARAMETERS
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("5. Kymographic Parameters Evaluated")
story += para(
    "The following vibratory parameters are systematically assessed from the kymogram:"
)

params_data = [
    ["Parameter", "Definition", "Clinical Significance"],
    ["Fundamental Frequency (F0)", "Number of complete open-close cycles per second (Hz)", "Directly read from kymogram; objective measure"],
    ["Amplitude of Vibration", "Maximum lateral displacement of each vocal fold from midline", "Reduced in stiff/scarred folds, paralysis, sulcus vocalis"],
    ["Open Quotient (OQ)", "Ratio of open phase duration to total cycle duration", "Increased in breathy voice, paresis; decreased in pressed voice"],
    ["Speed Quotient (SQ)", "Ratio of opening phase duration to closing phase duration", "Reflects cover stiffness; altered in pathology"],
    ["Symmetry (Phase Symmetry)", "Synchrony of right and left fold vibration timing", "Asymmetry in paralysis, mass lesions, sulcus"],
    ["Regularity (Periodicity)", "Cycle-to-cycle consistency of waveform shape", "Irregular in aperiodic pathologies; cycle aberration seen as 'ripples'"],
    ["Mucosal Wave", "Superior-to-inferior travelling wave visible as edge undulation", "Absent/reduced: scarring, Reinke's oedema, leukoplakia, carcinoma"],
    ["Glottal Closure Pattern", "Shape of closure: complete, incomplete, posterior gap, spindle gap", "Incomplete closure in bowing, paresis, presbyphonia"],
    ["Vertical Phase Difference", "Timing difference between inferior and superior vocal fold margins", "Diminished in stiff folds"],
    ["Adynamic Segments", "Areas of the fold that do not vibrate", "Scarring, submucosal lesions, carcinoma"],
    ["Lateral Peak Shape", "Rounded vs. angular peaks on kymogram", "Rounded: stiffened mucosa (laryngitis, scarring); angular: normal compliance"],
    ["Interference Pattern", "Distortion by surrounding structures (false cords, etc.)", "Suggests supraglottic hyperfunction"],
]
params_table = Table(params_data, colWidths=[W*0.22, W*0.36, W*0.42])
params_table.setStyle(TableStyle([
    ("BACKGROUND", (0,0), (-1,0), MED_BLUE),
    ("TEXTCOLOR", (0,0), (-1,0), white),
    ("FONTNAME", (0,0), (-1,0), "Helvetica-Bold"),
    ("FONTSIZE", (0,0), (-1,-1), 9),
    ("ALIGN", (0,0), (-1,-1), "LEFT"),
    ("VALIGN", (0,0), (-1,-1), "TOP"),
    ("ROWBACKGROUNDS", (0,1), (-1,-1), [LIGHT_GREY, white]),
    ("GRID", (0,0), (-1,-1), 0.5, BORDER_GREY),
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    ("RIGHTPADDING", (0,0), (-1,-1), 5),
    ("FONTNAME", (0,1), (0,-1), "Helvetica-Bold"),
]))
story.append(params_table)
story += spacer(6)

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 6 – NORMAL vs. PATHOLOGICAL KYMOGRAMS
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("6. Normal and Pathological Kymographic Patterns")
story += sub_heading("6.1 Normal Kymogram")
story += para(
    "In a normal kymogram, both vocal fold waveforms are <b>symmetric, regular, and sinusoidal</b>. "
    "The open phase slightly exceeds the closed phase. The peaks are angular (sharp), indicating "
    "compliant mucosa with a well-defined mucosal wave. The glottis achieves complete closure "
    "during the closed phase."
)
story += sub_heading("6.2 Pathological Patterns")

path_patterns = [
    ("Vocal Fold Polyp / Nodule",
     "Reduced amplitude at the lesion site. Asymmetric waveforms - the affected fold shows "
     "phase asynchrony relative to the normal fold. Greatest contact area and overlapping "
     "images at the nodular thickening. Anterior commissure area may show absent contact points. "
     "Phase asymmetry within the same fold (anterior vs. middle third). Cycle variability may "
     "remain regular early on."),
    ("Vocal Fold Paralysis / Paresis",
     "Unilateral absence or gross reduction of vibration on the paralysed side. "
     "Marked amplitude asymmetry. Incomplete glottal closure (open quotient increased). "
     "The normal fold may compensate with increased amplitude. Smooth vocal fold edges on kymogram."),
    ("Sulcus Vocalis",
     "Reduced amplitude with smooth vocal fold edges. Mucosal wave is diminished or absent "
     "over the sulcus. Phase symmetry may be maintained. VKG provides superior characterisation "
     "to stroboscopy, which may show 'normal' vibration in mild cases."),
    ("Reinke's Oedema / Polypoid Degeneration",
     "Large amplitude, slow, irregular vibrations. Prolonged open phase. "
     "Mucosal wave may be exaggerated or erratic. Low fundamental frequency."),
    ("Vocal Fold Carcinoma",
     "Adynamic segments (no vibration) over the tumour. Stiff, irregular pattern. "
     "Loss of mucosal wave. Asymmetric, aperiodic waveforms. VKG helps delineate extent of "
     "pliable vs. non-pliable mucosa — critical for surgical planning."),
    ("Chronic Laryngitis / Scarring",
     "Reduced mucosal wave. Rounded lateral peaks (indicating mucosal stiffness). "
     "Reduced amplitude. Regular cycle variability maintained in early disease. "
     "VKG confirmed laryngitis and altered treatment from antibiotics to anti-reflux therapy "
     "(Saindani et al., 2023)."),
    ("Spasmodic Dysphonia (Adductor Type)",
     "Episodic spasms visible as abrupt irregular contact forces. LHSV-derived kymography "
     "has been shown to help differentiate adductor spasmodic dysphonia from muscle tension "
     "dysphonia — a distinction not reliably achievable with stroboscopy alone (Patel et al.)."),
    ("Muscle Tension Dysphonia",
     "Supraglottic compression visible. Erratic vibratory patterns. Vertical phase difference "
     "may be exaggerated or absent."),
    ("Cyst (Intracordal)",
     "The cyst itself appears as an adynamic area. Surrounding mucosa may vibrate normally, "
     "allowing delineation of cyst boundaries. Overlapping images noted at site of maximal contact."),
    ("Presbyphonia (Vocal Fold Bowing)",
     "Persistent spindle-shaped posterior gap (incomplete closure). Reduced amplitude "
     "bilaterally. Regular but small vibrations. Smooth edges."),
]
for name, desc in path_patterns:
    story += KeepTogether([
        Paragraph(f"<b>{name}</b>", h3),
        Paragraph(desc, body),
        Spacer(1, 3),
    ]),

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 7 – VKG vs. STROBOSCOPY
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("7. VKG versus Videostroboscopy")
story += para(
    "Videostroboscopy (VLS) is considered the <b>current gold standard</b> for assessment of "
    "vocal fold vibration in clinical practice. However, it has fundamental limitations that "
    "VKG overcomes."
)

comp_data = [
    ["Feature", "Videostroboscopy (VLS)", "Videokymography (VKG)"],
    ["Principle", "Stroboscopic illumination — creates an apparent slow-motion image by flashing light slightly out of phase with phonation", "Single scan-line, high-speed acquisition — directly captures every vibratory cycle"],
    ["Frame equivalent rate", "25–30 fps (apparent slow motion)", "Up to 8,000 fps equivalent"],
    ["Requires periodic vibration?", "YES — fails in aperiodic / severely dysphonic voice", "NO — works equally well for regular AND irregular vibration"],
    ["Real-time display", "YES", "YES (original VKG); post-processing for LHSV-derived"],
    ["Spatial coverage", "Full 2D laryngeal image", "Single horizontal scan line (or multiple with 2D-VKG)"],
    ["Mucosal wave assessment", "Excellent (full fold visible)", "Good (at scan line level)"],
    ["Voice onset/offset capture", "Poor", "Excellent"],
    ["Quantitative measures", "Limited (mainly perceptual)", "OQ, SQ, amplitude, frequency (objective)"],
    ["Cost / Availability", "Widely available; moderate cost", "Less widely available; moderate-high cost"],
    ["Added diagnostic value", "Gold standard for routine use", "Changes diagnosis in 18-51% of cases vs. VLS alone (Saindani 2023; Phadke 2017)"],
]
comp_table = Table(comp_data, colWidths=[W*0.22, W*0.39, W*0.39])
comp_table.setStyle(TableStyle([
    ("BACKGROUND", (0,0), (-1,0), ACCENT),
    ("TEXTCOLOR", (0,0), (-1,0), white),
    ("FONTNAME", (0,0), (-1,0), "Helvetica-Bold"),
    ("BACKGROUND", (0,1), (0,-1), LIGHT_BLUE),
    ("FONTNAME", (0,1), (0,-1), "Helvetica-Bold"),
    ("FONTSIZE", (0,0), (-1,-1), 9),
    ("ALIGN", (0,0), (-1,-1), "LEFT"),
    ("VALIGN", (0,0), (-1,-1), "TOP"),
    ("ROWBACKGROUNDS", (0,1), (-1,-1), [LIGHT_GREY, white]),
    ("GRID", (0,0), (-1,-1), 0.5, BORDER_GREY),
    ("TOPPADDING", (0,0), (-1,-1), 5),
    ("BOTTOMPADDING", (0,0), (-1,-1), 5),
    ("LEFTPADDING", (0,0), (-1,-1), 5),
    ("RIGHTPADDING", (0,0), (-1,-1), 5),
]))
story.append(comp_table)
story += spacer(6)

story += [Paragraph(
    "<b>Key Point:</b> VKG is COMPLEMENTARY to, not a replacement for, stroboscopy. "
    "In the study by Saindani et al. (Indian J Otolaryngol HNS, 2023), VKG confirmed the "
    "stroboscopic diagnosis in 31% of cases, made the diagnosis more accurate in 51% of "
    "cases, and resulted in adjustment of the treatment offered in 18% of cases.",
    key_point)]
story += spacer(4)

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 8 – INDICATIONS & CLINICAL APPLICATIONS
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("8. Indications and Clinical Applications")
story += sub_heading("8.1 Indications for VKG")
for ind in [
    "Dysphonia with aperiodic or severely irregular vocal fold vibration (where stroboscopy fails)",
    "Evaluation of voice onset and offset abnormalities",
    "Differentiation of adductor spasmodic dysphonia from muscle tension dysphonia",
    "Assessment of subtle mucosal stiffness (sulcus vocalis, early scar)",
    "Characterisation of lesions — to determine extent of adynamic segments before phonosurgery",
    "Post-surgical voice monitoring",
    "Patients with severe dysphonia in whom stroboscopy cannot trigger (aperiodic voice)",
    "Research — quantitative phonatory analysis",
    "Professional voice users requiring objective baseline documentation",
    "Evaluation of vocal fold paralysis — to assess residual vibration in the paretic fold",
]:
    story += blt(ind)
story += spacer(4)

story += sub_heading("8.2 Specific Disease Applications")
story += para(
    "VKG has been studied across a wide range of laryngeal conditions. In a prospective study "
    "(Phadke et al., Eur Arch Otorhinolaryngol 2017), VKG altered diagnosis or management in "
    "a significant proportion of patients with dysphonia. In patients with vocal fold nodules, "
    "polyps, cysts, sulcus vocalis, laryngitis, and paralysis, VKG provided information that "
    "was either not obtainable or not reliable with stroboscopy alone — particularly in cases "
    "where vibration was aperiodic. The 2D scanning VKG system (Wang et al., 2016) further "
    "extends the technique by capturing the whole mucosal wave pattern along the entire "
    "vocal fold length."
)

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 9 – ADVANTAGES AND LIMITATIONS
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("9. Advantages and Limitations")
adv_lim_data = [
    ["ADVANTAGES", "LIMITATIONS"],
    [
        "• Works in aperiodic/irregular phonation\n"
        "• Real-time display\n"
        "• Captures voice onset & offset\n"
        "• Objective quantitative measures (OQ, SQ, amplitude)\n"
        "• No stroboscopic trigger required\n"
        "• Detects subtle mucosal pathology\n"
        "• Differentiates spasmodic dysphonia from MTD\n"
        "• Small data file size (vs. full LHSV)\n"
        "• Reproducible, documented for medicolegal use\n"
        "• Useful in professional voice artists",
        "• Single scan line only (standard VKG) — misses lesions outside scan plane\n"
        "• Requires still endoscope position — movement artefact\n"
        "• Limited spatial resolution vs. full LHSV\n"
        "• Less widely available than stroboscopy\n"
        "• No audio playback synchronised in original system\n"
        "• Cannot examine full vocal fold length simultaneously (standard VKG)\n"
        "• Requires training for interpretation\n"
        "• No standardised clinical protocol established\n"
        "• Not useful for structural laryngeal diagnosis (needs endoscopy too)\n"
        "• Cost of specialised camera system"
    ],
]
adv_lim_table = Table(adv_lim_data, colWidths=[W*0.5, W*0.5])
adv_lim_table.setStyle(TableStyle([
    ("BACKGROUND", (0,0), (0,0), MED_BLUE),
    ("BACKGROUND", (1,0), (1,0), ACCENT),
    ("TEXTCOLOR", (0,0), (1,0), white),
    ("FONTNAME", (0,0), (1,0), "Helvetica-Bold"),
    ("FONTSIZE", (0,0), (-1,-1), 9.5),
    ("ALIGN", (0,0), (-1,-1), "LEFT"),
    ("VALIGN", (0,0), (-1,-1), "TOP"),
    ("BACKGROUND", (0,1), (0,1), HexColor("#EAF4FF")),
    ("BACKGROUND", (1,1), (1,1), HexColor("#FFF0EF")),
    ("GRID", (0,0), (-1,-1), 0.5, BORDER_GREY),
    ("TOPPADDING", (0,0), (-1,-1), 8),
    ("BOTTOMPADDING", (0,0), (-1,-1), 8),
    ("LEFTPADDING", (0,0), (-1,-1), 8),
    ("RIGHTPADDING", (0,0), (-1,-1), 8),
    ("FONTSIZE", (0,0), (1,0), 11),
    ("ALIGN", (0,0), (1,0), "CENTER"),
]))
story.append(adv_lim_table)
story += spacer(6)

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 10 – RELATED INVESTIGATIONS
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("10. Related Investigations: Objective Voice Assessment")
story += para(
    "A comprehensive voice evaluation requires a <b>multidimensional approach</b>. No single "
    "investigation covers all aspects of voice production. The following investigations are "
    "complementary to VKG and are used in the clinical voice laboratory "
    "(Scott-Brown's ORL HNS, Table 62.1):"
)

# ── 10.1 Laryngeal Endoscopy
story += sub_heading("10.1 Standard Laryngeal Endoscopy (Continuous Light)")
story += para(
    "Provides assessment of <b>laryngeal structure and gross function</b>. Evaluates arytenoid "
    "mobility, mucosal colour, oedema, lesions, vascularity, and posterior laryngeal changes "
    "of reflux laryngitis. Limitations: cannot visualise vocal fold vibration (too fast). "
    "Both rigid (70°/90°) and flexible (transnasal) endoscopes are used."
)

# ── 10.2 Videostroboscopy
story += sub_heading("10.2 Videolaryngostroboscopy (VLS)")
story += para(
    "<b>Gold standard</b> for clinical assessment of vocal fold vibration. Uses stroboscopic "
    "illumination (Talbot's law and persistence of vision) to create an apparent slow-motion "
    "image. Requires relatively periodic vibration to trigger the strobe. Provides excellent "
    "visualisation of the mucosal wave, glottal closure pattern, pliability, and symmetry. "
    "Parameters assessed include: symmetry, regularity, mucosal wave, amplitude, glottal "
    "closure (complete / incomplete / posterior gap / spindle / irregular), vertical phase "
    "difference, adynamic segments, and vocal fold edge shape. <b>LVES (laryngeal "
    "videoendoscopy + stroboscopy)</b> is the standard term used in the literature."
)
story += [Paragraph(
    "Limitation: Fails in severely dysphonic / aperiodic voice. Cannot capture voice onset/offset. "
    "Stroboscopy shows 63% failure rate in some series when vibration is highly aperiodic (Patel et al.).",
    highlight)]

# ── 10.3 LHSV
story += sub_heading("10.3 Laryngeal High-Speed Videoendoscopy (LHSV)")
story += para(
    "Records <b>2,000 to 10,000+ fps</b>, capturing the full 2D laryngeal image at sufficient "
    "temporal resolution for every vibratory cycle. Unlike VKG, covers the <b>entire vocal "
    "fold length</b> simultaneously. Allows:"
)
for item in [
    "Observation of voice onset, offset, pitch breaks, and phonation perturbations",
    "Analysis of ventricular fold vibration and its relationship to true fold vibration",
    "Objective quantification: open quotient, speed quotient, jitter, shimmer (via software)",
    "Phonovibrogram — a colour-coded visual representation of the vibratory cycle",
    "Kymogram extraction (digital kymography) from any selected horizontal line",
    "Differentiation of spasmodic dysphonia from muscle tension dysphonia",
]:
    story += blt(item)
story += para(
    "Limitations: Short recording duration (~2 sec = ~90 MB storage); no synchronised audio; "
    "prolonged data saving time; no insurance billing code; high equipment cost. "
    "<b>Minimum recommended frame rate: 4,000 fps</b> (degradation to 2,000 fps alters "
    "perceptual ratings in 16% of samples). LHSV with digital kymography complements — "
    "and in some analyses surpasses — standard VKG by allowing retrospective line selection."
)

# ── 10.4 NBI
story += sub_heading("10.4 Narrow-Band Imaging (NBI)")
story += para(
    "Uses specific wavelengths of light (415 nm and 540 nm) corresponding to haemoglobin "
    "absorption peaks to enhance visualisation of <b>mucosal vascularity</b>. In the larynx:"
)
for item in [
    "Identifies abnormal vascular patterns (intrapapillary capillary loops — IPCLs) associated with dysplasia and malignancy",
    "Guides biopsy to highest-yield areas",
    "Screens for recurrent respiratory papillomatosis extent",
    "Delineates margins of early glottic carcinoma",
    "Not a vibration assessment tool — purely structural/vascular",
]:
    story += blt(item)

# ── 10.5 EGG
story += sub_heading("10.5 Electroglottography / Electrolaryngography (EGG / ELG)")
story += para(
    "Two surface electrodes placed over the thyroid laminae measure changes in "
    "<b>electrical impedance</b> across the glottis during phonation. Impedance falls when "
    "the vocal folds are in contact (low resistance) and rises during the open phase. "
    "The EGG waveform reflects the <b>degree of vocal fold contact area over time</b>. "
    "Parameters: fundamental frequency (F0), closed quotient (CQ), contact index, Lx waveform "
    "symmetry. Non-invasive; useful for objective F0 measurement and contact pattern analysis. "
    "Limitation: does not provide visual information; cannot distinguish left from right fold "
    "contributions; influenced by soft tissue thickness."
)

# ── 10.6 Acoustic Analysis
story += sub_heading("10.6 Acoustic Analysis")
story += para(
    "Recorded with a calibrated microphone at a standard distance (30 cm). Parameters include:"
)
acoustic_data = [
    ["Parameter", "Description", "Normal Range"],
    ["Fundamental Frequency (F0)", "Average phonation frequency", "Male ~110 Hz; Female ~220 Hz"],
    ["Jitter", "Cycle-to-cycle F0 perturbation", "< 1.04% (relative)"],
    ["Shimmer", "Cycle-to-cycle amplitude perturbation", "< 3.81 dB"],
    ["Harmonics-to-Noise Ratio (HNR)", "Ratio of harmonic to noise energy in voice signal", "> 20 dB (normal)"],
    ["Cepstral Peak Prominence (CPP)", "Strength of harmonic structure; most robust acoustic measure", "Higher = less dysphonic"],
    ["CSID (Cepstral Spectral Index of Dysphonia)", "Combined cepstral + spectral measure", "Validated severity index"],
    ["Noise-to-Harmonics Ratio (NHR)", "Inverse of HNR; increases with dysphonia", "< 0.19"],
    ["Maximum Phonation Time (MPT)", "Duration of sustained /a/ at comfortable pitch", "Male >15 sec; Female >12 sec"],
    ["Phonation Quotient", "Vital capacity / MPT — indirect glottic efficiency measure", "< 190 mL/sec (normal)"],
]
acoustic_table = Table(acoustic_data, colWidths=[W*0.27, W*0.46, W*0.27])
acoustic_table.setStyle(TableStyle([
    ("BACKGROUND", (0,0), (-1,0), DARK_BLUE),
    ("TEXTCOLOR", (0,0), (-1,0), white),
    ("FONTNAME", (0,0), (-1,0), "Helvetica-Bold"),
    ("FONTSIZE", (0,0), (-1,-1), 9),
    ("ALIGN", (0,0), (-1,-1), "LEFT"),
    ("VALIGN", (0,0), (-1,-1), "TOP"),
    ("ROWBACKGROUNDS", (0,1), (-1,-1), [LIGHT_GREY, white]),
    ("GRID", (0,0), (-1,-1), 0.5, BORDER_GREY),
    ("TOPPADDING", (0,0), (-1,-1), 4),
    ("BOTTOMPADDING", (0,0), (-1,-1), 4),
    ("LEFTPADDING", (0,0), (-1,-1), 5),
    ("RIGHTPADDING", (0,0), (-1,-1), 5),
    ("FONTNAME", (0,1), (0,-1), "Helvetica-Bold"),
]))
story.append(acoustic_table)
story += spacer(6)

# ── 10.7 Aerodynamic Measures
story += sub_heading("10.7 Aerodynamic Measures")
story += para(
    "Assess the <b>airflow and pressure forces</b> that drive vocal fold vibration:"
)
for item in [
    ("Mean Airflow Rate (MAR)",
     "Volume of air passing through the glottis per second during sustained phonation. "
     "Normal: ~100 mL/sec. Elevated in glottal incompetence (paralysis, bowing); reduced in hyperfunction."),
    ("Subglottal Pressure (Psub)",
     "Air pressure beneath the glottis; estimated indirectly via intraoral pressure during /pa/ syllables. "
     "Drives vocal fold abduction during phonation onset."),
    ("Laryngeal Airway Resistance (Rlaw)",
     "Psub / Airflow. Reflects overall glottal resistance. Elevated in hyperfunction, reduced in paresis."),
    ("Maximum Phonation Time (MPT)",
     "Sustained /a/: indirect measure of glottic efficiency and vocal fold closure. "
     "Simple, widely used screening test. Normal: males >15 s, females >12 s."),
    ("s/z Ratio",
     "Ratio of sustained /s/ to /z/. Normal < 1.4. Elevated ratio suggests glottic insufficiency."),
]:
    story += [Paragraph(f"• <b>{item[0]}:</b> {item[1]}", bullet)]
story += spacer(4)

# ── 10.8 Patient Self-Report
story += sub_heading("10.8 Patient Self-Report / Quality of Life Measures")
qol_data = [
    ["Scale", "Full Name", "Items", "Features"],
    ["VHI-30", "Voice Handicap Index", "30", "Physical, functional, emotional subscales. Threshold 12 = dysfunction. 14-pt change = significant treatment response."],
    ["VHI-10", "Voice Handicap Index-10", "10", "Abbreviated version; faster to complete."],
    ["VPQ", "Voice Performance Questionnaire", "12", "Functional impact of voice on performance activities."],
    ["V-RQOL", "Voice-Related Quality of Life", "10", "Social-emotional and physical functioning domains."],
    ["VoiSS", "Voice Symptom Scale", "30", "Three subscales: impairment, emotional, physical."],
    ["CAPE-V", "Consensus Auditory-Perceptual Evaluation of Voice", "6 parameters", "Perceptual rating: overall severity, roughness, breathiness, strain, pitch, loudness."],
    ["GRBAS", "Grade-Roughness-Breathiness-Asthenia-Strain", "5 parameters, 0-3 each", "Widely used perceptual scale; quick clinical tool."],
]
qol_table = Table(qol_data, colWidths=[W*0.1, W*0.27, W*0.1, W*0.53])
qol_table.setStyle(TableStyle([
    ("BACKGROUND", (0,0), (-1,0), MED_BLUE),
    ("TEXTCOLOR", (0,0), (-1,0), white),
    ("FONTNAME", (0,0), (-1,0), "Helvetica-Bold"),
    ("FONTSIZE", (0,0), (-1,-1), 9),
    ("ALIGN", (0,0), (-1,-1), "LEFT"),
    ("VALIGN", (0,0), (-1,-1), "TOP"),
    ("ROWBACKGROUNDS", (0,1), (-1,-1), [LIGHT_GREY, white]),
    ("GRID", (0,0), (-1,-1), 0.5, BORDER_GREY),
    ("TOPPADDING", (0,0), (-1,-1), 4),
    ("BOTTOMPADDING", (0,0), (-1,-1), 4),
    ("LEFTPADDING", (0,0), (-1,-1), 5),
    ("RIGHTPADDING", (0,0), (-1,-1), 5),
    ("FONTNAME", (0,1), (0,-1), "Helvetica-Bold"),
]))
story.append(qol_table)
story += spacer(6)

# ── 10.9 Stiffness Testing
story += sub_heading("10.9 Other Specialised Investigations")
for item in [
    ("Laryngeal EMG (LEMG)",
     "Percutaneous needle EMG of intrinsic laryngeal muscles (cricothyroid, thyroarytenoid, "
     "posterior cricoarytenoid). Differentiates neurogenic from mechanical immobility of the "
     "arytenoid. Characterises reinnervation patterns in recurrent laryngeal nerve paralysis. "
     "Guides prognostication and surgical timing."),
    ("CT / MRI Larynx",
     "CT: primary imaging for laryngeal malignancy staging (cartilage invasion, subglottic "
     "extension, lymph nodes). MRI: superior soft tissue characterisation; helpful for "
     "paraglottic space and pre-epiglottic space involvement."),
    ("Flexible Endoscopic Evaluation of Swallowing (FEES)",
     "Assesses pharyngeal phase of swallowing and laryngeal sensation (FEESST). "
     "Identifies penetration/aspiration with various food consistencies."),
    ("Transnasal Flexible Laryngoscopy",
     "Provides dynamic view during natural speech and swallowing; allows assessment of "
     "laryngeal sensation, velopharyngeal function, and laryngopharyngeal reflux signs."),
    ("Sensory Testing (FEESST)",
     "Delivers air pulse to laryngeal mucosa via endoscope port; assesses laryngeal adductor "
     "reflex threshold. Elevated threshold indicates sensory neuropathy."),
]:
    story += [Paragraph(f"• <b>{item[0]}:</b> {item[1]}", bullet)]
story += spacer(4)

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 11 – INTEGRATED APPROACH
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("11. Integrated Voice Assessment Protocol")
story += para(
    "A comprehensive voice clinic assessment combines multiple modalities. The recommended "
    "protocol for ENT practice is:"
)
protocol_data = [
    ["Step", "Investigation", "Information Obtained"],
    ["1", "History + perceptual voice assessment (GRBAS/CAPE-V)", "Severity, quality, impact, onset, triggers"],
    ["2", "Patient self-report (VHI-30 / VPQ)", "Quality-of-life impact; baseline for treatment comparison"],
    ["3", "Flexible nasopharyngolaryngoscopy (continuous light)", "Structure, gross movement, mucus, reflux changes, arytenoid mobility"],
    ["4", "Rigid videostroboscopy (70°)", "Mucosal wave, glottal closure, vibratory symmetry and regularity (gold standard for periodic voice)"],
    ["5", "Videokymography (VKG)", "High-speed vibratory analysis; aperiodic voice; adynamic segments; onset/offset; objective quantitative measures"],
    ["6", "Acoustic analysis (MDVP/Praat)", "F0, jitter, shimmer, HNR, CPP; objective severity index"],
    ["7", "Aerodynamic measures (MPT, MAR, Psub)", "Glottic efficiency, airflow, subglottic pressure"],
    ["8", "Electroglottography (EGG)", "Closed quotient, contact pattern, F0 tracking"],
    ["9", "LEMG (if paralysis / arytenoid fixation suspected)", "Neurogenic vs. mechanical; reinnervation status"],
    ["10", "CT/MRI (if malignancy/structural lesion suspected)", "Staging, cartilage invasion, subglottic extent"],
]
protocol_table = Table(protocol_data, colWidths=[W*0.05, W*0.3, W*0.65])
protocol_table.setStyle(TableStyle([
    ("BACKGROUND", (0,0), (-1,0), DARK_BLUE),
    ("TEXTCOLOR", (0,0), (-1,0), white),
    ("FONTNAME", (0,0), (-1,0), "Helvetica-Bold"),
    ("FONTSIZE", (0,0), (-1,-1), 9),
    ("ALIGN", (0,0), (-1,-1), "LEFT"),
    ("ALIGN", (0,0), (0,-1), "CENTER"),
    ("VALIGN", (0,0), (-1,-1), "TOP"),
    ("ROWBACKGROUNDS", (0,1), (-1,-1), [LIGHT_GREY, white]),
    ("GRID", (0,0), (-1,-1), 0.5, BORDER_GREY),
    ("TOPPADDING", (0,0), (-1,-1), 5),
    ("BOTTOMPADDING", (0,0), (-1,-1), 5),
    ("LEFTPADDING", (0,0), (-1,-1), 5),
    ("RIGHTPADDING", (0,0), (-1,-1), 5),
    ("FONTNAME", (0,1), (1,-1), "Helvetica-Bold"),
    # Highlight VKG row
    ("BACKGROUND", (0,5), (-1,5), HexColor("#D5F0E8")),
    ("FONTNAME", (0,5), (-1,5), "Helvetica-Bold"),
]))
story.append(protocol_table)
story += spacer(6)

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 12 – HISTORY & DEVELOPMENT
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("12. Historical Development")
timeline = [
    ("1878", "Mach", "First laryngeal kymography using rotating drum and mirror"),
    ("1940s-60s", "von Leden, Moore, Timcke", "High-speed cinematography of vocal folds (400-4000 fps); established basis of vibration knowledge"),
    ("1991", "Svec, Schutte", "Development of the original videokymography system — single scan-line from modified video camera at 7,200 fps equivalent"),
    ("1996", "Svec & Schutte", "First clinical results of VKG published; demonstrated advantage for irregular vibration assessment"),
    ("1998", "Published first results", "Videokymography shown advantageous for accurate diagnosis of voice disorders (PubMed PMID 9707245)"),
    ("2000s", "Various groups", "Integration of VKG with synchronised audio; digital post-processing; kymogram extraction from LHSV"),
    ("2016", "Wang et al.", "2D scanning VKG — simultaneous multi-line acquisition covering entire vocal fold length"),
    ("2017", "Phadke et al.", "Clinical value of VKG confirmed: altered diagnosis/management in significant proportion of dysphonia patients"),
    ("2017", "Kim et al.", "Real-time dual visualisation — simultaneous endoscopy + 2D scanning VKG display"),
    ("2023", "Saindani et al.", "Prospective study confirms VKG adds diagnostic value over stroboscopy in 100% of cases evaluated"),
]
for year, author, desc in timeline:
    story += [Paragraph(
        f"<font color='#1A3560'><b>{year}</b></font> <font color='#C0392B'>[{author}]</font> — {desc}",
        bullet)]
story += spacer(4)

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 13 – EXAM HIGH YIELD POINTS
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("13. High-Yield Points for ENT PG Examination")

hy_items = [
    "VKG = single horizontal scan-line, high-speed (up to 8,000 fps) kymographic technique for vocal fold vibration analysis",
    "Introduced by Svec and Schutte in the mid-1990s",
    "Kymogram: X-axis = glottal width (displacement); Y-axis = time",
    "Works equally in periodic AND aperiodic phonation — key advantage over stroboscopy",
    "Stroboscopy is GOLD STANDARD for clinical voice assessment; VKG is COMPLEMENTARY",
    "VKG captures voice onset and offset — stroboscopy cannot",
    "Open Quotient (OQ) = open phase / total cycle; increased in paresis and breathy voice",
    "Adynamic segments on VKG suggest scarring, sulcus, or malignancy",
    "Rounded lateral peaks = mucosal stiffness (laryngitis, scar)",
    "Normal kymogram: symmetric, regular, angular peaks, complete glottal closure",
    "VKG differentiates adductor spasmodic dysphonia from muscle tension dysphonia",
    "Patel et al: stroboscopy failed in 63% of patients with severely aperiodic voice; LHSV succeeded in all",
    "Minimum recommended LHSV frame rate: 4,000 fps",
    "VHI-30 threshold: 12 points = voice dysfunction; 14-point change = significant treatment response",
    "s/z ratio >1.4 = glottal incompetence (normal <1.4)",
    "GRBAS scale: Grade, Roughness, Breathiness, Asthenia, Strain — 0 to 3",
    "EGG measures electrical impedance across glottis — reflects vocal fold contact area",
    "NBI uses 415 nm and 540 nm wavelengths — identifies abnormal mucosal vasculature",
    "LEMG differentiates neurogenic from mechanical arytenoid immobility",
    "MPT normal: males >15 sec, females >12 sec; reflects glottic efficiency",
]
for i, item in enumerate(hy_items, 1):
    colour = GOLD if i % 2 == 0 else MED_BLUE
    story += [Paragraph(
        f"<font color='{colour.hexval() if hasattr(colour,'hexval') else str(colour)}'><b>{i}.</b></font> {item}",
        bullet)]
story += spacer(4)

# ═══════════════════════════════════════════════════════════════════════════════
# SECTION 14 – REFERENCES
# ═══════════════════════════════════════════════════════════════════════════════
story += section_heading("14. References")
refs = [
    "Cummings CW et al. (eds). <i>Cummings Otolaryngology Head and Neck Surgery</i>, 7th ed. Elsevier. Chapter 54 (Laryngeal Videoendoscopy, Stroboscopy, High-Speed Videoendoscopy, and Narrow-Band Imaging). ISBN 9780323612173.",
    "Scott-Brown's Otorhinolaryngology Head and Neck Surgery, 8th ed. CRC Press. Chapter 61 (Assessment and Examination of the Larynx), Chapter 62 (Voice Evaluation). ISBN 9781138094642.",
    "Svec JG, Schutte HK. Videokymography: high-speed line scanning of vocal fold vibration. J Voice. 1996;10(2):201-205.",
    "Phadke KV, Vydrov&#225; J, Domagalsk&#225; R. Evaluation of clinical value of videokymography for diagnosis and treatment of voice disorders. Eur Arch Otorhinolaryngol. 2017;274(11):3941-3949. PMID 28856469.",
    "Saindani S, Gandhi S, Bhatta S. A Prospective Observational Study to Determine the Added Clinical Value of Videokymography to Videostroboscopy in Patients with Change in Voice. Indian J Otolaryngol Head Neck Surg. 2023;75(2):567-574. PMID 37275088.",
    "Kim GH, Wang SG, Lee BJ. Real-time dual visualization of two different modalities for the evaluation of vocal fold vibration - Laryngeal videoendoscopy and 2D scanning videokymography. Auris Nasus Larynx. 2017;44(2):197-202. PMID 27421819.",
    "Wang SG et al. A new videokymography system for evaluation of the entire mucosal wave pattern. Auris Nasus Larynx. 2016;43(2):178-183.",
    "Patel RR et al. Clinical feasibility of high-speed videoendoscopy to examine pediatric vocal fold vibration. Ann Otol Rhinol Laryngol. 2012.",
    "Hintze JM, Ludlow CL, Bansberg SF. Spasmodic Dysphonia: A Review. Part 2: Characterization of Pathophysiology. Otolaryngol Head Neck Surg. 2017;157(4):592-600. PMID 28850796.",
    "Chao S, Song SA. Videostroboscopy. StatPearls. Updated 2021. PMID 33620851.",
]
for i, ref in enumerate(refs, 1):
    story += [Paragraph(f"{i}. {ref}", ref_style)]

story += spacer(6)
story += hr()
story += [Paragraph(
    "Prepared for ENT Postgraduate Examination | July 2026 | Based on Cummings ORL and Scott-Brown's ORL HNS",
    ParagraphStyle("footer", fontName="Helvetica-Oblique", fontSize=8,
        textColor=HexColor("#888888"), alignment=TA_CENTER))]

# ── Build PDF ─────────────────────────────────────────────────────────────────
doc.build(story)
print(f"PDF saved: {OUTPUT_PATH}")

cd /home/daytona/workspace/videokymography-essay && python generate_pdf.py 2>&1

ls -lh /home/daytona/workspace/videokymography-essay/

ls -lh /home/daytona/workspace/videokymography-essay/ && echo "File exists"

cd /home/daytona/workspace/videokymography-essay && python generate_pdf.py 2>&1 …